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Transgenic Res. 2010 Apr;19(2):285-9. doi: 10.1007/s11248-009-9305-9. Epub 2009 Jul 8.

Mice with podocyte-specific overexpression of wild type alpha-actinin-4 are healthy controls for K256E-alpha-actinin-4 mutant transgenic mice.

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  • 1Kidney Research Centre, Division of Nephrology, Department of Medicine, Ottawa Health Research Institute, Ottawa Hospital and University of Ottawa, Ottawa, ON K1H 8M5, Canada.


Mutations in the gene ACTN4 encoding the actin bundling protein-alpha-actinin-4 underlie an inherited form of kidney lesions known as focal segmental glomerulosclerosis (FSGS). Previously, we developed a model for this condition by generating mice with podocyte-specific overexpression of a disease-causing mutant alpha-actinin-4 (K256E-ACTN4 (pod+)). However, whether alpha-actinin-4 overexpression artifacts and not the gain of affinity effects of the mutation accounted for the robust FSGS phenotype in these mice was unclear. To address this question, we developed a control line of mice with podocyte-specific overexpression of wildtype alpha-actinin-4 (wt-ACTN4 (pod+)). An 8.3 kb fragment of the mouse nephrin promoter (NPHS1) was used to drive expression of a hemagglutinin (HA)-tagged wildtype alpha-actinin-4 coding sequence in mice. Five founder lines expressing the HA-tagged alpha-actinin-4 protein in a podocyte-specific manner were obtained, as determined by co-immunofluorescence with HA and synaptopodin antibodies. Quantitative PCR revealed that renal transgene mRNA levels of wt-ACTN4 (pod+) mice are similar to K256E-ACTN4 (pod+) mice. In contrast to K256E-ACTN4 (pod+) mice which exhibit albuminuria, podocyte foot process effacement and glomerular scarring, wt-ACTN4 (pod+) mice are healthy and indistinguishable from non-transgenic littermates. These findings suggest that the K256E mutation itself and not overexpression of alpha-actinin-4 protein per se accounts for the FSGS phenotype in our transgenic model.

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