title: Variable imprinting of the MEST gene in human preimplantation embryos.
abstract: 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.
authors: Division of Reproduction and Early Development, Leeds Institute of Genetics, Health and Therapeutics, University of Leeds, The LIGHT Laboratories, Leeds, UK. j.huntriss@leeds.ac.uk
authors: John D
authors: JD
authors: Huntriss
authors: Karen E
authors: KE
authors: Hemmings
authors: Matthew
authors: M
authors: Hinkins
authors: Anthony J
authors: AJ
authors: Rutherford
authors: Roger G
authors: RG
authors: Sturmey
authors: Kay
authors: K
authors: Elder
authors: Helen M
authors: HM
authors: Picton
mesh_terms: D020413:3' Untranslated Regions; D017398:Alternative Splicing; D001755:Blastocyst / Q000502:physiology; D015331:Cohort Studies; D018076:DNA, Complementary; D005260:Female; D005307:Fertilization in Vitro; D018507:Gene Expression Regulation, Developmental; D018392:Genomic Imprinting; D006579:Heterozygote; D006801:Humans; D008297:Male; D009028:Morula; D009865:Oocytes / Q000502:physiology; D011110:Polymorphism, Genetic; D011506:Proteins / Q000235:genetics*; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*; D020554:Sperm Injections, Intracytoplasmic
chemical_list: D020413:3' Untranslated Regions; D018076:DNA, Complementary; D011506:Proteins; C103637:mesoderm specific transcript protein