NEURODEVELOPMENT

Was Voldemort losing Robo signaling?

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Science  20 Jul 2018:
Vol. 361, Issue 6399, pp. 241-242
DOI: 10.1126/science.361.6399.241-b

Primates have larger and more complex brains than those of reptiles. The cortices of reptile and bird brains are formed through direct neurogenesis, as radial glia divide to generate neurons. In primates, on the other hand, an amplification step is thrown in with the intermediate progenitors that results in more neurons. Cárdenas et al. look at the patterns and regulators of neurogenesis in snake, chicken, mouse, and human brain organoids. Experimental manipulations that directed more signaling from Roundabout (Robo) transmembrane receptors and less from the Notch ligand Dll1 caused human brain organoids to lose indirect neurogenesis, whereas less Robo and more Dll1 caused snake embryos to gain indirect neurogenesis. Thus, shifts in Robo and Dll expression during evolution may have tilted the balance of direct and indirect neurogenesis. The indirect neurogenesis characteristic of primate brain development may be a slower way to build a brain, but the resulting brain has a lot more neurons than a snake's does.

Cell 10.1016/j.cell.2018.06.007 (2018).

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