May associate with CadN and participate in the transmission of developmental information. Can associate with alpha-catenin. Accumulates through wg signaling; arm function in wg signal transduction is required early in development for determination of neuroblast fate. Arm and Abl proteins function cooperatively at adherens junctions in both the CNS and epidermis (By similarity). Interacts with Mer and Moe at the adherens junction. Inner surface of cell membrane and adherens junction. Phosphorylated on Ser, Thr and Tyr residues. Level of phosphorylation varies both during embryonic development and from embryonic tissue to tissue. Sgg is required for phosphorylation and wg signal negatively regulates arm phosphorylation. Hypophosphorylated form of arm increases in steady-state levels (By similarity). Development of anterior structures in the posterior part of the segment. Belongs to the beta-catenin family.