Any of a group of proteins that are components of nuclear intermediate filaments and form the nuclear lamina on the inner surface of the nuclear envelope. Classified into three types—A, B, and C—they help to connect the nucleus to the cytoskeleton and are involved in maintaining the mechanical stability of the nucleus, positioning of chromosomal regions inside the nucleus, and control of gene expression. Mutations in lamin genes cause a variety of diseases—the laminopathies—affecting muscles (e.g. congenital muscular dystrophy), nerves, and metabolism; they have been implicated in certain cancers, possibly through greater nuclear deformability promoting the spread (metastasis) of cancer cells.