Post-natal nutritional management alters transcription regulator gene networks in Longissimus muscle of Angus x Simmental offspring

Abstract Text: The aim of this study was to evaluate potential carryover effects of the maternal diet during late gestation and also effects of weaning age on the transcription regulator (TR) gene networks in Longissimus muscle. Angus x Simmental beef cows blocked by breed were utilized in a 2 x 2 factorial design. Three months prior to the projected parturition date, cows were assigned to treatments (low or medium plane of nutrition). Low plane of nutrition was achieved by grazing endophyte-infected tall fescue/red clover pastures with no supplement, while medium plane of nutrition was achieved by grazing endophyte-infected tall fescue/red clover pastures supplemented with 2.3 kg of dried distiller’s grains with solubles and soyhulls. Steer calves were randomly assigned to early- or normal-weaning groups (n=20). At 80 days of age, early-wean offspring were weaned and received a high-energy finishing diet. At 186 days of age, normal-wean offspring were weaned and joined early-wean steers at the feedlot where they received the same diet. Steers were group-fed and intake recorded using the GrowSafe system. Longissimus muscle (LM) biopsies were harvested at 81, 187 and 354 days of age. A 45,220 bovine microarray (Agilent) was used for transcript profiling (n=5 steers/group). Differentially-expressed TR, ligand-dependent nuclear receptors, and their networks with differentially-expressed genes (DEG) were mined using Ingenuity Pathways Analysis (FDR<0.05 and P<0.05). The statistical model included treatment, maternal diet, time and its interactions, as fixed effects, and steer as random effect. Among the 8,400 DEG (P < 0.05) affected by the overall effect of time IPA analysis revealed 625 TR and ligand-dependent nuclear receptors (NR). TP53 was the TR with the highest network of target genes. Considering only the DEG due to treatment (P<0.05), among 856 DEG the IPA analysis revealed that 78 were classified as TR and NR. TP53 was also the TR with the highest network of target genes. In the separate analysis of genes affected by time and treatment (P<0.05) TP53, MYC, HTT and ERS1 were the TR with highest networks of DEG in both analyses. Results suggest that different plane of nutrition during the last 90 d prior to calving did not markedly affect the expression of transcription regulators or ligand-dependent nuclear receptors in the offspring’s skeletal muscle transcriptome. However, post-natal nutritional management seems to affect TR and NR by activating their expression at growthing stage (i.e. 81 to 187 days) especially when early-weaned.

Keywords: gene networks, nutrigenomics, bioinformatics