The study of evolution is an evidence-based science. This means that scientists are always looking for the evidence, and mechanisms, by which evolutionary change occurs. Recently, a group of researchers at the University of Ediburgh discovered a gene that is found only in humans, and not any of our closest primates. This gene is called miR-941, and it appears that it plays an important role in how the human brain functions.
What is interesting about mIR-941 is that it is not a modified version of an existing gene. The “repurposing” of genes, and the formation of gene families (groups of genes with similar functions – such as the globin genes) is common in life. But miR-941 appears to have been formed out of “junk” DNA – regions of the genome that historically have not been known to have much of a function. In recent years that perception has been changing as new methods of analyzing our genomes are being developed.
miR-941 is not a conventional gene. Normally, at least in many intro biology courses, genes produce proteins or RNA molecules that are involved in the gene expression pathways (such as tRNA and rRNA). miR-941 is different, it produces a small RNA strand called a micro-RNA. Micro-RNAs have a lot of interest right now, since they are believed to function extensively in the regulation of gene expression. Thus the excitement around miR-941. A new regulatory mechanism means that you can potentially introduce new functionality – and this appears to be what miR-941 does.
So where is miR-941 active in the brain? It appears that it is active in two areas – the prefrontal cortex and the cerebellum.
The prefrontal cortex and cerebellum are processing areas of the brain. It is here that our reasoning, critical thinking, language and many of our personality traits are established.
This genetic change occurred sometime between 1 and 6 million years ago, after our split from the other Interestingly, this same time frame was an important one in the development of the human brain. If you take a look at the human evolution timeline, you will notice that this coincides with some significant changes in the human brain.
During this time not only was the human brain getting larger, but the processing areas were becoming more sophisticated. Whether miR-941 played a major role in that process has yet to be determined, but the findings provides excellent material for discussions on the changes that occurred between apes and humans, and the overall process of how evolutionary change occurs.
1. Research Article: Hai Yang Hu, Liu He, Kseniya Fominykh, Zheng Yan, Song Guo, Xiaoyu Zhang, Martin S. Taylor, Lin Tang, Jie Li, Jianmei Liu, Wen Wang, Haijing Yu, Philipp Khaitovich.Evolution of the human-specific microRNA miR-941.Nature Communications, 2012; 3: 1145 DOI:10.1038/ncomms2146
2. ScienceDaily article: University of Edinburgh (2012, November 14). New brain gene gives us edge over apes, study suggests. ScienceDaily. Retrieved November 24, 2012, from http://www.sciencedaily.com/releases/2012/11/121114113458.htm
3. Arizona State’s Institute of Human Origins
4. Bits of Mystery DNA, Far From ‘Junk,’ Play Crucial Role; Gina Kolata; NY Times Sept 12, 2012