Dr Justin Chan Hsian Loon1
1Jiang Group, John Curtin School Of Medical Research, Australian National University, Acton, Australia
Biography:
Justin Chan is a nephrologist working in Canberra, and is currently undertaking a PhD at the John Curtin School of Medical Research at the ANU, studying the contributions of RelB variants to the mechanism of glomerulonephritis
Background:
Fibrosis affecting renal glomeruli and tubular structures results in the loss of glomerular filtration function and subsequent end stage renal disease (ESRD). Profibrotic processes in kidneys are mediated by abnormalities in TGF-β signalling pathways. Mutations in RelB, a component of the non-canonical NF-kB signalling pathway, can result in multiorgan autoimmunity with kidney sparing. RelB acts as a negative regulator in the TGF-β pathway. We identify a RelB variant affecting the TGF-β signalling pathway resulting in advanced glomerulosclerosis by 6-10 weeks in mice.
Aim:
To study the mechanism which RelB variants contribute to renal fibrosis.
Methods:
RelBtrunc mice were generated using CRISP/Cas9 resulting in a truncation in the dimerisation domain. Bone marrow chimeric mice models were used to assess if RelBtrunc drives kidney fibrosis in a cell or kidney intrinsic manner. Organs were harvested for histopathological analysis and spleen for immunophenotyping with flow cytometry. To assess the effect of RelBtrunc on TGF-B signalling, HEK293 cells were transfected with a TGF-B luciferase reporter, plasmid construct combinations with different concentrations of RelB wild type (WT) , RelB trunc, SMAD2, SMAD3, and SMAD4 DNA.
Results:
Splenic immunophenotype displayed increased activated T cells, marked B cell depletion, increased neutrophils, and globally sclerosed kidneys by 6 weeks. T and myeloid cell abnormalities and kidney fibrosis were absent in all chimeric mice, suggesting that that RelBtrunc abnormality is kidney intrinsic rather than cell intrinsic. Unlike RelB WT, RelBtrunc was not able to repress TGF-B expression when coexpressed with SMAD2/3/4.
Conclusion:
We identified a novel process where RelB variants can cause renal fibrosis in a kidney intrinsic manner, likely driven by RelB variant which drives excess profibrotic TGF-B expression.