Neurogenetic cascade in the embryonic thalamus of zebrafish. Highly proliferating neural epithelial Type A cells are marked by Notch, SoxB1 and Her/Hes expression. After downregulation of SoxB1/Her/Hes, thalamic progenitors become proneural Type B cells. Type C cells are immature, post-mitotic neurons, which express transcription factors, such as lhx2b and lhx9. Mature, post-mitotic Type B neurons can be identified by, for example, neurotransmitter-specific factors.