MDGA-1 (MAM domain-containing GPI anchor protein 1) is a 135-140 kDa, novel member of the Ig-superfamily. It is expressed on embryonic neurons destined for cortical layers 2/3, as well as migrating basilar pontine neurons and D1 interneurons of the spinal cord. Human proMDGA-1 is 937 amino acids (aa) in length (SwissProt #:Q8NFP4). It is a GPI-linked glycoprotein that contains six consecutive Ig-like domains (aa #24-631), followed by one fibronectin type III domain (aa #640-739), a MAM region (aa #751-918), and a cleavable propeptide (aa #933-955). There are at least three potential variants. One shows a 48 aa substitution for aa #936-955, a second shows a 58 aa substitution for aa #847-955, and a third shows a 51 aa substitution for aa #537-955. Over aa #19-931, human MDGA-1 is 95% aa identical to mouse MDGA-1.