The UCMD-Causing COL6A1 () Intron Mutation Leads to the Secretion and Aggregation of Single Mutated Collagen VI α1 Chains

Figure 2

Secretion of collagen VI tetramers and non-assembled mutant α1 chains by patient dermal fibroblasts. (a) Duplicates of samples from the cell layer and supernatants of control (CTRL) and patient fibroblasts (R1, US10) were subjected to electrophoresis in composite 0.5% agarose/2.4% polyacrylamide gels. Proteins were transferred to a membrane and signals were detected with the α3N and the Pex11-α1 antibodies. (b) Supernatants from (a) were subjected to SDS-PAGE on 6% gels under nonreducing (-βMe) or reducing (+βMe) conditions. (c) Negative stain electron micrographs of immunogold labelled supernatants of control and patient fibroblasts (US8). The α3N antibody was labelled with 10 nm and the Pex11-α1 antibody with 5 nm gold particles. Fields marked by white frames are further magnified in the bottom row. Arrows mark the periodic beaded region of collagen VI visualized by α3N signals, arrowheads point to Pex11-α1 signals, and tangles of mixed α3N and Pex11-α1 signals are indicated by asterisks. Scale . The results indicate that, despite being present, the mutant chains cannot assemble into tetramers but form aggregates and, sometimes, decorate collagen VI microfibrils.

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