GSE158904
Prox1 inhibits axon outgrowth during central nervous system development
During central nervous system (CNS) development, proper and timely induction of axon elongation is critical for generating functional, mature neurons and neuronal networks. Despite the wealth of information on the action of extracellular cues, little is known about the intrinsic gene regulatory factors that control this developmental decision. Here we report the identification of Prox1, a homeobox transcription factor, as a key player in inhibiting axon elongation. Although Prox1 promotes acquisition of early neuronal identity and is expressed in nascent post-mitotic neurons, it is heavily down-regulated in the majority of terminally differentiated neurons, indicating a regulatory role in delaying axon outgrowth in newly formed neurons. Consistently, we show that Prox1 is sufficient to inhibit neurite extension in neuroblastoma cell lines. Furthermore, shRNA-mediated knock-down of Prox1 in Neuro2A cells induces the extension of neurites. More importantly, Prox1 overexpression suppresses axon elongation in primary neuronal cultures as well as in the developing mouse brain, while Prox1 knock-down promotes axon outgrowth. Mechanistically, RNA-Seq analysis reveals that Prox1 affects critical pathways for neuronal maturation and neurite extension. Interestingly, Prox1 strongly inhibits many components of Ca2+ signaling pathway, an important mediator of axon extension and neuronal maturation. In accordance, Prox1 represses Ca2+ entry upon KCl-mediated depolarization and reduce CREB phosphorylation. These observations suggest that Prox1 acts as a potent suppressor of axon elongation by inhibiting Ca2+ signaling pathway. This action may provide the appropriate time window for nascent neurons to find the correct position in the CNS prior to initiation of axon elongation. Overall design: 3'mRNA-Seq (Quant-seq) of Neuro2A Prox1 and GFP overexpressing cells (GFP-Tet-On and Prox1-Tet-On Neuro2A cells)