prox1 expression pattern and functional analysis in the CNS and lateral line of zebrafish embryo (Danio rerio)

Embryonic prox1 expression pattern and functional analyses in the CNS and lateral line of zebrafish (Danio rerio) Zebrafish prox1 is a divergent homeobox transcription factor whose homologues in Drosophila and mice regulate cell proliferation, fate determination and differentiation in Central Nervous System (CNS) and sensory organs. In an attempt to identify prox1 roles in zebrafish, we focused our attention on the CNS and the posterior lateral line (PLL), a fish sensorial system. By means of whole-mount in situ experiments, we evidenced prox1 expression in the posterior tuberculum (PT) a region of the basal diencephalon that houses a discrete population of nascent catecholaminergic (CA) neurons. Down-regulation of prox1 expression led to a marked decrease of the number of such CA neurons, and its over-expression resulted in PT supernumerary CA neurons. We also demonstrated that prox1 in the PT acts as a positive regulator of otp1 and finally, we searched for potential prox1 regulators affecting prox1 expression at the level of the PT. prox1 is also expressed in the migrating primordium of the PLL. Loss of function experiments showed that the gene is necessary for neuromast differentiation, while it plays little or no role in primordium migration and neuromast deposition. In order to understand prox1 role in PLL cell differentiation, we correlated the expression pattern of neurogenic ath1 and notch3 genes in wild type and prox1 knock-down embryos, concluding that prox1 could function as a mitotic suppressor in the proneural ath1 expressing cells, switching their fate from proliferative to differentiative.