Introduction: The Renin-Angiotensin-System is essential to maintain blood pressure and fluid electrolyte homeostasis. Because precise regulation of expression and release of renin is critical for survival, understanding the molecular regulation of the renin cell identity is a vital area of study. Advances in epigenetics have enabled finer dissection of chromatin factors which maintain the identity of the renin cell. By studying genes with heightened accessibility profiles that are unique to the JG cell, we now have the capacity to unravel the determinants of the renin cell identity. Hypothesis: That transcription factors central to the governance of renin cell identity can be identified through the Assay for Transposase Accessible Chromatin (ATAC-seq) differential accessibility analysis. Methods: Native renin cell ATAC-seq was compared to existing ENCODE ATAC-seq datasets from 40 other cell types to define regions/peaks which characterize the JG program. Peaks with high intensity and ≥2-fold increase in signal were selected for Motif analysis to search for transcription factors (TFs) whose consensus sequence is enriched in those regions. Identified TFs were then selected for validation by in-situ hybridization and conditional deletion in renin cells. Results: 1) The Mef2c transcription factor was identified as having a consensus sequence in regulatory regions unique to the JG cell. It has clear expression in RNA-seq of renin cells (65 transcripts per million, n=3) and a predicted binding site in the renin gene. These results were validated by in-situ hybridization where signal localized at the JG area was detected in concordance with our in-silico results. 2) We generated Mef2c conditional knockout animals using our Ren1d-Cre mouse to study the effect in renin expression and identity. These mice displayed reduced renin immunostaining at the JG area and a 40% reduction in renin mRNA expression by qPCR from kidney cortices relative to wild-type (n=2, preliminary data). Conclusions: Our studies identified Mef2c as a TF target which likely has an essential role in maintaining and preserving renin cell identity. Experiments involving transcriptomics and epigenomics are ongoing to understand the changes wrought by Mef2c deletion in renin cells.