Identification of testis-specific (Limk2t) and brain-specific (Limk2c) isoforms of mouse LIM-kinase 2 gene transcripts.

LIM-kinase 1 (LIMK1) and LIM-kinase 2 (LIMK2) are members of a novel serine/threonine kinase subfamily with structural features composed of N-terminal two LIM domains, an internal PDZ-like domain, and a C-terminal protein kinase domain. We recently identified and characterized the mouse Limk2 gene and two Limk2 transcripts (Limk2a and Limk2b) coding for proteins with distinct N-terminal LIM structures. Here we describe two additional transcripts of the mouse Limk2 gene. One is a 1.7-kb transcript, termed Limk2t, which is specifically expressed in the testis and codes for an N-terminally truncated form of LIMK2 consisting of only a part of a PDZ-like domain and a protein kinase domain. The other is a transcript, termed Limk2c, which is specifically expressed in the brain and codes for a protein with a 6-amino-acid insert within the protein kinase domain. Exons specific to the 5'-terminal extra sequence of Limk2t and the insert sequence of Limk2c locate between exons 5-6 and exons 8-9 in the mouse Limk2 gene, respectively. Testis- and brain-specific expression of Limk2t and Limk2c suggests specific roles in these tissues.