Universidad de Buenos Aires, Facultad de Ciencias Veterinarias, Cátedra de Genética, Chorroarín 280 (1427), Buenos Aires, Argentina.
Universidad Nacional de Mar del Plata, Facultad de Ciencias Agrarias, Unidad Integrada Balcarce, Departamento de Producción Animal, CC276 (CP7620) Balcarce, Argentina.
Meat Sci. 2021 Jan;171:108267. doi: 10.1016/j.meatsci.2020.108267. Epub 2020 Jul 28.
This study aimed to evaluate the expression of calpastatin (CAST) isoforms and their potential associations with fiber type composition (%RA), calpastatin activity (CA) and myofibril fragmentation index (MFI) in three muscles with known differences in tenderness (infraspinatus, triceps brachii and semitendinosus) of Angus steers. Expression of total CAST (CAST-T) and CAST isoforms I, II, III (2-3) and III (2-4) (including or not exon 3) was evaluated by qRT-PCR. CAST expression and CA were significantly higher and MFI was lower in semitendinosus, the muscle with the highest %RA of IIX fibers. Differential expression of isoforms defined the variability in CAST-T among muscles. Semitendinosus had a higher expression of isoforms II and III (2-3), but lower expression of III (2-4) compared to the other two muscles. Relative expression of isoforms II and III that were defined by promoter preference linked to alternative splicing, seem to be the main factors explaining differences in CAST expression and ultimately in MFI among muscles.
本研究旨在评估三种不同嫩度（冈下肌、肱三头肌和半腱肌）牛的钙蛋白酶抑制蛋白（CAST）同工型的表达及其与纤维类型组成（%RA）、CAST 活性（CA）和肌原纤维碎片化指数（MFI）的潜在关联。通过 qRT-PCR 评估总 CAST（CAST-T）和 CAST 同工型 I、II、III（2-3）和 III（2-4）（包括或不包括外显子 3）的表达。CAST 表达和 CA 在半腱肌中显著较高，而 MFI 则较低，半腱肌的 IIX 纤维比例最高。同工型的差异表达定义了 CAST-T 在肌肉间的变异性。与选择性剪接相关的启动子偏好定义的同工型 II 和 III 的相对表达似乎是解释 CAST 表达和最终肌肉间 MFI 差异的主要因素。
