A novel population of Hopx-dependent human-like basal radial glial cells in the developing mouse neocortex

A specific subpopulation of neural progenitor cells, the basal radial glia cells (bRGCs) of the outer subventricular zone (OSVZ), are thought to have a key role in the evolutionary expansion of mammalian neocortex. In the developing lissencephalic mouse neocortex, bRGCs exist at low abundance and show significant molecular differences from bRGCs in developing gyrencephalic species. Here, we demonstrate that developing mouse medial neocortex, in contrast to the canonically studied lateral neocortex, exhibits an OSVZ and an abundance of bRGCs similar to that in developing gyrencephalic neocortex. Unlike bRGCs in developing mouse lateral neocortex, the bRGCs in medial neocortex exhibit human bRGC-like gene expression, including expression of Hopx, a human bRGC marker. Disruption of Hopx expression in mouse embryonic medial neocortex and forced Hopx expression in mouse embryonic lateral neocortex demonstrate that Hopx is required and sufficient, respectively, for a bRGC abundance as found in developing gyrencephalic neocortex. Taken together, our data identify a novel bRGC subpopulation in developing mouse medial neocortex that is highly related to bRGCs of developing gyrencephalic neocortex. Overall design: 221 single-cell transcriptomes from microdissected medial neocortex of E18.5 mouse embryos (two independent analyses using a pool of 8 neocortices each).

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Vaid S, Camp JG, Hersemann L, Eugster Oegema C, Heninger AK, Winkler S, Brandl H, Sarov M, Treutlein B, Huttner WB, Namba T