Colocalization of myostatin and decorin in bovine skeletal muscle

Abstract. The objectives of this study were to investigate the expression and localization of myostatin (MSTN) and decorin (DCN) in bovine skeletal muscle and to find associations with muscle fibre and adipocyte development. Samples of two muscles, known for differences in meat quality and fibre composition, namely longissimus muscle (LD) and semitendinosus muscle (ST), were obtained from 18 months old bulls of the F₂ generation of a Charolais×Holstein cross. Individual muscle sections were stained for determination of size and type of muscle fibres and immunohistochemical detection of the proteins. The mRNA abundance and protein expression of MSTN and DCN were quantified by real-time PCR and Western blot, respectively. As expected, the ST had more fast fibres, less fibres of the intermediate and the slow type, and less intramuscular fat than the LD. Despite these differences, the mRNA and protein abundance of MSTN was comparable in both muscles. The protein abundance of MSTN inhibitors, namely MSTN propeptide and DCN, was greater in LD, which may have affected the biological activity of mature MSTN. Myostatin propeptide was detected in all muscle fibres; however the mature MSTN was detected to a much lower extent and mainly in slow fibres. Furthermore, MSTN was localized in close proximity to DCN in intermyocellular space, suggesting possible interactions between both proteins and effects on muscle structure and meat quality. The role of MSTN and DCN as well as their interactions in the determination of muscle composition needs to be further elucidated.