Category Archives: Human Genetics

Its been 10 years sinceMichael Wiglerhad a breakthrough revelation in autism geneticsone that arguably launched the field as we know it.

In April 2007, Wigler and his then colleague,Jonathan Sebat, reported that de novo mutationsthose that arise spontaneously instead of being inheritedoccur more often in people with autism than in typical people. The mutations they noted were in the form of copy number variants (CNVs), deletions or duplications of long stretches of DNA. CNVs crop up frequently in cancer, an earlier focus of Wiglers work. But his find that they are also involved in autism came as a surprise to those in the field. Genetics was striking out with other efforts based on transmission and inheritance, Wigler says. In that vacuum, the new idea was quickly embraced.

The discovery fast led to further advances. Focusing primarily onde novomutations, three teams of scientists, including one led by Wigler, began hunting for genes that contribute to autism. Their approach was efficient: Rather than looking at the entire genome, they scoured the 2 percent that encodes proteins, called theexome. And they looked specifically at simplex families, which have a single child with autism and unaffected parents and siblings. The premise was that comparing the exomes of the family members might exposede novomutations in the child with autism. The approachyielded a bumper crop: Based on data from more than 600 families, the teams together predicted that there are hundreds of autism genes. They identified six as leading candidates. Some of the genes identified at the time CHD8,DYRK1A,SCN2A quickly became hot areas of research.

In 2014, the number of strong candidates jumped higher. In two massive studies analyzing the sequences of more than 20,000 people, researchers linked 50 genes to autism with high confidence. Wiglers team looked at simplex families and found rarede novomutations in 27 genes. In the second study, researchers screened for both inherited andde novomutations and implicated 33 genes. The two studies identified 10 genes in common.

Two years ago, the tally of autism gene candidates shot up again. Deploying statistical wizardry to combine the data onde novoand inherited mutations, along with CNV data from theAutism Genome Project, researchers pinpointed 65 genes and six CNVsas being key to autism. They also identified 28 genes that they could say with near certainty are autism genes.

For so long, weve been saying if we could just find these genes, wed be able to really make some headway, saysStephan Sanders, assistant professor of psychiatry at the University of California, San Francisco, who co-led the study. Suddenly, youve got this list of 65-plus genes, which we know have a causative role in autism, and as a foundation for going forward, its amazing.

These advances establish beyond doubt that autism is firmly rooted in biology. More and more, we are erasing this idea of autism being a stigmatizing psychiatric disorder, and I think this is true for the whole of psychiatry, Sanders says. These are genetic disorders; this is a consequence of biology, which can be understood, and where traction can be made.

This is just the start, however. As scientists enter the next chapter of autism genetics, they are figuring out how to build on what they have learned, using better sequencing tools and statistics, bigger datasets and more robust models. For example, they are looking for common variantswhich are found in more than 1 percent of the population but may contribute to autism when inherited en masse. And they are also starting to look beyond the exome to the remaining 98 percent of the genome they have largely neglected thus far.

Most of the genetic advances fall into a category of large-effect-sizede novovariants, which is only one piece of the puzzle, saysDaniel Geschwind, professor of human genetics at the University of California, Los Angeles. Its an important piece, but one that still cannot explain why autism clusters in families, for instance, or why close relatives of people with autism often share some of the conditions traits.

So how much of autisms genetic architecture have scientists uncovered? Current estimates suggest that rare mutations, whetherde novoor inherited, contribute to the condition somewhere between 10 and 30 percent of the time. Before the recent spate of discoveries, the proportion of individuals whose autism had a known genetic cause was only 2 to 3 percentmuch of that from rare related genetic syndromes, such asfragile X syndromeand tuberous sclerosis complex, which stem from mutations in a single known gene. These syndromes often involve some core features of autism, along with their own set of characteristic traits, and intellectual disability.

Two generations ago, at least 75 percent of the time autism was comorbid with severe intellectual disability and other neurodevelopmental abnormalities, saysMark Daly, associate professor of medicine at Harvard University. It was also a much rarer diagnosis.

The large increase in diagnoses in recent decades overwhelmingly reflects cases at the mild end of the spectrum, Daly says, creating a new challenge. The genetics of autism has us wrestling with the fact that rare mutations, and especially these spontaneously arising ones, are the strongest risk factors, he says. But at the same time, theres a majority of cases now that dont have any of those high-impact risk factors.

Instead, much of the risk in these instances likely comes from common variants, which have small effects on their own, but can add up to increase overall risk. Researchers have tried to identify those relevant to autism using genome-wide association studies (GWAS), which compare the genomes of people with and without a condition to find differences in single-letter swaps of DNA called single nucleotide polymorphisms.

Because common variants have small effects individually, they are difficult to find, but multiple studies suggest that theyplay a major rolein autism risk. In a 2014 study, for instance, researchers used statistical tools to estimate the heritability of autism from the amount of common variation shared by unrelated people with autism. They applied the method to data from more than 3,000 people in Swedens national health registry. Their calculations indicated thatcommon variants account for 49 percentof the risk for autism in the general population; rare variants, equal partsde novoand inherited, explain 6 percent. Some scientists dispute these figures, but its clear that common variants, rare inherited variants and spontaneous mutations all play a part in autism.

Wigler says he is skeptical of using GWAS studies for autism precisely because they focus on common variants. Most of the disorders that will cause pain and suffering and require expensive treatments, if theyre genetic, are caused by rare variants that are not going to stay around in the population, he says.

Common variants may turn out to be more relevant at the milder end of the spectrum than in those who are severely affected. The people who havede novomutations, en masse, tend to have lower intelligence quotients and more cognitive problems, Sanders says.

Researchers are grappling with how to fit these pieces together: Finding and diagnosing rare variants linked to severe outcomes is important, but so is unraveling how the core traits of autism relate to other psychiatric conditions and manifest in the general population. Both goals are important, and they shouldnt be seen as at odds with each other, Daly says. In fact, a study published in May reported thatrare and common variants can combineto increase an individuals risk.

The landscape of autism genetics becomes even more complex when considering the sheer number of genes that could be involvedsome researchers estimate up to a thousandand the fact that many high-confidence autism genes are also associated with other conditions, ranging from intellectual disability andepilepsyto schizophrenia and congenital heart disease.

This many-to-one and one-to-many relationship is not surprising, Sanders says. But it does mean there are probably no unique autism genes per se. But I could flip that round and say weve not found anything which is a pure intellectual disability or schizophrenia gene [either]; on a fundamental level, these disorders seem to be related, he says. If I was to say, Can we find something which contributes more to autism than other disorders? then I think the answers yes. The genes that seem particularly tied to autism could offer important clues about the conditions biology.

The genes identified so far have hinted at a handful of underlying mechanisms that contribute to autism. Most of them seem to be involved in three broad categories of tasks: maintaining the function ofsynapses, or the connections between neurons; controlling the expression of genes; and modifying chromatin, structures of DNA wound around protein spools called histones. Chromatin determines which stretches of DNA can be read and so influences gene expression.

The idea of a brain condition originating with atypical neuronal connections made logical sense from the start. There had been a lot of interest in the synapse, Sanders says. But the candidates that control gene expression only emerged in the genetic studies. Two genes that consistently top the high-confidence listsCHD8 and SCN2Awere both somewhat of a surprise. CHD8 encodes a chromatin regulator that controls the expression of thousands of other genes. SCN2A codes for a sodium channel and had primarily been associated with infantile seizures.

Using gene expression maps, such as theBrainSpan Atlas, researchers have traced when and where autism genes are active in the brain. They have found that many of the genes, CHD8 and SCN2A included, are expressed in parts of the cortex during mid- to late fetal developmentwhich happens to be the peak period when neurons are forming. We dont really understand it yet, but theyre more likely than not to disrupt fetal brain development in mid-gestation, Geschwind says. That timing suggests they interfere with processes that are critical to setting up the cortex, including which types of cells form and where in the brain they migrate. If the cortex isnt set up right, he says, you create ongoing problems with how neurons communicate, among other important functions. Within the next few years, he says, researchers will have a refined understanding of the neurons and circuits affected.

Work in animal and cell models reveals similar problems with the genesis, structure and fate of new neurons and the connections between them. In some cell and animal models of syndromic forms of autism, scientists have managed to at least partially correct some of these problems with drugs. The unrealized promise of these findings is that some traits of autism may ultimately prove reversible, even in adults.

The idea that theres something plastic here, not set in stone at birth, is very important, saysMatthew State, chair of psychiatry at the University of California, San Francisco, and lead investigator on many of the big autism genetics studies.

In the meantime, genetic discoveries have delivered some immediate benefits for people with the condition. If you go into a clinic today, theres about a 10 percent chance of you getting a genetic diagnosis, and I would expect to find evidence which was suggestive in about another 5 to 10 percent, Sanders says. We cant then turn round and say, Heres your cure, but what we can do, at least, is put people in touch with other people with that same mutation. Becoming part of such a group gives people a better idea about what the future holds for them and provides them with support and understanding.

Advocacy groups can lobby researchers and funding bodies, contribute to research on their condition and help find participants for clinical trialswhich, by grouping people according to their underlying genetics, would then have a greater chance of success. It becomes very empowering, saysJoseph Buxbaum, director of the Seaver Autism Center for Research and Treatment in New York.

Genetic diagnoses can also help families make decisions about family planning and treatment options. For example, deletion of a region on chromosome 17, called 17q12, is associated with autism and schizophrenia, but treating someone who has this CNV with certain mood stabilizers or antipsychotics could be dangerous: It is also associated with renal failure and adult-onset diabetes, which the drugs would exacerbate. Whats more, certain mutations increase therisk for some types of cancer. Knowing those mutations can be very helpful in those cases, not just in treating autism, but in treating the patient more broadly, Geschwind says.

Debates abound on how best to move the field forward, but one thing most researchers agree on is the need to identify more mutations linked to autism. Theres great benefit now in just doing more exome sequencing, Sanders says. Theres more genes to be found: Those will hopefully help patients; theyll also give us more of an understanding of what autism is.

Much of the variation that predisposes someone to autism, however, may lie in noncoding regions. If half of the variants are outside of the coding region, we need to know how to interpret them, Wigler says. For that reason alone, we have to study that region. Plus, were going to learn an enormous amount of biology in the process.

Noncoding regions make up the dark genome, which is about 98 percent of the whole. Because of the cost and effort involved in sequencing the whole genome, most autism researchers have stayed focused on exomes, until recently. Several teams are now sequencing whole genomes of people with autism, with the aim of identifying risk variants in these noncoding regions. Whole-genome sequencing inevitably will overtake exome sequencing, Sanders says. Its just a question economically of whether its moment is now, or in two years, or five years. Right now, thats a hard question to answer.

In March, researchers in Canada reported results from the largest set of whole genomes of people with autism to date. They sequenced the whole genomes of more than 5,000 individuals, about half of whom have autism. Among the61 variants the researchers identified, 18 had not beenfirmly linked to autismbefore. The team found that many of the CNVs in people with autism rest in noncoding regions.

Some teams are applying other resources, such as gene co-expression maps and protein-protein interaction networks, to understanding the underlying biology of the condition. These networks are only likely to become more powerful as researchers uncover more risk genes for autism. The question is how to integrate all that genetic data with other -omics data, and network-type approaches are probably going to be critical there, Geschwind says.

Most autism research arising from gene discovery is focused on repercussions at the molecular and cellular levels, but theres an important gap from there to whole circuits and behavior. Ultimately, the value of genetics is very likely to play out through an improved understanding of circuit-level function and anatomy, State says.

Stem cells and emerging technologies such as brain organoidsso called mini-brains in a dishcould afford researchers a prime opportunity to study the effects of genetic variation in human neurons. Faced with the limitations of mouse models in studying a condition characterized by behavioral problems, some teams are alsoturning to monkeys, which enable them to study more complex social interactions. Something we should be doing for the future is taking the precise mutations we find in humans and making those in primates, Wigler says.

These days, Wigler is on to another big idea: risk modifiers. Rare variants strongly associated with autism also occur in people without autismespecially women. Researchers know that mutations can contribute to autism by amplifying or attenuating the effects of other genes, so its feasible that two mutations could cancel each other out. But few teams have looked into these combinations as yet. People talk about autism as being an additive disorder, Wigler says, but nobodys really looking at additivity.

This idea brings him to a possible experiment: Take two mutations that individually have damaging effects, and introduce them both into mouse or monkey. Having the combination would be predicted to be worse than having either mutation alone. But what if the net result is correction? Wigler asks. Then we know modifiers exist. Theres not much of that kind of scientific exploration happening now.

A finding of that nature would herald a whole new wave of advances. It might also help to explain why the mutations identified so far vary in their effector what geneticists call penetranceonly sometimes resulting in autism. And it might help researchers develop therapies. If we ever saw a self-correcting defect in two mutations in autism, Wigler says, I would stand up and cheer.

This story wasoriginally publishedonSpectrum.

See more here:
Using Big Data to Hack Autism - Scientific American

In BriefResearchers have identified a single gene deletion in E. colibacteria that influence longevity in C. elegans worms. This pointsto the role of gut bacteria in life extension and points to thepossibility of a life-extending probiotic in the future.

Researchers at the Baylor College of Medicine have found the key to longevity in Caenorhabditis elegans (C. elegans) worms and maybe, someday, humans. The team noticed that genetically identical worms would occasionally live for much longer, and looked to their gut bacteria to find the answer. They discovered that a strain of E. coli with a single gene deletion might be the reason that its hosts lives were being significantly extended.

This study is one among a number of projects that focus on the influence of the microbiome the community of microbes which share the body of the host organism on longevity. Ultimately, the goal of this kind of research is to develop probiotics that could extend human life. Ive always studied the molecular genetics of aging, Meng Wang, one of the researchers who conducted the study, told The Atlantic. But before, we always looked at the host. This is my first attempt to understand the bacterias side.

Even in cases like this, where it seems fairly obvious that the microbiome is influencing longevity, parsing out the details of how and why this happens among a tremendous variety of chemicals and microbe species is extremely complex. The team, in this case, was successful because they simplified the question and focused on a single relationship.

Genetically engineering bacteria to support and improve human health and even to slow aging and turning it into a usable, life-extending probiotic wont be easy. It is extremely difficult to make bacteria colonize the gut in a stable manner, which is a primary challenge in this field. The team, in this case, is looking to the microbiome, because the organisms used would be relatively safe to use because they would originate in the gut.

Clearly, researchers dont know yet whether these discoveries will be able to be applied to people, though it seems promising. Despite the obvious differences between the tiny C. elegans worm and us, its biology is surprisingly similar; many treatments that work well in mice and primates also work in the worm. The team will begin experiments along these same lines with mice soon.

Other interesting and recent research hoping to stop or slow the march of time includes work with induced pluripotent stem (iPS) cells, antioxidants that target the mitochondria, and even somewhat strangework with cord blood. It seems very likely that we wont have a single solution offering immortality anytime soon, but instead a range of treatment options that help to incrementally hold back time. And, with an improving quality of life, this kind of life extension sounds promising.

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This Study Could Help Extend the Human Lifespan - Futurism

The world learned the details of the Islamic States systemic rape and slavery of women through shocking stories told to the New York Times in 2015.Our collective outrage also showed how war has changed. Rape, torture and slavery are considered beyond taboo; they are criminalized even in war. This archaic behavior is not supposed to happen in our modern world.

But thats a pretty recent development. Systemic rape used to go hand in hand with war as women, resources and landswere assimilated into the victors communities. The victorious menhad more children, more land and more power. Some researchers have argued that this is proof of the deep roots theory of war: Human males fight each other for reproductive advantage, proving that war is an evolutionary advantageous behavior.

But this theory has been hard to prove. In fact, studies of human groups and other primates have added to the evidence both for and against the controversial idea that humans were made for war, evolutionarily speaking. A January 2015study indicates that societies dont actually benefit from head-to-head action, though other forms of violence do pay off.

Harvard evolutionary biologists Luke Glowaki and Richard Wrangham studied the Nyangatom people of East Africa. The group are polygamous shepherds who raise small livestock and can have multiple wives. At times, the Nyangatom go to war with other groups. But there is a another pervasive and nearly constant form of violence in the group. Young riders make raids on nearby camps with the goal of stealing cattle. Glowaki and Wrangham asked if either or both of these types of violence was beneficial to the men who engaged in them. They measured by counting the the number of wives and kids they had.

This study is one of many that has heightened thedebate over how muchwar has had an impact on a warriors evolutionary success. At least in this society,sneaking around after dark and stealing cows may have beenmore consequential. Robert Sapolosky at the Wall Street Journal explained:

By contrast, lots of battle raidingopen-field, daytime combat with hundreds of participantsdid not serve as a predictor of elevated reproductive success, probably because such fighting carried a nontrivial chance of winding up dead. In other words, in this society, being a warrior on steroids did not predict reproductive success; being a low-down sneaky varmint of a cattle rustler did.

But researchers only discovered this by looking at the elders in the community. Stealthy animal raiding did lead to better outcomes but decades later. In Nyangatom culture, most of the stolen livestock goes to fathers and other paternal relatives rather than being kept by the young men who stole them. The male heads of families made marriage decisions for their younger relatives. So, while it this kind of violence makes a difference, the payoff is quite delayed. The researchers speculated the cattle-rustling effect would be stronger in a group where the raiders got to keep the livestock they stole and incentives were strengthened.

Other studies also point to the idea that inter-group warfare might not be beneficial, but intra-group violence is. Chimpanzee tribes, for example dont often go to war with other tribes. Instead the most common types of violence involve a group of males ganging up on one individual male. This often happens when conditions are crowded or there were increased numbers of males in the tribe. And the researchers found that chimps participation in violence happened outside of the spheres of human influence, meaning violence was not a behavior the chimpanzees learned from us.

But other evidence suggests that humans likely didnt participate in war as we know it until relatively recently. A 2013 survey of killings in 21 groups (foragers rather than shepherds) found that group warfare was rare compared to homicide. John Horgan categorized the evidence at Scientific American:

Some other points of interest: 96 percent of the killers were male. No surprise there. But some readers may be surprised that only two out of 148 killings stemmed from a fight over resources, such as a hunting ground, water hole or fruit tree. Nine episodes of lethal aggression involved husbands killing wives; three involved execution of an individual in a group by other members of the group; seven involved execution of outsiders, such as colonizers or missionaries. Most of the killings stemmed from what Fry and Soderberg categorize as miscellaneous personal disputes, involving jealousy, theft, insults and so on. The most common specific cause of deadly violenceinvolving either single or multiple perpetratorswas revenge for a previous attack.So it maybe that a proclivity for violence and an innate sense of revenge that perpetuates war, rather than war itself.

Another factor to consider is that while our common ancestors lived in groups like these thousands of years ago, almost no one does anymore. In fact, finding these undisturbed cultures is hard to do. Having more cows doesnt carry the same appeal it once did. Its unlikely stealing your neighbors TV for your uncle will fetch you a better bride. Some scientists worry that if we accept the idea that violence was a beneficial tool for our ancestors, it somehow overturns the societal progress that has moved us beyond the rape and pillage culture to something still imperfect, but largely more peaceful.

This is the biggest struggle with the deep roots theory of human violence. Just because something garnered an advantage thousands of years ago doesnt make it okay today. Harvard psychologist Steven Pinker, who has written a book on human violence, said in the Boston Globe:

romantics worry that if violence is a Darwinian adaptation, that must mean that it is good, or that its futile to work for peace, because humans have an innate thirst for blood that has to be periodically slaked. Needless to say, I think all this is profoundly wrongheaded.

Meredith Knight is a contributor to the human genetics section for Genetic Literacy Project and a freelance science and health writer in Austin, Texas. Follow her @meremereknight.

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Evolution and war: The 'deep roots' theory of human violence - Genetic Literacy Project

Human genetics is the study of how genes influence human traits, diseases, and behaviors, including how genetic and non-genetic factors interact. Public health genetics applies advances in human genetics and genomics to improve public health and prevent disease. Genetic counselors work as members of a health care team, providing information and support to patients dealing with birth defects or genetic disorders and those who may be at risk for inherited conditions.

The program emphasizes the study of genetic mechanisms related to the transition from normal to disease states, and studies how genes and the environment interact to affect the distribution of health and disease in human populations.

Human genetics research has helped answer fundamental questions about human nature and led to the development of effective treatments for many diseases that greatly impact human health. Faculty in the Department of Human Genetics have developed and used genetic methods to investigate the causes and treatment of hereditary and acquired human illness and to understand and explore the impact of genetics on public health, education, and disease prevention.

Originally posted here:
Human Genetics | Pitt Public Health | University of Pittsburgh

When the first humans left Africa around 100,000 years ago, they got shorter.

The evolutionary shift helped them cope with the colder conditionsa more compact body size helped protect them from frostbite, whileand shorter limbs would be less breakable when they fellbut it also appears to have come with a downside: arthritis.

In a study published in Nature Genetics on Monday, scientists at Stanford University, California, have shown how variants within the GDF5 gene, which are related to reduced growth, was repeatedly favored by our ancestors as they migrated out of Africa and across the continents.

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But GDF5 has also been linked with osteoarthritis,a degenerative joint disease that affects an estimated 27 million Americans. Risk increases with ageit is sometimes referred to as wear and tear arthritisbut it also has a strong genetic component.

Previous research has shown how mutations in part of the GDF5 gene cause malformation in bone structure in mice. In humans, it has been associated with a shortness and joint problems, and two changes in particular are linked with a heightened risk of osteoarthritis.

In the latest research, the scientists find GDF5 provided an evolutionary boost for our ancestors, with arthritis apparently a byproduct of it."The gene we are studying shows strong signatures of positive selection in many human populations," senior author David Kingsley said in a statement

"It's possible that climbing around in cold environments was enough of a risk factor to select for a protective variant even if it brought along an increase likelihood of an age-related disease like arthritis, which typically doesn't develop until late in life."

A display of a series of skeltons showing the evolution of humans at the Peabody Museum, New Haven, Connecticut, circa 1935. Study finds humans became shorter when they first left Africa 100,000 years ago. Hulton Archive/Getty Images

To better understand GDF5, the team studied the DNA sequences that might affect how the gene is expressedspecifically those that are known as promoters and enhancers. From this they found a previously unidentified region they called GROW1.

When they looked for GROW1 in the 1,000 Genomes Project databasea huge database of genetic sequences of human populations around the worldthe team found a single change that is very common in European and Asian populations, but is hardly ever seen in Africans. The team then introduced this change to mice and found it led to reduced activity in the growth of bones.

They then looked at the change to the genetic variant over the course of human evolution, and found it had been repeatedly favored after Homo sapiens left Africa between 50,000 and 100,000 years ago. The team says the benefits of being shorter in colder conditions probably outweighed the risk of developing osteoarthritis in later life.

Because evolutionary fitness requires successful reproduction, alleles that confer benefits at young or reproductive ages may be positively selected in populations, even if they have some deleterious consequences in post-reproductive ages, they wrote.

Researchers believe this change could help explain why osteoarthritis is rarely seen in Africa, but is more common in other populations.Concluding, Kingsley said: "Because it's been positively selected, this gene variant is present in billions of people. So even though it only increases each person's risk by less than twofold, it's likely responsible for millions of cases of arthritis around the globe.

"This study highlights the intersection between evolution and medicine in really interesting ways, and could help researchers learn more about the molecular causes of arthritis."

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Human Evolution: Africa Exodus Made Homo Sapiens Shorter and Gave Them Arthritis - Newsweek

Three courts in Britain agreed with the hospital, as did the European Court of Human Rights, which last week rejected a last-ditch appeal by Charlies parents.

But Pope Francis and Mr. Trump have also weighed in, adding another dimension to an extraordinarily thorny bioethical and legal dispute that pits Britains medical and judicial establishment against the wishes of the childs parents.

Judges in the case have acknowledged that the case highlights differences in law and medicine and an American willingness to try anything, however unlikely the possibility of success but have held that prolonging the infants life would be inhumane and unreasonable. The case echoes the one of Terri Schiavo, a Florida woman who was left in a persistent vegetative state after a cardiac arrest and was also the subject of a court battle.

A Vatican spokesman, Greg Burke, told Vatican Radio on Sunday that the pope had been following the parents case with affection and sadness, praying that their desire to accompany and care for their own child to the end is not ignored.

Italys top pediatric hospital, which is run by the Vatican, told the Italian news agency ANSA on Monday that it would be willing to take Charlie.

We understand that the situation is desperate, said Mariella Enoc, director of the Bambino Ges hospital in Rome, noting that she had been in touch with British officials to signal a willingness to take the patient, the agency reported. We are close to the parents in prayer and, if this is their desire, we are open to receiving their child at our structure for the time it will take for him to live.

Mr. Trump, who was not known to have previously expressed a view on the matter, wrote on Twitter on Monday that if the United States could help, we would be delighted to do so.

Both the pope and the president stopped short of criticizing the court rulings or the hospital. Helen Aguirre Ferr, the director of the White House office of media affairs, said Mr. Trump had decided to speak out after he learned about this heartbreaking situation. Mr. Trump has not spoken with the family, she said, and does not want to pressure them in any way.

The president is just trying to be helpful if at all possible, she added.

Charlie was born on Aug. 4 with encephalomyopathic mitochondrial DNA depletion syndrome. He is thought to be one of only 16 children globally with the condition, the result of a genetic mutation.

Brendan Lee, the chairman of the department of molecular and human genetics at Baylor College of Medicine, who is not involved the case, said in a phone interview that mitochondrial depletion syndrome has no cure. Treatments involve different types of vitamin supplementation, but none have been shown to definitively work through studies, he said.

Charlies parents, Connie Yates and Chris Gard, both in their 30s, have been waging a long and wrenching legal battle to keep him alive. They have raised more than 1.3 million pounds, or about $1.7 million, to help finance experimental treatment in the United States. There is also an international campaign, with an online petition, and there have been street protests in front of Buckingham Palace.

Charlie has been treated since October at Great Ormond Street Hospital, where doctors eventually decided that withdrawing life support was the only justifiable option. Although Charlies parents have parental responsibility, overriding control is by law vested in the court exercising its independent and objective judgment in the childs best interests, the hospital said in a statement laying out its position.

Siding with the hospital were the High Court, on April 11; the Court of Appeal, on May 25; and the Supreme Court of the United Kingdom, on June 8.

The High Court ruled that Charlie would face significant harm if his suffering were to be prolonged without any realistic prospect of improvement. Moreover, it said the experimental treatment, known as nucleoside therapy, would not be effective.

Money is not at issue; an academic medical center in the United States has offered to provide the experimental treatment. But a neurologist at the hospital, who has offered to oversee the treatment, told the court by telephone: I can understand the opinion that he is so severely affected by encephalopathy that any attempt at therapy would be futile. I agree that it is very unlikely that he will improve with that therapy.

Neither the hospital nor the neurologist was identified in court documents, and the White House has declined to identify either.

The Court of Human Rights ruled last week that the British courts had acted appropriately in concluding that it was most likely Charlie was being exposed to continued pain, suffering and distress, and that undergoing experimental treatment with no prospects of success would offer no benefit, and continue to cause him significant harm.

The case has drawn attention to important differences in legal systems.

Claire Fenton-Glynn, a legal scholar at the University of Cambridge who studies childrens rights, said that under British law, the courts were the final arbiter in medical disputes about the treatment of children.

She noted a 2001 case of conjoined twins, Jodie and Mary, who were born sharing an aorta. Separating the twins would lead to the death of the weaker twin; if they were not separated, both would die. A court ruled that the twins should be separated against the wishes of their parents; as expected, one died.

Courts in the United States are less inclined to get involved when there are disputes between parents and doctors, said Professor Moreno of the University of Pennsylvania, stressing that it was usually left to doctors, in consultation with parents, to decide on a childs treatment.

He noted the case of Baby Jane Doe, who was born in 1983 with spina bifida and whose parents declined to approve surgery to prolong her life. That case led to a law, signed by President Ronald Reagan, that defined instances in which withholding medical treatment from infants could be considered child abuse, but also provided that in certain cases doctors and parents might choose to withhold treatment from seriously handicapped babies when such action would merely prolong dying.

G. Kevin Donovan, the director of the Pellegrino Center for Clinical Bioethics at Georgetown University Medical Center and a professor of pediatrics, said that in the United States, if parents insisted on continuing life-prolonging treatment against a doctors advice, the child would simply be transferred to another institution willing to comply with the parents wishes.

It doesnt seem to be a supportable position morally or ethically, he said of the stance taken by the hospital in London, adding that what is legal and what is ethical are not always the same.

In the Schiavo case, her husband, who was her legal guardian, wanted to have her feeding tube removed, but her parents disagreed, setting off a seven-year fight that ended in 2005, after courts ruled in the husbands favor. Life support was removed from Ms. Schiavo, who died at 41.

In that case, too, the pope, then John Paul II, and the president, George W. Bush, weighed in. Mr. Bush signed an act of Congress allowing federal courts to intercede in the case. But their interventions did not ultimately affect the outcome.

There was no immediate response to Mr. Trumps statement from Charlies parents, who last week appeared to accept the finality of the courts rulings. Photographs of the couple sleeping with their sick child have circulated on social media recently.

We are really grateful for all the support from the public at this extremely difficult time, Ms. Yates said on Friday. Were making precious memories that we can treasure forever with very heavy hearts. Please respect our privacy while we prepare to say the final goodbye to our son Charlie.

There was also no immediate reaction from the hospital.

In Charlies case we have been discussing for many months how the withdrawal of treatment may work, the hospital said. There would be no rush for any action to be taken immediately. It added that it would consult the family and that discussions and planning in these situations usually take some days.

Follow Dan Bilefsky @DanBilefsky and Sewell Chan @sewellchan on Twitter.

Reporting was contributed by Aneri Pattani and Roni Caryn Rabin from New York, Michael D. Shear from Washington, and Elisabetta Povoledo from Rome.

A version of this article appears in print on July 4, 2017, on Page A1 of the New York edition with the headline: Dispute Over British Babys Fate Draws In President and Pope.

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Dispute Over British Baby's Fate Draws In Pope and US President - New York Times

Human mitochondrial genetics is the study of the genetics of human mitochondrial DNA (the DNA contained in human mitochondria). The human mitochondrial genome is the entirety of hereditary information contained in human mitochondria. Mitochondria are small structures in cells that generate energy for the cell to use, and are hence referred to as the "powerhouses" of the cell.

Mitochondrial DNA (mtDNA) is not transmitted through nuclear DNA (nDNA). In humans, as in most multicellular organisms, mitochondrial DNA is inherited only from the mother's ovum. There are theories, however, that paternal mtDNA transmission in humans can occur under certain circumstances.[1]

Mitochondrial inheritance is therefore non-Mendelian, as Mendelian inheritance presumes that half the genetic material of a fertilized egg (zygote) derives from each parent.

Eighty percent of mitochondrial DNA codes for mitochondrial RNA, and therefore most mitochondrial DNA mutations lead to functional problems, which may be manifested as muscle disorders (myopathies).

Because they provide 30 molecules of ATP per glucose molecule in contrast to the 2 ATP molecules produced by glycolysis, mitochondria are essential to all higher organisms for sustaining life. The mitochondrial diseases are genetic disorders carried in mitochondrial DNA, or nuclear DNA coding for mitochondrial components. Slight problems with any one of the numerous enzymes used by the mitochondria can be devastating to the cell, and in turn, to the organism.

In humans, mitochondrial DNA (mtDNA) forms closed circular molecules that contain 16,569,[2][3] DNA base pairs,[4] with each such molecule normally containing a full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules, with the quantity ranging between 1 and 15.[4] Each human cell contains approximately 100 mitochondria, giving a total number of mtDNA molecules per human cell of approximately 500.[4]

Because mitochondrial diseases (diseases due to malfunction of mitochondria) can be inherited both maternally and through chromosomal inheritance, the way in which they are passed on from generation to generation can vary greatly depending on the disease. Mitochondrial genetic mutations that occur in the nuclear DNA can occur in any of the chromosomes (depending on the species). Mutations inherited through the chromosomes can be autosomal dominant or recessive and can also be sex-linked dominant or recessive. Chromosomal inheritance follows normal Mendelian laws, despite the fact that the phenotype of the disease may be masked.

Because of the complex ways in which mitochondrial and nuclear DNA "communicate" and interact, even seemingly simple inheritance is hard to diagnose. A mutation in chromosomal DNA may change a protein that regulates (increases or decreases) the production of another certain protein in the mitochondria or the cytoplasm; this may lead to slight, if any, noticeable symptoms. On the other hand, some devastating mtDNA mutations are easy to diagnose because of their widespread damage to muscular, neural, and/or hepatic tissues (among other high-energy and metabolism-dependent tissues) and because they are present in the mother and all the offspring.

Mitochondrial genome mutations are passed on 100% of the time from mother to all her offspring. So, if a female has a mitochondrial trait, all offspring inherit it. However, if a male has a mitochondrial trait, no offspring inherit it. The number of affected mtDNA molecules inherited by a specific offspring can vary greatly because

It is possible, even in twin births, for one baby to receive more than half mutant mtDNA molecules while the other twin may receive only a tiny fraction of mutant mtDNA molecules with respect to wildtype (depending on how the twins divide from each other and how many mutant mitochondria happen to be on each side of the division). In a few cases, some mitochondria or a mitochondrion from the sperm cell enters the oocyte but paternal mitochondria are actively decomposed.

Genes in the human mitochondrial genome are as follows.

It was originally incorrectly believed that the mitochondrial genome contained only 13 protein-coding genes, all of them encoding proteins of the electron transport chain. However, in 2001, a 14th biologically active protein called humanin was discovered, and was found to be encoded by the mitochondrial gene MT-RNR2 which also encodes part of the mitochondrial ribosome (made out of RNA):

Unlike the other proteins, humanin does not remain in the mitochondria, and interacts with the rest of the cell and cellular receptors. Humanin can protect brain cells by inhibiting apoptosis. Despite its name, versions of humanin also exist in other animals, such as rattin in rats.

The following genes encode rRNAs:

The following genes encode tRNAs:

In humans, the light strand of mtDNA carries 28 genes and the heavy strand of mtDNA carries only 9 genes.[5] Eight of the 9 genes on the heavy strand code for mitochondrial tRNA molecules. Human mtDNA consists of 16,569 nucleotide pairs. The entire molecule is regulated by only one regulatory region which contains the origins of replication of both heavy and light strands. The entire human mitochondrial DNA molecule has been mapped[1][2].

The genetic code is, for the most part, universal, with few exceptions: mitochondrial genetics includes some of these. For most organisms the "stop codons" are "UAA", "UAG", and "UGA". In vertebrate mitochondria "AGA" and "AGG" are also stop codons, but not "UGA", which codes for tryptophan instead. "AUA" codes for isoleucine in most organisms but for methionine in vertebrate mitochondrial mRNA.

There are many other variations among the codes used by other mitochondrial m/tRNA, which happened not to be harmful to their organisms, and which can be used as a tool (along with other mutations among the mtDNA/RNA of different species) to determine relative proximity of common ancestry of related species. (The more related two species are, the more mtDNA/RNA mutations will be the same in their mitochondrial genome).

Using these techniques, it is estimated that the first mitochondria arose around 1.5 billion years ago. A generally accepted hypothesis is that mitochondria originated as an aerobic prokaryote in a symbiotic relationship within an anaerobic eukaryote.

Mitochondrial replication is controlled by nuclear genes and is specifically suited to make as many mitochondria as that particular cell needs at the time.

Mitochondrial transcription in Human is initiated from three promoters, H1, H2, and L (heavy strand 1, heavy strand 2, and light strand promoters). The H2 promoter transcribes almost the entire heavy strand and the L promoter transcribes the entire light strand. The H1 promoter causes the transcription of the two mitochondrial rRNA molecules.[6]

When transcription takes place on the heavy strand a polycistronic transcript is created. The light strand produces either small transcripts, which can be used as primers, or one long transcript. The production of primers occurs by processing of light strand transcripts with the Mitochondrial RNase MRP (Mitochondrial RNA Processing). The requirement of transcription to produce primers links the process of transcription to mtDNA replication. Full length transcripts are cut into functional tRNA, rRNA, and mRNA molecules.[citation needed]

The process of transcription initiation in mitochondria involves three types of proteins: the mitochondrial RNA polymerase (POLRMT), mitochondrial transcription factor A (TFAM), and mitochondrial transcription factors B1 and B2 (TFB1M, TFB2M). POLRMT, TFAM, and TFB1M or TFB2M assemble at the mitochondrial promoters and begin transcription. The actual molecular events that are involved in initiation are unknown, but these factors make up the basal transcription machinery and have been shown to function in vitro.[citation needed]

Mitochondrial translation is still not very well understood. In vitro translations have still not been successful, probably due to the difficulty of isolating sufficient mt mRNA, functional mt rRNA, and possibly because of the complicated changes that the mRNA undergoes before it is translated.[citation needed]

The Mitochondrial DNA Polymerase (Pol gamma, encoded by the POLG gene) is used in the copying of mtDNA during replication. Because the two (heavy and light) strands on the circular mtDNA molecule have different origins of replication, it replicates in a D-loop mode. One strand begins to replicate first, displacing the other strand. This continues until replication reaches the origin of replication on the other strand, at which point the other strand begins replicating in the opposite direction. This results in two new mtDNA molecules. Each mitochondrion has several copies of the mtDNA molecule and the number of mtDNA molecules is a limiting factor in mitochondrial fission. After the mitochondrion has enough mtDNA, membrane area, and membrane proteins, it can undergo fission (very similar to that which bacteria use) to become two mitochondria. Evidence suggests that mitochondria can also undergo fusion and exchange (in a form of crossover) genetic material among each other. Mitochondria sometimes form large matrices in which fusion, fission, and protein exchanges are constantly occurring. mtDNA shared among mitochondria (despite the fact that they can undergo fusion).[citation needed]

Mitochondrial DNA is susceptible to damage from free oxygen radicals from mistakes that occur during the production of ATP through the electron transport chain. These mistakes can be caused by genetic disorders, cancer, and temperature variations. These radicals can damage mtDNA molecules or change them, making it hard for mitochondrial polymerase to replicate them. Both cases can lead to deletions, rearrangements, and other mutations. Recent evidence has suggested that mitochondria have enzymes that proofread mtDNA and fix mutations that may occur due to free radicals. It is believed that a DNA recombinase found in mammalian cells is also involved in a repairing recombination process. Deletions and mutations due to free radicals have been associated with the aging process. It is believed that radicals cause mutations which lead to mutant proteins, which in turn led to more radicals. This process takes many years and is associated with some aging processes involved in oxygen-dependent tissues such as brain, heart, muscle, and kidney. Auto-enhancing processes such as these are possible causes of degenerative diseases including Parkinson's, Alzheimer's, and coronary artery disease.[citation needed]

Because mitochondrial growth and fission are mediated by the nuclear DNA, mutations in nuclear DNA can have a wide array of effects on mtDNA replication. Despite the fact that the loci for some of these mutations have been found on human chromosomes, specific genes and proteins involved have not yet been isolated. Mitochondria need a certain protein to undergo fission. If this protein (generated by the nucleus) is not present, the mitochondria grow but they do not divide. This leads to giant, inefficient mitochondria. Mistakes in chromosomal genes or their products can also affect mitochondrial replication more directly by inhibiting mitochondrial polymerase and can even cause mutations in the mtDNA directly and indirectly. Indirect mutations are most often caused by radicals created by defective proteins made from nuclear DNA.[citation needed]

In total, the mitochondrion hosts about 3000 different types of proteins, but only about 13 of them are coded on the mitochondrial DNA. Most of the 3000 types of proteins are involved in a variety of processes other than ATP production, such as porphyrin synthesis. Only about 3% of them code for ATP production proteins. This means most of the genetic information coding for the protein makeup of mitochondria is in chromosomal DNA and is involved in processes other than ATP synthesis. This increases the chances that a mutation that will affect a mitochondrion will occur in chromosomal DNA, which is inherited in a Mendelian pattern. Another result is that a chromosomal mutation will affect a specific tissue due to its specific needs, whether those may be high energy requirements or a need for the catabolism or anabolism of a specific neurotransmitter or nucleic acid. Because several copies of the mitochondrial genome are carried by each mitochondrion (2-10 in humans), mitochondrial mutations can be inherited maternally by mtDNA mutations which are present in mitochondria inside the oocyte before fertilization, or (as stated above) through mutations in the chromosomes.[citation needed]

Mitochondrial diseases range in severity from asymptomatic to fatal, and are most commonly due to inherited rather than acquired mutations of mitochondrial DNA. A given mitochondrial mutation can cause various diseases depending on the severity of the problem in the mitochondria and the tissue the affected mitochondria are in. Conversely, several different mutations may present themselves as the same disease. This almost patient-specific characterization of mitochondrial diseases (see Personalized medicine) makes them very hard to accurately recognize, diagnose and trace. Some diseases are observable at or even before birth (many causing death) while others do not show themselves until late adulthood (late-onset disorders). This is because the number of mutant versus wildtype mitochondria varies between cells and tissues, and is continuously changing. Because cells have multiple mitochondria, different mitochondria in the same cell can have different variations of the mtDNA. This condition is referred to as heteroplasmy. When a certain tissue reaches a certain ratio of mutant versus wildtype mitochondria, a disease will present itself. The ratio varies from person to person and tissue to tissue (depending on its specific energy, oxygen, and metabolism requirements, and the effects of the specific mutation). Mitochondrial diseases are very numerous and different. Apart from diseases caused by abnormalities in mitochondrial DNA, many diseases are suspected to be associated in part by mitochondrial dysfunctions, such as diabetes mellitus, forms of cancer and cardiovascular disease, lactic acidosis, specific forms of myopathy, osteoporosis, Alzheimer's disease, Parkinsons's disease, stroke, male infertility and which are also believed to play a role in the aging process.[citation needed]

Human mtDNA can also be used to help identify individuals.[7] Forensic laboratories occasionally use mtDNA comparison to identify human remains, and especially to identify older unidentified skeletal remains. Although unlike nuclear DNA, mtDNA is not specific to one individual, it can be used in combination with other evidence (anthropological evidence, circumstantial evidence, and the like) to establish identification. mtDNA is also used to exclude possible matches between missing persons and unidentified remains.[8] Many researchers believe that mtDNA is better suited to identification of older skeletal remains than nuclear DNA because the greater number of copies of mtDNA per cell increases the chance of obtaining a useful sample, and because a match with a living relative is possible even if numerous maternal generations separate the two. American outlaw Jesse James's remains were identified using a comparison between mtDNA extracted from his remains and the mtDNA of the son of the female-line great-granddaughter of his sister.[9] Similarly, the remains of Alexandra Feodorovna (Alix of Hesse), last Empress of Russia, and her children were identified by comparison of their mitochondrial DNA with that of Prince Philip, Duke of Edinburgh, whose maternal grandmother was Alexandra's sister Victoria of Hesse.[10] Similarly to identify Emperor Nicholas II remains his mitochondrial DNA was compared with that of James Carnegie, 3rd Duke of Fife, whose maternal great-grandmother Alexandra of Denmark (Queen Alexandra) was sister of Nicholas II mother Dagmar of Denmark (Empress Maria Feodorovna).[11]

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Human mitochondrial genetics - Wikipedia

A 21-month-old girl in North Carolina is turning heads thanks to her unusual hair.

Phoebe Brasswell, of Smithfield, was born with a rare genetic condition that makes her locks always look as if theyve just been hit with static electricity.

The condition, uncombable hair syndrome, causes her hair follicles to be kidney-shaped instead of round. It also affects the hairs protein, which gives it shape, according to Inside Edition.

As a result, Phoebes hair is fine, coarse, constantly tangled and constantly staticky, according to SWNS.com.

SWNScom

Phoebe is one of only around 100 children worldwide with the condition, according toProfessor Regina Betz, who researches UHS at the Institute for Human Genetics at the University of Bonn, Germany.

Betz told SWNS, There may be many more which have not been reported.

Phoebes mom, Jamie, said no haircare products seem to work on her daughters hair, but she loves it anyway.

Every morning it is sticking straight up and throughout the day, she told SWNS.com. I try and spray stuff in it to keep it down, but within 30 minutes its spiky again.

Jamie Brasswell has nicknamed her little girl, Poppy, after a character in the movie Trolls, according to Inside Edition.

SWNS

Still, people unfamiliar with the condition arent shy about making suggestions to Phoebes mom when they are in public.

We were in the grocery store once and a lady said, She is going to hate you when she looks at her baby photos because you let her go out in public like that, Jamie told SWNS.com.People say, You should brush it better. Why dont you put it in a ponytail? But that hurts her.

Jamie has tried to minimize those comments by having Phoebe wear a headband when out in public.

SWNS

Although Phoebes hair sticks out in a crowd and pretty much everywhere else doctors expect it will become more manageable when she reaches puberty.

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Toddler's Hair Stands Up Like Troll Doll Thanks To Rare Genetic Condition - HuffPost

When Daniel Benjamin was just beginning his PhD program in economics in 2001, he attended a conference with his graduate school advisers. They took in a presentation on neuroeconomics, a nascent field dealing with how the human brain goes about making decisions.

Afterward, as they took a stroll outside, they couldnt stop talking about what they had learned, how novel and intriguing it was. What would be next, they wondered. What would come after neuroeconomics?

The human genome project had just been completed, and we decided that even more fundamental than the brain would be genes, and that someday this was going to matter a lot for social science, said Benjamin, associate professor (research) of economics at the USC Dornsife College of Letters, Arts and Sciences Center for Economic and Social Research (CESR). Indeed, his excitement that day was the foundation of a visionary academic path.

Fast forward to today. Genoeconomics is now an emerging area of social science that incorporates genetic data into the work that economists do. Its based on the idea that a persons particular combination of genes is related to economic behavior and life outcomes such as educational attainment, fertility, obesity and subjective well-being.

Theres this rich new source of data that has only become available recently, said Benjamin, also co-director of the Social Science Genetic Association Consortium, which brings about cooperation among medical researchers, geneticists and social scientists.

Collecting genetic data and creating the large data sets used by economists and other social scientists have become increasingly affordable, and new analytical methods are getting more and more powerful as these data sets continue to grow. The big challenge, he said, is figuring out how scientists can leverage this new data to address a host of important policy questions.

Were ultimately interested in understanding how genes and environments interact to produce the kinds of outcomes people have in their lives, and then what kinds of policies can help people do better. That is really what economics is about and were trying to use genetics to do even better economics.

Only a handful of economists are working with genetics, but this brand of research is perfectly at home at CESR. The center, founded three years ago, was conceived as a place where visionary social science could thrive and where research could be done differently than in the past.

Being in a place where thats the shared vision is pretty rare, said econometrician Arie Kapteyn, professor (research) of economics and CESR director. Theres no restriction on which way you want to go or what you want to do. It doesnt mean that there are no restrictions on resources, but its the opportunity to think about your vision of whats really exciting in social science research. Then being able to actually implement it is absolutely fantastic.

The mission of CESR is discovering how people around the world live, think, interact, age and make important decisions. The centers researchers are dedicated to innovation and combining their analysis to deepen the understanding of human behavior in a variety of economic and social contexts.

What we try to do is mold a disciplinary science in a very broad sense, Kapteyn said. Because todays problems in society, theyre really all multidisciplinary.

Case in point: Benjamins work combining genetics and economics.

The flagship research effort for Benjamins CESR research group deals with genes and education. In a 2016 study, the team identified variants in 74 genes that are associated with educational attainment. In other words, people who carry more of these variants, on average, complete more years of formal schooling.

Benjamin hopes to use this data in a holistic way to create a predictive tool.

Were also creating methods for combining the information in a persons entire genome into a single variable that can be used to partially predict how much education a persons going to get.

Daniel Benjamin

Rather than just identifying specific genes, he said, were also creating methods for combining the information in a persons entire genome into a single variable that can be used to partially predict how much education a persons going to get.

The young field of genoeconomics is still somewhat controversial, and Benjamin is careful to point out that individual genes dont determine behavior or outcome.

The effect of any individual gene on behavior is extremely small, Benjamin explained, but the effects of all the genes combined on almost any behavior were interested in is much more substantial. Its the combined information of many genes that has predictive power, and that can be most useful for social scientists.

While the cohort of researchers actively using the available genome-wide data in this way is still somewhat limited, Benjamin says it is growing quickly.

I think across the social sciences, researchers are seeing the potential for the data, and people are starting to use it in their work and getting excited about it, but right now its still a small band of us trying to lay the foundations.

Were putting together huge data sets of hundreds of thousands of people approaching a million people in our ongoing work on educational attainment because you need those really big sample sizes to accurately detect the genetic influences.

As CESR works to improve social welfare by informing and influencing decision-making in the public and private sectors, big data such as Benjamins is a growing part of that process, according to Kapteyn.

What big data reflects is the fact that nowadays there are so many other ways in which we can learn about behavior, he said. As a result, I think well see many more breakthroughs and gain a much better understanding of whats going on in the world and in social science than in the past.

I think were really at the beginning of something pretty spectacular. What we are doing is really only scratching the surface theres so much more that can be done.

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Report comes as the university nears the opening of USC Village, the largest economic development project in the history of South Los Angeles.

The USC Dornsife Economics Department launches the USC Economics Review to spotlight students research.

The program at USC Dornsife offers tailored training in preparation for Fall Career Fair.

Conference covers methods of prompting change in human behavior for the public good.

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Can genetics play a role in education and well-being? - USC News

Like many others, Ive been rewatching the Game of Thronestelevision series in preparation for the start of the seventh season later this month. So I dont think its all that odd that an image of Jon Snows first trip to the jaw-dropping Wall of ice (which rises 700 feet high) in the frozen north of Westeros popped up in my head as I began research for my latest release about human evolution, migration and genetic selection.

You see, like Snow, our early human ancestors moved north out of Africa into the much colder climates of Europe and Asiatens of thousands of years ago. And as their surroundings and weather changed, they adapted to these changing conditions by passing on genes that would enhance their descendants chances of survival. Paradoxically, however, this fancy genetic footwork seems to have favored a DNA sequence that not only reduces human height, but also increases the risk of osteoarthritis. It seems somewhat contrary to the survival of the fittest mantra that we all learned in high school.

The researchers, Stanford developmental biologist David Kingsley, PhD, and Harvard human evolutionary biologist Terence Capellini, PhD,Harvard graduate studentJiaxue Cao, and former Stanford postdoctoral scholarHao Chen, PhD, published their findings today in Nature Genetics.

From our release:

Now, researchers at the Stanford University School of Medicine and at Harvard University have shown that, despite its association with the painful joint disease, this genetic variant has been repeatedly favored as early humans migrated out of Africa and into colder northern climates. At least half of Europeans and Asians harbor the gene variant, which is relatively rare in African populations. []

A more compact body structure due to shorter bones could have helped our ancestors better withstand frostbite and reduce the risk of bone fracture from falling, the researchers speculate. These advantages in dealing with chilly temperatures and icy surfaces may have outweighed the threat of osteoarthritis, which usually occurs after prime reproductive age.

It wasnt just our early human ancestors who hit upon this solution, the researchers found. Our even more ancient cousins, the Neanderthals and the Denisovans, also singled out this same gene variant (through a process known in genetic circles as positive selection) when they left Africa about 600,000 years ago. Its evolutionary popularity means it is now present in billions of people.

As Kingsley explained:

The potential medical impact of the finding is very interesting because so many people are affected. This is an incredibly prevalent, and ancient, variant. Many people think of osteoarthritis as a kind of wear-and-tear disease, but theres clearly a genetic component at work here as well. Now weve shown that positive evolutionary selection has given rise to one of the most common height variants and arthritis risk factors known in human populations.

Previously: From whence the big toe? Stanford researchers investigate the genetics of upright walking, Its a blond thing: Stanford researchers suss out the molecular basis of hair colorand Comprehensive review of humans expansion out of Africa could lead to medical advances Photo by Jeff S. PhotoArt at HDCanvas.ca

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Genetic variant linked to osteoarthritis favored in cold climates - Scope (blog)