Membrane Damage Added to FSHD Picture

A research group coordinated by Robert Bloch, an MDA grantee at the University of Maryland, has added more pieces to the puzzle that facioscapulohumeral muscular dystrophy (FSHD) continues to be.

Bloch and colleagues, who published their results in the February issue of Annals of Neurology, found unusual diagonal structures in the membranes of muscle cells taken from people with FSHD, as well as a marked increase in the gap between each cell and its surrounding membrane. Both these changes were found in all nine FSHD biceps and deltoid muscle samples (although they weren’t present throughout each sample), with none found in samples from people without FSHD.

The researchers say the abnormalities are likely to interfere with force transmission in the affected muscles. They also say they they don’t know if, or how, these abnormalities are related to a recent finding that the FRG1 protein is overproduced in FSHD (see “Scientists ID Molecular Consequences of FSHD Mutation”) or to other genes in the FSHD region of chromosome 4.

“It remains unclear whether the basic defect in FSHD resides in a [membrane]-associated protein or whether the observed changes at the [membrane] are secondary to a primary defect that lies elsewhere,” the authors say.