Cost-effective development of highly polymorphic microsatellite in Japanese quail facilitated by next-generation sequencing.

Next-generation sequencing technologies permit rapid and cost-effective identification of numerous putative microsatellite loci. Here, from the genome sequences of Japanese quail, we developed microsatellite markers containing dinucleotide repeats and employed these for characterisation of genetic diversity and population structure. A total of 385 individuals from 12 experimental and one wild-derived Japanese quail lines were genotyped with newly developed autosomal markers. The maximum number of alleles, expected heterozygosity and polymorphic information content (PIC) per locus were 10, 0.80 and 0.77 respectively. Approximately half of the markers were highly informative (PIC ≥ 0.50). The mean number of alleles per locus and observed heterozygosity within a line were in the range of 1.3-4.1 and 0.11-0.53 respectively. Compared with the wild-derived line, genetic diversity levels were low in the experimental lines. Genetic differentiation (FST ) between all pairs of the lines ranged from 0.13 to 0.83. Genetic clustering analyses based on multilocus genotypes of individuals showed that most individuals formed clearly defined clusters corresponding to the origins of the lines. These results suggest that Japanese quail experimental lines are highly structured. Microsatellite markers developed in this study may be effective for future genetic studies of Japanese quail.

Age-associated changes in bovine oocytes and granulosa cell complexes collected from early antral follicles.

PURPOSE: To assess the age-associated changes in oocytes and granulosa cells derived from early antral follicles (EAFs). METHOD: Gene expression analysis of granulosa cells of the EAFs using a genome analyzer (Illumina) and in vitro culture of oocyte-granulosa cell complexes (OGCs) of EAFs (400-700 µm in diameter) collected from ovaries of aged (>120 months) and young (<50 months) cows. RESULTS: Gene expression profiles in granulosa cells of EAFs of aged cows, which included changes in genes that encode chaperone proteins and antioxidants. In vivo development of EAFs, as determined by oocyte diameter of EAFs and AFs (3-6 mm in diameter), appeared to be impaired in aged cows and the OGCs of aged cows contained low GSH compared to younger counterparts. When the OGCs were cultured in a medium containing low estradiol (E2, 0.1 µg/mL), the ratio of antrum formation was higher for OGCs from aged animals than that from young animals, while higher abnormal fertilization rate and lower total cell number of the blastocysts were observed in the OGCs of aged cows compared with those of young cows. On the contrary, when the OGCs were cultured in a medium containing 10 µg/mL E2, the ratio of antrum formation and fertilization outcome was comparable between the two age groups, whereas the total cell number of the blastocysts was still low in the aged group. CONCLUSION: Aging affects the gene expression profiles of the granulosa cells, and impairs in vitro developmental ability of OGCs collected from EAFs.

Estradiol supports in vitro development of bovine early antral follicles.

Antrum formation and estradiol (E(2)) secretion are specific features of oocyte and granulosa cell complexes (OGCs). This study investigates the effect of E(2) on the in vitro development of bovine OGCs derived from early antral follicles as well as on the expression of genes in granulosa cells (GCs). The supplementation of culture medium with either E(2) or androstenedione (A(4)) improved the in vitro development of OGCs and the nuclear maturation of enclosed oocytes. When OGCs were cultured in medium containing A(4), developmentally competent OGCs secreted more E(2) than OGCs that were not competent. In addition, fulvestrant inhibited the effect of both E(2) and A(4) on OGCs development. Comprehensive gene expression analysis using next-generation sequence technology was conducted for the following three types of GCs: i) GCs of OGCs cultured for 4 days with E(2) (1 µg/ml; E(2)(+)), ii) GCs of OGCs cultured for 4 days without E(2) (E(2)(-)) or iii) OGCs that formed clear antrum after 8 days of in vitro culture in medium containing E(2) (1 µg/ml; AF group). GCs of the E(2)(+) group had a similar gene expression profile to the profile reported previously for the in vivo development of large follicles. This genetic profile included factors implicated in the up-regulation of E(2) biosynthesis and down-regulation of cytoskeleton and extracellular matrices. In addition, a novel gene expression profile was found in the AF group. In conclusion, E(2) impacts the gene expression profile of GCs to support the in vitro development of OGCs.

Age-associated changes in gene expression and developmental competence of bovine oocytes, and a possible countermeasure against age-associated events.

In general, maternal age affects the quality of oocytes and embryos. The present study aimed to examine the features and age-associated gene expression profiles of bovine oocytes and embryos as well as to discover possible countermeasures against age-associated events. Comprehensive gene expression assays of germinal vesicle and metaphase II (MII)-stage oocytes and 8- to 16-cell-stage embryos were conducted using next-generation sequencing technology. The gene expression profiles of aged cows showed high expression of genes related to oxidative phosphorylation, eIF4 and p70S6K signaling, and mitochondrial dysfunction in MII-stage oocytes. Oocytes derived from aged cows, compared with those derived from their younger counterparts, exhibited high levels of abnormal fertilization and blastocysts with low total cell numbers. Levels of reactive oxygen species (ROS) and SIRT1 were higher in in vitro-matured oocytes derived from aged cows than in those derived from their younger counterparts. Supplementation of maturation medium with N-acetyl-cysteine (NAC), but not resveratrol, reduced the levels of ROS in the oocytes derived from cows of both age groups; however, resveratrol, but not NAC, improved the fertilization ratio. Conversely, EX 527, an inhibitor of SIRT1, increased the ratio of abnormal fertilization. In conclusion, gene expression profiles of oocytes and embryos derived from aged cows differ from those of oocytes and embryos derived from young cows; in particular, oocytes derived from aged cows show protein and mitochondrial dysfunction. In addition, activation of SIRT1 in oocytes may be a potential countermeasure against age-associated events in oocytes derived from aged cows.