The X-linked imprinted gene family Fthl17 shows predominantly female expression following the two-cell stage in mouse embryos

Medical Top Track Program, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
Nucleic Acids Research (Impact Factor: 9.11). 02/2010; 38(11):3672-81. DOI: 10.1093/nar/gkq113
Source: PubMed


Differences between male and female mammals are initiated by embryonic differentiation of the gonad into either a testis or
an ovary. However, this may not be the sole determinant. There are reports that embryonic sex differentiation might precede
and be independent of gonadal differentiation, but there is little molecular biological evidence for this. To test for sex
differences in early-stage embryos, we separated male and female blastocysts using newly developed non-invasive sexing methods
for transgenic mice expressing green fluorescent protein and compared the gene-expression patterns. From this screening, we
found that the Fthl17 (ferritin, heavy polypeptide-like 17) family of genes was predominantly expressed in female blastocysts. This comprises seven
genes that cluster on the X chromosome. Expression analysis based on DNA polymorphisms revealed that these genes are imprinted
and expressed from the paternal X chromosome as early as the two-cell stage. Thus, by the time zygotic genome activation starts
there are already differences in gene expression between male and female mouse embryos. This discovery will be important for
the study of early sex differentiation, as clearly these differences arise before gonadal differentiation.

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    • "A 44K custom microarray24 was used for gene expression profiling throughout this study. This custom array covers all the known protein-coding genes as well as expression sequence tags derived from PGC cDNA libraries (Abe, unpublished) and was manufactured by Agilent Technologies. "
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    ABSTRACT: To understand the epigenetic regulation required for germ cell-specific gene expression in the mouse, we analysed DNA methylation profiles of developing germ cells using a microarray-based assay adapted for a small number of cells. The analysis revealed differentially methylated sites between cell types tested. Here, we focused on a group of genomic sequences hypomethylated specifically in germline cells as candidate regions involved in the epigenetic regulation of germline gene expression. These hypomethylated sequences tend to be clustered, forming large (10 kb to ∼9 Mb) genomic domains, particularly on the X chromosome of male germ cells. Most of these regions, designated here as large hypomethylated domains (LoDs), correspond to segmentally duplicated regions that contain gene families showing germ cell- or testis-specific expression, including cancer testis antigen genes. We found an inverse correlation between DNA methylation level and expression of genes in these domains. Most LoDs appear to be enriched with H3 lysine 9 dimethylation, usually regarded as a repressive histone modification, although some LoD genes can be expressed in male germ cells. It thus appears that such a unique epigenomic state associated with the LoDs may constitute a basis for the specific expression of genes contained in these genomic domains.
    Full-text · Article · Jul 2013 · DNA Research
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    • "Oocytes, the female germ cells, contain all of the messenger RNAs necessary to start a new life, but typically wait until fertilization to begin development. The transition from oocyte to zygote involves many changes, including protein synthesis, protein and RNA degradation, organelle remodeling, and even the onset of sexual differentiation [43-45]. Fifteen to thirty percent of mRNA transcripts are degraded during zygote gene activation [46]. "
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    ABSTRACT: Detailed knowledge of the molecular and cellular mechanisms that direct spatial and temporal gene expression in pre-implantation embryos is critical for understanding the control of the maternal-zygotic transition and cell differentiation in early embryonic development. In this study, twenty-three clones, expressed at different stages of early mouse development, were identified using differential display reverse transcription polymerase chain reaction (DDRT-PCR). One of these clones, which is expressed in 2-cell stage embryos at 48 hr post-hCG injection, shows a perfect sequence homology to the gene encoding the granzyme G protein. The granzyme family members are serine proteases that are present in the secretory granules of cytolytic T lymphocytes. However, the pattern of granzyme G expression and its function in early mouse embryos are entirely unknown. Upon the introduction of an antisense morpholino (2 mM) against granzyme G to knock-down endogenous gene function, all embryos were arrested at the 2- to 4-cell stages of egg cleavage, and the de novo synthesis of zygotic RNAs was decreased. The embryonic survival rate was dramatically decreased at the late 2-cell stage when serine protease-specific inhibitors, 0.1 mM 3,4-dichloroisocoumarin (3,4-DCI), and 2 mM phenyl methanesulphonyl fluoride (PMSF), were added to the in vitro embryonic culture medium. Survival was not affected by the addition of 0.5 mM EDTA, a metalloproteinase inhibitor. We characterized for the first time the expression and function of granzyme G during early stage embryogenesis. Our data suggest that granzyme G is an important factor in early mouse embryonic development and may play a novel role in the elimination of maternal proteins and the triggering of zygotic gene expression during the maternal-zygotic transition.
    Full-text · Article · Aug 2010 · BMC Developmental Biology
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    ABSTRACT: In vitro-produced (IVP) equine blastocysts can give rise to successful pregnancies, but their morphology and developmental rate differ from those of in vivo-derived equine blastocysts. The aim of the present study was to evaluate this difference at the genetic level. Suppression subtractive hybridisation (SSH) was used to construct a cDNA library enriched for transcripts preferentially expressed in in vivo-derived equine blastocysts compared with IVP blastocysts. Of the 62 different genes identified in this way, six genes involved in embryonic development (BEX2, FABP3, HSP90AA1, MOBKL3, MCM7 and ODC) were selected to confirm this differential expression by reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR). Using RT-qPCR, five genes were confirmed to be significantly upregulated in in vivo-derived blastocysts (i.e. FABP3, HSP90AA1 (both P<0.05), ODC, MOBKL3 and BEX2 (P<0.005 for all three)), confirming the results of the SSH. There was no significant difference in MCM7 expression between IVP and in vivo-derived blastocysts. In conclusion, five genes that are transcriptionally upregulated in in vivo-derived equine blastocysts compared with IVP blastocysts have been identified. Because of their possible importance in embryonic development, the expression of these genes can be used as a marker to evaluate in vitro embryo production systems in the horse.
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