[Wieland Huttner, a Max Planck Institute neurobiologist,] and his team set out to find genetic differences between Neanderthals and modern humans, especially in cells that give rise to neurons of the neocortex. This region behind the forehead is the largest and most recently evolved part of our brain, where major cognitive processes happen.
The team focused on TKTL1, a gene that in modern humans has a single amino acid change—from lysine to arginine—from the version in Neanderthals and other mammals. By analyzing previously published data, researchers found that TKTL1 was mainly expressed in progenitor cells called basal radial glia, which give rise to most of the cortical neurons during development.
When the researchers introduced the human version of the gene into ferrets, the animals produced more cortical neurons and had larger brain folds, the researchers report today in Science. “I was not expecting to see an increase in [folds],” says first author Anneline Pinson, a postdoc at Max Planck. “It makes sense because we have more neurons, but to look at it was quite striking and surprising.”
Finally, the team compared the effect of both versions of the gene in brain organoids made of human embryonic cells floating in petri dishes. The human version again led to more progenitor cells and eventually more neurons compared with the archaic gene. Although additional genes may be involved, the finding “makes the point that this one gene is an essential player,” in shaping our big brains, Huttner says.
You can read more of Huttner’s research here, in Science.