Mice deficient in α-actinin-4 have severe glomerular disease
Claudine H. Kos, … , Robert E. Gerszten, Martin R. Pollak
Claudine H. Kos, … , Robert E. Gerszten, Martin R. Pollak
Published June 1, 2003
Citation Information: J Clin Invest. 2003;111(11):1683-1690. https://doi.org/10.1172/JCI17988.
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Mice deficient in α-actinin-4 have severe glomerular disease

Abstract

Dominantly inherited mutations in ACTN4, which encodes α-actinin-4, cause a form of human focal and segmental glomerulosclerosis (FSGS). By homologous recombination in ES cells, we developed a mouse model deficient in Actn4. Mice homozygous for the targeted allele have no detectable α-actinin-4 protein expression. The number of homozygous mice observed was lower than expected under mendelian inheritance. Surviving mice homozygous for the targeted allele show progressive proteinuria, glomerular disease, and typically death by several months of age. Light microscopic analysis shows extensive glomerular disease and proteinaceous casts. Electron microscopic examination shows focal areas of podocyte foot-process effacement in young mice, and diffuse effacement and globally disrupted podocyte morphology in older mice. Despite the widespread distribution of α-actinin-4, histologic examination of mice showed abnormalities only in the kidneys. In contrast to the dominantly inherited human form of ACTN4-associated FSGS, here we show that the absence of α-actinin-4 causes a recessive form of disease in mice. Cell motility, as measured by lymphocyte chemotaxis assays, was increased in the absence of α-actinin-4. We conclude that α-actinin-4 is required for normal glomerular function. We further conclude that the nonsarcomeric forms of α-actinin (α-actinin-1 and α-actinin-4) are not functionally redundant. In addition, these genetic studies demonstrate that the nonsarcomeric α-actinin-4 is involved in the regulation of cell movement.

Authors

Claudine H. Kos, Tu Cam Le, Sumita Sinha, Joel M. Henderson, Sung Han Kim, Hikaru Sugimoto, Raghu Kalluri, Robert E. Gerszten, Martin R. Pollak

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Figure 2

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(a) Targeting construct. The construct used was originally designed for ...
(a) Targeting construct. The construct used was originally designed for the development of a knock-in model. A neomycin resistance cassette is 438 bp from the 3′ end of exon (Ex) 8 of Actn4. (b) Genotyping assay. A PCR fragment amplified from wild-type genomic DNA does not digest with EarI. The targeted allele has an EarI site, allowing simple genotyping. The two left-hand lanes show this assay in two wild-type mice; the middle five lanes show amplification and digestion products of heterozygous mice. The final lane is derived from a mouse homozygous for the targeted allele. (c) Northern blot analysis of Actn4 expression in mice homozygous for the wild-type allele (+/+) and for the targeted allele (–/–). Rehybridization of membrane with β-actin as a control for RNA loading is shown below. (d) Western blot of kidney lysates using anti–α-actinin-4 antibody. The same pattern was seen with lung, liver, brain, and spleen. No difference was seen in the expression of α-actinin-1 (not shown).