Times of neuron origin and neurogenetic gradients in mice Purkinje cells and deep cerebellar nuclei neurons during the development of the cerebellum. A review

This current review is focused on the generation and settled patterns of mouse Purkinje cells (PCs) and deep cerebellar nuclei (DCN) neurons. By mean of progressively delayed comprehensive labeling procedure, I will show, with the technique of [3H] thymidine autoradiography, the quantitative determination of PCs and DCN neurons production along the mediolateral and rostrocaudal axes of the cerebellum. The procedure consists of injecting groups of pregnant mice, on specific embryonic (E) days, with two doses of [3H] thymidine in an overlapping series with 24 h delays between groups (E11–12, E12–13, E13–14, E14–15). The analysis of the autoradiograms revealed that PCs and DCN neurons are sequentially generated following precise neurogenetic timetables. PCs are born somewhat later than the DCN neurons. Both macroneurons are produced following two gradients. The first of these is mediolateral and the second is rostrocaudal. On the other hand, it will be also shown that PCs and DCN neurons were settled in the cerebellum following accurate neurogenetic gradients. These data have suggested that the chronological sequence of neuron production is a key factor in facilitating, in the adulthood, the cytoarchitecture of the cerebellum, and the establishment of patterns of orderly connections between PCs and DCN neurons.