Our experiments revealed expression of the BAT-gal reporter at the rhombic lip at E12.5 and early EGL at E14.5. The rhombic lip gives birth to projection neurons of the deep cerebellar nuclei from E10.5 to E12.5 followed by GPCs and unipolar brush cells from E12.5 onwards. Because unipolar brush cells migrate along a different path than the dorsal stream that forms the EGL, we conclude that the BAT-gal reporter expression observed at E12.5 and E14.5 is potentially limited to GPCs and late born DCN neurons. Consistent with this, a number of studies have identified expression of Wnt1 at the rhombic lip and at the isthmus and loss of Wnt1 leads to a severe developmental phenotype of the cerebellum, most likely due to a failure to maintain the isthmus. Due to the consistency between the known expression pattern of Wnt1, and its proven role as a key signalling molecule in this area, it is possible that Wnt1 activity is responsible for the active Wnt/b-catenin signalling at the embryonic isthmus and rhombic lip identified in our experiments. However, it remains to be established whether additional Wnt genes are expressed in this area. While active Wnt/b-catenin signalling was observed in the early migrating GPCs at E14.5, this was lost in the GPCs observed in the EGL VE-822 during later stages of development. By E18.5, BAT-gal expression within the EGL was minimal and from P1 onwards, it was undetectable. These data are consistent with a potential role for Wnt/b-catenin signalling during early specification of GPCs but not in their further migration or proliferation. This is consistent with the fact that proliferation of this cell population during late embryogenesis and early postnatal development is driven by Sonic hedgehog secreted by neighbouring Purkinje cells. Additionally, the absence of NeuN expression in any of the bgal+ cells observed from P5-P21 demonstrates that Wnt/b-catenin signalling is also not active in the migration of terminally differentiated GCs from the EGL to the IGL.. NeuN is abundantly expressed in most classes of neurons and has been identified in all stages of post-mitotic granule cell development. Bergmann glia are thought to follow a slightly different developmental path. Rather than arising during gliogenesis from WM progenitors like the rest of the astrocyte lineage, a population of early Bergmann glia arise from the ventricular zone and migrate in close proximity to – and remain developmentally intertwined with – Purkinje cells.