Lamins in disease: why do ubiquitously expressed nuclear envelope proteins give rise to tissue-specific disease phenotypes?

The nuclear lamina is a filamentous structure composed of lamins that supports the inner nuclear membrane. Several integral membrane proteins including emerin, LBR, LAP1 and LAP2 bind to nuclear lamins in vitro and can influence lamin function and dynamics in vivo. Results from various studies suggest that lamins function in DNA replication and nuclear envelope assembly and determine the size and shape of the nuclear envelope. In addition, lamins also bind chromatin and certain DNA sequences, and might influence chromosome position. Recent evidence has revealed that mutations in A-type lamins give rise to a range of rare, but dominant, genetic disorders, including Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy with conduction-system disease and Dunnigan-type familial partial lipodystrophy. An examination of how lamins A/C, emerin and other integral membrane proteins interact at the INM provides the basis for a novel model for how mutations that promote disease phenotypes are likely to influence these interactions and therefore cause cellular pathology through a combination of weakness of the lamina or altered gene expression.