The inner nuclear envelope protein Sun1 interacts with the nuclear lamina and participates in nuclear architecture and cellular morphology. Sun1 is anchored in the inner nuclear membrane by tethering to the nuclear matrix protein Lamin A. Mutations in the human LMNA gene have been associated with a variety of muscular dystrophies, cardiomyopathies and Progeria, collectively called the laminopathies. Mice deficient for Lmna (Lmna–/–) are indistinguishable at birth from their wild type littermates, but soon develop pathologies similar to human laminopathies including cardiomyopathy and muscular dystrophy, as well as scoliosis/kyphosis with death occurring at 6–8 weeks. The objectives of this study were to examine how knocking out Sun1 might synergize such diseases. Here we show that mice doubly knocked out for the inner nuclear envelope protein Sun1 and lamin A are unexpectedly rescued from the laminopathy and premature death phenotype of the Lmna–/– animals. In Lmna–/– mice, the additional knock out of Sun1 significantly corrects deficits in body weight, body size, tissue pathologies, and longevity. Our results demonstrate that loss of Lmna leads to substantive dysfunction in Lamin A-associated Sun1 protein whose removal critically ameliorates disease. We anticipate that this finding will impact the thinking on extant and future clinical trials treating Progeria and other human laminopathies.
