Type B mandibuloacral dysplasia with congenital myopathy due to homozygous ZMPSTE24 missense mutation
Résumé
Mutation in ZMPSTE24 gene, encoding a major metalloprotease, leads to defective prelamin A processing and causes type B mandibulo-acral dysplasia as well as the lethal neonatal restrictive dermopathy syndrome. Phenotype severity is correlated with the residual enzyme activity of ZMPSTE24 and accumulation prelamin A. We had previously demonstrated that a complete loss of function in ZMPSTE24 was lethal in the neonatal period whereas, compound heterozygous mutations including one PTC and one missense mutation were associated with type B mandibulo-acral dysplasia. Here, we report on a 30 year longitudinal clinical survey of a patient harboring a novel severe and complex phenotype, combining an early onset progeroid syndrome and a congenital myopathy with fibre type disproportion. A unique homozygous missense ZMPSTE24 mutation (c.281T>C, p.Leu94Pro) was identified and predicted to produce 2 possible ZMPSTE24 conformations, leading to a partial loss of function. Western blot analysis revealed a major reduction of ZMPSTE24 together with the presence of unprocessed prelamin A and decreased levels of lamin A in the patient's primary skin fibroblasts. These cells exhibited significant reductions in lifespan associated with major abnormalities of the nuclear shape and structure. This is the first report of MAD presenting with confirmed myopathic abnormalities associated to ZMPSTE24 defects, extending the clinical spectrum of ZMPSTE24 gene mutations. Moreover, our results suggest that defective prelamin A processing affects muscle regeneration and development thus providing new insights into disease mechanism of Prelamin A defective associated syndromes in general.
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