Scientists found that a piece of human DNA greatly enlarges the brain of laboratory mice when inserted during their embryonic period. The researchers hope that the discovery would shed a new light on what exactly makes us different from other species on a biological level.
The piece of genetic code, dubbed HARE5, is a piece of human DNA that controls the genes around it. Evolutionary scientists are over trilled with the new finding since they hope that they will be able to better understand how the human brain evolved to such a size over the past millions of years.
“[The DNA] could easily be a huge component in how the human brain expanded. It opens up a whole world of possibilities about brain evolution,”
said Mary Ann Raghanti, an biological anthropologist not involved with the study.
Past studies had also mapped the human genome to find the pieces of genetic code responsible for our varied diet, brain size and the skeletal adaptation to bipedalism. However, the recent research is one of the few to actually test a piece of DNA in laboratory conditions and prove its purpose.
“You could imagine [their roles], but they were just sort of ‘just so’ stories,”
stated Greg Wray, co-author of the experiment and an evolutionary scientist at the Duke University in Durham, North Carolina.
Mr. Wray and Lomax Boyd, a graduate student of Durham University, focused mostly on studying pieces of our genetic code that are called enhancers. They assessed about 100 of them and tested a half dozen, including HARE5.
During their study, scientists inserted the genetic enhancers into embryonic mice to see whether they triggered some particular genes. For the HARE5, the most active enhancer in the cortex area of the brain, researchers used two sets – one set taken from human brain cells and other from monkey brain cells.
They then tested both sets on embryonic mice. Wherever the enhancer turned a gene on, the developing mouse embryos turned blue, scientists reported. The team learned that the brain of developing embryos turned blue sooner and at a broader expanse whenever a human genetic enhancer was used.
The authors of the study found that the HARE5 genetic enhancer triggers a gene dubbed Frizzled 8, which is located in a major molecular pathway responsible for brain development. The team also found that human gene enhancers caused the future nerve cells to divide at a faster pace providing the cortex with an additional influx of cells.
As a result, mouse embryos enhanced with human HARE5 had 12 percent larger brains than the mice carrying the chimp enhancer. As a follow up, researchers will test to see if mice with bigger brains were any smarter than their normal counterparts.
The latest findings were published online February 19 in the journal Current Biology.
Image Source: Science Daily