?-syntrophin modulates myogenin expression in differentiating myoblasts.

ABSTRACT:

Background

?-Syntrophin is a scaffolding protein linking signaling proteins to the sarcolemmal dystrophin complex in mature muscle. However, ?-syntrophin is also expressed in differentiating myoblasts during the early stages of muscle differentiation. In this study, we examined the relationship between the expression of ?-syntrophin and myogenin, a key muscle regulatory factor.

Methods and findings

The absence of ?-syntrophin leads to reduced and delayed myogenin expression. This conclusion is based on experiments using muscle cells isolated from ?-syntrophin null mice, muscle regeneration studies in ?-syntrophin null mice, experiments in Sol8 cells (a cell line that expresses only low levels of ?-syntrophin) and siRNA studies in differentiating C2 cells. In primary cultured myocytes isolated from ?-syntrophin null mice, the level of myogenin was less than 50% that from wild type myocytes (p<0.005) 40 h after differentiation induction. In regenerating muscle, the expression of myogenin in the ?-syntrophin null muscle was reduced to approximately 25% that of wild type muscle (p<0.005). Conversely, myogenin expression is enhanced in primary cultures of myoblasts isolated from a transgenic mouse over-expressing ?-syntrophin and in Sol8 cells transfected with a vector to over-express ?-syntrophin. Moreover, we find that myogenin mRNA is reduced in the absence of ?-syntrophin and increased by ?-syntrophin over-expression. Immunofluorescence microscopy shows that ?-syntrophin is localized to the nuclei of differentiating myoblasts. Finally, immunoprecipitation experiments demonstrate that ?-syntrophin associates with Mixed-Lineage Leukemia 5, a regulator of myogenin expression.

Conclusions

We conclude that ?-syntrophin plays an important role in regulating myogenesis by modulating myogenin expression.

SUBMITTER: Kim MJ 

PROVIDER: S-EPMC3003685 | biostudies-literature | 2010 Dec

REPOSITORIES: biostudies-literature