CRELD1 is a transmembrane glycoprotein. Epidermal growth factor(EGF)­like domain exists in CRELD1. EGF-like repeats are a class of cysteine-rich domains that mediate interactions between proteins of diverse function. EGF domains are found in proteins that are either completely secreted or have transmembrane regions that tether the protein to the cell surface. CRELD1 contains a 333 amino acid acid (aa) extracellular domain (ECD), two tandem transmembrane segments, and a second ECD of 15 aa. Defects in CRELD1 may cause susceptibility to atrioventricular septal defect type 2 which results in a persistent common atrioventricular canal.