Gene structure and chromosomal mapping of the rat smooth muscle calponin gene

Smooth muscle cells (SMC) express a battery of lineage-restricted genes who se encoded proteins impart the unique contractile phenotype that characteri zes this muscle type. While the encoded function of many SMC-restricted gen es has been extensively analyzed, less is known about their position within the genome and the regulatory factors governing their transcription. In th is report, we define the gene structure, 5' promoter analysis, and chromoso mal mapping of the rat smooth muscle calponin (CnnI) gene. The rat CnnI gen e is comprised of seven exons spanning approximately 8 kb of genomic sequen ce. The intron-exon boundaries of the rat CnnI gene match precisely those i n human and mouse. Primer extension and RNase protection assays indicate tw o major transcription start positions (tsp). Comparative sequence analysis of the 5' promoter region reveals several conserved cis regulatory elements , including a TA-rich element within 30 nt of the tsp that could be a recog nition site for TATA-binding protein and two CCAAT boxes. Transient and sta ble transfection studies support the hypothesis that distal regulatory elem ents confer SMC-restricted expression of CnnI. Finally, using an F-2 interc ross, we have mapped the rat CnnI gene to the telomeric end of Chromosome ( Chr) 8. These studies provide additional information relating to the contro l of CnnI gene expression and provide a platform to begin assessing the pot ential linkage of CnnI to spontaneous and experimental disease phenotypes i n rats.