Divergence and rewiring of regulatory networks for neural development between human and other species.

Neural and brain development in human and other mammalian species are largely similar, but distinct features exist at the levels of macrostructure and underlying genetic control. Comparative studies of epigenetic regulation and transcription factor (TF) binding in humans, chimpanzees, rodents, and other species have found large differences in gene regulatory networks. A recent analysis of the cistromes of REST/NRSF, a critical transcriptional regulator for the nervous system, demonstrated that REST binding to syntenic genomic regions (i.e., conserved binding) represents only a small percentage of the total binding events in human and mouse embryonic stem cells. While conserved binding is significantly associated with functional features (e.g., co-factor recruitment) and enriched at genes important for neural development and function, >3000 genes, including many related to brain and neural functions, either contain extra REST-bound sites (e.g., NRXN1) or are targeted by REST only (e.g. PSEN2) in humans. Surprisingly, several genes known to have critical roles in learning and memory, or brain disorders (e.g., APP and HTT) exhibit characteristics of human specific REST regulation. These findings indicate that more systematic studies are needed to better understand the divergent wiring of regulatory networks in humans, mice, and other mammals and their functional implications.