Comparative Studies of Renin-Null Zebrafish and Mice Provide New Functional Insights.

Background: The renin-angiotensin system is highly conserved across vertebrates, including zebrafish, which possess orthologous genes coding for renin-angiotensin system proteins, and specialized mural cells of the kidney arterioles, capable of synthesising and secreting renin.

Methods: We generated zebrafish with CRISPR-Cas9-targeted knockout of renin () to investigate renin function in a low blood pressure environment. We used single-cell (10×) RNA sequencing analysis to compare the transcriptome profiles of renin lineage cells from mesonephric kidneys of with zebrafish and with the metanephric kidneys of and mice.

Results: The larvae exhibited delays in larval growth, glomerular fusion and appearance of a swim bladder, but were viable and withstood low salinity during early larval stages. Optogenetic ablation of renin-expressing cells, located at the anterior mesenteric artery of 3-day-old larvae, caused a loss of tone, due to diminished contractility. The mesonephric kidney exhibited vacuolated cells in the proximal tubule, which were also observed in mouse kidney. Fluorescent reporters for renin and smooth muscle actin ()), revealed a dramatic recruitment of renin lineage cells along the renal vasculature of adult fish, suggesting a continued requirement for renin, in the absence of detectable angiotensin metabolites, as seen in the YFP mouse. Both phenotypes were rescued by alleles lacking the potential for glycosylation at exon 2, suggesting that glycosylation is not essential for normal physiological function.

Conclusions: Phenotypic similarities and transcriptional variations between mouse and zebrafish renin knockouts suggests evolution of renin cell function with terrestrial survival.