Age-associated alteration of oocyte-specific gene expression in polar bodies: potential markers of oocyte competence

Abstract

Objective To confirm that oocyte-specific mRNAs are detectable in the polar body (PB) of MII oocytes and determine the effect of age on oocyte-specific transcript levels. Design Prospective study Setting Hospital-based academic research laboratory Animals CD1 female mice Intervention(s) Aged (40–50 weeks) and young (7–9 weeks) mice were administered pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotrophin (hCG). Oocytes were fertilized in vitro to assess fertilization and developmental competence. MII oocytes were obtained and first PBs was removed. mRNA from each PB and its sibling oocyte was reverse transcribed and analyzed by real-time quantitative PCR. Main Outcome Measure(s) Fertilization and developmental rates and expression of 6 oocyte-specific genes (Bmp15, Gdf9, H1foo, Nlrp5, Tcl1, and Zp3) in PBs and sibling oocytes from young vs. aged mice. Result(s) Oocytes from aged mice had lower developmental competence. Four genes (H1foo, Nlrp5, Tcl1, and Zp3) were differentially expressed in aged vs. young oocytes (P < 0.05). All 6 transcripts were present in PBs from aged and young mice at lower levels than in the sibling oocytes; transcript levels were lower in aged PBs compared with young PBs (P < 0.05). Conclusion(s) There is a significant difference in the transcript levels of oocyte-specific genes in aged vs. young PB that correlates with age-related decreases in oocyte competence. Differences in gene expression in PB may be potential biomarkers of MII oocyte competence.

Fetal bovine serum is associated with polar body degeneration after in vitro maturation of bovine oocytes

“…In addition, different batches of FBS were used during the experiments, and the results remained unchanged (data not shown). In mice, PB degeneration has been associated to oocyte's ageing (Miao et al, 2004) and apoptosis (Jiao et al, 2012). In our conditions, FBS …”

Age-related increase in aneuploidy and alteration of gene expression in mouse first polar bodies

“…The depletion of maternal stores of Filia causes a high incidence of aneuploidy that results from abnormal spindle assembly, chromosome misalignment, and SAC inactivation [32]. Our prior work demonstrated that there is a significant decrease in the transcript levels of oocyte-specific genes in aged vs. young PB [12]. Taken together a decline in a large number of different processes, including reduction in chromosome cohesion, alteration in cytoskeletal function and permissive checkpoint control, leading to decline in general fitness of older oocytes, may be contribute to age-related aneuploidy and decline in egg quality [33].…”

“…Collection and culture of MII oocytes MII oocytes were collected from young (2-month-old) and aged (12-to 15-month-old) female mice after superovulation as previously described [12]. Oocyte-cumulus cell complexes were recovered from ampullae into Leibovitz L15 medium containing 1 % fetal bovine serum (FBS) 14 h after human chorionic gonadotropin (hCG) administration.…”

Maternal control of oocyte quality in cattle “a review”

“…Collectively, these data suggest that impaired mitochondrial output in oocyte is associated with advanced maternal age. Furthermore, oocytes from aged mice exhibited lower expression of oocyte-specific genes (H1foo, Nlrp5, Tcl1, and Zp3) than those derived from their young counterparts (Jiao et al, 2012), suggesting that there is a lower capacity of aged oocytes to produce and store proteins necessary for oocyte function in the time between fertilization and embryonic genome activation.…”