The maternal to zygotic transition in mammals

Progressive obesity alters the steroidogenic response to ovulatory stimulation and increases the abundance of mRNAs stored in the ovulated oocyte

Obese women who are able to attain pregnancy are at increased risk for early-pregnancy loss due, in part, to reduced oocyte quality. We and others have demonstrated that female Lethal Yellow (LY) mice and female C57BL/6 mice fed a high fat diet (B6-HFD) exhibit phenotypes consistent with human obesity. These studies also showed that zygotes collected from LY and B6-HFD females have reduced developmental competence. The current hypothesis is that LY and B6-HFD females exhibit an abnormal response to gonadotropin stimulation compared to C57BL/6 controls fed normal rodent chow (B6-ND), resulting in the ovulation of oocytes with an altered molecular phenotype which may contribute to its reduced developmental competence. To test this hypothesis, age-matched B6-ND, B6-HFD, and LY females were stimulated with exogenous gonadotropins, then circulating hormone levels and the phenotypes of ovulated oocytes were analyzed. There was no difference in ovulation rate or in the percentage of morphologically abnormal oocytes collected from the oviduct of any females. Progesterone and progesterone/estradiol ratios, however, were increased in B6-HFD and LY compared to B6-ND females 16 hr post-human chorionic gonadotropin treatment. The transcript abundance of several candidate oocyte genes was also increased in B6-HFD- and LY-derived oocytes compared to B6-ND-derived oocytes. These data suggest that increased insulin and leptin levels of obese females elevated circulating progesterone concentrations, altered transcriptional activity during oocyte growth, and/or impaired mechanisms of RNA translation and degradation during oocyte maturation. These changes in mRNA abundance likely contribute to reduced oocyte quality and the subsequent poor embryogenesis associated with obesity.

Live pups from evaporatively dried mouse sperm stored at ambient temperature for up to 2 years

The purpose of this study is to develop a mouse sperm preservation method based on evaporative drying. Mouse sperm were evaporatively dried and stored at 4°C and ambient temperature for 3 months to 2 years. Upon rehydration, a single sperm was injected into a mature oocyte to develop into a blastocyst after culture or a live birth after embryo transfer to a recipient female. For the samples stored at 4°C for 3, 6, 12, 18, and 24 months, the blastocyst formation rate was 61.5%, 49.1%, 31.5%, 32.2%, and 41.4%, respectively. The blastocyst rate for those stored at ambient temperature (∼22°C) for 3, 6, 12, and 18 months was 57.8%, 36.2%, 33.6%, and 34.4%, respectively. Fifteen, eight and three live pups were produced from sperm stored at room temperature for 12, 18, and 24 months, respectively. This is the first report of live offspring produced from dried mouse sperm stored at ambient temperature for up to 2 years. Based on these results, we suggest that evaporative drying is a potentially useful method for the routine preservation of mouse sperm.