Maternal and zygotic activin signaling promotes adequate pattern and differentiation of mesoderm through regulation of pluripotency genes during zebrafish development

To investigate the role of maternal Activin-like factors in the preservation of stemness and mesendoderm induction, their effects were promoted and inhibited using synthetic human Activin A or SB-505124 treatments, respectively, before the maternal to zygotic transition (MZT). To study the role of zygotic Activin-like factors, SB-505124 treatment was also used after the MZT. Promoting the signaling intensity of maternal Activin-like factors led to premature differentiation, loss of stemness, and no mesendoderm malformation, while its alleviation delayed the differentiation and caused various malformations. Inhibition of the zygotic Activin-like factors was associated with suppressing the ndr1, ndr2, oct4 (pou5f3), mycb and notail transcription as well as differentiation retardation at the oblong stage, and a broad spectrum of anomalies in a dose-dependent manner. Together, promoting the signal intensity of maternal Activin-like factors drove development along with mesendodermal differentiation, while suppression of the maternal or zygotic ones maintained the pluripotent state and delayed differentiation.