Knockout of Rlim Results in a Sex Ratio Shift toward Males but Superovulation Cannot Compensate for the Reduced Litter Size

SIMPLE SUMMARY: Maternal Rlim is required for imprinted X-chromosome inactivation (XCI), which is essential for normal development of female mouse embryos. In this study, we used a novel approach to inactivate the maternal Rlim allele in female embryos, resulting in a male sex-ratio shift in the offspring. However, the reduced litter size caused by the loss of female embryos could not be compensated for by superovulation in the mother mice. The present study develops a new approach to select offspring sex according to the difference in Rlim function between male and female mouse embryos. This gender control approach may help to improve the productivity in livestock and prevent the sex-associated hereditary diseases in humans. ABSTRACT: Technologies that can preselect offspring gender hold great promise for improving farm animal productivity and preventing human sex-related hereditary diseases. The maternal Rlim allele is required for imprinted X-chromosome inactivation, which is essential for the normal development of female mouse embryos. In this study, we inactivated the maternal Rlim allele in embryos by crossing a male transgenic mouse line carrying an X-linked CMV-Cre transgene with a female line carrying a loxP-flanked Rlim gene. Knockout of the maternal Rlim gene in embryos resulted in a male-biased sex ratio skew in the offspring. However, it also reduced litter size, and this effect was not compensated for by superovulation in the mother mice. In addition, we showed that siRNA-mediated knockdown of Rlim in mouse embryos leads to the birth of male-only progenies. This study provides a new promising method for male-biased sex selection, which may help to improve the productivity in livestock and prevent sex-associated hereditary diseases in humans.