Lamins are nuclear membrane structural components that are important in maintaining normal cell functions, such as cell cycle control, DNA replication, and chromatin organization. Lamins have been subdivided into types A and B. Type-A lamins consist of lamin A and C, which arise from alternative splicing of the lamin A gene LMNA. Lamin A and C are cleaved by caspases into large (41-50 kDa) and small (28 kDa) fragments, which can be used as markers for apoptosis. Type-B lamins consist of lamin B1 and B2, encoded by separate genes. Lamin B1 is also cleaved by caspases during apoptosis. Research studies have shown that duplication of the lamin B1 gene LMNB1 is correlated with pathogenesis of the neurological disorder adult-onset leukodystrophy.
Research studies show that both lamin B2 and lamin B1 knockout mice exhibit neuronal developmental defects and that both proteins are essential for typical brain development. Lamin B1 and B2 deficiencies result in changes in nuclear morphology, with lamin B1 playing a role in regulating nuclear lamina integrity and lamin B2 inhibiting elongation of neuronal nuclei. Mutations in the corresponding lamin B2 gene (LMNB2) can result in a susceptibility to developing acquired partial lipodystrophy, a rare disorder characterized by the progressive loss of subcutaneous fat in a bilaterally symmetrical fashion.