Abstract: FR-PO718

ENU-Induced Point Mutation in the Laminin Alpha 5 L4a Domain Results in Nephrotic Syndrome

Session Information

Category: Glomerular

  • 1002 Glomerular: Basic/Experimental Pathology

Authors

  • Falcone, Sara, Medical Research Council, Didcot, OxfordShire, United Kingdom
  • Nicol, Thomas, Medical Research Council, Didcot, OxfordShire, United Kingdom
  • Miner, Jeffrey H., Washington University School of Medicine, St. Louis, Missouri, United States
  • Tam, Frederick W.K., Imperial College Kidney and Transplant Institute, London, United Kingdom
  • Potter, Paul K., Medical Research Council, Didcot, OxfordShire, United Kingdom
Background

Nephrotic syndrome (NS) is a heterogeneous group of disorders characterised by renal and extrarenal manifestations. Classic symptoms of NS include severe proteinuria and hypoalbuminemia, oedema and hyperlipidemia. Genetic studies of hereditary forms of NS have led to the identification of proteins playing a crucial role in slit diaphragm signalling, regulation of actin cytoskeleton dynamics and cell-matrix interactions. As part of the MRC Harwell ageing screen a missense mutation was identified in the gene Lama5 coding for the laminin alpha 5 chain, a major component of the renal extracellular matrix. Homozygous mice showed symptoms of NS including a severe proteinuria that preceded histological lesions and alteration of renal markers in plasma.

Methods

The Lama5E884G mouse line was derived from a G3 pedigree produced in the MRC Harwell N-ethyl-N-nitrosourea (ENU) mutagenesis screen. The mutation was identified by combining the use of a dense SNP panel and whole genome sequencing. Lama5E884G/+ mice were then backcrossed for a total of 10 generations to C57BL/6J mice. Urine and plasma were collected at different time points and markers of kidney function were measured. Kidneys were also collected for pathological assessment and study of the molecular mechanism. Concurrently, an in vitro study is ongoing to look at the expression and secretion of LAMA5 and its interaction with other laminin chains.

Results

Time course studies of Lama5E884G homozygotes showed high levels of proteinuria from 25 weeks of age but no other signs of kidney impairment. Affected mice also have significantly elevated cholesterol levels. The Lama5E884G/- compound heterozygote exhibited severe proteinuria, thus confirming the Lama5E884G mutation as the causative allele.
Alterations in the expression of genes and proteins associated with integrin signal-mediation show an abnormal response of the glomeruli that could possibly have an effect on the podocytes’ F-actin bundles. Preliminary in vitro results show an impaired secretion of the LAMA5 short arm.

Conclusion

We have identified a novel mutant mouse line exhibiting NS resulting from a point mutation in Lama5. This gene has recently been associated with renal disease in patients. We are currently dissecting the molecular pathogenesis of disease in these animals to provide insight into human disease.

Funding

  • Government Support - Non-U.S.