Fertilization offsets the maternal age effect on mouse oocytes provided the oviduct is not itself aged

Fertilization in vitro largely offsets the maternal-age effect on mouse oocyte proteome propagation, with blastocyst protein synthesis higher and maternal protein retention lower than young.

• Why it matters: Advanced maternal age is linked to poorer implantation after in vivo conception, but it has been unclear whether deficits come from oocyte aging or from an aged fertilization environment.
• What they did: Aged and young mouse oocytes were fertilized in vitro using a shared young-donor sperm preparation, then assessed for blastocyst development and proteome changes via proteomics, stable-isotope labeling, and puromycin labeling.
• The result: Blastocysts from aged, fertilized oocytes synthesized more new protein and retained less maternal protein than young controls, while parthenogenesis showed neither effect, implying fertilization-dependent, labile proteomic changes when the maternal environment is not aged.

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