218 A blood transcriptomic signature predicts the expression of energy-regulatory genes altered in the skeletal muscle of 3-month-old dairy heifers conceived by in vitro fertilization
M. Rabaglino A , A. Crowe A B , S. Moore B , S. Butler B and P. Lonergan AA
B
The global growth in the transfer of in vitro-produced (IVP) bovine embryos has resulted in the birth of millions of healthy calves. This technology involves developing the embryo in an artificial environment until transfer, potentially resulting in epigenomic modifications of the embryo genome, and impacting the transcriptome. These alterations might be compensated during gestation, so the calf is born phenotypically normal. A recent study demonstrated that dairy cows conceived by IVF have a greater incidence of ovarian cysts, however, which could be associated with de-regulation of energy metabolism (Lafontaine et al. 2023 Theriogenology 198, 282–291). Furthermore, 3-month-old male dairy calves derived from an IVP or an in vivo embryo exhibited divergence in hepatic and muscular energy regulation (Rabaglino et al. 2022 Biol. Reprod. 107, 1113–1124), but the molecular changes in these organs in females are unknown. The objectives were to identify differences in the muscular transcriptome between dairy heifers conceived by IVF or AI and to use the blood transcriptome as a tool to predict the muscular expression of specific genes. Whole blood samples and biopsies of the semitendinosus muscle were collected from 3-month-old heifers derived from either the transfer of frozen IVP embryos or AI (n = 4 per group) and submitted for RNAseq. Weight at birth and at ~4 months did not differ among the heifers. Raw RNAseq data were aligned to the ARS-UCD1.3 genome, and the processed data were analysed using R software. Compared with the AI heifers, the muscle of IVP heifers had 1980 up-regulated genes (false discovery rate (FDR) < 0.05) strongly associated with oxidative phosphorylation (OXPHOS; FDR = 3.6 × 10−21) and skeletal muscle development (FDR = 3.6 × 10−14), and 1819 down-regulated genes enriched for autophagy (FDR = 4.1 × 10−10) and histone modification (FDR = 7.0 × 10−05). For the blood transcriptome, co-expressed genes were identified with the WGCNA method and correlated with the average expression (in counts per million) of the 40 genes involved in OXPHOS in muscle. Of the 462 co-expressed genes with positive correlation, 19 were enriched for OXPHOS in blood, with 9 in common for both organs. These 9 genes were used to build an XGBoost regression model, trained and validated with the expressions in muscle and blood, respectively. Expression of the 9 genes in blood successfully predicted their expression in muscle with low error (RMSE = 0.07, R2 = 0.93). In conclusion, these results support the notion that the IVP process might impair the expression of energy-regulatory genes, affecting metabolically demanding organs, such as muscle, after the animal is born. The blood transcriptome profile can be harnessed to predict the expression of these genes in muscle (or potentially other organs such as the ovaries) during early postnatal life and estimate heifer predisposition to develop metabolic diseases during her productive life.
Supported by a H2020-MSCA-Individual Fellowship to MR (101021311) and the Irish Department of Agriculture, Food and the Marine to SB and PL (2021R665).
