Correlation of clinical and molecular features in myotonic dystrophy type 1 (DM1)

Objectives: (1) To correlate RNA splicing misregulation in human DM1 vastus lateralis (VL) muscle of two DM1 splice events identified from the literature and the myotonic dystrophy deep sequencing data repository (nuclear factor I/X (NFIX) and insulin receptor (INSR)), with primary clinical outcome measures. (2) Determine if the clinical outcome measures and these splicing defects changed after 18 months follow-up. (3) Compare differential gene expression in DM1 VL skeletal muscle from patients with a severe phenotype to controls and DM1 patients with a mild phenotype. (4) Establish preliminary proteomic profile of DM1 VL skeletal muscle using mass spectrometry. Methods: I performed a cross-sectional evaluation of 45 Southern blot genotyped DM1 patients who underwent VL needle muscle biopsy (for RT-PCR splicing analysis in NFIX and INSR), bilateral grip dynamometry, quantitative muscle testing (QMT) of ankle dorsiflexion strength and the six-minute walk test. In addition, I established prospective 18 month interval data of these parameters and used a targeted custom annotated qPCR array for the differential gene expression analysis in a subset of DM1 patients and healthy control skeletal muscle. In addition, with a collaborator (Dr Marzena Wojciechowska) mass spectrometry was used to establish a proteomic profile of DM1 VL skeletal muscle comparing four DM1 samples with four control samples. Results: Splicing misregulation in INSR and NFIX differentiated DM1 patients with severe phenotype from healthy controls and DM1 patients with a mild phenotype (one way ANOVA p<0.05). In addition, linear regression of alternative splicing in these genes correlated with all clinical outcome measures (p