Ectopic clusters contain mature granule cells, but not other types of cerebellar neurons. (a,b) Immunofluoresence of the mature granule cell-specific marker GABARa6, with βgal and DAPI as counterstains. βgal positive ectopias contain large numbers of differentiated granule cells. (c–h) Immunofluorescence for the PC marker Calbindin (c,d) and the general interneuron markers Parvalbumin (e,f) and GAD67 (g,h), with βgal and DAPI as counterstains. Neuronal ectopias do not co-label with any of these three markers and therefore do not contain PCs, stellate, or basket cells that normally occupy the ML. Interestingly, Purkinje cell dendrites appear to avoid invading the clusters. Scale bar, 50 μm for all.