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Abstract: Faithful transcriptome regulation is important in development and also crucial for applications in reproductive and regenerative medicine. Intracytoplasmic sperm injection (ICSI), one of the human assisted reproductive technologies (ART), has long raised concerns about its influence on development. No clear consensus has been reached, however, in spite of many cohort studies carried out in the last two decades on the children conceived by ICSI and/or in vitro fertilization (IVF). In this study, the pre- and postnatal effects of ICSI were assessed using comprehensive transcriptome and phenotypic analyses in mice under strict conditions. Here we demonstrate that, in contrast to IVF, ICSI induces distinct long-lasting transcriptome change that remains at the neonatal stage. Importantly, no remarkable differences were observed in the ICSI adults in either the gene expression or phenotypic profiles, and there was no indication of transmission to the next generation via natural mating. Our results suggest there are no lifelong or transgenerational effects of ICSI, but the ICSI effects during neonatal period remain to be evaluated. [Copyright &y& Elsevier]

Recent cloning technology has been demonstrated successfully using nuclear transfer (NT) techniques to generate embryonic stem (ES) cells. Mice can be cloned from adult somatic cells or ES cells by NT, and such cloned embryos can be used to establish new NT-ES cell lines. However, ES cells derived from parthenogenetic embryos show epigenetic disorders and low potential for normal differentiation unless used to produce subsequent generations of NT-ES lines. Thus, enucleated oocytes can initialize epigenetic modification, but the extent and efficacy of this remain unclear. In this study, our goal was to clarify why the contribution rate of ES cells derived from parthenogenetic embryos (pES) cells appears to improve after NT. We compared gene expression profiles between pES and NT-pES cell lines using DNA microarray analysis and allele-specific DNA methylation analysis. Although changes in expression level were observed for 4% of 34,967 genes, only 81 (0.2%) showed common changes across multiple cell lines. In particular, the expression level of a paternally expressed gene, U2af1-rs1, was significantly increased in all NT-pES cell lines investigated. The methylation status at the upstream differentially methylated region of U2af1-rs1 was also changed significantly after NT. This was observed in NT-pES cells, but also in conventionally produced NT-ES cells, which has never been reported previously. These results suggest that NT affects the epigenetic status of a few gene regions in common and that a change in the methylation status of U2af1-rs1 could be used as a genetic marker to investigate the effects of NT. [ABSTRACT FROM AUTHOR]

Abstract: Paternally expressed 1 (Peg1)/mesoderm specific transcript (Mest) is an imprinted gene, which is only transcribed from the paternal (father’s) allele. In some human cancer tissues, an alternatively spliced variant of PEG1/MEST mRNA using a different promoter of a distinct first exon is expressed from both paternal and maternal alleles. We previously reported that Peg1/Mest expression was markedly up-regulated in obese adipose tissue in mice. Moreover, transgenic overexpression of Peg1/Mest in the adipose tissue resulted in the enlargement of adipocytes in size. Given the potential pathophysiologic relevance in obesity, we examined the nature of increased expression of Peg1/Mest in obese adipose tissue. In obese adipose tissue, expression of Peg1/Mest was increased, but not that of other imprinted genes tested. The transcription rate of Peg1/Mest was increased in obese adipose tissue. We found at least four isoforms of mouse Peg1/Mest generated by use of the alternative first exons. We also demonstrated that the abundantly expressed Peg1/Mest in obese adipose tissue retained monoallelic expression. This is the first report of monoallelic induction of Peg1/Mest in adult tissues. [Copyright &y& Elsevier]

Genomic imprinting is a system of non-Mendelian inheritance that is unique to mammals. Two types of imprinted genes show parent-of-origin-specific expression patterns: the paternally expressed genes (Pegs), and the maternally expressed genes (Megs). Parental genomic imprinting memory is maintained in the somatic cell lineage and regulates the expression of Pegs and Megs, while it is erased and re-established in the germ cell lineage according to the sex of the individual. The paternal and maternal imprinting mechanisms, which regulate different sets of Pegs and Megs, are essential for establishing the parental expression profiles of imprinted genes that are observed in sperms and eggs. Based on recent evidence, we outline the relationship between parental imprinting and the expression profiles of Pegs and Megs and discuss a novel view of the regulation of genomic imprinting. We also discuss the biological significance of genomic imprinting and propose hypotheses on the essential nature of genomic imprinting and the close relationship between genomic imprinting and the acquisition of placental tissues during mammalian evolution. [ABSTRACT FROM PUBLISHER]

Paternally expressed imprinted genes (Pegs) were systematically screened by comparing gene expression profiles of parthenogenetic and normal fertilized embryos using an oligonucleotide array. A novel imprinted gene, Peg12/Frat3, was identified along with 10 previously known Pegs. Peg12/Frat3 is expressed primarily in embryonic stages and might be a positive regulator of the Wnt signaling pathway. It locates next to the Zfp127 imprinted gene in the mouse 7C region, which has syntenic homology to the human Prader–Willi syndrome region on chromosome 15q11-q13, indicating that this imprinted region extends to the telomeric side in the mouse. [Copyright &y& Elsevier]

Genomic imprinting significantly influences development, growth and behaviour in mammals. Systematic screening of imprinted genes has been extensively carried out to identify the genes responsible for imprinted phenotypes and to elucidate the biological significance of this phenomenon. In this study, we applied DNA chip technology for isolating paternally expressed imprinted genes (Pegs). We compared the resulting expression profiles of parthenogenetic and fertilized control embryos to identify novel imprinted genes. A novel paternally expressed mouse imprinted gene, Peg9/Dlk1, was identified. Consistent with this finding, the paternal expression of its human homologue, PEG9/DLK1, was also confirmed. These two genes form imprinted gene clusters with the reciprocally imprinted mouse Meg3/Gtl2 and human MEG3 genes that we first identified on distal chromosome 12 and chromosome 14q32, respectively. As DNA chip technology allows us to quickly screen a large number of genes, using this technology to search for imprinted genes could accelerate the identification of genes responsible for human and mouse genetic diseases. Dlk1 and DLK1, which encode transmembrane proteins, have six EGF-like repeats and show homology to the Delta gene in Drosophila melanogaster. Because of its homology to mammalian Delta homologues, PEG9/DLK1 may contribute to the scoliosis phenotype observed in maternal uniparental disomy 14 (mUPD14) patients. [ABSTRACT FROM AUTHOR]

Abstract: Genomic imprinting is widespread amongst mammals, but has not yet been found in birds. To gain a broader understanding of the origin and significance of imprinting, we have characterized three genes, from three separate imprinted clusters in eutherian mammals in the developing fetus and placenta of an Australian marsupial, the tammar wallaby Macropus eugenii. Imprinted gene orthologues of human and mouse p57KIP2, IGF2 and PEG1/MEST genes were isolated. p57KIP2 did not show stable monoallelic expression suggesting that it is not imprinted in marsupials. In contrast, there was paternal-specific expression of IGF2 in almost all tissues, but the biased paternal expression of IGF2 in the fetal head and placenta, demonstrates the occurrence of tissue-specific imprinting, as occurs in mice and humans. There was also paternal-biased expression of PEG1/MESTα. The differentially methylated region (DMR) of the human and mouse PEG1/MEST promoter is absent in the wallaby. These data confirm the existence of common imprinted regions in eutherians and marsupials during development, but suggest that the regulatory mechanisms that control imprinted gene expression differ between these two groups of mammals. [Copyright &y& Elsevier]