Female-biased embryonic death from inflammation induced by genomic instability.

Adrian J Mcnairn,John C Schimenti,Chen-Hua Chuang,Marsha D Wallace,Jordana C Bloom

doi:10.1038/s41586-019-0936-6

Abstract

Genomic instability (GIN) can trigger cellular responses including checkpoint activation, senescence, and inflammation 1,2. Though extensively studied in cell culture and cancer paradigms, little is known about the impact of GIN during embryonic development, a period of rapid cellular proliferation. We report that GIN-causing mutations in the MCM2–7 DNA replicative helicase 3,4 render female mouse embryos to be dramatically more susceptible than males to embryonic lethality. This bias was not attributable to X-inactivation defects, differential replication licensing, or X vs Y chromosome size, but rather “maleness,” since XX embryos could be rescued by transgene-mediated sex reversal or testosterone (T) administration. The ability of exogenous or endogenous T to protect embryos was related to its anti-inflammatory properties 5. The NSAID ibuprofen rescued female embryos containing mutations not only in MCM genes but also Fancm, which like MCM mutants have elevated GIN (micronuclei) from compromised replication fork repair 6. Additionally, deficiency for the anti-inflammatory IL10 receptor was synthetically lethal with the Mcm4Chaos3 helicase mutant. Our experiments indicate that DNA replication-associated DNA damage during development induces inflammation that is preferentially lethal to female embryos, whereas male embryos are protected by high levels of intrinsic T.

Highlights

Our experiments indicate that DNA replication-associated DNA damage during development induces inflammation that is preferentially lethal to female embryos, whereas male embryos are protected by high levels of intrinsic T
Upon closer examination of those and additional breeding data, we noticed that females of the MCMdepleted, semi-lethal genotypes Mcm4C3/Gt, Mcm4C3/C3 Mcm2Gt/+, Mcm4C3/C3 Mcm6Gt/+, and Mcm4C3/C3 Mcm7Gt/+ (Gt = gene trap allele) were drastically under-represented compared to males of the same mutant genotype (Fig. 1a; Tables S1, S2, S3, S4)
Administration of ibuprofen to pregnant females completely abolished sex bias of Mcm4C3/C3 Mcm2Gt/+ offspring (Fig. 2a, Extended Data Table 1a) without affecting embryonic or placental MCM levels (Extended Data Fig. 2b, c). While these data indicate that Genomic instability (GIN)-driven inflammation underlies preferential female embryonic lethality, we considered the possibility that unrelated alterations in gene expression by ibuprofen and the androgen receptor 22,23 were responsible

Summary

Introduction

This dramatically rescued viability of Mcm4C3/Gt and Mcm4C3/C3 Mcm6Gt/+ female embryos preferentially, increasing female viability from 0% to 27% in the former, and from 3% to 42% in the latter (Fig. 1a, Tables S1,S2). We injected pregnant females daily with T beginning at E7.5, and found that the viability of XX Mcm4C3/C3 Mcm2Gt/+ E19.5 fetuses increased dramatically from 22% to 54% (Fig. 2a; Table S7). We observed no increase of Mcm mRNA or chromatin-bound MCMs in T-treated MEFs (Fig. 2b, c), and no sex-specific differences in MCM2 or MCM4 protein levels in E13.5 fetuses or placentae of various genotypes (Extended Data Fig. 2).

Results

Conclusion