Background: The Six1 transcription factor is implicated in controlling the development of several tissue types, notably skeletal muscle. Six1 also contributes to muscle metabolism and its activity is associated with the fast-twitch, glycolytic phenotype. Six1 regulates the expression of certain genes of the fast muscle program by directly stimulating their transcription or indirectly acting through a long non-coding RNA. We hypothesized that additional mechanisms of action of Six1 might be at play. Methods: A combined analysis of gene expression profiling and genome-wide location analysis data was performed. Results were validated using in vivo RNA interference loss-of-function assays followed by measurement of gene expression by RT-PCR and transcriptional reporter assays. Results: The Slc16a10 gene, encoding the thyroid hormone transmembrane transporter MCT10, was identified as a gene with a transcriptional enhancer directly bound by Six1 and requiring Six1 activity for full expression in adult mouse tibialis anterior, a predominantly fast-twitch muscle. Of the various thyroid hormone transporters, MCT10 mRNA was found to be the most abundant in skeletal muscle, and to have a stronger expression in fast-twitch compared to slow-twitch muscle groups. Loss-of-function of MCT10 in the tibialis anterior recapitulated the effect of Six1 on the expression of fast-twitch muscle genes and led to lower activity of a thyroid hormone receptor-dependent reporter gene. Conclusions: These results shed light on the molecular mechanisms controlling the tissue expression profile of MCT10 and identify modulation of the thyroid hormone signaling pathway as an additional mechanism by which Six1 influences skeletal muscle metabolism.
Bibliographical noteKAUST Repository Item: Exported on 2021-11-30
Acknowledgements: The authors would like to thank the following individuals or groups for their contributions: Sarah Hemens and Jack Guthrie for experimental assistance; the staff of the animal care and veterinary services of the University of Ottawa for technical assistance; the McGill University and Génome Québec Innovation Centre for ChIP-seq library preparation and high-throughput sequencing; Compute Canada and technical staff for high-performance computing access and support; and Warner Simonides (Amsterdam, The Netherlands) for the TRE reporter plasmid. The E7 hybridoma against beta-tubulin, developed by M. Klymkowsky was obtained from the Developmental Studies Hybridoma Bank, created by the NICHD of the NIH, and maintained at The University of Iowa, Department of Biology, Iowa City, IA 52242. The authors acknowledge the financial support of the Canadian Institutes of Health Research.
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology
- Orthopedics and Sports Medicine