REGA-1 is a GPI-Iinked member of the immunoglobulin superfamily present on restricted regions of sheath cell processes in grasshopper

REGA-1 is a glycoprotein localized to sheath cell processes in the developing CNS when NBs are producing progeny and neurons are maturing and extending processes. It is also present on a subset of muscles and on the lumenal surface of the ectoderm in the embryonic appendages when pioneer neurons are growing into the CNS. REGA-1 is associated with the extracellular side of the cell membrane by a glycosyl-phosphatidylinositol linkage. We have identified a cDNA clone encoding REGA-1 using a sequence from purified protein. Sequence analysis defines REGA-1 as a novel member of the immunoglobulin superfamily containing three immunoglobulin domains and one fibronectin type III repeat. Each Ig domain has distinct sequence characteristics that suggest discrete functions. REGA-1 is similar to other Ig superfamily members involved in cell adhesion events and neurite outgrowth.