Project description:It has been demonstrated previously that the reprogramming factors are sequestered in the pronuclei of zygote after fertilization, as the enucleated zygotes at interphase cannot support the development of cloned embryos whereas the enucleated zygotes at M-phase can reprogram somatic cells to full pluripotency. However, it remains unknown whether the parental pronucleus, derived either from the sperm or oocyte, possesses the similar reprogramming ability. Here, we provide evidence demonstrating that the parental pronuclei are asymmetric in reprogramming and the reprogramming factors reside mainly in the male pronucleus. As a result, only the female pronucleus-depleted mouse zygotes enucleated at M-phase of mitosis can support the somatic cell reprogramming, the derivation of chromosome transfer embryonic stem (ctES) cells with full pluripotency and the full term development of cloned embryos. In striking contrast, the male pronucleus-depleted zygotes enucleated at M-phase of mitosis fail to support the pre-implantation development of somatic cell cloned embryos. Furthermore, we demonstrated that the distinct epigenetic reprogramming ability of the parental pronucleus might contribute directly to the developmental difference of somatic cloned embryos. Our study highlights the developmental asymmetry of parental pronuclei in reprogramming.
Project description:Embryogenesis begins with a zygote, a single cell with two pronuclei that separately enclose maternal and paternal chromosomes. The functional significance of the separation of parental chromosomes into distinct pronuclei remains unexplored, despite the fact that one-pronuclear biparental zygotes are used clinically. Here, using a combination of mouse zygote manipulation, quantitative imaging and theoretical approaches, we show a cytoplasm-mediated competition mechanism between separate parental pronuclei that ensures developmental potential. This mechanism limits pronuclear volume and prevents epigenetic mark dysregulation, including loss of maternal trimethylated histones. One-pronuclear biparental zygotes lack this mechanism, resulting in a reduced rate of development to term. This low developmental potential can be rescued by competition-based or drug-based restoration of epigenetic marks. This study provides a spatial mechanism linking fertilization to the establishment of the full developmental potential for the next generation, highlighting caveats in clinical use of one-pronuclear biparental zygotes.
Project description:Embryogenesis begins with a zygote, a single cell with two pronuclei that separately enclose maternal and paternal chromosomes. The functional significance of the separation of parental chromosomes into distinct pronuclei remains unexplored, despite the fact that one-pronuclear biparental zygotes are used clinically. Here, using a combination of mouse zygote manipulation, quantitative imaging and theoretical approaches, we show a cytoplasm-mediated competition mechanism between separate parental pronuclei that ensures developmental potential. This mechanism limits pronuclear volume and prevents epigenetic mark dysregulation, including loss of maternal trimethylated histones. One-pronuclear biparental zygotes lack this mechanism, resulting in a reduced rate of development to term. This low developmental potential can be rescued by competition-based or drug-based restoration of epigenetic marks. This study provides a spatial mechanism linking fertilization to the establishment of the full developmental potential for the next generation, highlighting caveats in clinical use of one-pronuclear biparental zygotes.
Project description:Embryogenesis begins with a zygote, a single cell with two pronuclei that separately enclose maternal and paternal chromosomes. The functional significance of the separation of parental chromosomes into distinct pronuclei remains unexplored, despite the fact that one-pronuclear biparental zygotes are used clinically. Here, using a combination of mouse zygote manipulation, quantitative imaging and theoretical approaches, we show a cytoplasm-mediated competition mechanism between separate parental pronuclei. This mechanism limits pronuclear volume and prevents the loss of epigenetic marks, including maternally inherited trimethylated histones. One-pronuclear biparental zygotes lack this mechanism, resulting in a reduced rate of development to term. This low developmental potential can be rescued by competition-based or drug-based restoration of epigenetic marks. In human zygotes, epigenetic loss correlates with pronuclear volume. This study provides insight into strategies to improve the clinical use of one-pronuclear biparental zygotes.
Project description:The epigenomes of mammalian sperm and oocytes, characterized by gamete-specific 5-methylcytosine (5mC) patterns, are reprogrammed during early embryogenesis to establish full developmental potential. Previous studies have suggested that the paternal genome is actively demethylated in the zygote while the maternal genome undergoes subsequent passive demethylation via DNA replication during cleavage. Active demethylation is known to depend on 5mC oxidation by Tet dioxygenases and excision of oxidized bases by thymine DNA glycosylase (TDG). Here we show that both maternal and paternal genomes undergo widespread active and passive demethylation in zygotes before the first mitotic division. Passive demethylation was blocked by the replication inhibitor aphidicolin, and active demethylation was abrogated by deletion of Tet3 in both pronuclei. At actively demethylated loci, 5mCs were processed to unmodified cytosines. Surprisingly, the demethylation process was unaffected by the deletion of TDG from the zygote, suggesting the existence of other demethylation mechanisms downstream of Tet3-mediated oxidation. The dataset includes RRBS anlysis of 2 MII oocyte samples, 3 WT female pronuclei samples PN3-4 stage, 2 Tet3 KO female pronuclei samples and 2 Aphidicolin treated female pronuclei samples. Also as male counterpart, a Sperm sample, 2 WT male pronuclei samples PN3-4 stage, 2 Tet3 KO male pronuclei samples and 2 Aphidicolin treated male pronuclei samples were included.
Project description:PURPOSE: To provide a detailed gene expression profile of the normal postnatal mouse cornea. METHODS: Serial analysis of gene expression (SAGE) was performed on postnatal day (PN)9 and adult mouse (6 week) total corneas. The expression of selected genes was analyzed by in situ hybridization. RESULTS: A total of 64,272 PN9 and 62,206 adult tags were sequenced. Mouse corneal transcriptomes are composed of at least 19,544 and 18,509 unique mRNAs, respectively. One third of the unique tags were expressed at both stages, whereas a third was identified exclusively in PN9 or adult corneas. Three hundred thirty-four PN9 and 339 adult tags were enriched more than fivefold over other published nonocular libraries. Abundant transcripts were associated with metabolic functions, redox activities, and barrier integrity. Three members of the Ly-6/uPAR family whose functions are unknown in the cornea constitute more than 1% of the total mRNA. Aquaporin 5, epithelial membrane protein and glutathione-S-transferase (GST) omega-1, and GST alpha-4 mRNAs were preferentially expressed in distinct corneal epithelial layers, providing new markers for stratification. More than 200 tags were differentially expressed, of which 25 mediate transcription. CONCLUSIONS: In addition to providing a detailed profile of expressed genes in the PN9 and mature mouse cornea, the present SAGE data demonstrate dynamic changes in gene expression after eye opening and provide new probes for exploring corneal epithelial cell stratification, development, and function and for exploring the intricate relationship between programmed and environmentally induced gene expression in the cornea. Keywords: other