A glycine substitution in the collagenous domain of Col4a3 in mice recapitulates late onset Alport syndrome.
Matrix Biol Plus 2020;
9:100053. [PMID:
33718859 PMCID:
PMC7930875 DOI:
10.1016/j.mbplus.2020.100053]
[Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2020] [Revised: 11/18/2020] [Accepted: 11/20/2020] [Indexed: 12/13/2022] Open
Abstract
Alport syndrome (AS) is a severe inherited glomerulopathy caused by mutations in the genes encoding the α-chains of type-IV collagen, the most abundant component of the extracellular glomerular basement membrane (GBM). Currently most AS mouse models are knockout models for one of the collagen-IV genes. In contrast, about half of AS patients have missense mutations, with single aminoacid substitutions of glycine being the most common. The only mouse model for AS with a homozygous knockin missense mutation, Col4a3-p.Gly1332Glu, was partly described before by our group. Here, a detailed in-depth description of the same mouse is presented, along with another compound heterozygous mouse that carries the glycine substitution in trans with a knockout allele. Both mice recapitulate essential features of AS, including shorten lifespan by 30–35%, increased proteinuria, increased serum urea and creatinine, pathognomonic alternate GBM thinning and thickening, and podocyte foot process effacement. Notably, glomeruli and tubuli respond differently to mutant collagen-IV protomers, with reduced expression in tubules but apparently normal in glomeruli. However, equally important is the fact that in the glomeruli the mutant α3-chain as well as the normal α4/α5 chains seem to undergo a cleavage at, or near the point of the mutation, possibly by the metalloproteinase MMP-9, producing a 35 kDa C-terminal fragment. These mouse models represent a good tool for better understanding the spectrum of molecular mechanisms governing collagen-IV nephropathies and could be used for pre-clinical studies aimed at better treatments for AS.
Two mouse models were generated that recapitulate essential features of AS patients.
Glomeruli and tubuli respond differently to mutant collagen IV protomers.
The mutant colIV protomers in glomeruli probably undergo a cleavage process by MMP9.
The two AS mouse models represent a good tool for studying collagen-IV nephropathies.
These models could be used for pre-clinical studies aimed at better treatments.
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