Section of Reproductive Medicine, Department of Obstetrics and Gynaecology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands.
Hum Reprod Update. 2011 Sep-Oct;17(5):620-7. doi: 10.1093/humupd/dmr014. Epub 2011 Apr 29.
Although chromosomal mosaicism in human preimplantation embryos has been described for almost two decades, its exact prevalence is still unknown. The prevalence of mosaicism is important in the context of preimplantation genetic screening in which the chromosomal status of an embryo is determined by the analysis of a single cell from that embryo.
Here we report a systematic review and meta-analysis of studies on the chromosomal constitution of human preimplantation embryos. In 36 studies, out of 2117 citations that met our search criteria, data were provided extensively enough to allow classification of each analysed embryo with prespecified criteria for its chromosomal makeup. The main outcome of this classification was the prevalence of chromosomal mosaicism in human preimplantation embryos.
A total of 815 embryos could be classified. Of these, 177 (22%) were diploid, 599 (73%) were mosaic, of which 480 (59% of the total number of embryos) were diploid-aneuploid mosaic and 119 (14% of the total number of embryos) were aneuploid mosaic, and 39 (5%) contained other numerical chromosomal abnormalities. The distribution of the embryos over these categories was associated with the developmental stage of the embryos, the method used for analysis and the number of chromosomes analysed.
Diploid-aneuploid mosaicism is by far the most common chromosomal constitution in spare human preimplantation embryos after IVF. This undermines the reliable determination of the ploidy status of a cleavage-stage embryo based on the analysis of a single cell. Future research should determine the origin and developmental potential of mosaic embryos.
尽管人类胚胎植入前的染色体嵌合现象已经被描述了近二十年，但它的确切流行率仍不清楚。在胚胎植入前遗传学筛查中，胚胎的染色体状态是通过对该胚胎的单个细胞进行分析来确定的，因此嵌合体的流行率很重要。
我们在此报告了一项对人类胚胎植入前染色体构成的研究进行的系统回顾和荟萃分析。在 36 项研究中，在符合我们检索标准的 2117 篇文献中，有足够的数据提供，可以根据预先规定的胚胎染色体构成分类标准，对每个分析胚胎进行分类。这种分类的主要结果是人类胚胎植入前染色体嵌合体的流行率。
总共可以对 815 个胚胎进行分类。其中，177 个（22%）为二倍体，599 个（73%）为嵌合体，其中 480 个（占胚胎总数的 59%）为二倍体-非整倍体嵌合体，119 个（占胚胎总数的 14%）为非整倍体嵌合体，39 个（5%）含有其他数目异常的染色体。这些胚胎在这些类别中的分布与胚胎的发育阶段、分析方法和分析的染色体数量有关。
到目前为止，在体外受精后的备用人类胚胎中，二倍体-非整倍体嵌合体是最常见的染色体构成。这使得基于单个细胞分析来可靠地确定卵裂期胚胎的ploidy 状态变得不可行。未来的研究应确定嵌合胚胎的起源和发育潜力。
