AUTHOR=Ji Kaixi , Jiao Dan , Yang Guo , Degen Abraham Allan , Zhou Jianwei , Liu Hu , Wang Wenqiang , Cong Haitao 

TITLE=Transcriptome analysis revealed potential genes involved in thermogenesis in muscle tissue in cold-exposed lambs

JOURNAL=Frontiers in Genetics

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2022.1017458

DOI=10.3389/fgene.2022.1017458

ISSN=1664-8021

ABSTRACT=<p>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 <italic>longissimus dorsi</italic> 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, <italic>PCK1</italic> (<italic>phosphoenolpyruvate carboxykinase1</italic>) increased glyceroneogenesis in cold-exposed Altay lambs, and <italic>APOC3</italic> (<italic>apolipoprotein C3</italic>), <italic>LPL</italic> (<italic>lipoprotein lipase</italic>), and <italic>FABP4</italic> (<italic>fatty acid binding protein 4, adipocyte</italic>) were involved in the intake and transport of free fatty acids. In Hu sheep, cAMP biosynthesis from ATP hydrolysis was regulated by <italic>ADCY10</italic> (<italic>adenylate cyclase</italic>) and <italic>ADORA2a</italic> (<italic>adenosine A2a receptor</italic>). Skeletal muscle contraction was regulated by <italic>MYL2</italic> (<italic>myosin light chain 2</italic>). 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.</p>