The nuclear envelope in muscular dystrophy and cardiovascular diseases.

Considerable interest has been focused on the nuclear envelope in recent years following the realization that several human diseases are linked to defects in genes encoding nuclear envelope specific proteins, most notably A-type lamins and emerin. These disorders, described as laminopathies or nuclear envelopathies, include both X-linked and autosomal dominant forms of Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy with conduction system defects, limb girdle muscular dystrophy 1B with atrioventricular conduction disturbances, and Dunnigan-type familial partial lipodystrophy. Certain of these diseases are associated with nuclear structural abnormalities that can be seen in a variety of cells and tissues. These observations clearly demonstrate that A-type lamins in particular play a central role, not only in the maintenance of nuclear envelope integrity but also in the large-scale organization of nuclear architecture. What is not obvious, however, is why defects in nuclear envelope proteins that are found in most adult cell types should give rise to pathologies associated predominantly with skeletal and cardiac muscle and adipocytes. The recognition of these various disorders now raises the novel possibility that the nuclear envelope may have functions that go beyond housekeeping and which impact upon cell-type specific nuclear processes.