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You’ve probably noticed that journalists everywhere (including yours truly) are covering a huge breakthrough in autism: the discovery of the first common genetic risk variants for autism.
The study — by far the biggest to date — pinned six variants, all nestled between two genes on chromosome 5.
Adding even more grist to the mill, another study released yesterday also pointed to this region. Scanning about 900 families, that study found eight genetic variants that are more common in family members with autism than in their healthy kin. And again, all eight variants sit — you guessed it — in that same hot spot on chromosome 5.
The immediately obvious question is: what exactly are those variants doing there?
…I’m not sure I do. But in case you’re interested, via Razib:
The Personal Genome Project, an initiative founded by George Church that ultimately seeks to sequence the complete genomes of 100,000 people, has called for the next wave of volunteers. The PGP will sequence your genome and give you back the data for the bargain-basement price of zero dollars (not bad compared to the $68,000 that the Knome auction is starting at).
The benefits to volunteers are straightforward: you get access to your own genome sequence before most human beings on the planet, and you get the warm fuzzy glow that comes with benefiting humanity. I’m not being at all sarcastic about the latter benefit. The PGP is an audacious experiment in overcoming both the technological and social challenges of providing access to large-scale genetic information, and whatever progress it makes will have a very real impact on the future of human genomics.
…read the rest
One of the two new studies, which screened more than 10,000 people, for the first time identifies a cluster of common variants — defined as mutations that occur in five percent or more of the general population — that are more prevalent in people with autism than in healthy controls.
Other research groups have found common variants that are disproportionately prevalent in people with autism. But because their sample sizes have been too small, none have found associations with genome-wide significance.
For that sizable group, here’s some welcome news: melatonin, the over-the-counter food supplement that some travelers use to shake jet lag, may help children with autism fall asleep faster, according to a report published last week.
In the study, children with autism or fragile X syndrome who took melatonin before bed fell asleep a half-hour earlier, and slept about 20 minutes longer, than kids taking placebo.
Melatonin is a natural hormone. The brain releases it to lower body temperature and make us feel drowsy. A couple of reports have found that children with autism have unusually low levels of melatonin in their blood, which seems like a plausible explanation for why they have trouble getting to sleep.
Civil rights groups in Minnesota and Texas are fighting their state governments in some of the first legal battles over newborn blood screening.
Every newborn, at nearly any hospital worldwide, is put through a standard screening procedure within a few hours of birth. Doctors prick the infant’s heel, and a few drops of blood are screened for rare diseases, anonymized, stored and, sometimes, given to scientific researchers. These samples have proven invaluable to scientists who are studying the basis of complex psychiatric disorders, including autism.
from a Nature interview…he’s not giving enough credit to neuroscientists, of course, but still makes a good point:
Nature: Why are you skeptical about genetic explanations for human behaviour?
Wolfe: So many neuroscientists have become gnostics — convinced they see things the rest of us can’t see because they’ve had a revelation. They have a secret: what we call ’soul’, ‘mind’ and even ’self’ must go into quotation marks. There’s no ‘me’ inside of me. We are machines programmed at birth; we think we have free choice but we don’t. But none of this has any scientific basis. As Delgado’s son has said, we are not two miles down the long road of understanding the brain, we are two millimetres, and all the rest is literature.
The word schizophrenia comes from the Greek skhizein, meaning ‘to split’ and phren, which means ‘mind’.
Schizophrenia now refers to the apparent separation of memory, thinking and perceptual abilities that trigger a disjointed personality in those with the disorder. But this split may also grant those individuals unusual abilities.
The disconnection between what the eyes see and what the brain perceives may be the reason that people with schizophrenia aren’t fooled by some visual illusions, according to a new study published in March in NeuroImage.
In the ‘hollow-mask illusion’, a well known test of visual ability, a mask of a human face rotates slowly around a vertical axis. When the mask has turned 180 degrees — and the inside of the mask is what’s visible — most people still see it as normal. It’s as if their brain refuses to see the face as hollow, presumably because that’s an extremely improbable sight in the real world.
In contrast, several studies have found that people with schizophrenia easily distinguish between normal and inverted photos of a face – something that has baffled scientists until now.
In the new study, the researchers found that confronted with an inverted face, the brains of healthy people, but not of those with schizophrenia, show more activity in the fronto-parietal network. This brain region is involved in ‘high-level’ thinking processes, such as perceiving a combination of lines and shadings as a human face.
Increased activity in the region suggests that when a healthy brain receives unusual visual information from the eyes — the curved lines of an inverted nose, say — high-level regions such as the fronto-parietal network send out commands to low-level regions, such as the primary visual cortex, to ignore the strange sight, and still perceive what it sees as a nose.
In those with schizophrenia, those high- and low-level regions may not be properly connected, the researchers suggest. The study is small, and tested just 13 people with the disorder, but it’s still an intriguing look at the mysterious split.
It’s Monday: your eyes deserve a break. Plus, I’m still unpacking boxes, meeting story deadlines, and have no time to seriously blog. So check out the two new pavilions planned for Chicago’s Millennium Park (one of my favorite Midwestern spots), designed by Zaha Hadid and Ben van Berke. The structures will be up June 19!
(Hat tip: Fast Company)
Is autism more common in children of some ethnicities than in others?
Last fall, I wrote about a mysterious cluster of autism among Somali children in Minnesota. At the time, the Minneapolis school system reported that although Somalis make up just 6 percent of the city’s public school population, they comprise 17 percent of the special education students labeled ‘autistic’.
Public health clusters are usually suspect, but in a report released last week, the Minnesota Health Department and the Centers for Disease Control and Prevention confirmed that, among 3- and 4-year-old children, those of Somali origin are two to seven times more likely to be placed in preschool programs for autism. The report also found other ethnic trends in these classes: just two Asians and one Native American between 2005 and 2007.
The report is unusual, sure, but it is hardly solid evidence. For one thing, the autism diagnoses weren’t standardized: some of the children received their diagnosis from school evaluators, others from medical doctors.
Second, there are any number of social factors that could explain the numbers. For instance, Asian and Native American children with autism may be more likely to go to private schools instead of public ones. Because some Somali parents have been outspoken about the disorder’s prevalence in their community, school evaluators may also be more likely to give a Somali child a diagnosis of autism.
The report made no attempt to explain why autism numbers may be higher in Somali communities. Some scientists claim that the disorder may result from a deficiency of Vitamin D, but this, too, is far from proven.
What would convince me are comprehensive surveys of autism prevalence in ethnic communities across the world — something that, so far at least, is sorely lacking.
Do most cases of autism result from extremely rare and spontaneous genetic mutations or from more common variations? That question brought about a spirited debate Wednesday at the SFARI annual meeting.
Most researchers estimate that rare variants account for about 15 percent of autism cases. But geneticist David Ledbetter bet $1 for every person in the room yesterday that that number will turn out to be at least 50 percent.
On first glance, it seems as if Ledbetter might be right.
Autism researchers have in the past two years uncovered several rare, spontaneous duplications and deletions, collectively dubbed copy number variations, in the chromosomal regions 16p, 15q13, 1q21 and others.
But so far at least, they have only found a few common variants — defined as mutations that crop up in five percent or more of the general population — that are disproportionately common in people with autism. For example, Pat Levitt found that common variations in two genes of the MET pathway nearly double the risk for autism.
Levitt, Aravinda Chakravarti, and others argued that Ledbetter is probably wrong. They said basic statistics can explain why common variants are harder to find: because common variants are, by definition, relatively commonplace, you would need large numbers of people to find differences in the variations’ prevalence between people with autism and healthy controls.
What’s more, they noted, even though rare variations associated with autism have cropped up with some regularity, many of them are located in regions of the genome that don’t have any known functional significance. And the variations don’t have predictable effects, either: two siblings may carry the same rare variation, for example, but only one is diagnosed with autism. “Basically,” Levitt told me during a coffee break, “genetics is complicated.”
