Suf is not essential for meiosis, but mitosis.
(A) Steps of meiotic maturation. Zebrafish oocytes are arrested in prophase I (PI) of the first meiotic cell cycle indicated by the huge germinal vesicle (red). Maturation initiates with germinal vesicle breakdown (GVBD) and the first meiosis leads to the formation of a polar body (red circle). The egg arrests again in metaphase of the second meiotic cell cycle (MII), ready to be fertilized. (B) Stage III oocytes treated with carrier (EtOH) or maturation-inducing hormone (DHP). The germinal vesicle is highlighted with Phalloidin (green) showing no difference between wt and mutant. Scale bar: 100 μm. (C) Living stage III oocytes from wt and suf/spastizin mothers treated with carrier or DHP. The chromatin is highlighted by a Histon2A-GFP transgene (green) showing that GVBD occurs at the same time in mutant oocytes as in wt, whereas the cytoplasm stays opaque in suf/spastizin oocytes. Scale bar: 100 μm (D) suf/spastizin oocytes form a polar body. In vitro matured oocytes from wt and mutants stained with DAPI (blue) to highlight the nuclei and f-actin (green) to mark the polar body. Scale bar: 25 μm. (E) suf/spastizin oocytes arrest in metaphase II. Confocal images of β-tubulin (green) highlight the spindle in wt and mutant oocytes, which is located in the lower left corner, whereas the polar body is in the upper right corner. Scale bar: 25 μm. (F) Suf/Spastizin is required for cytokinesis. Embryos at 32-cell stage from heterozygous wt (top panel) or homozygous (bottom panel) suf/spastizin mothers with labeled nuclei (DAPI; blue) and plasma membranes (Phalloidin; green). In contrast to wt, few eggs from mutant mothers initiate cell division after fertilization, but then show cells with multiple nuclei (arrowhead).