Oocyte vitrification disrupts zygotic genome activation in embryos by impairing maternal spliceosome translation and Crxos splicing.

Abstract

Oocyte vitrification is indispensable in assisted reproduction, yet its link to compromised embryonic development remains mechanistically unresolved. Here, this study demonstrate through integrated transcriptome and translatome analysis that vitrification disrupts maternal mRNA translation-sparing global transcriptional output-in mouse oocytes. This translational perturbation prominently suppresses genes encoding spliceosome components, including Phf5a, leading to persistent and widespread alternative splicing defects in subsequent 2-cell embryos. Importantly, aberrant splicing specifically depletes the functional full-length transcript of the essential zygotic genome activation (ZGA) regulator Crxos (Egam1) while elevating a truncated, non-functional variant (Egam1ΔEXON3). Functional analyses confirm that loss of Crxos in 2‑cell embryos not only compromises developmental progression but also reduces global transcriptional activity, likely via impaired RNA Pol II recruitment and elongation at ZGA genes. Together, this work delineates a linear pathological cascade triggered by oocyte vitrification, comprising maternal translational suppression, spliceosome impairment, Crxos aberrant splicing, impaired ZGA, and developmental compromise, thereby offering a mechanistic basis for refining cryopreservation protocols in reproductive medicine.