Phenotypic Differences Between Tissues and Sex Observed in Mice with Human Gout Causing ABCG2 Variant

Hyperuricemia is a risk factor for gout and other complex human disorders. We have established in humans that ABCG2 codes a high‐capacity uric acid (UA) efflux transporter, that when dysfunctional causes hyperuricemia and significantly increases the risk for gout. Recent work has demonstrated ABCG2 mediated secretion is important for intestinal excretion of UA, so to better understand the intestinal contribution of ABCG2 dysfunction to hyperuricemia and gout, we created a new model where a Q140K (human Q141K) point mutation in the Abcg2 gene was made using CRISPR Cas9 gene editing techniques on a C57BL/6 mouse background. We employed both western blot and confocal microscopy to generate profiles of ABCG2 in both sexes and multiple tissues and assessed the differences of luminal UA excretion using mouse intestinal closed loop method. We observed in the wild type mice ABCG2 expression varies along the GI tract with the highest levels in the jejunum and ileum, and with low levels in the colon of both male and female mice. The localization of the wild type ABCG2 protein was exclusive to the brush border of villus cells and luminal membrane of the crypt cells. In contrast, one or two copies of the Q140K Abcg2 allele resulted in significant decreases (53% and 88% respectively) in total intestinal ABCG2 expression and apical membrane staining in villus cells. In female mice, the Q140K ABCG2 mutation resulted in little difference of ABCG2 expression, similar to the mostly unaltered expression of ABCG2 in the renal cortex of both male and female Q140K ABCG2 mice. Concomitant with the protein abundance defect, Q140K ABCG2 male mice had higher serum UA (3.31 ± 0.37 mg/dl) than WT mice (2.13 ± 0.14 mg/dl) and significantly reduced (−40%) acute UA flux in an intestinal loop assay. The reduction in the UA flux in the Q140K loop model was comparable to the reduction observed when the WT intestinal loop was treated with the ABCG2 inhibitor FTC (30%), suggesting the Q140K mutation approximates a complete loss of ABCG2 function in the small intestines. The sex dependence of the pathology of the Q140K mutation suggested that ABCG2 and UA secretion could be under hormonal control. In intestinal loop experiments we found FBS and more specifically angiotensin II modulated UA secretion. We conclude that (i) The Q141K ABCG2 mutation (Q140K in mouse) results in severe loss of ABCG2 mediated UA secretion in the small intestine (ii) sex determines the pathology and abundance of the mutant ABCG2 protein along the intestine and (iii) Small intestines may be the site of hormonal regulation of both ABCG2 and UA secretion. Support or Funding Information National Institute of Health RO1 grant (DK114091‐01) & American Hear Association grant: 14SDG18060004 This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .