Identification of Distinct Myocardin Splice Variants in the Bladder

Purpose: Although the importance of myocardin in smooth muscle development is well established, many tissue specific intricacies of smooth muscle differentiation remain to be determined. We characterized myocardin expression in the developing and adult bladder to identify potential tissue specific differences that may have a role in detrusor smooth muscle development. Materials and Methods: Reverse transcriptase and quantitative polymerase chain reaction were done to determine myocardin expression in the mouse and human bladder vs various other tissues. Sequence analysis was done to confirm the genomic location of the various polymerase chain reaction products. Results: Exonic profiling of the mouse myocardin gene identified a series of unique myocardin splice variants derived from a novel 305 bp exon between exons 2 and 3 of the previously identified myocardin gene. Each variant showed a differential pattern of expression in the mouse and primary protein sequences suggested a unique function for each myocardin variant identified. Identical myocardin splice variants were also observed in the human bladder as well as a unique human specific exon 12 myocardin splice variant that was not observed in the mouse. Conclusions: Identifying a series of unique myocardin splice variants that are differentially expressed in the bladder, and other muscle and nonmuscle tissues provides a potential molecular platform for mediating many unique tissue specific functions associated with the myocardin transcriptional program.