Molecular regulation of the calcitonin in receptor (CTR) gene in osteoclasts and CTR expressing tissues
Orasa Anusaksathien, Asst. Prof., D. of Conservative Dentistry, F. of Dentistry, PSU.
Grant : Harvard Medical School
Published : J Periodont 1999 : 105
Presented : Orban Competition American Academy of Periodontology Boston, 1998
Key words : murine, calcitonin receptor, osteoclasts
Osteoclasts (OC) mediate bone loss in periodontal disease and osteoporosis. To study OC regulation, we have focused our efforts on the calcitonin receptor (CTR) which is expressed on OC and inhibits OC-mediated bone resorption. Primer extension, 5' RACE and RT-PCR were used to characterize the genomic structure and identify the 5' regulatory regions of the murine CTR gene. Three putative promoters (P1-3) were identified. The P1 promoter, located upstream of exon 1, and the P2 promoter, located upstream of exon 2, are used in OC, brain and kidney. Of interest, the P3 promoter, located upstream of exon 3, appeared to be exclusively utilized in OC. The 5' regulatory region upstream of exon 2 contains no TATA or CCAAT box. It is highly GC rich with several potential bind-ing sites for transcription factors Sp1 and AP-1. The 5' flanking sequence upstream of exon 3 also contains no TATA motif. However, a CCAAT box and a weak initiation element (Inr) have been iden-tified at the assigned transcriptional start site. The promoter activity of P2 was tested by subcloning part of exon 2 and the adjacent upstream genomic DNA into pGL3 Basic luciferase vector in both forward and reverse orientations. Transient transfection in a CTR expressing mouse kidney cell line revealed 7-fold increase in the promoter activity compared to the non-insert pGL3 basic vector. These studies provide the first evidence that the CTR is regulated in a tissue specific manner by alternative promoter usage. Identification of molecular regulation of the CTR gene in OC could lead to novel approaches in treating periodontal and related bone disorders.
BACK