Breast cancer 1 (BRCA1)-deficient embryos develop normally but are more susceptible to ethanol-initiated DNA damage and embryopathies

• Heterozygous (+/−) brca1 conditional knockout (cKO) embryos develop normally.
• +/− brca1 cKO embryos have 28% less BRCA1 protein than wild-type (WT) littermates.
• Ethanol-exposed BRCA1-deficient mice have more oxidatively damaged DNA than WTs.
• Ethanol-exposed BRCA1 cKO embryos exhibit more embryopathies than WT littermates.
• BRCA1 protects the embryo from ethanol-enhanced oxidative stress—a novel role.

The breast cancer 1 (brca1) gene is associated with breast and ovarian cancers, and heterozygous (+/−) brca1 knockout progeny develop normally, suggesting a negligible developmental impact. However, our results show BRCA1 plays a broader biological role in protecting the embryo from oxidative stress. Sox2-promoted Cre-expressing hemizygous males were mated with floxed brca1 females, and gestational day 8 +/− brca1 conditional knockout embryos with a 28% reduction in protein expression were exposed in culture to the reactive oxygen species (ROS)-initiating drug ethanol (EtOH). Untreated +/− brca1-deficient embryos developed normally, but when exposed to EtOH exhibited increased levels of oxidatively damaged DNA, measured as 8-oxo-2'-deoxyguanosine, γH2AX, which is a marker of DNA double strand breaks that can result from 8-oxo-2'-deoxyguanosine, formation, and embryopathies at EtOH concentrations that did not affect their brca1-normal littermates. These results reveal that even modest BRCA1 deficiencies render the embryo more susceptible to drug-enhanced ROS formation, and corroborate a role for DNA oxidation in the mechanism of EtOH teratogenesis.

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