Human evolution; a gene for primate brains (Introduction)

by David Turell , Tuesday, December 11, 2018, 17:52 (2172 days ago) @ David Turell

Found in a new study. Our brains are different than other mammals:

https://www.sciencedaily.com/releases/2018/12/181206120047.htm

"University of Otago researchers have discovered information about a gene that sets primates -- great apes and humans -- apart from other mammals, through the study of a rare developmental brain disorder.

"Dr Adam O'Neill carried out the research as part of his PhD at the University of Otago, under the supervision of Professor Stephen Robertson, discovering that the PLEKHG6 gene has qualities that drives aspects of brain development differently in primates compared to other species.

"'Broadly speaking, this gene can be thought of as one of the genetic factors that make us human in a neurological sense,"...

***

"Their results showed that the particular genetic change that disabled a component of this gene (PLEKHG6) altered its ability to support the growth and proliferation of specialised stem cells in the developing brain. In addition, some of these cells also failed to migrate to their correct position in the growing "mini-brain" during the first few weeks of brain development.

"Professor Robertson says it has been known for a while that these stem cells behave differently between primates/humans and other animals, but understanding what genes regulate these differences has been a mystery.

"Adam's achievement has been to show that this particular component of the PLEKHG6 gene is one such regulator that humans have 'acquired' very recently in their evolution to make their brains 'exceptional'."

"Dr O'Neill says there are very few genetic elements that are primate specific in our genome, so this discovery adds to a very short list of genetic factors that, at least in one sense, make us human."

Comment: A lucky chance break? If that is the case all of the preparatory steps to reach the point where primates could appear are lucky contingencies. Doubtful.

The original paper summary:

The mammalian neocortex has undergone remarkable changes through evolution. A consequence of
such rapid evolutionary events could be a trade-off that has rendered the brain susceptible to certain neurodevelopmental and neuropsychiatric conditions. We analyzed the exomes of 65 patients with the structural brain malformation periventricular nodular heterotopia (PH). De novo coding variants were observed in excess in genes defining a transcriptomic signature of basal radial glia, a cell type linked to brain evolution. In addition, we located two variants in human isoforms of two genes that have no ortholog in mice. Modulating the levels of one of these isoforms for the gene PLEKHG6 demonstrated its role in regulating neuroprogenitor differentiation and neuronal migration via RhoA, with phenotypic recapitulation of PH in human cerebral organoids. This suggests that this PLEKHG6 isoform is an example of a primate-specific genomic element supporting brain development.

https://www.cell.com/cell-reports/pdf/S2211-1247(18)31775-3.pdf