Renin, a key component in the regulation of blood pressure in mammals, is produced by the rare and highly specialized juxtaglomerular (JG) cells of the kidney. Although these cells line the media of the glomerular afferent arterioles and share some characteristics with contractile cells, they are filled with lysosome-like organelles where renin is activated and stored for regulated secretion in response to physiological and pathophysiological stimuli. Chronic stimulation of renin release results in a recruitment of new JG cells by the seeming conversion of adjacent smooth muscle cells along the afferent arterioles. Because JG cells rapidly de-differentiate when removed from the kidney, their developmental origin and the mechanism that explains their phenotypic plasticity remain largely unclear. In an effort to overcome this limitation, we have performed RNA expression analysis on four human renin-producing tumors. The most highly expressed genes that were common between the reninomas were subsequently used for in situ hybridization in mouse kidney. Our results add 40 new genes to the list that characterize renin-producing cells and reveal a significant variation in the expression patterns of developing, mature and recruited JG cells. Overall design: RNA-Seq was performed with a HiSeq 2000 on three biopsies of a first reninoma from Paris (Par1B1-B3), one biopsy from a reninoma from Montreal (Mon), two biopsies from a reninoma from Rotterdam (RotB1, B2), and a second reninoma from Paris (Par2) along with a biopsy from adjacent supposedly normal tissue from the same patient (Par2N).