Emery-Dreifuss muscular dystrophy (EDMD), clinically characterized by scapulo-humero-peroneal muscle atrophy and weakness, multi-joint contractures with spine rigidity and cardiomyopathy with conduction defects, is associated with structural/functional defect of genes that encode the proteins of nuclear envelope, including lamin A and several lamin-interacting proteins. This paper presents clinical aspects of EDMD in context to causative genes, genotype-phenotype correlation and its emplacement within phenotypic spectrum of skeletal muscle diseases associated with envelopathies.

Hutchinson-Gilford progeria is a rare genetic disorder resulting from mutations in the LMNA gene encoding lamin A/C. In addition to the classical phenotype usually caused by the 1824C>T mutation of LMNA, a number of atypical progeroid syndromes have been described. They have some distinct features, such as skeletal deformities or scleroderma-like skin changes. The underlying defect is usually a homozygous mutation of LMNA, or a combined defect of LMNA and another gene, for example, ZMPSTE-24. We present a 2-year-old girl born to consanguineous parents affected by progeroid syndrome with scleroderma-like skin changes. Genetic analysis revealed the homozygous LMNA mutation 1303C>T (R435C). The same heterozygous mutation was found in the patient's parents and 11 other family members. The progeroid syndrome in our patient shares the signs of two laminopathies: progeria and restrictive dermatopathy. Two other children in the family died at the age of 2 due to a disease similar to that in the proposita. On the basis of the family pedigree we presume that these children probably had the same homozygous LMNA mutation. Scleroderma-like skin changes in infants, associated with growth retardation and dysmorphic features, suggest premature aging syndrome, requiring genetic testing and counseling of asymptomatic carriers of LMNA mutations.

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LMNA gene encodes for nuclear intermediate filament proteins lamin A/C. Mutations in this gene lead to a spectrum of genetic disorders, collectively referred to as laminopathies. Lamin A/C are widely expressed in most differentiated somatic cells but not in early embryos and some undifferentiated cells. To investigate the role of lamin A/C in cell phenotype maintenance and differentiation, which could be a determinant of the pathogenesis of laminopathies, we examined the role played by exogenous lamin A and its mutants in differentiated cell lines (HeLa, NHDF) and less-differentiated HEK 293 cells. We introduced exogenous wild-type and mutated (H222P, L263P, E358K D446V, and ∆50) lamin A into different cell types and analyzed proteins’ impact on proliferation, protein mobility, and endogenous nuclear envelope protein distribution. The mutants give rise to a broad spectrum of nuclear phenotypes and relocate lamin C. The mutations ∆50 and D446V enhance proliferation in comparison to wild-type lamin A and control cells, but no changes in exogenous protein mobility measured by FRAP were observed. Interestingly, although transcripts for lamins A and C are at similar level in HEK 293 cells, only lamin C protein is detected in western blots. Also, exogenous lamin A and its mutants, when expressed in HEK 293 cells underwent posttranscriptional processing. Overall, our results provide new insight into the maintenance of lamin A in less-differentiated cells. Embryonic cells are very sensitive to lamin A imbalance, and its upregulation disturbs lamin C, which may influence gene expression and many regulatory pathways.Electronic supplementary materialThe online version of this article (doi:10.1007/s00412-016-0610-9) contains supplementary material, which is available to authorized users.