DNA methylation in skeletal muscle development and rhabdomyosarcoma

DNA cytosine methylation is an epigenetic modification that plays a critical role in transcriptional regulation of tissue development and disease. This work highlights newly described methylation patterns in skeletal muscle development and cancer-specific patterns of methylation in rhabdomyosarcoma. The studies presented here also address the role of cytosine methylation in congenital myotonic dystrophy.;The Dmpk locus is hypermethylated relative to WT in a severe form of the triplet repeat expansion disease, myotonic dystrophy, called congenital myotonic dystrophy (CDM1). This hypermethylation might be due to a large expansion at the Dmpk locus that disrupts binding of the insulator protein CTCF at this locus. Studies to link disruption of CTCF binding and DNA methylation did not show that lack of CTCF binding alone is associated with increased methylation at the Dmpk locus.;A global study of DNA methylation patterns during skeletal muscle development, using the methylated DNA immunoprecipitation technique, suggests that there is a wave of methylation that occurs in the commitment phase of muscle development, during the transition from embryonic stem-cell to committed myoblast. Few methylation changes occur during the differentiation phase of muscle development during the transition from myoblast to differentiated skeletal muscle. This study shows that promoter methylation changes occur at muscle regulatory factors during muscle development. The Myod1 promoter is demethylated during skeletal muscle determination. The Mrf4 promoter is demethylated during skeletal muscle differentiation. Conversely, the Myf5 promoter is methylated during differentiation.;Global methylation mapping in cell lines isolated from two subtypes of the pediatric muscle tumor, rhabdomyosarcoma, using the Denaturation Analysis of Methylated DNA yielded many hypermethylated promoters in the cancer cell-lines relative to normal skeletal muscle. The hypermethylated promoters significantly overlap between different cancer cell-lines. However, these hypermethylated promoters are not normally associated with DNA methylation changes in normal skeletal muscle development based on my MeDIP studies. These findings indicate a cancer-specific pattern of methylation that is distinct from an aberration of a normal developmental process.