Facioscapulohumeral muscular dystrophy (FSHD), one of the most common types of muscular dystrophy, is characterized by the development of progressive weakness in the face, proximal arm, and scapular stabilizer muscles. In more severe cases, the pelvic girdle may be involved leading to confinement in a wheelchair. FSHD is inherited as an autosomal dominant trait. The genetic lesion accounting for most cases is the deletion of integral copies of a tandemly repeated 3.3kb unit (""""""""D4Z4 repeat"""""""") from chromosome 4q35. Previous studies have failed to identify a gene within the region of the D4Z4 repeats themselves, or distal to the D4Z4 repeat region. Therefore we hypothesize that the gene(s) involved in the development of FSHD lie proximal to the D4Z4 repeat region; the FSHD gene(s) most likely do not themselves contain any mutations, but will display aberrant expression levels in patients compared to their control counterpart(s). Thus, the overall objective of this project is to identify genes lying proximal to the D4Z4 repeat region of chromosome 4q35 and to test each gene for its possible involvement in the pathogenesis of FSHD. In addition, genes whose expression changes downstream of the primary FSHD gene(s) will be identified. Specifically, we aim to: (1) Acquire FSHD patient material--blood samples and muscle biopsy specimens-- for DNA analysis and for gene expression studies. (2) Characterize small-fragment phage libraries of expressed sequences which have been derived from chr. 4q35 yeast artificial chromosomes (YACs) using the direct selection protocol. (3) Characterize mRNAs which are uniquely expressed in FSHD patient skeletal muscle samples vs. control samples, identified via the technique of differential display or gene chip hybridization analysis. (4) Test all appropriate candidate gene fragments for expression in mRNA from control and FSHD skeletal muscle, and from cultured myoblasts of different stages which have been derived from these tissues, using competitive quantitative RT/PCR and Northern Blot techniques. (5) When expression and mapping studies suggest that a given candidate gene might be the FSHD gene, functional studies will be undertaken to characterize the gene, its expression, and the role of its protein product. Our long-term goals are: to identify the gene(s) involved in FSHD; to work closely with our FSHD patient population to characterize the spectrum of genetic effects in muscle biopsy and cultured myoblasts derived from each individual; and to correlate these changes with variations in phenotypic expression of the disease. The ultimate aim is to identify rational therapeutic strategies for FSHD.
