Neurogenic role of prox1 in the CNS and lateral line development

In teleost, the lateral line is a sensory organ composed of neuromasts containing hair cells, expressing athl, and surrounded by supporting cells, expressing notch3. notch3 signalling seems to limit the number of cells that are allowed to adopt the hair cell fate while failure of notch3 signal generates an overproduction of athl expressing hair cells in the middle of the neuromast. In this report we analyze the role of prox1 in zebrafish (z-prox1) on neural and proneural genes in the neuromasts of the posterior lateral line. We have examinated the z-prox1 interaction with ath1 and notch3 in the lateral line system of zebrafish by both z-prox1 morpholino-mediated inactivation and z-prox1 mRNA overexpression. This gene is expressed in the migrating primordium, and its inactivation results in a reduced number of neuromasts at 48 hpf but does not affect the primordium migration. In particular, lack of prox1 inhibits the differentiation of ath1 expressing hair cells, while enhances the number of the supporting cells, expressing notch3. Injection of prox1 synthetic mRNA generates the opposite phenotype: the number of the pre-determined ath1 expressing hair cells is increased, while notch3 expression in the supporting cells is reduced. Moreover prox1 could have a role in timing regulation of the neuromasts development because morphant embryos rigenerate neuromasts after 48 hpf.