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 Ca v 3.2 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 Ca v 3.2 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 Ca v 3.2 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 Ca v 3.2 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 Ca v 3.2 but not in the one without Ca v 3.2. To further validate ECP in vivo, Ca v 3.2 reporter mice were generated by fusing the Ca v 3.2 promoter with the reporter gene luciferase. ECP confers the reporter expressing as the endogenous Ca v 3.2 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 Ca v 3.2. At the end, we found the early growth response 1 (Egr1) is the important transcription factor to enhance Ca v 3.2 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 Ca v 3.2 T-type Calcium Channel in the cardiac hypertrophy.