Alanine–glyoxylate aminotransferase-deficient mice, a model for primary hyperoxaluria that responds to adenoviral gene transfer

Abstract

Mutations in the alanine-glyoxylate amino transferase gene (AGXT) are responsible for primary hyperoxaluria type I, a rare disease characterized by excessive hepatic oxalate production that leads to renal failure. We generated a null mutant mouse by targeted mutagenesis of the homologous gene, Agxt, in embryonic stem cells. Mutant mice developed normally, and they exhibited hyperoxaluria and crystalluria. Approximately half of the male mice in mixed genetic background developed calcium oxalate urinary stones. Severe nephrocalcinosis and renal failure developed after enhancement of oxalate production by ethylene glycol administration. Hepatic expression of human AGT1, the protein encoded by AGXT, by adenoviral vector-mediated gene transfer in Agxt ؊/؊ mice normalized urinary oxalate excretion and prevented oxalate crystalluria. Subcellular fractionation and immunofluorescence studies revealed that, as in the human liver, the expressed wild-type human AGT1 was predominantly localized in mouse hepatocellular peroxisomes, whereas the most common mutant form of AGT1 (G170R) was localized predominantly in the mitochondria.gene therapy ͉ knockout mouse ͉ oxalate ͉ urolithiasis ͉ nephrocalcinosis

Enteric oxalate elimination is induced and oxalate is normalized in a mouse model of primary hyperoxaluria following intestinal colonization withOxalobacter

“…The hyperoxaluric phenotype reported (12,23) for Agxt mice was confirmed in the present study. Agxt mice of either sex in the pure C57BL/6 background do not form kidney stones, nor do they show any other pathology (23).…”

“…Male and female mice (25-30 g) were used in the following studies; they were given free access to a standard mouse chow (diet 2018S, Harlan Teklad) and drinking water before initiation of the colonization procedure. Several experimental series involved use of an AGT knockout mouse model on a C57BL/6 background strain (Agxt), as described by Salido et al (23), and another series included C57BL/6 [wild-type (WT)] mice as controls. At the time of the flux studies, the mice were euthanized by 100% CO 2 inhalation, and the entire large intestine, including the cecum, proximal colon, and distal colon, was removed.…”

“…Agxt mice of either sex in the pure C57BL/6 background do not form kidney stones, nor do they show any other pathology (23). Baseline urinary excretion values for oxalate, calcium, and creatinine compiled for the WT and Agxt mice used in different experimental series in this study are tabulated in Table 1.…”

Pharmacologic rescue of an enzyme-trafficking defect in primary hyperoxaluria 1

“…Briefly, the Prestwick library of FDA-approved compounds (∼2,000) at a concentration of ∼10 μM was screened against the yeast strain WT[Su9-URA3]. The strain was aliquotted into 384-well pates consisting of 24 columns followed by compound addition with robotic pinning into the assay wells (column [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] in minimal glucose media lacking uracil. For a negative control of cell growth, column 2 contained the WT[Su9-URA3] strain with 1% DMSO.…”

“…Current treatments for PH1 include pyridoxine supplementation and, later, liver or liver/kidney transplantation (10)(11)(12). However, the success has been limited (13); and the recommendation ultimately is an organ transplant, which has obvious complications.…”