HNF1B controls proximal-intermediate nephron segment identity in vertebrates by regulating Notch signalling components and Irx1/2

Abstract

SUMMARYThe nephron is a highly specialised segmented structure that provides essential filtration and resorption renal functions. It arises by formation of a polarised renal vesicle that differentiates into a comma-shaped body and then a regionalised S-shaped body (SSB), with the main prospective segments mapped to discrete domains. The regulatory circuits involved in initial nephron patterning are poorly understood. We report here that HNF1B, a transcription factor known to be involved in ureteric bud branching and initiation of nephrogenesis, has an additional role in segment fate acquisition. Hnf1b conditional inactivation in murine nephron progenitors results in rudimentary nephrons comprising a glomerulus connected to the collecting system by a short tubule displaying distal fates. Renal vesicles develop and polarise normally but fail to progress to correctly patterned SSBs. Major defects are evident at late SSBs, with altered morphology, reduction of a proximo-medial subdomain and increased apoptosis. This is preceded by strong downregulation of the Notch pathway components Lfng, Dll1 and Jag1 and the Irx1/2 factors, which are potential regulators of proximal and Henle's loop segment fates. Moreover, HNF1B is recruited to the regulatory sequences of most of these genes. Overexpression of a HNF1B dominant-negative construct in Xenopus embryos causes downregulation specifically of proximal and intermediate pronephric segment markers. These results show that HNF1B is required for the acquisition of a proximo-intermediate segment fate in vertebrates, thus uncovering a previously unappreciated function of a novel SSB subcompartment in global nephron segmentation and further differentiation.

Hepatocyte nuclear factor 1β controls nephron tubular development

“…Interestingly, the inactivation of Hnf1b in nephron progenitors using a Wnt4-Cre line and another Hnf1b floxed allele gave rise to the same phenotype. This confirms the crucial role of HNF1b in nephron tubular specification (Heliot et al, 2013). …”

Hnf1b controls pancreas morphogenesis and the generation of Ngn3+ endocrine progenitors

“…A direct regulation of Dll1 by Hnf1b, as recently shown in the kidney (Heliot et al, 2013;Massa et al, 2013), does not seem to occur in the pancreas, as ChIP on E12.5 pancreata showed no Hnf1b recruitment to a conserved region of Dll1 (data not shown). Recent data suggested a role for Dll1, which is activated by Ptf1a, in MPC proliferation (Ahnfelt-Ronne et al, 2012).…”

“…We performed a conditional deletion of Hnf1b in pancreatic MPCs using a Hnf1b-floxed mouse line (Heliot et al, 2013) crossed with the Pdx1-Cre (Wells et al, 2007) or the tamoxifen (TM)-inducible Sox9-CreER T2 line (Kopp et al, 2011), as Pdx1 and Sox9 share a common expression domain with Hnf1b in the early pancreas Maestro et al, 2003;Seymour et al, 2007). Pdx1-Cre;Hnf1b +/LacZ and Hnf1b Flox/Flox mice were crossed to generate Pdx1-Cre;Hnf1b…”

“…Flox/Flox ) carrying LoxP sites flanking exon 4 (Heliot et al, 2013), Pdx1-Cre (Wells et al, 2007) and Sox9-CreER T2 (Kopp et al, 2011) lines have been previously described. The R26R YFP line (B6.129X1-Gt (ROSA)26Sortm1(EYFP)Cos/J) was from The Jackson Laboratory.…”

The Integrin β1 Subunit Regulates Paracellular Permeability of Kidney Proximal Tubule Cells

“…There is evidence that certain transcription factors such as Hnf1b are critical for nephron patterning, and Hnf1b-null mice do not develop a differentiated tubule (36,37). Notch signaling is also required for proximal tubule differentiation, and mice with deficiencies in this pathway have abnormal tubule differentiation (38 -44).…”