Effects of the Expressions and Variants of the CAST Gene on the Fatty Acid Composition of the Longissimus Thoracis Muscle of Grazing Sonid Sheep

SIMPLE SUMMARY: This study aimed to evaluate the relationship between the expression levels of the CAST gene and the fatty acid (FA) composition in the longissimus thoracis (LL) muscle and to identify novel variants of CAST and perform association analysis with the FA composition in grazing Sonid sheep. The correlation results showed that high expression levels of CAST are correlated with better FA compositions and classes in LL. Four c.646G>C (G216R), c.1210C>T (R404C), c.1437G>A (479T), and c.2097C>T (699G) mutations were identified in the CAST gene of Sonid sheep. The association studies showed that c.1210C>T is associated with C14:0, C18:0, C18:1n9c, C18:3n3, n3, C12:0, n6, and n6/n3; c.646G>C and c.1437G>A in linkage disequilibrium-Mongolia (r(2) = 0.964) were associated with C14:0, C18:0, SFA, C18:1n9c, n3, C10:0, C18:1n9t, and n6/n3; and c.2097C>T was associated with C18:3n3, n3, C10:0, and n6/n3 in the LL of Sonid sheep. Thus, the correlation results and associated mutations were expected to be genetic selection markers for the FA composition and meat quality of Sonid sheep muscle and provide new insight into sheep meat quality traits influenced by the ovine CAST gene. ABSTRACT: Fatty acid (FA) composition has an important impact on the nutrition and flavor of meat, and on consumer health, and is receiving more attention in the sheep industry. This study aimed to evaluate the relationship between the expression levels of the CAST gene and the FA composition in the longissimus thoracis (LL) muscle, to identify novel variants of CAST, and to perform association analysis with the FA composition in grazing Sonid lambs. The correlation results showed that high expression levels of CAST are correlated with better FA compositions and classes in LL. For association studies, the results showed that c.1210C>T and c.1437G>A in LD-M, and c.2097C>T mutations are associated with some compositions and classes of FA in the LL of grazing Sonid sheep. Two missense c.646G>C (G216R) and c.1210C>T (R404C) mutations were predicted to influence the Calpain_inhib domains of CAST. Thus, the correlation results and associated mutations are expected to be genetic selection markers for the FA composition and meat quality of grazing Sonid lamb muscle and provide new insights into sheep meat quality traits influenced by the ovine CAST gene.