Kidney Week

Abstract: SA-PO540

Stromal Progenitor-Derived Netrin-1 Signals Are Required for Proper Kidney Development

Session Information

• Developmental Biology
  November 04, 2017 | Location: Hall H, Morial Convention Center
  Abstract Time: 10:00 AM - 10:00 AM

Category: Developmental Biology and Inherited Kidney Diseases

• 401 Developmental Biology

Authors

• O'Brien, Lori L., University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States

Lori L. O'Brien,

• Hardesty, Deanna Marie, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States

Deanna Marie Hardesty,

• Cooper, Shamus Luke, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States

Shamus Luke Cooper,

Background

Kidney morphogenesis is driven by reciprocal signaling between progenitor populations. However, novel signaling pathways may remain unknown. We recently uncovered targets of Six2/SIX2 in the nephron progenitors of mouse and human kidneys through a combination of ChIP-seq and RNA-seq. We analyzed these lists to identify novel signaling pathways acting in the developing kidney.

Methods

We identified Unc5C/UNC5C as a common target expressed within nephron progenitors. Unc5c is a receptor for the ligand Netrin-1 (Ntn1) which has roles in axon guidance as well as vascular, lung, and mammary gland development. In situ analyses show that Ntn1 expression is restricted to the stromal progenitors. Other receptors for Ntn1 such as Unc5b are expressed in the vascular endothelium and medullary collecting ducts. Therefore, we focused on assessing the knockout phenotype of their common ligand Ntn1. We utilized the Foxd1^GC line to conditionally ablate Ntn1 in the stromal progenitors.

Results

Ntn1 mutant kidneys are hypoplastic. At E15.5, immunostaining for Six2, cytokeratin, and Wt1 reveals relatively normal nephron progenitor and ureteric tree organization with developing nephrons and glomeruli present despite kidneys being smaller. Since Ntn1 has roles in vascular development and axon guidance, we also stained kidneys for CD31 (endothelium) and Tuj1 (neuron). Mutant kidneys often had additional endothelial and neuronal projections extending over the outer cortex. Subsets of P0 mutant collecting ducts showed extensive dilation. Numbers of each genotype were assessed at P14 and indicate that most conditional Ntn1 mutants die postnatally.

Conclusion

We have identified a novel signaling pathway acting in the embryonic kidney. Stromal progenitor-derived Ntn1 may play several roles including regulating the nephron progenitor population through Unc5c as well as guiding vascular and neuronal cell networks. Current studies are underway to assess cell and tip numbers, proliferation, and any consequences to ureteric, vascular, and neuronal networks. Additionally, we are analyzing Unc5c mutant kidneys. Our studies will help shed light onto new signaling pathways controlling mammalian kidney development and may have implications on vascularization and innervation of the kidney where much less in known about their development and regulation during morphogenesis.