Chromosomal missegregation and aberrant embryo development in repro57 female mice with Rnf212 homozygous mutation.

Repro57 mice, induced with N-ethyl-N-nitrosourea and harboring a mutation in the Rnf212 gene, exhibit infertility in both homozygous mutant males and females. Rnf212 plays a crucial role in recombination and crossover designation. In male repro57 homozygous mutants, spermatocytes often degenerate during late prophase, and mature spermatozoa are absent in the seminiferous epithelium, indicating arrested spermatogenesis as the cause of infertility. Despite reports of infertility in Rnf212-knockout female mice, the specific mechanisms underlying infertility in female repro57 homozygous mutants remain elusive. This study investigates the chromosomal and kinetochore patterns of mature oocytes and their developmental potential following in vitro fertilization in female repro57 homozygous mutant mice. While all wild-type oocytes progress to metaphase II and exhibit euploidy, all repro57 homozygous mutant mouse oocytes display aneuploidy. Additionally, kinetochore distances in repro57 homozygous mutant oocytes exceed those observed in wild-type counterparts. Although no significant differences are noted in fertilization and early embryo development rates between wild-type and repro57 homozygous mutant mice, embryos derived from repro57 homozygous mutants exhibit significantly lower morula and blastocyst rates, accompanied by frequent cytokinesis failure and vacuole formation. These findings suggest that the premature segregation of sister chromatids in repro57 homozygous mutant mice adversely impacts the later stages of embryo development.