We recently described two outbred mouse lines that were selected for large litter size at first delivery. However, lifetime fecundity appears to be economically more important for the husbandry of many polytocous species for which mouse lines might serve as bona fide animal models (e.g., for pigs). In the present study, we compared the lifetime fecundities of two highly fertile mouse lines (FL1 and FL2: >20 offspring/litter at first delivery) with those of an unselected control line (ctrl) and two lines that were selected for high body weight (DU6) and high protein mass (DU6P) without selection pressure on fertility. We tested the hypothesis that selection for large litter size at first parturition would also increase lifetime fecundity in mice, and we observed very large differences between lines. Whereas FL1 and ctrl delivered up to 9 and 10 litters, none of the DU6 and DU6P females gave birth to more than 5 litters. In line with this observation, FL1 delivered the most pups per lifetime (85.7/female). FL2 females produced the largest average litter sizes (20.4 pups/litter) in the first four litters; however, they displayed a reduced number of litters. With the exception of ctrl, litter sizes declined from litter to litter. Repeated delivery of litters with high offspring numbers did not affect the general health of FL females. The presented data demonstrate that two biodiverse, highly fertile mouse lines selected for large litter size at first delivery show different lifetime reproductive fitness levels.
Martina Langhammer, Erika Wytrwat, Marten Michaelis, Jennifer Schoen, Armin Tuchscherer, Norbert Reinsch, and Joachim M Weitzel
Martina Langhammer, Marten Michaelis, Andreas Hoeflich, Alexander Sobczak, Jennifer Schoen, and Joachim M Weitzel
Animal models are valuable tools in fertility research. Worldwide, there are more than 400 transgenic or knockout mouse models available showing a reproductive phenotype; almost all of them exhibit an infertile or at least subfertile phenotype. By contrast, animal models revealing an improved fertility phenotype are barely described. This article summarizes data on two outbred mouse models exhibiting a ‘high-fertility’ phenotype. These mouse lines were generated via selection over a time period of more than 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 and endurance fitness on a treadmill) were 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, these models will therefore be a precious information source for human reproductive medicine.
A German translation of abstract is freely available at http://www.reproduction-online.org/content/147/4/427/suppl/DC1.
Inga Laezer, Sergio E Palma-Vera, Fan Liu, Marcus Frank, Nares Trakooljul, Andreas Vernunft, Jennifer Schoen, and Shuai Chen
In mammals, around the time of ovulation, the hormonal profile dynamically changes in synchrony with reproductive events occurring in the oviduct, that is, sperm arrival, fertilization, and early embryo development. Extracellular vesicles (EVs) have been recently recognized as key components of the embryonic milieu; however, composition and function of oviductal EVs during this crucial period remains to be further explored. Therefore, we initially characterized EVs from porcine oviductal fluid specifically around the critical ovulation window: that is, estrus (E), late estrus (LE, day of expected ovulation), post ovulation (PO), and additionally diestrus (D). Total EV numbers gradually rose from D to E, LE and PO (P < 0.05), which corresponded to the total EV protein amount (P < 0.05). Strikingly, the mean size of EVs in PO was significantly smaller than in E and LE groups, which also had a lesser proportion of small EVs (P < 0.05). The EV protein cargoes during the periovulatory period were further analyzed by mass spectrometry. Qualitative analysis detected 1118 common proteins, which are most enriched in the cellular component of EVs/exosomes. Hierarchical clustering indicated similar protein profile within the biological replicates, but large discrepancy among stages. Further quantitative analysis discovered 34 and 4 differentially expressed proteins in the comparison between E and PO and in the comparison between E and LE, respectively. The dynamic EV protein profile together with the quick adaption in EV size and quantity suggests that porcine oviductal EV secretion are under the hormonal influence during the estrus cycle.