Characterization of transcriptomic and proteomic changes in bovine myocytes subject to temporal heat stress

This study elucidated the degree of molecular response to heat stress (HS) in bovine myocytes by measuring changes in the transcriptome and proteome. Bovine satellite cells (BSCs) were extracted from holstein bull calves (n = 3, BW: 77.10 ± 2.02 kg). Following myogenic differentiation, myocytes were exposed to one of three treatment groups for 3 h: 38 °C (control; CON; n = 3), 39.5 °C (moderate heat stress; MHS; n = 3), and 41 °C (extreme heat stress; EHS; n = 3). RNA and protein were extracted for transcriptomic and proteomic sequencing analyses, respectively. Differentially expressed genes (DEGs) for the contrasts MHS vs. CON and EHS vs. CON were selected using an FDR adjusted significance threshold of P < 0.05, regardless of Log₂ fold change, with differentially abundant proteins (DAPs) selected at an FDR adjusted significance threshold of P < 0.05 and absolute fold change ± 1.2. DEGs were then subjected to gene set enrichment analysis. A total of 888 DEGs were detected for MHS and 2590 for EHS, with 590 DEGs shared between MHS and EHS. EHS resulted in elevated expression of multiple heat shock protein (HSP) isoforms especially those related to HSP70, in addition to increased expression of FOXO6 and PPARGC1A. Alteration of key anabolic pathways associated with protein synthesis, modulation of myogenic regulatory factors, and the large number of DEGs detected in HS-myocytes demonstrates the speculation of phenotypic alterations to myotube size and protein synthesis.