The Loom : And the award for the fastest-evolving piece of human DNA goes to...Elsewhere I read this gene is most active in humans from 7-19 weeks of gestation. How long before we tweak it in chimps? Just a bit ...
... The scientists found 49 candidate segments. These segments have evolved a lot in our lineage. The most drastically altered of all is a segment the scientists dubbed HAR1 (for human accelerated region). It is 118 base pairs long. Chimpanzees and chickens, separated by over 300 million years, carry versions of HAR1 that are identical except for two base pairs. In humans, on the other hand, 18 base pairs have changed since we split from chimps.
What's HAR1 for? This is the sort of question that seems like it should be easy to answer unless you're the scientist doing the answering. The scientists found that human cells make RNA molecules out of the HAR1 segment. Specifically, they found that brain cells do. Specifically, brain cells in the cortex, the hippocampus, and certain other regions. We do love our brains, and so it is reasonable to consider that HAR1 took on some new role in the brains of human ancestors. The sequence of HAR1 suggests that an RNA molecule produced from it would be stable enough to carry out some important job, such as regulating the activity of protein-coding genes. HAR1 probably plays several roles. It is not just active in the adult brain, but in development-guiding cells in the fetus.
In a commentary that also appears in Nature, two Oxford scientists point out that HAR1 is also active in the ovary and testis of adult humans. And it is true that genes associated with sex are fast-evolving. So they don't want to rule out the possibility that selection has acted on HAR1 in connection with reproduction, rather than with thought. It's a fair point, but I was struck by the fact that the expression of HAR1 is far smaller in the sex cells than in the brain.
Still, it's a strange point that may be worth raising at your next party: we have genes that are only active in our brains and sex cells.
It would be interesting to study the effect of ultrasound on the operation of RNA that doesn't code for proteins.
Maybe this is a source of autism? As a minor malfunction in the gene arranges things a little differently.
Post a Comment