Defective Mitochondrial Morphology and Bioenergetic Function in Mice Lacking the Transcription Factor Yin Yang 1 in Skeletal Muscle

Abstract

The formation, distribution, and maintenance of functional mitochondria are achieved through dynamic processes that depend strictly on the transcription of nuclear genes encoding mitochondrial proteins. A large number of these mitochondrial genes contain binding sites for the transcription factor Yin Yang 1 (YY1) in their proximal promoters, but the physiological relevance is unknown. We report here that skeletal-muscle-specific YY1 knockout (YY1mKO) mice have severely defective mitochondrial morphology and oxidative function associated with exercise intolerance, signs of mitochondrial myopathy, and short stature. Gene set enrichment analysis (GSEA) revealed that the top pathways downregulated in YY1mKO mice were assigned to key metabolic and regulatory mitochondrial genes. This analysis was consistent with a profound decrease in the level of mitochondrial proteins and oxidative phosphorylation (OXPHOS) bioenergetic function in these mice. In contrast to the finding for wild-type mice, inactivation of the mammalian target of rapamycin (mTOR) did not suppress mitochondrial genes in YY1mKO mice. Mechanistically, mTOR-dependent phosphorylation of YY1 resulted in a strong interaction between YY1 and the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α), a major regulator of mitochondrial function. These results underscore the important role of YY1 in the maintenance of mitochondrial function and explain how its inactivation might contribute to exercise intolerance and mitochondrial myopathies.

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SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://dx.doi.org/10.1128/MCB.00337-12.

ACKNOWLEDGMENTS

We thank the members of the Puigserver lab for advice and fruitful discussions, Christine Chin for technical assistance, Eric Olson for the myogenin CRE mice, and Sebastian Valentin, Roderick Bronson, and Maria Ericsson for help with histochemistry, H&E staining, and electron microscopy, respectively. We also thank James White for advice on exercise protocols and cross-sectional area measurements.

These studies were supported by a postdoctoral fellowship from the Swiss National Science Foundation (to S.M.B.) and by NIH/NIDDK grant RO1 DK081418 and Muscular Dystrophy Association grant MDA202237 (to P.P.).