Study On The RNA Poly(A) Tail Variation Of Pig Oocyte Maturation And Early Embryonic Development

In eukaryotes,the poly(A)tail of messenger RNA(m RNA)is a highly important posttranscriptional modification.The poly(A)tail is one of the key factors which regulate the nuclear export,stability and translation of m RNAs.Recent studies have shown that the length of poly(A)tail is very important for the regulation of m RNAs.Moreover,non-A modifications(such as guanosylation and uridylation)are discovered at the 3’ end of the poly(A)tails,which can regulate the stability of m RNAs.The poly(A)tail profile refers to the length and the nucleotide composition of RNA poly(A)tails.The process of oocyte maturation and early embryonic development refers to the process from germinal vesicle(GV)to germinal vesicle breakdown(GVBD),The first meiosis(Meiosis I,MI),the second meiosis(Meiosis II,MII),and then through fertilization to zygote and all the way to the blastocyst.The most important event of the process is oocyte-to-embryo transition(OET)and poly(A)tail length and non-A residues are vital for OET in mice and humans,yet remain unexplored in other commonly used mammalian animal models,such as rat and pig.In addition,the degree of conservation in maternal m RNA poly(A)tail dynamics during OET across different mammal species is unknown.The similarity of pigs to humans in anatomical size and structure,physiology,immunology,and genome enhances their potential as models for humans.In recent years,pigs have become popular in human xenotransplantation.Oocyte maturation and early embryonic development are the basis of reproductive biology and developmental biology,so studying the dynamics of poly(A)tails during pig OET will contribute to reveal the species-specific developmental mechanism of pigs.Which has great guiding significance for pig-based disease model construction and regenerative medicine fields such as xenogeneic organ reconstruction.In this study,we use poly(A)inclusive RNA isoform sequencing(PAIso-seq)to obtained a complete profile for the first time of poly(A)tail dynamics during OET in pigs and rats.Across bioinformatics analysis,we revealed the dynamics of poly(A)tail during pigs and rats OET.The results are as follows:(1)we found that a fall-rise trend in poly(A)tail length of maternal m RNA distribution during pigs OET.Specifically,the average length gradually decreases during oocyte maturation,and then gradually increases after fertilization.Which suggests that maternal m RNA deadenylation during oocyte maturation and re-polyadenylation after fertilization.(2)We discovery a rise-fall trend in the ratio of poly(A)tails with non-A residues of maternal m RNA during pigs OET unlike poly(A)tail length,specifically the average content gradually increases during the oocyte maturation,and the average content gradually decreases after fertilization.(3)Compared the content of non-A residues in poly(A)tails of maternal m RNA and ZGA m RNA,the results showed that higher abundance of non-A residues in poly(A)tails of maternal m RNA than in zygotic genome activation(ZGA)m RNA.Which indicates that the non-A residues in the poly(A)tail play a key role in the metabolism of maternal m RNA.(4)The content of U residues is higher than that of C and G residues in non-A residues,and maternal m RNA with U residues degrades faster than those without U residues at the stage when ZGA takes place,indicating that poly(A)tails with U residues promotes rapid degradation of the maternal m RNA.(5)The maternal m RNA deadenylation is abnormal in parthenogenetic embryos in both mouse and rat,indicating that in the absence of male participation,maternal m RNA deadenylation is impaired,revealing an unreported defect in parthenogenetic embryos.(6)ZGA inhibition leads to blocked maternal m RNA deadenylation in mice and humans,indicating that ZGA products play a role in accelerating the degradation of maternal m RNA.In summary,we described the conserved dynamics of poly(A)tails length and non-A residues content during pigs and rats OET,revealing the post-transcriptional regulatory mechanism of highly evolutionarily conserved maternal m RNAs.These findings provide new insights for the further study of the molecular mechanism of porcine oocyte maturation and early embryonic development,and is contributed to promote the development of pig-based medical model construction and regenerative medicine fields such as organ reconstruction.