Dynamic changes in gene expression during human early embryo development: from fundamental aspects to clinical applications.
BACKGROUND
The first week of human embryonic development comprises a series of events that change highly specialized germ cells into undifferentiated human embryonic stem cells (hESCs) that display an extraordinarily broad developmental potential. The understanding of these events is crucial to the improvement of the success rate of in vitro fertilization. With the emergence of new technologies such as Omics, the gene expression profiling of human oocytes, embryos and hESCs has been performed and generated a flood of data related to the molecular signature of early embryo development.


METHODS
In order to understand the complex genetic network that controls the first week of embryo development, we performed a systematic review and study of this issue. We performed a literature search using PubMed and EMBASE to identify all relevant studies published as original articles in English up to March 2010 (n = 165). We also analyzed the transcriptome of human oocytes, embryos and hESCs.


RESULTS
Distinct sets of genes were revealed by comparing the expression profiles of oocytes, embryos on Day 3 and hESCs, which are associated with totipotency, pluripotency and reprogramming properties, respectively. Known components of two signaling pathways (WNT and transforming growth factor-β) were linked to oocyte maturation and early embryonic development.


CONCLUSIONS
Omics analysis provides tools for understanding the molecular mechanisms and signaling pathways controlling early embryonic development. Furthermore, we discuss the clinical relevance of using a non-invasive molecular approach to embryo selection for the single-embryo transfer program.
Assou
Said
S
CHU Montpellier, Institute for Research in Biotherapy, Hôpital Saint-Eloi, INSERM U847, Montpellier, France.
Boumela
Imène
I
Haouzi
Delphine
D
Anahory
Tal
T
Dechaud
Hervé
H
De Vos
John
J
Hamamah
Samir
S
D047108:Embryonic Development / Q000235:genetics*; D053595:Embryonic Stem Cells / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008423:Maternal Age; D009865:Oocytes / Q000378:metabolism; D011085:Polycystic Ovary Syndrome / Q000235:genetics / Q000378:metabolism; D011247:Pregnancy; D011256:Pregnancy Outcome