Localization of the human TAX-1 gene to 1q32.1: a region implicated in microcephaly and Van der Woude syndrome

Cell adhesion molecules TAX-1, TAG-1 and axonin-1 are homologous cell surface glycoproteins expressed in the neural tissue of human, rat and chicken respectively. They are members of a family of proteins composed of repeated immunoglobulin-like (IgC2) and fibronectin type III-like (FNIII) domains that mediate adhesion between components of the nervous system. Studies of neurite outgrowth on immobilized axonin-1 indicate that it participates in a heterophilic interaction with L1, a related member of the immunoglobulin superfamily that is expressed on the axons of migrating neurones. Recently, we demonstrated that mutations in the human L1 gene give rise to X-linked hydrocephalus, a congenital disorder of brain development. In view of the structural similarity and functional association between L1 and TAX-1 homologues we anticipate that disruption of TAX-1 would also result in developmental impairment. As a first step towards determining whether TAX-1 is associated with a genetically mapped inherited disorder we have established its chromosomal location.