The L1 cell adhesion molecule is a member of an evolutionarily well-conserved superfamily of immunoglobulin (Ig)-related CAMs that have essential functions in the developing nervous system, especially during neurogenesis, neuronal migration, and axonal growth and guidance. Structurally, L1 cell adhesion is an integral glycoprotein with a complex ectodomain consisting of multiple immunoglobulin and fibronectin-like repeats.
The L1 cell adhesion molecule (L1CAM) plays a key role in neuronal migration and neurite outgrowth by mediation of axon bundling. It is a member of a large class of immunoglobulin superfamily cell adhesion molecules (CAMs), which mediate cell-to-cell adhesion at the cell surface. L1CAM is a 200-kDa transmembrane glycoprotein, containing six Ig-like domains in the amino-terminal region, followed by five fibronectin type III repeats, one transmembrane domain, and a cytoplasmic domain.
Mutation in the L1-CAM gene display a phenotype, which includes a range of severe neurological dysfunctions, including X-linked hydrocephalus, MASA syndrome, X-linked complicated spastic paraparesis and X-linked corpus callosum agenesis. Clinical variability is large between and sometimes within families. As the most typical features of L1-associated disease include corpus callosum hypoplasia, mental retardation, adducted thumbs, spastic paraplegia and hydrocephalus, the acronym CRASH syndrome has been proposed.