Division of Reproduction and Early Development, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, The LIGHT Laboratories, Leeds, UK.
Eur J Hum Genet. 2013 Jan;21(1):40-7. doi: 10.1038/ejhg.2012.102. Epub 2012 Jul 4.
There is evidence that expression and methylation of the imprinted paternally expressed gene 1/mesoderm-specific transcript homologue (PEG1/MEST) gene may be affected by assisted reproductive technologies (ARTs) and infertility. In this study, we sought to assess the imprinting status of the MEST gene in a large cohort of in vitro-derived human preimplantation embryos, in order to characterise potentially adverse effects of ART and infertility on this locus in early human development. Embryonic genomic DNA from morula or blastocyst stage embryos was screened for a transcribed AflIII polymorphism in MEST and imprinting analysis was then performed in cDNA libraries derived from these embryos. In 10 heterozygous embryos, MEST expression was monoallelic in seven embryos, predominantly monoallelic in two embryos, and biallelic in one embryo. Screening of cDNA derived from 61 additional human preimplantation embryos, for which DNA for genotyping was unavailable, identified eight embryos with expression originating from both alleles (biallelic or predominantly monoallelic). In some embryos, therefore, the onset of imprinted MEST expression occurs during late preimplantation development. Variability in MEST imprinting was observed in both in vitro fertilization and intracytoplasmic sperm injection-derived embryos. Biallelic or predominantly monoallelic MEST expression was not associated with any one cause of infertility. Characterisation of the main MEST isoforms revealed that isoform 2 was detected in early development and was itself variably imprinted between embryos. To our knowledge, this report constitutes the largest expression study to date of genomic imprinting in human preimplantation embryos and reveals that for some imprinted genes, contrasting imprinting states exist between embryos.
有证据表明，印迹的父系表达基因 1/中胚层特异性转录本同源物（PEG1/MEST）基因的表达和甲基化可能受到辅助生殖技术（ART）和不孕的影响。在这项研究中，我们试图评估大量体外衍生的人类胚胎植入前胚胎中 MEST 基因的印迹状态，以描述 ART 和不孕对人类早期发育中这一位点的潜在不利影响。从桑葚胚或囊胚期胚胎的胚胎基因组 DNA 中筛选 MEST 中的转录 AflIII 多态性，然后在从这些胚胎衍生的 cDNA 文库中进行印迹分析。在 10 个杂合胚胎中，7 个胚胎的 MEST 表达为单等位基因，2 个胚胎的 MEST 表达主要为单等位基因，1 个胚胎的 MEST 表达为双等位基因。对 61 个额外的人类胚胎植入前胚胎进行 cDNA 筛选，这些胚胎的 DNA 无法进行基因分型，结果鉴定出 8 个胚胎的表达源自两个等位基因（双等位基因或主要单等位基因）。因此，在一些胚胎中，印迹 MEST 表达的起始发生在植入前晚期发育。在体外受精和胞浆内精子注射衍生的胚胎中都观察到 MEST 印迹的可变性。双等位基因或主要单等位基因 MEST 表达与任何一种不孕原因都无关。对主要 MEST 同工型的特征描述表明，同工型 2 存在于早期发育中，并且在胚胎之间也存在可变印迹。据我们所知，这是迄今为止对人类胚胎植入前胚胎基因组印迹的最大表达研究，表明对于一些印迹基因，胚胎之间存在不同的印迹状态。
