Prox1 identifies proliferating neuroblasts and nascent neurons during neurogenesis in sympathetic ganglia

Abstract

Neurogenesis in embryonic sympathetic ganglia involves neuroblasts that resume proliferation following neuronal differentiation. As cell cycle exit is not associated with neuronal differentiation, the identity of proliferating neuroblasts is incompletely understood. Here, we use sympathetic ganglia of chick embryos to define the timing of neurogenesis and neuroblast identity focusing on the expression and function of the transcription factor Prox1. We show that a large fraction of neuroblasts has initially withdrawn from the cell cycle at embryonic day 3 (E3), which is reflected by a high proportion of p27(+)/Islet1(+) neuroblasts (63%) and low numbers of EdU(+)/Islet1(+) cells (12%). The proportion of proliferating Islet1(+) neuroblasts, identified by EdU pulse labeling and by the absence of the postmitotic marker p27 increases to reach maximal levels at E5, when virtually all neuroblasts are in the cell cycle (95%). Subsequently, the proportion of EdU-labeled and p27(-) neuroblasts is reduced to reach low levels at E11. Interestingly, the expression of the transcription factor Prox1 is restricted to the neuronal lineage, that is, Sox10(+)/Phox2b(+) neuron progenitors, proliferating p27(-)/Islet1(+) neuroblasts and nascent neurons but is rapidly lost in postmitotic neurons. In vitro and in vivo knockdown and overexpression experiments demonstrate effects of Prox1 in the support of neuroblast proliferation and survival. Taken together, these results define the neurogenesis period in the chick paravertebral sympathetic ganglia including an initial cell cycle withdrawal and identify Prox1 as a marker and regulator of proliferating sympathetic neuroblasts.

CellTag Indexing: genetic barcode-based sample multiplexing for single-cell genomics

“…S5D). For example, Reln and Prox1 are known for their roles in neuronal migration 46,47 and neurogenesis 48,49 ; we, therefore, speculate that they may mark a peripheral neuronal cell type in cluster 11.…”

Sympathetic tales: subdivisons of the autonomic nervous system and the impact of developmental studies

“…This marks a difference to parasympathetic neurogenesis as observed in ciliary ganglia [ 136 ]. A detailed kinetic analysis of cell division and differentiation in postganglionic sympathetic neurons of mice and chick has been obtained by the comparison of incorporation of two labeled nucleotides, BrdU and EdU, into the newly synthesized DNA [ 137 , 138 ]. The studies show a temporary deceleration or complete interruption of cell cycling only to resume proliferation after differentiation to the noradrenergic phenotype.…”

The transcription factor prospero homeobox protein 1 is a direct target of SoxC proteins during developmental vertebrate neurogenesis

“…Recent studies have shown that the same cells also express Prox1 and may also require it for neuroblast proliferation and survival (Holzmann et al . ). It will be interesting to analyze the functional relationship between SoxC proteins and Prox1 in these cells and compare it to CNS neurons.…”