AQP7 and obesity due to melanocortin 4 receptor deficiency: In this regard, Aqp7-deficient mice backcrossed into the C57BL/6N genetic background develop adult-onset obesity (33, 35) but not in the young state (22, 36), whereas Aqp7-knockout mice generated in CD1 mice did not exhibit excess body weight but showed an increase in whole-body fat content (34).