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

Capsule:
Differences in gene expression in individual polar bodies of metaphase II oocytes may be potential markers for minimally invasive testing of oocyte competence.

Authors:
Ze-Xu Jiao, M.D., Ph.D., Min Xu, M.D., Ph.D., Teresa K. Woodruff, Ph.D.

Volume 98, Issue 2 , Pages 480-486, August 2012

Abstract:

Objective:
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.

Design:
Prospective study.

Setting:
Hospital-based academic research laboratory.

Animal(s):
CD1 female mice.

Intervention(s):
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).

Main Outcome Measure(s):
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.

Result(s):
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.

Conclusion(s):
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.

  • Very interesting study looking at oocyte-specific transcript levels in MII oocytes and their corresponding polar bodies which, in the future, may enable more highly evolved selection of competent gametes and embryos for embryo transfer in humans.

  • j.utah

    Great study highlighting the importance of consideration for oocyte cytoplasmic competence in addition to the traditionally considered meiotic accuracy in the development of new testing strategies for gametes and embryos.

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