Histone H3.3 maintains genome integrity during mammalian development

Lethality and fertility phenotypes of H3.3 gene knockout mutants. (A) The number of embryos/pups of specific genotypes observed at different stages from H3f3a^−/+; H3f3b^−/+ mouse intercrosses. Numbers in parenthesis are expected numbers at the Mendelian ratio. The red background indicates that the observed numbers were significantly lower than expected. All of the A^nullB^het pups died after birth. Significant differences from the expected numbers are indicated by (*) P < 0.05 and (**) P < 0.01 in χ² test. (B) Double-knockout embryos (H3f3a^−/−; H3f3b^−/−) and their littermate control (H3f3a^−/+; H3f3b^−/+) at different stages. E8.5 embryos were hybridized with Brachyury probe, showing expression at the tail (arrow) and notochord (arrowhead) in the control and presumably the primitive streak in the double-knockout mutant (arrow). (C) Box plot of body weight distribution of E18.5 C-sectioned embryos. Raw values were first normalized to the average weight in the litter. Significant difference from wild type (WT) is indicated. (***) P < 0.001 in ANOVA test. (D) Survival of C-sectioned E18.5 embryos. Shown are total numbers of observed embryos (blue bars) and those that did not survive after C-section (red bars) in each genotype group. (E) Hematoxylin and eosin (H&E) sections of testes from 6- to 8-mo-old adult males of the indicated genotypes.