Abstract 013: The Molecular Program of Renin Null Cells

Abstract

Mice homozygous for the Ren1c gene disruption ( Ren1c -/- ) display structural and functional defects characterized by a poorly developed renal medulla, urine concentration failure, polydipsia, polyuria, hydronephrosis, renal failure and anemia. Underlying this complex phenotype, mice exhibit unique renal vascular abnormalities, including concentric arteriolar hypertrophy. Using lineage and promoter activity tracking, we showed that renin null cells contribute directly to blood vessel thickening and distribute throughout renal arterial trees. We hypothesize that renin null cells synthesize factors that lead to arterial thickening and maintain an active molecular memory of the renin phenotype. To test this hypothesis, we performed RNA-seq of YFP sorted single cells from kidneys of Ren1c -/- ; Ren1c -YFP (KO) and Ren1c +/+ ; Ren1c -YFP (wildtype, WT) adult mice. We captured individual cells using a microfluidic C1 system and sequenced cDNA from cellular mRNA. We also performed ATAC-seq of KO cells to identify open chromatin regions available for transcription factor binding. KO and WT cell populations were distinct, with the average Euclidean distance between genotypes 1.9x greater than within genotypes. Differential expression analysis revealed that KO cells upregulated 1395 genes and downregulated 364 compared to WT (log fold change > 1, p < 0.05). Among the upregulated genes were 107 potentially secreted proteins and 64 putative transcription factors. Secreted protein genes were enriched for GO terms such as angiogenesis and cell proliferation (p < 0.01), suggesting a possible cause of arteriolar abnormalities in KO kidneys. We identified several upregulated transcription factors, including Foxp1, Stat1, and KLF family genes, that had predicted binding motifs in open chromatin regions, such as upstream the Ren1 gene (p < 1.0E-10). These factors are key candidates for regulating the molecular memory of the renin cell. This study shows that over activation of the renin program due to lack of renin causes expression of a distinct suite of genes that may be responsible for vascular pathologies observed in KO mice. These data also provide insight into how the cell regulates the renin cell program in response to chronic stimuli that jeopardize homeostasis.