G.P.215: Ullrich congenital muscular dystrophy: A new cellular study on cultured skin fibroblasts

Abstract

Ullrich congenital muscular dystrophy (UCMD) is a severe congenital dystrophy caused by collagen VI (COL VI) mutations and resulting in absent or aberrant collagen VI secretion in fibroblasts. The link between the mutated collagen VI, and Col VI synthesis, secretion into the ECM, interaction with the cell, mitochondrial defect, cell death, ... is not well characterized. The objective of our study was to provide additional proteomics based insight into the cellular impact of the defective ColVI in cultured skin fibroblasts. To reach this objective, a quantitative iTRAQ based LC-MALDI method was used to compare the proteome in cultured skin fibroblasts from UCMD patients with control fibroblasts. We used western blot as a confirmatory method to assess the dysregulation of proteome identified candidates. The most important findings were the differences in protein expression patterns linked to ER collagen-chaperone functioning and collagen I synthesis (alpha 1 chain, alpha 2 chain) together with fibronectin. A number of proteins involved in the formation of adhesions points that form an important link between the ECM and the intracellular space were found dysregulated. Additionally, Immunofluorescence (IF) for vinculin evaluated by several independent observers showed an increased number of focal adhesions on Col VI deficient fibroblasts. Finally IF collagen V evidenced disturbed extracellular network formation with intracellular retention of the protein. Our findings suggest that the dysregulation of the extracellular network in Col VI deficient fibroblasts possibly leads to intracellular stress and compensatory mechanisms. Proteins involved in molecular pathways such us the mitochondrial defect and the impairment of the autophagocytic flux, implicated in UCMD muscle fibers, were not found as differentially regulated in our proteomics experiment on fibroblasts, suggesting different pathophysiological mechanisms at play in these two important cell types in UCMD.