Transcription profiling by array of skeletal muscle from PGC-1 beta transgenic mice

Skeletal muscle must perform a wide range of kinds of work, and different fiber types have evolved to accommodate these different tasks. The attributes of fibers are determined in large part by the coordinated regulation of oxidative capacity, as reflected by mitochondrial content, and the specific makeup of myofibrillar proteins. Adult muscle fibers contain four myosin heavy chain isotypes: I, IIa, IIx and IIb. Type I and IIa fibers have slower twitches and are rich in mitochondria, while type IIb fibers are fast-twitch and predominantly glycolytic. The intermediate IIx fibers are less well understood. Previous work had shown that the transcriptional coactivator PGC-1 alpha could drive the formation of type I and IIa muscle fibers. We show here that mice with transgenic expression of PGC-1 beta in skeletal muscle results in marked induction of IIx fibers. The fibers in transgenic mice are rich in mitochondria and are highly oxidative. As a result, PGC-1 beta transgenic animals can perform oxidative activity for longer and at higher work loads than wild type animals. In cell culture, PGC-1 beta coactivates the MEF2 family of transcription factors to stimulate the MHC IIx promoter. Together, these data indicate that PGC-1 beta is sufficient to drive the formation in vivo of highly oxidative fibers with type IIx characteristics.

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Arany Z, Lebrasseur N, Morris C, Smith E, Yang W, Ma Y, Chin S, Spiegelman BM