248 DIESTRUS TRANSCRIPTOME DYNAMICS OF BOVINE ENDOMETRIUM IN RELATION TO PREGNANCY SUCCESS AFTER EMBRYO TRANSFER

Abstract

This experiment aimed to investigate the diestrus transcriptome dynamics of endometrium that resulted in calf delivery or no pregnancy after embryo transfer. Endometrium biopsies were collected from Simmental cyclic heifers at Days 7 and 14 of estrus cycle. On the next cycle, in vivo-produced Day 7 blastocysts were transferred to all animals at Day 7 of estrous cycle. Following pregnancy diagnosis, the endometrial biopsies collected at Day 7 and 14 were categorized based on the pregnancy success. Those endometrial biopsies collected from heifers that subsequently delivered a calf were assigned to the calf-delivery group, and those collected from heifers that did not conceive were assigned to the no-pregnancy group. The endometrial temporal transcriptome profile was compared between Days 7 and 14 in both heifer groups. Total RNA was isolated from each sample in triplicate. Two rounds of RNA amplification were performed using MEGAscript^® T7 Kit (Ambion, Inc., Austin, TX, USA) and GeneChip^® IVT Labeling Kit (Affymetrix, Inc., Santa Clara, CA, USA), respectively. Following fragmentation, biotin-labeled cRNA samples were hybridized to Affymetrix bovine gene chip array. The microarray data normalization and background correction were performed using GCRMA, and the differentially expressed genes (DEG) (fold change >2,P < 0.05, FDR < 0.3) were identified using LIMMA written on R package integrated with Bioconductor. The result showed that in the calf-delivery group, there were 1867 DEG, among which 1015 and 852 were up- and down-regulated, respectively, in Day 7 compared with Day 14 of the estrous cycle. Some of those genes are believed to be involved in reproductive system development and function (F3, PTGER2, PTGER4, MFGE8, PTGS2, and TDGF1), embryonic development (ALDH1A1,ALDH1A3, FGF2, TGFBR2, PDGFB, and TGFBR2), and nervous system development and function (CYP3A4, CYP3A4, HSD17B4, FOXA2, MET, TDGF, WNT11). The bioinformatic analysis using KEGG revealed that those DEG were classified into several pathways including the MAPK signaling pathway. On the other hand, in the no-pregnancy group, 254 genes were found to be differentially expressed, of which 160 and 94 were up- and down-regulated, respectively, in Day 7 compared with Day 14 of the estrous cycle. Some of these genes were found to be involved in signal transducer activity (AXIN2, AGTR1, MAPK10, NTRK2, TLR2, DMBT1, IL1RN, CDK5, CHRNE), transferase activity (DGKI, TXNDC6, RPS6KA5, RIOK3, MYLK, CDK5, MET, NTRK2), receptor activity (MET,AGTR1, NTRK2, TLR2, DMBT1, CHRNE), regulation of transcription (FOS, ELF1, BHLHB2,ATF3, HOXA11), signal transduction (TLR2, AGTR1, FCNB, DGK, NOTCH2, ADAM9, PLEK), and transcription regulator activity (BHLHB2, FOS, ELF1,ATF3, HOXA11). Those DEG were found to be involved in different pathways including the focal adhesion pathway. In conclusion, the result of the current study revealed a remarkable transcriptome dynamics between Days 7 and 14 of the estrous cycle in cows resulted in calf delivery compared with those that did not support pregnancy.