SLC7A9 and cystinuria: To date, except for several natural models (cat, dog and wolf, all of which are suboptimal for human studies) [15–17], several mouse models of cystinuria, including two kinds of Slc3a1-deficient mice (exon 1 deletion [18] and D140G induced mutation [19]), type B Slc7a9 knockout mice (exons 3–9 deletion [20]) and type AB cystinuria heterozygous mice [21] (Slc3a1±, Slc7a9±).