Properties of lamin A mutants found in Emery-Dreifuss muscular dystrophy, cardiomyopathy and Dunnigan-type partial lipodystrophy.
Autosomal dominant Emery-Dreifuss muscular dystrophy is caused by mutations in the LMNA gene, which encodes lamin A and lamin C. Mutations in this gene also give rise to limb girdle muscular dystrophy type 1B, dilated cardiomyopathy with atrioventricular conduction defect and Dunnigan-type partial lipodystrophy. The properties of the mutant lamins that cause muscular dystrophy, lipodystrophy and dilated cardiomyopathy are not known. We transfected C2C12 myoblasts with cDNA encoding wild-type lamin A and 15 mutant forms found in patients affected by these diseases. Immunofluorescence microscopy showed that four mutants, N195K, E358K, M371K and R386K, could have a dramatically aberrant localization, with decreased nuclear rim staining and formation of intranuclear foci. The distributions of endogenous lamin A/C, lamin B1 and lamin B2 were also altered in cells expressing these four mutants and three of them caused a loss of emerin from the nuclear envelope. In the yeast two-hybrid assay, the 15 lamin A mutants studied interacted with themselves and with wild-type lamin A and lamin B1. Pulse-chase experiments showed no decrease in the stability of several representative lamin A mutants compared with wild-type. These results indicate that some lamin A mutants causing disease can be aberrantly localized, partially disrupt the endogenous lamina and alter emerin localization, whereas others localize normally in transfected cells.
Ostlund
C
C
Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
Bonne
G
G
Schwartz
K
K
Worman
H J
HJ
D000818:Animals; D019556:COS Cells; D002311:Cardiomyopathy, Dilated / Q000235:genetics* / Q000473:pathology; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D005455:Fluorescent Antibody Technique; D006801:Humans; D034904:Lamin Type A; D034921:Lamin Type B; D034882:Lamins; D008060:Lipodystrophy / Q000235:genetics* / Q000473:pathology; D051379:Mice; D020389:Muscular Dystrophy, Emery-Dreifuss / Q000235:genetics* / Q000473:pathology; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D014162:Transfection; D020798:Two-Hybrid System Techniques
D034904:Lamin Type A; D034921:Lamin Type B; D034882:Lamins; D009687:Nuclear Proteins; D011498:Protein Precursors; C440308:lamin C; C090764:prelamin A