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

Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USA.
Fertility and sterility (Impact Factor: 3.97). 05/2012; 98(2):480-6. DOI:10.1016/j.fertnstert.2012.04.035
Source: PubMed

ABSTRACT To confirm that oocyte-specific messenger RNAs are detectable in the polar body (PB) of metaphase II (MII) oocytes and determine the effect of age on oocyte-specific transcript levels.
Prospective study.
Hospital-based academic research laboratory.
CD1 female mice.
Aged (40-50 weeks) and young (7-9 weeks) mice were administered pregnant mare serum gonadotropin (PMSG) and hCG. Oocytes were fertilized in vitro to assess fertilization and developmental competence. The MII oocytes were obtained and first PBs were removed. Messenger RNAs from each PB and its sibling oocyte were reverse transcribed and analyzed by real-time quantitative polymerase chain reaction (PCR).
Fertilization and developmental rates and expression of six oocyte-specific genes (Bmp15, Gdf9, H1foo, Nlrp5, Tcl1, and Zp3) in PBs and sibling oocytes from young versus aged mice.
Oocytes from aged mice had lower developmental competence. Four genes (H1foo, Nlrp5, Tcl1, and Zp3) were differentially expressed in aged versus young oocytes. All six 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.
There is a significant difference in the transcript levels of oocyte-specific genes in aged versus 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.

0 0
  • [show abstract] [hide abstract]
    ABSTRACT: Various morphological and cytological traits of oocytes and their surrounding cumulus cells may be used to select oocytes for assisted reproduction. However, even with careful selection, successful in vitro fertilization and subsequent embryo development remain uncertain. The factors that ensure oocyte competence are unclear and other approaches to assessing developmental potential must be explored. With the constant development of the molecular toolbox, genomic/transcriptomic analysis is becoming a more and more interesting approach to understand oocyte quality on the basis of RNA composition. Using bovine and mouse models as well as human oocytes of known developmental potential, various efforts are underway to characterize the mRNA profile of the competent oocyte using microarray technology. The proliferation of gene expression datasets raises new opportunities to identify the mechanisms involved in this complex phenotype, which should lead to improved techniques of assisted reproduction. Although several molecular markers of oocyte quality are known, translating these into cellular functions remains challenging, due largely to the poor correlation between mRNA level and protein synthesis. Unlike most somatic cells, the oocyte can store mRNA for days, with transcriptional activity remaining at a halt during the 4-5 days beginning before ovulation and ending with embryonic genome activation. This review provides an overview of the transcriptomic data obtained from oocytes of different quality as well as interesting avenues to explore in order to improve our understanding of oocyte competence.
    Molecular Human Reproduction 11/2013; · 4.54 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: OBJECTIVE: To determine whether the follicle environment modulates oocyte-specific gene transcript levels in cultured oocytes and polar bodies (PBs). DESIGN: Animal study. SETTING: Large academic research center. ANIMAL(S): CD1 mice. INTERVENTION(S): In vitro growth of secondary mouse follicles in 0.25% or 1.5% alginate (ALG) in a three-dimensional culture system. MAIN OUTCOME MEASURE(S): Relative transcript levels of Gdf9, Bmp15, Nlrp5, Tcl1, and Zp3 were measured by real-time quantitative reverse transcriptase-polymerase chain reaction in oocytes during in vitro follicle development and oocyte maturation and in their first PBs after removal from metaphase II (MII) eggs. RESULT(S): All transcripts decreased earlier in oocytes cultured in 1.5% ALG compared with 0.25% ALG. Transcript levels were lower in MII eggs cultured in 1.5% ALG compared with in 0.25% ALG. All genes were expressed in PBs, and transcript levels were lower in PBs cultured in 1.5% ALG compared with in 0.25% ALG. Abundance of all transcripts was lower in PBs than in their sibling oocytes. CONCLUSION(S): Local follicle environment modulates oocyte-specific gene expression in the oocyte and first PB. There is a significant difference in the transcript levels of oocyte-specific genes in PBs of 1.5% versus 0.25% ALG that correlates with ovarian environment-related decreases in oocyte competence.
    Fertility and sterility 01/2013; · 3.97 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: OBJECTIVE: To test the hypothesis that quantification of messenger RNAs originating from the second polar body (PB2) provides a noninvasive tool for assessing embryo quality. DESIGN: Prospective study. SETTING: Hospital-based academic research laboratory. ANIMAL(S): CD1 female mice. INTERVENTION(S): Metaphase II oocytes obtained from 7- to 8-week-old mice after pregnant mare's serum gonadotropin and hCG priming. After in vitro fertilization, the PB2 was biopsied from zygote, followed by reverse transcription. Real-time polymerase chain reaction was performed to quantify gene expression levels in single PB2. The sibling zygotes were continuously cultured to blastocyst stage. MAIN OUTCOME MEASURE(S): Embryo developmental competence and six maternal-effect gene (Dnmt1, Mater, Nobox, Npm2, Tcl1, and Zar1) transcripts in the PB2. RESULT(S): Second polar body messenger RNA was detected in all candidate genes. Transcripts that were present in greater abundance in the zygote were more likely to be detected in quantitative polymerase chain reaction replicates from single PB2. Four candidate genes (Dnmt1, Nobox, Npm2, and Tcl1) expression levels in PB2 between two groups (two-cell embryo vs. blastocyts) approached statistical significance. CONCLUSION(S): Second polar bodies may contain a representative transcript profile to that of the zygote after fertilization. Differences in gene expression in PB2 may be potential biomarkers of embryo quality.
    Fertility and sterility 03/2013; · 3.97 Impact Factor

Ze-Xu Jiao