Reproduction Abstracts

Animal models are valuable tools in fertility research. Worldwide >800 transgenic or knockout mouse models are available showing a reproductive phenotype; almost all of them exhibit an infertile or at least subfertile phenotype. In contrast, animal models revealing an improved fertility phenotype are barely described. Here, we present data on two outbred mouse models showing a ‘high fertility’ phenotype. These mouse lines have been generated via selection over a time period of >40 years and 161 generations. During this selection period the number of offspring per litter and the total birth weight of the entire litter nearly doubled. Concomitantly with the increased fertility phenotype several endocrine parameters (e.g. serum testosterone concentrations in male animals), physiological parameters (e.g. body weight, accelerated puberty, and life expectancy) and behavioral parameters (e.g. behavior in an open field, endurance fitness on a treadmill) have been altered. We demonstrate that the two independently bred high fertility mouse lines warranted their improved fertility phenotype using different molecular and physiological strategies. The fertility lines display female- as well as male-specific characteristics. These genetically heterogeneous mouse models provide new insights into molecular and cellular mechanisms that enhance fertility. In view of decreasing fertility in men it will therefore be a precious information source for human reproductive medicine.