Mice with altered alpha-actinin-4 expression have distinct morphologic patterns of glomerular disease

Area of Science:

• Nephrology
• Genetics
• Molecular Biology

Background:

• Familial focal segmental glomerulosclerosis (FSGS) is a severe kidney disease.
• Mutations in ACTN4, encoding alpha-actinin-4, are a known cause of hereditary FSGS.
• Alpha-actinin-4 is a crucial actin-binding protein in podocytes.

Purpose of the Study:

• To investigate the impact of distinct ACTN4 alterations on kidney morphology and function.
• To establish and characterize mouse models mimicking human ACTN4-related kidney disease.
• To elucidate the relationship between ACTN4 genotype and glomerular lesion spectrum.

Main Methods:

• Development of two transgenic mouse strains: one with a human disease-associated ACTN4 mutation, and one ACTN4 knockout.
• Phenotypic analysis of homozygous and heterozygous mutant and knockout mice.
• Histopathological examination and ultrastructural analysis of kidney tissues.

Main Results:

• Most adult homozygous Actn4 mutant and knockout mice developed collapsing glomerulopathy.
• Homozygous mutant mice showed distinct cytoplasmic inclusions containing actin and alpha-actinin-4.
• Heterozygous mutant mice exhibited glomerular hypertrophy and mild ultrastructural changes, suggesting susceptibility to injury.

Conclusions:

• Different genetic defects in ACTN4 result in a spectrum of glomerular lesions.
• Altered alpha-actinin-4 expression levels and mutations can lead to progressive kidney disease.
• Even subtle glomerular damage in heterozygous models may predispose to further kidney injury.