Lin9 is required for mitosis and cell survival during early zebrafish development

LIN9 has been described as a regulator of G1/S and G2/M progression of the cell cycle in invertebrates and human cell lines. To elucidate the in vivo function of LIN9 during vertebrate development, we took advantage of the teleost zebrafish (Danio rerio). By means of antisense morpholinos we show here that Lin9-depleted embryonic cells accumulate in mitosis. Flow cytometry and confocal microscopy data demonstrate that the delay in mitotic progression is followed by apoptosis, which strongly manifests in the developing CNS. In accordance with these findings we identified a cohort of Lin9 regulated genes required for different mitotic processes, including mitotic entry, metaphase/anaphase transition and cytokinesis. Our data establish LIN9 as an essential regulator of mitosis in vertebrate development.