Abstract
BackgroundCongenital fibrosis of the extraocular muscles type 1 (CFEOM1) is an autosomal dominant eye movement disorder linked to the pericentromere of chromosome 12 (12p11.2 - q12). Sarcospan is a member of the dystrophin associated protein complex in skeletal and extraocular muscle and maps to human chromosome 12p11.2. Mutations in the genes encoding each of the other components of the skeletal muscle sarcospan-sarcoglycan complex (α - δ sarcoglycan) have been shown to cause limb girdle muscular dystrophy (LGMD2C-F). To determine whether mutations in the sarcospan gene are responsible for CFEOM1 we: (1) attempted to map sarcospan to the CFEOM1 critical region; (2) developed a genomic primer set to directly sequence the sarcospan gene in CFEOM1 patients; and (3) generated an anti-sarcospan antibody to examine extraocular muscle biopsies from CFEOM1 patients.ResultsWhen tested by polymerase chain reaction, sarcospan sequence was not detected on yeast or bacterial artificial chromosomes from the CFEOM1 critical region. Sequencing of the sarcospan gene in CFEOM1 patients from 6 families revealed no mutations. Immunohistochemical studies of CFEOM1 extraocular muscles showed normal levels of sarcospan at the membrane. Finally, sarcospan was electronically mapped to bacterial artificial chromosomes that are considered to be outside of the CFEOM1 critical region.ConclusionsIn this report we evaluate sarcospan as a candidate gene for CFEOM1. We have found that it is highly unlikely that sarcospan is involved in the pathogenesis of this disease. As of yet no sarcospan gene mutations have been found to cause muscular abnormalities.
Highlights
Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is an autosomal dominant eye movement disorder linked to the pericentromere of chromosome 12 (12p11.2 q12)
We find sarcospan to be unmutated in all six CFEOM1 families studied and sarcospan immunoreactivity to be identical in control and CFEOM1 extraocular muscle
Genomic organization of the human sarcospan gene Five independent clones were isolated from a human genomic phage library using hybridization probes that covered the entire coding region of sarcospan
Summary
Congenital fibrosis of the extraocular muscles type 1 (CFEOM1) is an autosomal dominant eye movement disorder linked to the pericentromere of chromosome 12 (12p11.2 q12). Mutations in the genes encoding each of the other components of the skeletal muscle sarcospan-sarcoglycan complex (α - δ sarcoglycan) have been shown to cause limb girdle muscular dystrophy (LGMD2C-F). CFEOM1 patients appear to be lacking the superior division of cranial nerve III, which innervates the levator and superior rectus muscles [3]. Whether this disease is caused by a primary defect in the nerve or the muscle remains unclear. Yeast and bacterial artificial chromosome (YAC and BAC) contigs have been generated and a positional clonhttp://www.biomedcentral.com/1471-2156/2/3 ing approach to identify the CFEOM1 causative gene is last 363 bp of coding sequence and over 1500 bp 3'-unongoing
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