Abstract
The objective of this study was to evaluate the effect of Akirin2 on slow myosin heavy chain (slow MyHC, MyHC I) gene expression and its molecular mechanisms. In this study, we showed that the protein expression of Akirin2 in pig slow oxidative Psoas major muscle is higher than that in fast glycolytic tibialis anterior muscle, suggesting that Akirin2 may play a role in myofiber typing. Knockdown of Akirin2 decreased the MyHC I expression and the calcineurin (CaN) activity, and also decreased the expressions of NFATc1 and MCIP1.4. Conversely, overexpression of Akirin2 got the opposite results. Furthermore, inhibition of CaN or knockdown of NFATc1 attenuated Akirin2 overexpression-induced upregulation of MyHC I. Together, these results demonstrate that Akirin2 promotes MyHC I expression via CaN/NFATc1 signaling pathway in porcine skeletal muscle satellite cells.
Highlights
Skeletal muscle is a heterogeneous tissue composed of a large variety of fiber types classified according to their myosin heavy chain (MyHC) isoforms
Western blot analysis with an antiAkirin2 antibody prepared in our lab showed that Akirin2 protein level in the pig slow oxidative Psoas major muscle (PM) was about six-fold higher than that in the fast glycolytic tibialis anterior muscle (TA) (Figure 1), suggesting that Akirin2 may play a role in muscle fiber typing
Western blot analysis showed that knockdown of Akirin2 by siRNA significantly repressed the protein expressions of Akirin2 (Figure 2A) and MyHC I (Figure 2C)
Summary
Skeletal muscle is a heterogeneous tissue composed of a large variety of fiber types classified according to their myosin heavy chain (MyHC) isoforms. Type I fiber, known as slow oxidative muscle fiber, is believed to be positively associated with meat quality [1, 2]. The intramuscular fat (IMF) content (marbling) is associated with a higher content of oxidative fibers in skeletal muscle [3]. The role of Akirin in skeletal muscle is far less understood. Akirin has been reported to be located within genomic region of a quantitative trait locus for marbling, and has been shown to be differentially expressed in musculus longissimus muscle of low-marbled and high-marbled steer groups [8]. A number of studies showed that Akirin is associated with marbling based on single nucleotide polymorphisms analysis and may be considered as a positional functional candidate for the gene responsible for marbling [9,10,11,12]
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