A mouse Col4a4 mutation causing Alport glomerulosclerosis with abnormal collagen α3α4α5(IV) trimers.

Area of Science:

• Nephrology
• Genetics
• Molecular Biology

Background:

• Alport syndrome is a hereditary kidney disease caused by mutations in collagen IV genes.
• A spontaneous mutation, bilateral wasting kidneys (bwk), was identified in mice, presenting with early-onset kidney damage.
• The mutation is located near the Col4a3 and Col4a4 genes, homologous to human Alport syndrome genes.

Purpose of the Study:

• To characterize the novel bwk mouse model of Alport syndrome.
• To investigate the genetic basis and phenotypic consequences of the Col4a4 mutation.
• To evaluate the utility of this model for Alport syndrome research and therapy development.

Main Methods:

• Genetic mapping and DNA sequencing to identify the mutation.
• Protein analysis to assess collagen IV trimer assembly and localization.
• Phenotypic analysis of kidney damage and albuminuria in different mouse genetic backgrounds.

Main Results:

• A G-to-A splice donor mutation in Col4a4 intron 30 causes exon 30 skipping.
• Mutant collagen α3α4α5(IV) is secreted and incorporated into the glomerular basement membrane at low levels, leading to Alport-like lesions.
• Modifier genes influence the severity and progression of kidney damage in the bwk model.

Conclusions:

• The bwk mouse is a unique model of Alport syndrome, accumulating abnormal collagen IV in the GBM, similar to some patients.
• This model provides a valuable platform for studying collagen IV assembly, Alport syndrome pathogenesis, and therapeutic interventions.
• Genetic background significantly impacts the phenotype, highlighting the role of modifier genes in Alport syndrome variability.