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How much mutant protein is needed to cause a protein aggregate myopathy in vivo? : Lessons from an exceptional desminopathy

Clemen, Christoph S. and Fischer, Dirk and Reimann, Jens and Eichinger, Ludwig and Müller, Clemens R. and Müller, Harald D. and Goebel, Hans H. and Schröder, Rolf. (2009) How much mutant protein is needed to cause a protein aggregate myopathy in vivo? : Lessons from an exceptional desminopathy. Human mutation : variations, databases, and diseases, Vol. 30 , E490-9.

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Official URL: http://edoc.unibas.ch/dok/A6006395

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Abstract

Myofibrillar myopathies are caused by mutations in desmin, alphaB-crystallin, myotilin, ZASP, and filamin C genes. Since the vast majority of myofibrillar myopathy causing mutations are heterozygous single amino acid substitutions or small in-frame deletions, the pathogenic role of mutant versus wild-type protein cannot be assessed in human skeletal muscle by standard immunodetection techniques. We report on an exceptional desminopathy due to a heterozygous c.735G<C mutation. Immunoblotting detected full-length 53 kDa desmin and a truncated 50 kDa variant in skeletal muscle from three affected patients of two different families. RT-PCR identified three desmin mRNA species encoding for wild-type and two mutant proteins, p.Glu245Asp and p.Asp214_Glu245del. Since previous functional studies on the p.Glu245Asp mutant showed biological properties identical to wild-type desmin, the truncated p.Asp214_Glu245del desmin is the disease-causing mutant. Semiquantitative RT-PCR established a fraction of the truncated desmin mRNA species in a range from 24% to 37%. Initial quantification of corresponding desmin proteins in the muscle biopsy of the index patient of one family indicated a fraction of only 10% of the truncated species. However, serial analyses of different sections from each muscle biopsy revealed a high intra- and interindividual variability of the truncated desmin protein level within a range from 5% to 43%. Desmin assembly studies in vitro have established clear-cut pathogenic ratios of mutant versus wild-type proteins. However, our findings point out a far more complex situation in human skeletal muscle. The heterogeneously distributed mutation load within and between individual specimens, which reflects local differences in the expression and/or turnover of the mutant protein in different areas containing multiple myonuclear domains, renders it impossible to define an exact pathogenic threshold of a specific mutant in vivo.
Faculties and Departments:03 Faculty of Medicine > Bereich Kinder- und Jugendheilkunde (Klinik) > Kinder- und Jugendheilkunde (UKBB) > Neuro- und Entwicklungspädiatrie (Weber)
03 Faculty of Medicine > Departement Klinische Forschung > Bereich Kinder- und Jugendheilkunde (Klinik) > Kinder- und Jugendheilkunde (UKBB) > Neuro- und Entwicklungspädiatrie (Weber)
UniBasel Contributors:Fischer, Dirk
Item Type:Article, refereed
Article Subtype:Research Article
Bibsysno:Link to catalogue
Publisher:Wiley-Liss
ISSN:1098-1004
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:01 Feb 2013 08:46
Deposited On:01 Feb 2013 08:42

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