ABSTRACT
The external granule layer (EGL) is a transient proliferative layer that gives rise to cerebellar granule neurons and drives the foliation of amniote cerebella. The formation of and differentiation from the EGL is incompletely understood, though BMP signalling has been implicated. Here, we characterise active BMP signalling during cerebellar development in chick and human and show that while in chick BMP signalling correlates with EGL formation, humans maintain BMP signalling throughout the EGL after the onset of foliation. Using in ovo electroporation in chick, we show that BMP signalling is necessary for EGL formation, but not for granule neuron fate. Our data are also consistent with a second role for BMP signalling in driving differentiation of granule progenitors in the EGL. These results elucidate two key, temporally distinct roles for BMP signalling in organising first the assembly of the EGL and then the tempo of granule neuron production within it.
Competing Interest Statement
The authors have declared no competing interest.
