Danio rerio Raw sequence reads

In most vertebrates, including zebrafish, the hypothalamicserotonergic cerebrospinal fluid-contacting (CSF-c) cells constitutea prominent population. In contrast to the hindbrain serotonergicneurons, little is known about the development and function of thesecells. Here, we identify fibroblast growth factor (Fgf )3 as the main Fgfligand controlling the ontogeny of serotonergic CSF-c cells. We showthat fgf3 positively regulates the number of serotonergic CSF-c cells,as well as a subset of dopaminergic and neuroendocrine cells in theposterior hypothalamus via control of proliferation and cell survival.Further, expression of the ETS-domain transcription factor etv5b isdownregulated after fgf3 impairment. Previous findings identifiedetv5b as critical for the proliferation of serotonergic progenitors in thehypothalamus, and therefore we now suggest that Fgf3 acts via etv5bduring early development to ultimately control the number of matureserotonergic CSF-c cells. Moreover, our analysis of the developinghypothalamic transcriptome shows that the expression of fgf3 isupregulated upon fgf3 loss-of-function, suggesting activation of a self-compensatory mechanism. Together, these results highlight Fgf3 in anovel context as part of a signalling pathway of critical importance forhypothalamic development.