Gene expression profiling of human oocytes developed and matured in vivo or in vitro

Abstract

The quality of the human oocyte determines the success of fertilization and affects the consequent embryo development, pregnancy and birth; it therefore serves as a basis for human reproduction and fertility. The possibility to evaluate oocyte quality in the in vitro fertilization programme is very limited. The only criterion which is commonly used to evaluate oocyte quality is its morphology. There is a mass of oocytes in the in vitro fertilization programme which are not fertilized in spite of normal morphology. In the past, several attempts focused on oocyte gene expression profiling by different approaches. The results elucidated groups of genes related to the human oocyte. It was confirmed that some factors, such as oocyte in vitro maturation, are detectable at the molecular level of human oocytes and their polar bodies in terms of gene expression profile. Furthermore, the first genetic evaluations of oocyte-like cells developed in vitro from human stem cells of different origin were performed showing that these cells express some genes related to oocytes. All these findings provide some new knowledge and clearer insights into oocyte quality and oogenesis that might be introduced into clinical practice in the future.

Figure 1

Human oocytes from the in vitro fertilization programme (a)–(c): immature germinal vesicle (GV) oocytes with a germinal vesicle (arrow) and without a polar body; (d)–(f): immature metaphase I (MI) oocytes without a polar body; (g)–(i): mature metaphase II (MII) oocytes with a polar body (arrow).

Figure 2

Analyses of nineteen human oocytes at different stages of maturity on the expression of fifty-six genes related to pluripotent stem cells and oocytes using a Fluidigm Real-Time system confirmed three outstanding oocytes (two MI and one IVM oocyte). (a) heatmap clustering (Ward's Algorithm, Euclidean Distance Measure), (b) hierarchical clustering (Ward's Algorithm, Euclidean Distance Measure), (c) principal component analysis (PCA) legend for (a) red—expressed, green—nonexpressed; legend for (b) and (c) aquamarine—GV oocytes, blue—metaphase I oocytes, red—MII oocytes, dark red—IVM oocytes. Analyzed genes: VASA, GPR125, DAZL, KIT, KIT-LIG, STELLA, GFRa1, PLZF, OCT4B, OCT4A, LIN28, GDF3, NANOG, MYC, KLF4, SOX2, UTF1, TDGF1, DNMT3B, LIN28B, TERT, CD9, NANOS, CDH1, STAT3, REX01, DNMT1, BMP15, ZP1, ZP2, ZP3, ZP4, SCP1, SCP2, SCP3, SMC1A, FSTL1, CCNB1, BNC1, BUB1, BUB3, NOBOX, MSH5, NLRP5, FMN2, HIFOO, MEST, CRKRS, MLH1, ZAR1, REC8, PRDM1, SAT1, FIGLA, STAG3, and DMC1.