Maternal factor PABPN1L is essential for maternal mRNA degradation during maternal-to-zygotic transition

Infertility affects 10% - 15% of families worldwide. However, the pathogenesis of female infertility caused by abnormal early embryonic development is not clear. We constructed a mouse model (Pabpn1l -/-) simulating the splicing abnormality of human PABPN1L and found that the female was sterile and the male was fertile. The Pabpn1l -/- oocytes can be produced, ovulated and fertilized normally, but cannot develop beyond the 2-cell stage. Using RNA-Seq, we found a large-scale upregulation of RNA in Pabpn1l -/- MII oocytes. Of the 2401 transcripts upregulated in Pabpn1l-/- MII oocytes, 1523 transcripts (63.4%) were also upregulated in Btg4 -/- MII oocytes, while only 53 transcripts (2.2%) were upregulated in Ythdf2 -/- MII oocytes. We documented that transcripts in zygotes derived from Pabpn1l -/- oocytes have a longer poly(A) tail than the control group, a phenomenon similar to that in Btg4-/- mice. Surprisingly, the poly(A) tail of these mRNAs was significantly shorter in the Pabpn1l -/- MII oocytes than in the Pabpn1l +/+. These results suggest that PABPN1L is involved in BTG4-mediated maternal mRNA degradation, and may antagonize poly(A) tail shortening in oocytes independently of its involvement in maternal mRNA degradation. Thus, PABPN1L variants could be a genetic marker of female infertility.