Failure of lamin A/C to functionally assemble in R482L mutated familial partial lipodystrophy fibroblasts: altered intermolecular interaction with emerin and implications for gene transcription.
Familial partial lipodystrophy is an autosomal dominant disease caused by mutations of the LMNA gene encoding alternatively spliced lamins A and C. Abnormal distribution of body fat and insulin resistance characterize the clinical phenotype. In this study, we analyzed primary fibroblast cultures from a patient carrying an R482L lamin A/C mutation by a morphological and biochemical approach. Abnormalities were observed consisting of nuclear lamin A/C aggregates mostly localized close to the nuclear lamina. These aggregates were not bound to either DNA-containing structures or RNA splicing intranuclear compartments. In addition, emerin did not colocalize with nuclear lamin A/C aggregates. Interestingly, emerin failed to interact with lamin A in R482L mutated fibroblasts in vivo, while the interaction with lamin C was preserved in vitro, as determined by coimmunoprecipitation experiments. The presence of lamin A/C nuclear aggregates was restricted to actively transcribing cells, and it was increased in insulin-treated fibroblasts. In fibroblasts carrying lamin A/C nuclear aggregates, a reduced incorporation of bromouridine was observed, demonstrating that mutated lamin A/C in FPLD cells interferes with RNA transcription.
Laboratory of Cell Biology, Istituti Ortopedici Rizzoli, Bologna, Italy.
Cristina
C
Capanni
Vittoria
V
Cenni
Elisabetta
E
Mattioli
Patrizia
P
Sabatelli
Andrea
A
Ognibene
Marta
M
Columbaro
Veena K
VK
Parnaik
Manfred
M
Wehnert
Nadir M
NM
Maraldi
Stefano
S
Squarzoni
Giovanna
G
Lattanzi
D017398:Alternative Splicing / Q000235:genetics; D002478:Cells, Cultured; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure; D006570:Heterochromatin / Q000235:genetics / Q000473:pathology / Q000648:ultrastructure; D006801:Humans; D007328:Insulin / Q000494:pharmacology; D007399:Interphase / Q000235:genetics; D034904:Lamin Type A / Q000235:genetics / Q000378:metabolism; D034882:Lamins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008060:Lipodystrophy / Q000235:genetics*; D008565:Membrane Proteins / Q000378:metabolism*; D008854:Microscopy, Electron; D009154:Mutation / Q000235:genetics; D009685:Nuclear Envelope / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D009687:Nuclear Proteins; D012313:RNA / Q000096:biosynthesis / Q000235:genetics; D013946:Thymopoietins / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects / Q000235:genetics*
D006570:Heterochromatin; D007328:Insulin; D034904:Lamin Type A; D034882:Lamins; D008565:Membrane Proteins; D009687:Nuclear Proteins; D013946:Thymopoietins; C092710:emerin; C440308:lamin C; D012313:RNA