Also called Type V intermediate filaments, lamins can bind with other nuclear proteins forming the nuclear lamina, a network of proteins located near the nucleus' membrane of most cell types. Lamins help to regulate DNA replication, cell division and other important cellular events. Lamins are the only intermediate filaments found in the nucleus.
Cytoplasmic intermediate filaments include several proteins, such as Types I and II keratins; Type III desmin, GFAP or glial fibrillary acidic protein, peripherin and vimentin; Type IV internexin, neurofilaments, synemin and syncoilin; and Type VI nestin. Keratins are often found in cells that form the skin, hair and nails, as well as horns and reptile scales. Desmin is part of the muscular cells, while GFAP and peripherin are found in cells of the nervous system. Vimentin is a widely distributed cytoplasmic intermediate filaments, forming blood cells and vessels, and playing an important role in the anchoring of cell organelles in the cytoplasm. Nestin is part of nerve cells.
Although the number of cytoplasmic intermediate filaments can reach 70 in vertebrates, these proteins are less abundant or nonexistent in invertebrates. According to research published in "BMC Biology" in February 2011, a new cytoplasmic intermediate filament was found in the intestine cells of the spring-tail Isotomurus maculatus. Named isomin, the protein is the only cytoplasmic intermediate filament found in arthropods, although lamins are present in the cells of these invertebrates.
Sometimes, a mutation or alteration occurs in the genes responsible for the production of intermediate filaments. This generates a faulty filament, which consequently can cause a disease. Mutations in the genes that produce lamins can cause several genetic conditions, such as progeria, a extremely rare disease whose symptoms include early aging. According to the Human Intermediate Filament Database, more than 90 diseases are related to faulty intermediate filaments.