Identification of circulating miRNA involved in meat yield of Korean cattle

Cattle plays an important role in providing essential nutrients through meat production. Thus, we focused on epigenetic factors associated with meat yield. To investigating circulating miRNAs that are involved with meat yield and connect biofluids and longissimus dorsi (LD) muscle in Korean cattle, we performed analyses of the carcass characteristics, miRNA array, qPCR, and bioinformatics. Carcass characteristics relative to the yield grade (YG) showed that the yield index and rib eye area were the highest, whereas the backfat thickness was the lowest for YG A (equal to high yield grade) cattle among the three YGs. miRNA array sorted the circulating miRNAs that connect biofluids and LD muscle. miRNA qPCR showed that miR-15a (r = 0.84), miR-26b (r = 0.91), and miR-29c (r = 0.92) had positive relationships with biofluids and LD muscle. In YG A cattle, miR-26b was considered to be a circulating miRNA connecting biofluids and LD muscle because the target genes of miR-26b was more involved with myogenesis. Then, miR-26b targeted genes, DIAPH3 and YOD1 were downregulated in YG A cattle. Our results suggest that miR-15a, miR-26b, and miR-29c are upregulated in biofluids and LD muscle whereas, downregulation of DIAPH3 and YOD1 in the LD muscle of finishing cattle steers. 29 or 30 month Korean cattle steers were classified by yield grade(YG) A, B, and C. miRNA expression patterns for exosome and LD muscle were compared among YGs.

牛通过肉类生产为人体提供必需营养素，发挥着至关重要的作用。因此，本研究聚焦于与肉用产量相关的表观遗传调控因子。为探究韩牛（Korean cattle）中与肉用产量相关、且可连接生物体液与背最长肌（longissimus dorsi, LD）的循环微小核糖核酸（microRNA, miRNA），本研究开展了胴体性状分析、miRNA芯片、qPCR以及生物信息学分析。相较于三种胴体产量等级（yield grade, YG），YG A（对应高产肉等级）韩牛的产量指数与眼肌面积均为最高，而背膘厚度最低。通过miRNA芯片筛选出了可连接生物体液与背最长肌的循环miRNA。qPCR结果显示，miR-15a（相关系数r=0.84）、miR-26b（r=0.91）与miR-29c（r=0.92）与生物体液及背最长肌均呈显著正相关。在YG A级韩牛中，miR-26b被认为是连接生物体液与背最长肌的循环miRNA，因其靶基因更多参与肌发生过程。此外，miR-26b的靶基因DIAPH3与YOD1在YG A级韩牛中呈下调表达。本研究结果表明，miR-15a、miR-26b与miR-29c在生物体液与背最长肌中均呈上调表达，而育肥阉牛背最长肌中的DIAPH3与YOD1则呈下调表达。本研究将29或30月龄的韩牛阉牛按胴体产量等级分为A、B、C三级，并比较了不同等级间外泌体与背最长肌的miRNA表达谱差异。