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XB-ART-49343
Development 2014 Jul 01;14114:2791-5. doi: 10.1242/dev.101758.
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Transit amplification in the amniote cerebellum evolved via a heterochronic shift in NeuroD1 expression.

Butts T , Hanzel M , Wingate RJ .


Abstract
The cerebellum has evolved elaborate foliation in the amniote lineage as a consequence of extensive Atoh1-mediated transit amplification in an external germinal layer (EGL) comprising granule cell precursors. To explore the evolutionary origin of this layer, we have examined the molecular geography of cerebellar development throughout the life cycle of Xenopus laevis. At metamorphic stages Xenopus displays a superficial granule cell layer that is not proliferative and expresses both Atoh1 and NeuroD1, a marker of postmitotic cerebellar granule cells. Premature misexpression of NeuroD1 in chick partially recapitulates the amphibian condition by suppressing transit amplification. However, unlike in the amphibian, granule cells fail to enter the EGL. Furthermore, misexpression of NeuroD1 once the EGL is established both triggers radial migration and downregulates Atoh1. These results show that the evolution of transit amplification in the EGL required adaptation of NeuroD1, both in the timing of its expression and in its regulatory function, with respect to Atoh1.

PubMed ID: 25005474
Article link: Development
Grant support: [+]

Species referenced: Xenopus laevis
Genes referenced: atoh1 barhl1 calb1 lhx9 neurod1 npat pcna shh zic1


Article Images: [+] show captions