ipo8 deficiency in zebrafish compromises maternal, but not paternal, fertility. (A) Representative wild type (left) and maternal zygotic ipo8 knockout (right) zebrafish embryo at 2.5 hpf. Embryos devoid of ipo8 show a less compact dome with loosened blastomeres, as indicated by the black arrows. Scale bar 250 µm. (B) At the 64-cell stage, prior the onset of zygotic transcription, endogenous ipo8 mRNA, revealed by whole-mount in situ hybridization, is contributed through maternal deposition in the egg and is absent in embryos derived from homozygous ipo8 knockout females. Scale bar 250 µm. (C) Endogenous ipo8 mRNA present in the 64-cell stage, measured by QPCR, originates from the maternal, but not paternal, contribution. (D) The size of clutches laid by wildtype, heterozygous or homozygous ipo8 knockout mothers is not statistically different. Paternal ipo8 genotype has no effect on egg clutch size. N > 6 for each cross. (E) Survival of embryos at 24 h post fertilization is solely dependent on maternal, but not paternal, presence of wild type ipo8. All error bars show 95% confidence interval. ∗∗P = <0.01, ∗∗∗P = <0.001; Mann–Whitney test.
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