Born too soon pg. 6
Muglia’s team also is pursuing GWAS studies. But he’s most excited about his team’s analysis of rapidly evolving genes. These are the genes that differ most between humans and chimps – our closest living relatives – and other animal species. And these are the genes that might have changed, Muglia proposes, to move birth timing earlier to accommodate our large heads.
The relative immaturity of a human baby at birth also appears to support an evolutionary push to earlier birth times. A newborn chimp has normally developed vision (can fix on an object and follow it), good motor coordination and nearly erupted teeth. Human infants can’t “fix and follow,” have very little motor control and won’t have a first tooth for about six months. Cross-species comparisons of measured traits like gestational duration and body size (“allometric scaling”) predict that human gestation should last 11 to 12 months (rather than the usual 9 months), again supporting evolutionary pressure for early birth.
In collaboration with Justin Fay, Ph.D., a comparative genomic biologist and assistant professor of Genetics at Washington University, Muglia and additional colleagues at Vanderbilt and Washington University have used computational methods to compare the human genome to the chimp, rhesus, cow, dog, rat and mouse genomes. With this approach, they have identified about 200 genes that specifically changed in humans.
The investigators have now examined these rapidly evolving genes for a role in preterm birth, and they have identified “some very interesting prospects that look like they’re associated with preterm birth,” Muglia says. They are working to validate these findings in other larger populations.
“What we’re hoping is that genetic variants we detect – in this relatively non-biased way – will give us insight into biomarkers for preterm birth and improve our ability to predict who is at increased risk and should be followed more closely.”
The genes might suggest ways to intervene – such as a nutritional supplement analogous to folic acid for the prevention of neural tube defects, he adds.
Muglia is keeping mum about exactly which genes are looking interesting. He estimates that within a year or two, his team will know if the prospects hold up.
But for now, it’s too early to say.
See related story on the "placental clock."
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