Differential dynamics and stability of lamin A rod domain mutants

Abstract

Mutations in the human lamin A gene give rise to highly debilitating diseases termed laminopathies. Laminopathic cells harboring certain mutations in lamin A display aberrant nuclear morphology due to abnormal lamina assembly. To understand the molecular mechanisms involved in these processes, we have studied the dynamics and stability of GFP-tagged lamin A constructs harboring disease-causing missense mutations in the rod and tail domains of the protein. Analysis of the mobilities of these proteins by fluorescence recovery after photobleaching (FRAP) and fluorescence loss in intensity after photobleaching (FLIP) techniques in live HeLa cells indicated that mutants that formed large aggregates, like E203G, G232E, Q294P and R386K were substantially more mobile than wild-type and mutant lamins H222P and R482L that assembled at the nuclear periphery. Nuclear extractions with detergent, nucleases and salt resulted in the dispersal of large aggregates into smaller foci throughout the nucleoplasm, whereas more stable lamins were retained at the nuclear periphery. The significant alterations in the dynamics and stability of certain rod domain mutants of lamin A are likely to have profound consequences for the organization of nuclear functions.