SEX AND DEATH IN THE MOUSE - GENETICALLY DELAYED REPRODUCTION AND SENESCENCE

A mammalian model of genetically postponed aging would be an important tool to test not only different mechanisms of aging but also the pred ictive value of various biomarkers of the aging process. Under convent ional conditions, the historical strains of the laboratory mouse produ ce their first litter between 9 and 13 weeks of age and have a median time of death in their 2nd year. Our POSCH-2 strain, which was derived from wild-caught Mus musculus domesticus, produces its first litter i n the current breeding generations at approximately 47 weeks of age an d continues to breed throughout its 2nd and into its 3rd year of life. The aging curve of POSCH-2 has not yet been determined for economic r easons. Late onset of breeding is a characteristic of both females and males, but sexual maturity is more reliably assessed in females. The later breeding phenotype of POSCH-2 is genetically recessive to early breeding of the C57BL/6J historical laboratory strain and, since POSCH -2 females can be induced to ovulate at 8 weeks of age (but pregnancy does not result), the signal rather than the ovarian receptor to ovula te may be delayed. The genetically delayed reproduction and potentiall y longer life of the POSCH-2 strain appears to be a new trait in the m ouse. The strain may be a useful mammalian model for aging studies and for the evaluation of antagonistic pleiotropy as a genetic model for the evolution of aging.