Bigger Brains With Human DNA

The human version of a DNA sequence called HARE5 turns on a gene important for brain development (gene activity is stained blue), and causes a mouse embryo to grow a 12 percent larger brain by the end of pregnancy than an embryo injected with the chimpanzee version of HARE5. Credit: Silver lab, Duke University

Duke scientists showed that they could point out differences in genetic code between chimpanzees and humans which would lead to early brain development in mouse embryos. They found that humans have a difference in regulatory gene dubbed HARE5 that when introduced into mouse embryo would lead to a 12% larger brain than that of an embryo which was treated with the HARE5 sequence from a chimpanzee.

Initially, the group screened enhancers expressed primarily in the brain tissue and early development. This gave them 106 candidates, but only 6 of them were near genes thought to be involved with brain development so they chose these to work with. They were named 'human-accelerated regulatory enhancors,' HARE1 through HARE6. HARE5 then became the prime candidate for their work as its chormosomal location is near a gene called Frizzled 8, which is part of a well-known molecular pathway in the brain for development and disease. The human HARE5 and the chimpanzee HARE5 differed by 16 letters of genetic code. The human HARE5 injected mice had a 12% larger brain than the chimpanzee HARE5 injected mice and showed the neocortex, a region of brain involved with language and reasoning, to be affected.

I found this piece very interesting because it gives us a part of the genetic puzzle as to why and how we have bigger brains. Also, I did not know it was possible for such specific sequences of DNA to be both taken from and inserted into other species. Furthermore, these findings may help to our understanding of diseases like autism and Alzheimer's which is present in humans, but not chimpanzees.

Original Article: http://www.sciencedaily.com/releases/2015/02/150219133104.htm