Proteins containing LIM motifs are typically involved in cell fate determination and growth control. A family of proteins designated LIM kinases, incuding LIMK-1 and LIMK-2, has been identified. LIMK-1 has been shown to regulate the stabilization of F-Actin structures and Cofilin activity, indicating that LIMK-1 plays a role in a signaling pathway involved in the regulation of cell motility and morpho-genesis. LIMK-1 inhibits neuronal differentiation of PC12 cells, and it is thought to act by interfering with events downstream of MAPK activation. Expression patterns of LIMK-1 and LIMK-2 suggest that these proteins may have different functions during development. A truncated form of LIMK-2 has been identified in adult testis that is thought to arise from an alternative initiation exon.