Comparative Transcriptome Reveals A Preliminary Study Of Genes Influencing In Vitro Maturation Of Horse And Donkey Oocytes

Horses and donkeys are economically important domesticated animals,providing meat,milk,servitude and medicinal herbs for humans.Compared with dairy and beef cattle oocyte maturation and embryo in vitro production technology,the oocyte maturation efficiency of horses and donkeys is lower,and the efficiency of embryo development in vitro is lower,especially the molecular mechanism of oocyte maturation is less studied.This study aims to explore the molecular mechanism of in vitro maturation of donkey oocyte by comparing transcriptome technology,and screen the key genes that are conducive to improving the maturation efficiency of oocytes,so as to optimize the in vitro maturation system of donkey oocyte.The main findings obtained are as follows:1.Differential expression gene study of horse GV phase and MII stage oocyte: In this experiment,a total of 1563 COCs were collected from 229 horse ovaries,with an average of 6.86 COCs per ovary,in order to obtain the in vitro maturation rate of horse oocytes,we performed 5 replicates of COCs in vitro culture experiments.The test results showed that after in vitro maturation,the proportion of MII oocytes was 37.18 ± 2.03%.A total of 6402 genes and4021 lnc RNA transcripts were differentially expressed in GV and MII oocytes by Smart-seq2 for oocyte differential expression genes in equine foaming(GV)and in vitro mature mid-stage II(MII).Further analysis by GO and KEGG found that differentially expressed m RNAs and lnc RNAs may be involved in multiple biological and signaling pathways associated with oocyte meiosis,such as ATP production and energy metabolism,especially lipid metabolism.2.Study on differential expression genes of donkey GV phase and MII stage oocyte: In this experiment,a total of 1692 COCs were collected from 229 donkey ovaries,with an average of 7.33 COCs per ovary,and after in vitro maturation,MII oocytes were 27.08 ± 3.23%.Donkey GV phase and in vitro maturation MII phase oocytes were collected separately for transcriptome sequencing.The results showed that a total of 9073 differentially expressed genes(DEGs)were identified in this experiment,and further gene ontology(GO)and Kyoto Gene and Genome Encyclopedia(KEGG)analysis showed that these genes were related to meiotic cell cycle,mitochondrial activity and N-glycan biosynthesis,and may be key genes and regulatory mechanisms affecting the maturation of donkey oocytes.In addition,the LGALS3 gene was mined by comparing the difference genes before and after maturation of oocytes in vitro,which appeared to mediate the regulation of oocyte meiotic recovery and fertilization acquisition.The results of this experiment show that horse and donkey oocytes have a low maturity rate during in vitro culture.Transcriptome sequencing analysis showed that DEGs were involved in a variety of key biological processes and signaling pathways related to oocyte meiosis and fertilization ability,and genes such as LGALS3 may be key genes affecting oocyte maturation.This study helps to understand the regulatory mechanism of oocyte maturation,reveal the energy source of horse oocyte maturation,and further provide a theoretical basis for improving the efficiency of oocyte maturation.