Nephronectin is a 565 amino acid member of the nephronectin family that contains five EGF-like domains and an Arg-Gly-Asp (RGD) cell binding motif, as well as a meprin, A5 protein and receptor protein-tyrosine phosphatase ? (MAM) domain. Expressed in kidney, thyroid and parathyroid glands, developing bone, tooth germ, skeletal and smooth muscle, brain and skin, POEM is involved in the development and function of bone, muscle and kidney tissue. The most established function of POEM is as a ligand to the receptor Integrin ?8/∫1. Highly expressed in the nephritic cord, Integrin ?8/∫1 plays a critical role in kidney morphogenesis and development. The POEM-Integrin ?8∫1 complex regulates the expression of GDNF, another protein that affects kidney development, specifically by regulating the growth of the uretic bud. There are two named isoforms of POEM, both of which form homodimers or homotrimers.