ABNORMAL MATERNAL-BEHAVIOR AND GROWTH-RETARDATION ASSOCIATED WITH LOSS OF THE IMPRINTED GENE MEST

Mest (also known as Peg1), an imprinted gene expressed only from the p aternal allele during development, was disrupted by gene targeting in embryonic stem (ES) cells. The targeted mutation is imprinted and reve rsibly silenced by passage through the female germ line. Paternal tran smission activates the targeted allele and causes embryonic growth ret ardation associated with reduced postnatal survival rates in mutant pr ogeny. More significantly. Mest-deficient females show abnormal matern al behaviour and impaired placentophagia, a distinctive mammalian beha viour. Our results provide evidence for the involvement of an imprinte d gene in the control of adult behaviour.