Integrins are membrane receptors that mediate cell-cell or cell-matrix adhesion. All integrins are transmembrane heterodimers composed of α and β subunits which are connected to the cytoskeleton. At least 20 integrins, formed from combinations of the 12 α and 9 β subunits, have been reported. Many of these have been implicated as transducers of molecular signals. Their roles are essential for embryonic development, tumor metastasis, cell motility, organ function, and proper immune cell function. Nischarin is a novel protein that binds, through its 464-562 amino-acid region, to the cytoplasmic domain of integrin α5. Expression of Nischarin is abundant in many tissues, especially brain and kidney, and its mRNA can be detected as early as day 7 in the mouse embryo. Nischarin might act as a negative regulator of cell migration by inhibiting Rac function. Nischarin has a predicted molecular weight of 148 kDa (NiceProt:Q9EPW8), although we detect it at 215 kDa in SDS/PAGE. mAb 50 reacts with Nischarin in rat (routinely tested for each lot), human (tested in development only), and mouse (tested in development only) tissue.