Dysferlin expression in monocytes: A source of mRNA for mutation analysis

Dysferlin protein is expressed in peripheral blood monocytes. The genomic analysis of the DYSF gene has proved to be time consuming because it has 55 exons. We designed a mutational screening strategy based on cDNA from monocytes to find out whether the mutational analysis could be performed in mRNA from a source less invasive than the muscle biopsy. We studied 34 patients from 23 families diagnosed with dysferlinopathy. The diagnosis was based on clinical findings and on the absence of protein expression using either immunohistochemistry or Western blot of skeletal muscle and/or monocytes. We identified 28 different mutations, 13 of which were novel. The DYSF mutations in both alleles were found in 30 patients and only in one allele in four. The results were confirmed using genomic DNA in 26/34 patients. This is the first report to furnish evidence of reliable mutational analysis using monocytes cDNA and constitutes a good alternative to genomic DNA analysis.