Abstract 133: Transcription Factor Early Growth Response 1 Promotes T-Type Calcium Channel Cav3.2 in Response to Hypertrophic Stimulation Through Evolutionary Conserved Promoter
Introduction: Although it is known that the Cav3.2 T-type calcium channel is predominantly expressed in the embryonic stage and re-expressed in adult hearts during the cardiac hypertrophy. What does regulate the reexpression of Cav3.2 in hearts?
Hypothesis: Because the mRNA re-expression is mainly through the transcriptional regulation in the promoter or enhancer conserved in different species, we assessed to the hypothesis that the evolutionary conserved promoter (ECP) of Cav3.2 carries important binding sites for transcription factors that regulate its re-expression in the hypertrophic hearts.
Methods and Results: In this study, the ECP is gotten by aligning Cav3.2 genes from different species. By fusing mouse ECP with the reporter gene firefly luciferase, we showed that the ECP drove high luciferase activity in the cells expressing endogenous Cav3.2 but not in the one without Cav3.2. To further validate ECP in vivo, Cav3.2 reporter mice were generated by fusing the Cav3.2 promoter with the reporter gene luciferase. ECP confers the reporter expressing as the endogenous Cav3.2 in the tissue distribution, development of hearts, and most importantly, the inducibility of hypertrophic stimuli. By injecting reporters driven by different truncated promoters followed with the trans-aortic banding (TAB) surgery, the hypertrophic regulatory elements are identified_ -41 to -81 relative to the transcription start site (TSS) of Cav3.2. At the end, we found the early growth response 1 (Egr1) is the important transcription factor to enhance Cav3.2 gene expression. Our EMSA data suggested that Egr1 can bind to three regions of the hypertrophic regulatory elements.
Conclusion: In conclusion, transcription factor early growth response 1 (Egr1) regulates the reexpression of Cav3.2 T-type Calcium Channel in the cardiac hypertrophy.
- © 2012 by American Heart Association, Inc.