Muscular Dystrophies Detected byImmunophenotyping and by Analysis of Genotype(m-RNA and DNA)

Overview

Complex diagnosis of muscular dystrophies including clinical, bioptical and molecular geneticapproaches has been provided in a limited extent in this country. Our group of neurologists,pathologists and geneticists has examined approximately 240 patients suspected of having muscu-lar dystrophies, mostly coming from Southern and Northern Moravia. The patients were sent tothe examination most often from departments of neurology and clinical genetics, and less frequ-ently from departments of internal medicine. According to the final diagnosis, the patients weredivided into groups: with dystrophinopathies and carriers of dystrophinopathies (DMD/BMD),merosin deficient form of congenital muscular dystrophy, and Emery-Dreifuss muscular dystrop-hy including the carriers of this disease. Some relatives of patients with dystrophinopathies werealso examined using the methods of segregation analysis. High proportion of the DMD/BMDpatients can be detected by the methods of molecular genetics. Analysis of mRNA using RT PCRand PTT enables the detection of deletions, duplications, and point mutations in dystrophin geneand encompasses a larger diagnostic scope in comparison with examinations of DNA level by themultiplex PCR method from the peripheral blood which enables only deletion detections. Immunophenotyping of the dystrophin protein plays an important role especially using antibodiesagainst carboxyterminal (DYS2) and rod domain (DYS1) of dystrophin. Deficient sarcolemmalexpression of DYS2 and DYS1 reveales unambiguously a pathological dystrophin. On the otherhand, less pronounced deficiencies in dystrophin expression in BMD patients and DMD/BMDcarriers may not always be detected in muscle biopsies. In this case, it is necessary to supplementthe examination by Western blotting and genotype analysis.The examination of patients with clinically diagnosed muscular dystrophy should start witha muscle biopsy which enables the estimation of presence and degree of structural changes.Application of antibodies against the components of DGC and emerin may reveal a deficiency inexpression of these proteins. Immunohistochemical examination completed by Western blottingleads to the subsequent molecular genetic analysis of DNA or mRNA. Secondary deficiencies inexpression of other DGC proteins are often revealed in muscle biopsies of dystrophinopathies andthis fact must be taken into account in the evaluation of immunohistochemical findings.There is a possibility of replacement of invasive muscle biopsy by skin biopsy or buccal mucosalsmears in cases of merosin and emerin deficiencies.Commercially available antibodies against merosin, emerin, calpain and sarcoglycans enable extensive identification and detailed classification of muscular dystrophies. Screening of the patients based on the application of methods described and discussed in this report is the task of theforthcoming period.

Key words:
immunophenotyping - molecular genetics - muscular dystrophy