Transcriptome analysis of collagen VI-related muscular dystrophy muscle biopsies.

Objective: To define the transcriptomic changes responsible for the histologic alterations in skeletal muscle and their progression in collagen VI-related muscular dystrophy (COL6-RD).

Methods: COL6-RD patient muscle biopsies were stratified into three groups based on the overall level of pathologic severity considering degrees of fibrosis, muscle fiber atrophy, and fatty replacement of muscle tissue. Using microarray and RNA-Seq, we then performed global gene expression profiling on the same muscle biopsies and compared their transcriptome with age- and sex-matched controls.

Results: COL6-RD muscle biopsy transcriptomes as a group revealed prominent upregulation of muscle extracellular matrix component genes and the downregulation of skeletal muscle and mitochondrion-specific genes. Upregulation of the TGFβ pathway was the most conspicuous change across all biopsies and was fully evident even in the mildest/earliest histological group. There was no difference in the overall transcriptional signature between the different histologic groups but polyserial analysis identified relative changes along with COL6-RD histological severity.

Interpretation: Overall, our study establishes the prominent dysregulation of extracellular matrix genes, TGFβ signaling, and its downstream cellular pathways at the transcriptomic level in COL6-RD muscle.