Females live longer than males in many mammalian species, including humans. It has been observed that women are at an advantage over men with regard to the lifespan; however, the reason for this sex difference in longevity is unclear. Bi-maternal mice (BM), which are produced in a 'sperm-free' manner, could provide an opportunity to analyse the longevity of animals lacking paternal genomes.
We studied the longevity of BM, which were generated using two sets of female genomes--one derived from fully grown oocytes from normal adults and the other from non-growing oocytes from newborn pups. These newborn pups were also genetically manipulated in two regions--the imprinting centres of Igf2-H19 and Dlk1-Gtl2--on chromosomes 7 and 12. We determined lifespan of the control (n = 13) and BM (n = 13). Our results revealed that the bi-maternal genotype clearly shifted the entire survival curve to the right, suggesting a delay in the expression of all causes of mortality. BM survived 186 days longer than controls. Furthermore, the body weight was significantly lower in the BM as compared with the controls at 20 months after birth (P < 0.05), and leukocyte composition analysis at 8 weeks revealed that the eosinophil count was significantly increased in the BM as compared with the controls (P < 0.05, n = 6).
These findings demonstrate that the maternal genome may play a role in ontogenetic longevity. Our results further suggested sex differences in longevity, originating at the genome level, implying that the sperm genome has a detrimental effect on longevity in mammals.