Foxd1 is an upstream regulator of the renin-angiotensin system during metanephric kidney development

BACKGROUND: We tested the hypothesis that Foxd1, a transcription factor essential for normal kidney development, is an upstream regulator of the renin-angiotensin system (RAS) during ureteric bud (UB)-branching morphogenesis. METHODS: UB branching, RAS gene, and protein expression were studied in embryonic mouse kidneys. RAS mRNA expression was studied in mesenchymal MK4 cells. RESULTS: The number of UB tips was reduced in Foxd1(-/-) compared with that in Foxd1(+/+) metanephroi on embryonic day E12.5 (14 +/- 2.1 vs. 28 +/- 1.3, P < 0.05). Quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) demonstrated that renin, angiotensin I-converting enzyme (ACE), and angiotensin (Ang) II receptor type 1 (AT(1)R) mRNA levels were decreased in Foxd1(-/-) compared with those in Foxd1(+/+) (E)14.5 metanephroi. Western blot analysis and immunohistochemistry showed decreased expression of AGT and renin proteins in Foxd1(-/-) metanephroi compared with that in Foxd1(+/+) metanephroi. Foxd1 overexpression in mesenchymal MK4 cells in vitro increased renin, AGT, ACE, and AT1R mRNA levels. Exogenous Ang II stimulated UB branching equally in whole intact E12.5 Foxd1(-/-) and Foxd1(+/+) metanephroi grown ex vivo (+ 364 +/- 21% vs. + 336 +/- 18%, P = 0.42). CONCLUSION: We conclude that Foxd1 is an upstream positive regulator of RAS during early metanephric development and propose that the cross-talk between Foxd1 and RAS is essential in UB-branching morphogenesis.