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Parental age and gene expression profiles in individual human blastocysts.

ABSTRACT: The epigenetic status of the genome changes dynamically from fertilization to implantation. In addition, the physiological environment during the process of gametogenesis, including parental age, may affect the epigenome of the embryo after fertilization. It is important to clarify the influence of parental age on gene expression in the embryo in terms of transgenerational epigenetics to improve the techniques currently used in assisted reproductive medicine. Here, we performed single-embryo RNA-seq analysis on human blastocysts fertilized by intracytoplasmic sperm injection, including from relatively elderly mothers, to elucidate the effects of parental age on the embryonic gene expression profile. We identified a number of genes in which the expression levels were decreased with increasing maternal age. Among these genes, several are considered to be important for meiotic chromosomal segregation, such as PTTG1, AURKC, SMC1B and MEIKIN. Furthermore, the expression levels of certain genes critical for autophagy and embryonic growth, specifically GABARAPL1 and GABARAPL3, were negatively correlated with advanced paternal age. In addition, levels of transcripts derived from major satellite repeats also decreased as the maternal age increased. These results suggest that epigenetic modifications of the oocyte genome may change with parental age and be transmitted to the next generation.

SUBMITTER: Kawai K

PROVIDER: S-EPMC5799158 | biostudies-literature | 2018 Feb

REPOSITORIES: biostudies-literature

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Parental age and gene expression profiles in individual human blastocysts.

Kawai Kiyotaka K Harada Tatsuya T Ishikawa Tomonori T Sugiyama Rikikazu R Kawamura Toshihiro T Yoshida Atsumi A Tsutsumi Osamu O Ishino Fumitoshi F Kubota Toshiro T Kohda Takashi T

Scientific reports 20180205 1

The epigenetic status of the genome changes dynamically from fertilization to implantation. In addition, the physiological environment during the process of gametogenesis, including parental age, may affect the epigenome of the embryo after fertilization. It is important to clarify the influence of parental age on gene expression in the embryo in terms of transgenerational epigenetics to improve the techniques currently used in assisted reproductive medicine. Here, we performed single-embryo RNA ...[more]

PMID: 29402920

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Project description:BackgroundMitochondrial DNA (mtDNA) copy number in oocytes correlates with oocyte quality and fertilisation outcome. The introduction of additional copies of mtDNA through mitochondrial supplementation of mtDNA-deficient Sus scrofa oocytes resulted in: (1) improved rates of fertilisation; (2) increased mtDNA copy number in the 2-cell stage embryo; and (3) improved development of the embryo to the blastocyst stage. Furthermore, a subset of genes showed changes in gene expression. However, it is still unknown if mitochondrial supplementation alters global and local DNA methylation patterns during early development.ResultsWe generated a series of embryos in a model animal, Sus scrofa, by intracytoplasmic sperm injection (ICSI) and mitochondrial supplementation in combination with ICSI (mICSI). The DNA methylation status of ICSI- and mICSI-derived blastocysts was analysed by whole genome bisulfite sequencing. At a global level, the additional copies of mtDNA did not affect nuclear DNA methylation profiles of blastocysts, though over 2000 local genomic regions exhibited differential levels of DNA methylation. In terms of the imprinted genes, DNA methylation patterns were conserved in putative imprint control regions; and the gene expression profile of these genes and genes involved in embryonic genome activation were not affected by mitochondrial supplementation. However, 52 genes showed significant differences in expression as demonstrated by RNAseq analysis. The affected gene networks involved haematological system development and function, tissue morphology and cell cycle. Furthermore, seven mtDNA-encoded t-RNAs were downregulated in mICSI-derived blastocysts suggesting that extra copies of mtDNA affected tRNA processing and/or turnover, hence protein synthesis in blastocysts. We also showed a potential association between differentially methylated regions and changes in expression for 55 genes due to mitochondrial supplementation.ConclusionsThe addition of just an extra ~ 800 copies of mtDNA into oocytes can have a significant impact on both gene expression and DNA methylation profiles in Sus scrofa blastocysts by altering the epigenetic programming established during oogenesis. Some of these changes may affect specific tissue-types later in life. Consequently, it is important to determine the longitudinal effect of these molecular changes on growth and development before considering human clinical practice.

Project description:Unveiling the transcriptome of human blastocysts can provide a wealth of important information regarding early embryonic ontology. Comparing the mRNA production of embryos with normal and abnormal karyotypes allows for a deeper understanding of the protein pathways leading to viability and aberrant fetal development. In addition, identifying transcripts specific for normal or abnormal chromosome copy number could aid in the search for secreted substances that could be used to non-invasively identify embryos best suited for IVF embryo transfer. Using RNA-seq, we characterized the transcriptome of 71 normally developing human blastocysts that were karyotypically normal vs. trisomic or monosomic. Every monosomy and trisomy of the autosomal and sex chromosomes were evaluated, mostly in duplicate. We first mapped the transcriptome of three normal embryos and found that a common core of more than 3,000 genes is expressed in all embryos. These genes represent pathways related to actively dividing cells, such as ribosome biogenesis and function, spliceosome, oxidative phosphorylation, cell cycle and metabolic pathways. We then compared transcriptome profiles of aneuploid embryos to those of normal embryos. We observed that non-viable embryos had a large number of dysregulated genes, some showing a hundred-fold difference in expression. On the contrary, sex chromosome abnormalities, XO and XXX displayed transcriptomes more closely mimicking those embryos with 23 normal chromosome pairs. Intriguingly, we identified a set of commonly deregulated genes in the majority of both trisomies and monosomies. This is the first paper demonstrating a comprehensive transcriptome delineation of karyotypic abnormalities found in the human pre-implantation embryo. We believe that this information will contribute to the development of new pre-implantation genetic screening methods as well as a better understanding of the underlying developmental abnormalities of abnormal embryos, fetuses and children.

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Parental age and gene expression profiles in individual human blastocysts.

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Parental age and gene expression profiles in individual human blastocysts.

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