May function as a scaffold on which the coordinated assembly of proteins can occur. May play a role as an adapter that, via its PDZ domain, localizes LIM-binding proteins to actin filaments of both skeletal muscle and nonmuscle tissues. Involved in both of the two fundamental mechanisms of bone formation, direct bone formation (e.g. embryonic flat bones mandible and cranium), and endochondral bone formation (e.g. embryonic long bone development). Plays a role during fracture repair. Involved in BMP6 signaling pathway (By similarity). Binds via its LIM zinc-binding 3 domain (LIM 3) to endocytic codes of INSR, but not with those of IGF1R, LDLR, TFRC, or EGFR. Interacts with various PKC isoforms through the LIM zinc-binding domains. Binds to RET in a phosphorylation-independent manner via its LIM zinc-binding domain 2 (LIM 2). Probably part of a complex with SHC and the RET dimer. Interacts with TPM2. Interacts with TBX4 and TBX5 (By similarity). Colocalizes with RET to the cell periphery and in some cytoskeletal components. Colocalizes with TPM2 near the Z line in muscle. Colocalizes with TBX4 and TBX5 to actin filaments (By similarity). Isoform 1 and isoform 2 are expressed ubiquitously, however, isoform 2 predominates in skeletal muscle, isoform 1 is more abundant in lung, spleen, leukocytes and fetal liver. The LIM zinc-binding 2 (LIM 2) domain interacts with TBX4. The LIM zinc-binding 3 (LIM 3) domain provides the structural basis for recognition of tyrosine-containing tight turn structures. This domain is necessary and sufficient for interaction with TBX5 (By similarity). Anchored to cell periphery via its N-terminal PDZ domain. Did not induce bone induction. Same activity as isoform 1 in bone nodule induction. May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay.