Detection and quantification of maternal-effect gene transcripts in mouse second polar bodies: potential markers of embryo developmental competence

Abstract

Objective To test the hypothesis that quantification of mRNAs originating the second polar body (PB2) provides a non-invasive tool for assessing embryo quality. Design Prospective study Setting Hospital-based academic research laboratory Animals CD1 female mice Intervention(s) MII oocytes obtained from 7- to 8-week-old mice after pregnant mare’s serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG) priming. After in vitro fertilization, the PB2 was biopsied from zygotes followed by reverse transcription. Real-time PCR 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 Results PB2 mRNA was detected in all candidate genes. Transcripts that were present in greater abundance in the zygote were more likely to be detected in qPCR replicates from single PB2. 4 candidate genes (Dnmt1, Nobox, Npm2 and Tcl1) expression levels in PB2 between two groups (2-cell embryo vs. blastocyts) approached statistical significance. Conclusion PB2 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.

Relationship of polar bodies morphology to embryo quality and pregnancy outcome

“…It was also shown that the D3 GER, GBR and AER of the intact group were all significantly higher than that of the fragmented group. These results were consistent with other groups' research (Ebner et al, 2000;Navarro et al, 2009;Younis et al, 2009;Reich et al, 2011;Jiao & Woodruff 2013). Thus, it is inferred that PB morphology, to some extent, can reflect embryo quality when using the present morphology grading system.…”

“…Moreover, our knowledge on the relationship of PB 2 morphology to oocyte competence, especially in human zygotes, is far from complete. A recent study using animal models has demonstrated that PB 2 also contains a representative transcript profile to that of the zygote, and the genes in PB 2 reflect the embryo developmental competence (Jiao & Woodruff, 2013). PB 1 and PB 2 can be observed simultaneously as a sign of fertilization, and assessed at the time of pronuclei (PN) observation on day 1 (D1) (Fabian et al , 2012).…”

Oocyte environment: follicular fluid and cumulus cells are critical for oocyte health

“…In mice, expression of four maternal effect genes (H1foo, Nlrp5, Tcl1, and Zp3) in the first polar body correlates with female age and oocyte quality (170), while expression of four additional maternal effect genes (Dnmt1, Nobox, Npm2, and Tcl1) in the second polar body correlates with blastocyst development (171). In humans, mRNA is detectable in polar bodies (172).…”

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

“…Current evaluations of embryo viability are based on morphology. Analysis transcripts in PB may supplement information on chromosomal status or development competence of a given oocyte and its resulting embryo, which would be of great benefit in IVF treatment, allowing the embryos with the highest implantation potential to be prioritized for transfer to the uterus [18,34].…”