REVERSAL OF SEX-ROLES IN GENETIC FEMALE MICE BY DISRUPTION OF ESTROGEN-RECEPTOR GENE

Deficiency of normal estrogen receptor (ER) gene function led to behav ioral change in female mice (ERKO females). Maternal behavior as measu red by retrieving of pups was reduced. In some cases, pups were killed by the ERKO females, which was not seen in wild-type animals. Aggress ion toward other females was increased. Female-typical lordosis behavi or was reduced for at least two reasons: less response to somatosensor y stimuli on the hindquarters, as well as the fact that ERKO females w ere immediately treated as intruder males by resident 'stud' males and were thus attacked. In sum, disruption of the ER gene led to a patter n of hormonal and neural changes which caused the females to lose thei r normal female-typical behavior and to behave and be treated more lik e males.