Fibroblast growth factor inhibits expression of neural markers in cultures of zebrafish early embryo cells.

Basic fibroblast growth factor (FGF) regulation of developmental markers in cell cultures derived from early zebrafish embryos was examined with the goal of in vitro culture of zebrafish embryonic stem cells and gaining an understanding of extracellular influences on early embryonic development. Markers were stem/primordial germ cell markers pou-2 and vas, neural markers zp-50, pax[zf-a], en-3, and wnt-1, and mesodermal markers gsc and myoD. Previously we had shown that FGF prevents the development of zebrafish pigment cells in vitro. In our culture system, FGF reduced expression of neural-specific markers, possibly implicating the FGF family in suppression of early neural cell development. Exposure to FGF for 24 hours at the time of seeding the cells was sufficient to suppress neural marker expression for a subsequent 4 days of culture, while absence of FGF for the first 24 hours of culture nullified the effect of FGF added subsequently. FGF predictably increased expression of gsc and myoD. Vas expression was unaffected, while pou-2 expression decreased with time in culture in the presence or absence of FGF. However, in situ hybridization identified a subpopulation of cells expressing pou-2, suggesting the possible continued existence of undifferentiated stem cells in the cultures.