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Abstract: FR-PO379

Indian Hedgehog Signalling in Kidney Development

Session Information

Category: Development‚ Stem Cells‚ and Regenerative Medicine

  • 500 Development‚ Stem Cells‚ and Regenerative Medicine

Authors

  • Russell, Lauren G., University College London Institute of Child Health, London, London, United Kingdom
  • Rowan, Christopher, SickKids Research Institute, Toronto, Ontario, Canada
  • Rosenblum, Norman D., SickKids Research Institute, Toronto, Ontario, Canada
  • Winyard, Paul, University College London Institute of Child Health, London, London, United Kingdom
  • Long, David A., University College London Institute of Child Health, London, London, United Kingdom
Background

Hedgehog (Hh) signalling is critical in the development of the kidney, with genetic alterations of Hh pathway components leading to defects in nephron formation. Indian hedgehog (Ihh) is one of three ligands that activate the Hh pathway, however the cellular sources and functional role of Ihh in kidney development is not well understood.

Methods

We utilised a novel 3D imaging technique, combining wholemount fluorescence in situ hybridisation, immunolabelling and optical clearing to visualise Ihh mRNA localisation in 3D in the developing mouse embryonic kidney at cellular resolution. Furthermore, we have utilised a total Ihh knockout mouse model and Cre recombinase-based techniques to conditionally delete Ihh in the intermediate mesoderm, using the inducible Osr1-CreERT2, to begin to interrogate the functional role of Ihh in the developing kidney.

Results

Ihh mRNA was detected in the developing mouse kidney from embryonic day (E)16.5; during the maturation of tubules and glomeruli and maintained at E18.5 and the first day postnatally. Double labelling with Lotus tetragonolobus lectin revealed that Ihh primarily localised to the proximal tubule. As Ihh is detected as the mature nephron is developing, we hypothesise that Ihh will be important in nephrogenic development. We observed that Ihh-/- kidneys are smaller at E16.5 with some observed displaying highly disorganised, abnormal morphology. Additionally, Ihh-/- kidneys have a significantly reduced total glomerular number (p=0.0297) and a reduction in SIX2+ nephron precursor cells in around 40% of Ihh-/- kidneys compared with wild-type littermates, overall suggesting defects in kidney development in Ihh-/- mice. Conditional deletion of Ihh in the Osr1+ intermediate mesoderm, results in a significantly decreased kidney/ bodyweight ratio at E18.5 (p=0.0089), providing initial evidence of an importance for Ihh in intermediate mesoderm derived cells in the development of the kidney.

Conclusion

In summary, using a novel imaging technique we identified the onset of Ihh expression in maturing proximal tubules of the mouse embryonic kidney. Further, we observed defects in the development of Ihh total knockout kidneys and initial data indicates a function for Ihh in intermediate mesoderm derived cells.