Table1_Transcriptome analysis revealed potential genes involved in thermogenesis in muscle tissue in cold-exposed lambs.DOCX

Cold tolerance is an important trait for sheep raised at high altitudes. Muscle tissue, comprising 30–40% of the total body mass, produces heat during cold exposure. However, little is known about the genetic mechanisms of this tissue and its role in thermogenesis in lambs. We examined genes in skeletal muscle tissue in a cold-adapted sheep breed, Altay, and a cold-intolerant sheep breed, Hu, when exposed to low air temperature. Three ewe-lambs of each breed were maintained at −5°C and three ewe-lambs of each breed were maintained at 20°C. After cold exposure for 25 days, the longissimus dorsi of each lamb was collected, and transcriptome profiles were sequenced and analyzed. The results of RNA-seq showed that the average reads among the four groups were 11.0 Gbase. The genome mapping rate averaged 88.1% and the gene mapping rate averaged 82.5%. The analysis of differentially expressed genes (DEGs) indicated that the peroxisome proliferator-activated receptors (PPAR), cAMP, and calcium signaling pathways and muscle contraction in muscle tissue were linked to thermogenesis in cold-exposed lambs. Furthermore, PCK1 (phosphoenolpyruvate carboxykinase1) increased glyceroneogenesis in cold-exposed Altay lambs, and APOC3 (apolipoprotein C3), LPL (lipoprotein lipase), and FABP4 (fatty acid binding protein 4, adipocyte) were involved in the intake and transport of free fatty acids. In Hu sheep, cAMP biosynthesis from ATP hydrolysis was regulated by ADCY10 (adenylate cyclase) and ADORA2a (adenosine A2a receptor). Skeletal muscle contraction was regulated by MYL2 (myosin light chain 2). In conclusion, cold exposure altered the expression level of genes involved in heat production in muscle tissue. Some potential mechanisms were revealed, including calcium ion transport in the calcium signaling pathway, fatty acid metabolism in the PPAR signaling pathway, and cAMP biosynthesis in the cAMP signaling pathway. This study implied that skeletal muscle plays an important role in thermoregulation in lambs.

高海拔养殖绵羊的耐寒性是一项重要性状。肌肉组织约占机体总质量的30%~40%，在寒冷暴露时可产生热量。然而，目前对于绵羊肌肉组织的遗传调控机制，及其在羔羊产热过程中的作用仍知之甚少。本研究以耐寒品种阿勒泰羊（Altay）与不耐寒品种湖羊（Hu）为研究对象，探究其在低温暴露下的骨骼肌组织基因表达情况。每个品种各3只母羔分别置于-5℃与20℃环境中饲养。冷暴露25天后，采集每只羔羊的背最长肌（longissimus dorsi）样本，对其转录组谱进行测序与分析。RNA测序结果显示，四组样本的平均测序产出达11.0 Gbase，基因组比对率平均为88.1%，基因比对率平均为82.5%。差异表达基因（differentially expressed genes, DEGs）分析结果显示，过氧化物酶体增殖物激活受体（peroxisome proliferator-activated receptors, PPAR）、环磷酸腺苷（cAMP）、钙信号通路以及肌肉收缩过程与寒冷暴露羔羊的产热过程密切相关。此外，在寒冷暴露的阿勒泰羊羔羊中，磷酸烯醇式丙酮酸羧激酶1（phosphoenolpyruvate carboxykinase1, PCK1）可增强甘油异生过程；载脂蛋白C3（apolipoprotein C3, APOC3）、脂蛋白脂酶（lipoprotein lipase, LPL）以及脂肪细胞型脂肪酸结合蛋白4（fatty acid binding protein 4, adipocyte, FABP4）则参与游离脂肪酸的摄取与转运过程。在湖羊中，腺苷酸环化酶10（adenylate cyclase, ADCY10）与腺苷A2a受体（adenosine A2a receptor, ADORA2a）可调控ATP水解生成cAMP的过程。骨骼肌收缩过程则由肌球蛋白轻链2（myosin light chain 2, MYL2）调控。综上，寒冷暴露可改变肌肉组织中产热相关基因的表达水平。本研究揭示了若干潜在调控机制，包括钙信号通路中的钙离子转运、PPAR信号通路中的脂肪酸代谢，以及cAMP信号通路中的cAMP生物合成。本研究表明，骨骼肌在羔羊的体温调节过程中发挥着重要作用。