Figure 2

Figure 2. osr1 is required to maintain and promote kidney development at the expense of hemangioblasts. (A) Although pax2a is restricted in 15 ss mutants, at 7 ss, ocn−/− embryos had a pax2a domain that appeared to occupy the same domain as WT siblings. Similarly, the hemangioblast marker tal1 appeared mostly WT in ocn−/− at 7 ss. Scale bar is 50 μm (B) FISH with probes for pax2a (green) and tal1 (red) and ICC using anti-caspase-3 (white) to mark apoptotic cells was conducted at 7 ss and 15 ss. The number of fragments in the combined pax2a and tal1 fields from somites 1–5 were increased in mutants at 7 ss but not at 15 ss. Scale bar is 35 μm (C–E) At 10 ss, little to no caspase-3 fragments were seen in pax2a or tal1 domains from somites 1–5, but a significant number were seen in osr1 morphants and ocn−/−. The tal1 domain was also expanded in both loss-of-function models. Scale bar is 35 μm. (F,G) ICC with the proliferative cell marker anti-pH3 was also conducted. Despite the expansion in tal1 in osr1-deficient models, there was no significant change in the number of proliferating cells. Scale bar is 10 μm. (H,I) FISH experiments were conducted to assess changes in apoptosis in wt1a+/pax2a+ podocyte progenitors. There was a significant increase in the number of apoptotic fragments within this field in mutants compared with WT siblings. Scale bar is 10 μm. A minimum of three individuals were assessed for each group across experiments. Photos are max intensity projections from z-stacks, and each side of mesoderm was quantified individually. p-values: ** p < 0.001, N.S. = not significant.