Recently, while conducting a study on obesity, we encountered a hydronephrosis-like phenomenon in genetically engineered mice expressing Cre recombinase under the adiponectin (Adipoq) promoter, targeting tetraspanin 7 (Tspan7) in an adipose-tissue-specific manner on a C57BL/6 background [31]. The gene discussed is TSPAN7; the disease is obesity due to melanocortin 4 receptor deficiency.