Fig 1: Immunostaining of putative stem cell markers.(a–j) Representative immunostaining of SIX2, NCAM1, FZD7, ACVR2B and NTRK2 in paraffin embedded sections of HFK (12, 13 and 18 weeks of human gestation); (a–b) localization of SIX2 to the MM, predominantly to the CM. (c–d) predominant staining of NCAM1 in the MM (including CM) and its derivatives (S- and comma- shaped bodies) and renal stroma, but not mature tubules or UBs. (e–f) FZD7 demonstrates preferential localization to the nephrogenic zone including MM and its derivatives, UBs, and newly forming tubules but not the stroma. (g–h) ACVRIIB immunostaining demonstrates predominant expression in the nephrogenic cortex; MM and its derivatives (S and comma shaped bodies), UBs, parietal epithelium of fetal glomeruli but not in the stroma. (i–j) NTRK2 is detected in the MM (including condensates) and its derivatives, UBs and some differentiated tubules. Figures c, e and g are shown in low magnification (original×4), Figures a, b, d, f and h–j are shown in higher magnifications (original×40; I, original×20).