CR16 is a 483 amino acid proline-rich cytoplasmic protein that is thought to regulate cytoskeletal organization. A member of both the verprolin and Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP) families, CR16 colocalizes with N-WASP (Neuronal Wiskott-Aldrich syndrome protein) in tips of growth cone filopodia, primary hippocampal neurons and Sertoli cell-spermatid junctions. CR16 and N-WASP functionally interact to influence spermatogenesis. CR16 is predominantly expressed in brain and testis, contains one WH2 domain, a KLKR motif, three profilin-binding motifs and is encoded by a gene that maps to human chromosome 7p15.1.