All mammals have a significantly expanded cerebral cortex compared with other vertebrates, but there is significant variation in both neocortical size and folding across mammals. The mouse has a small, smooth (lissencephalic) cortex, making it a poor model to understand development of the large and highly folded (gyrencephalic) human brain. A prominent feature of the human neocortex is the abundance of basal radial glial cells (bRGCs) – a self-renewing neurogenic progenitor population present in the subventricular zone (SVZ). bRGCs have been identified in the mouse SVZ but these are rare and show a molecular signature distinct from that of human bRGCs. Wieland Huttner, Takashi Namba and colleagues now identify a medial region of the mouse neocortex where bRGCs are much more common and more similar to their human counterparts. The authors show that these cells express Hopx (a key marker of human bRGCs) and that this homeodomain-only protein is both necessary and sufficient to define high bRGC numbers. These results tie several observations together: the idea that bRGC abundance may be linked to the degree of gyrencephaly, the proposal that the mouse may have evolved from a gyrencephalic ancestor, and the suggestion that the medial region is evolutionarily older than the lateral neocortex. They further suggest that the medial neocortex of the mouse may serve as a better model for human cortical development than the more frequently studied lateral neocortex.
Hopx – a key player for basal radial glial cell abundance?
Hopx – a key player for basal radial glial cell abundance?. Development 15 October 2018; 145 (20): e2003. doi:
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