Fat (fat) and tubby (tub): two autosomal recessive mutations causing obesity syndromes in the mouse.

This report describes the development of obesity syndromes in mice caused by two autosomal recessive mutations, fat (fat), located on chromosome 8, and tubby (tub), located on chromosome 7. Both mutations cause slowly developing but ultimately severe obesity conditions. Although hyperinsulinemia, hyperactivity of the beta cell of the islets of Langerhans, and beta-cell degranulation are consistent features, these obesity syndromes do not progress to severe diabetes. The many different single-gene mutations in the mouse that produce obesity-diabetes syndromes of varying degrees of severity make the mutant mouse a powerful tool for analyzing the number and nature of the primary defects than can cause obesity states.