Lamin A/C assembly defects in Emery-Dreifuss muscular dystrophy can be regulated by culture medium composition.
Emery-Dreifuss muscular dystrophy results from mutations in either emerin or lamin A/C and is caused by loss of some unknown function of emerin-lamin A/C complexes. This function must be of special importance in the skeletal and cardiac muscles that are affected by the disease. Some lamin A/C mutant proteins form 'nuclear foci' in the nucleoplasm when overexpressed by transient transfection and similar aggregates have been seen in cultured skin fibroblasts from patients with Emery-Dreifuss muscular dystrophy, suggesting that mis-assembly of the A-type lamina may be involved in the pathogenesis. Whereas an earlier study of cultured skin fibroblasts compared several different missense mutations in lamin A/C, we have chosen to study one particular Emery-Dreifuss mutation (R249Q) in greater detail. We found that the proportion of fibroblast nuclei containing abnormal lamin A/C aggregates can vary from 0.5 to 23.6% depending on the culture conditions. In particular, switching from a 'slow growth' medium to 'rapid growth' media increased both the number and size of nuclear aggregates. Similar results were obtained with fibroblasts from a second unrelated patient with the same mutation. In contrast to these aggregates of endogenous lamin A/C, 'nuclear foci' formed after transfection of mouse embryo fibroblasts by mutant lamin A/C were not affected by culture conditions. Faulty assembly of the nuclear lamina by mutated lamin A/C molecules could be partly responsible for the disease phenotype, though this has not been proven. The present study suggests that inappropriate lamin A/C assembly may be preventable by manipulation of cell growth conditions.
Holt
Ian
I
Centre for Inherited Neuromuscular Disease, RJAH Orthopaedic Hospital, Oswestry SY10 7AG, UK.
Nguyen
Thi Man
TM
Wehnert
Manfred
M
Morris
Glenn E
GE
D000328:Adult; D000818:Animals; D002467:Cell Nucleus / Q000737:chemistry / Q000187:drug effects / Q000473:pathology; D002478:Cells, Cultured; D002648:Child; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D034904:Lamin Type A / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D020389:Muscular Dystrophy, Emery-Dreifuss / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020125:Mutation, Missense / Q000235:genetics; D012867:Skin / Q000473:pathology; D014162:Transfection
D003470:Culture Media; D034904:Lamin Type A; C440308:lamin C