Crucial role of zebrafish prox1 in hypothalamic catecholaminergic neurons development

Background: Prox1, the vertebrate homolog of prospero in Drosophila melanogaster, is a divergent homeogene that regulates cell proliferation, fate determination and differentiation during vertebrate embryonic development. Results: Here we report that, in zebrafish, prox1 is widely expressed in several districts of the Central Nervous System (CNS). Specifically, we evidenced prox1 expression in a group of neurons, already positive for otp1, located in the hypothalamus at the level of the posterior tuberculum (PT). Prox1 knock-down determines the severe loss of hypothalamic catecholaminergic (CA) neurons, identified by tyrosine hydroxylase (TH) expression, and the synergistic prox1/otp1 overexpression induces the appearance of hypothalamic supernumerary TH-positive neurons and ectopic TH-positive cells on the yolk epitelium. Conclusion: Our findings indicate that prox1 activity is crucial for the proper development of the otp1-positive hypothalamic neuronal precursors to their terminal CA phenotype.