Punc, a novel mouse gene of the immunoglobulin superfamily, is expressed predominantly in the developing nervous system.

A search for genes regulated by the LlM/homeodomain transcription factor islet-1 during development identified the novel mouse gene punc (putative neuronal cell adhesion molecule). Punc is a member of the immunoglobulin superfamily, exhibits a novel configuration of four immunoglobulin domains and two fibronectin-type III repeats, and resembles proteins involved in axon guidance. Punc expression in the embryo occurs in restricted patterns in both the nervous system and limb mesoderm. A sharp decrease in punc expression after embryonic day 11.5 suggests a function for punc early in mouse embryogenesis.