Zscan4 mediates ubiquitination and degradation of the corepressor complex to promote chromatin accessibility in 2C-like cells.

Zygotic genome activation occurs in two-cell (2C) embryos, and a 2C-like state is also activated in sporadic (~1%) naïve embryonic stem cells in mice. Elevated chromatin accessibility is critical for the 2C-like state to occur, yet the underlying molecular mechanisms remain elusive. Zscan4 exhibits burst expression in 2C embryos and 2C-like cells.

The totipotent 2C-like state safeguards genomic stability of mouse embryonic stem cells.

Mouse embryonic stem cells (mESCs) sporadically transition to a transient totipotent state that resembles blastomeres of the two-cell (2C) embryo stage, which has been proposed to contribute to exceptional genomic stability, one of the key features of mESCs. However, the biological significance of the rare population of 2C-like cells (2CLCs) in ESC cultures remains to be tested. Here we generated an inducible reporter cell system for specific elimination of 2CLCs from the ESC cultures to disrupt the equilibrium between ESCs and 2CLCs.

The ICF syndrome protein CDCA7 harbors a unique DNA-binding domain that recognizes a CpG dyad in the context of a non-B DNA.

, encoding a protein with a C-terminal cysteine-rich domain (CRD), is mutated in immunodeficiency, centromeric instability and facial anomalies (ICF) syndrome, a disease related to hypomethylation of juxtacentromeric satellite DNA. How CDCA7 directs DNA methylation to juxtacentromeric regions is unknown. Here, we show that the CDCA7 CRD adopts a unique zinc-binding structure that recognizes a CpG dyad in a non-B DNA formed by two sequence motifs.

Genetic Studies on Mammalian DNA Methyltransferases.

Cytosine methylation at the C5-position-generating 5-methylcytosine (5mC)-is a DNA modification found in many eukaryotic organisms, including fungi, plants, invertebrates, and vertebrates, albeit its levels vary greatly in different organisms. In mammals, cytosine methylation occurs predominantly in the context of CpG dinucleotides, with the majority (60-80%) of CpG sites in their genomes being methylated. DNA methylation plays crucial roles in the regulation of chromatin structure and gene expression and is essential for mammalian development.

Zscan4 Contributes to Telomere Maintenance in Telomerase-Deficient Late Generation Mouse ESCs and Human ALT Cancer Cells.

Proper telomere length is essential for indefinite self-renewal of embryonic stem (ES) cells and cancer cells. Telomerase-deficient late generation mouse ES cells and human ALT cancer cells are able to propagate for numerous passages, suggesting telomerase-independent mechanisms responding for telomere maintenance. However, the underlying mechanisms ensuring the telomere length maintenance are unclear.

Chemical combinations potentiate human pluripotent stem cell-derived 3D pancreatic progenitor clusters toward functional β cells.

Human pluripotent stem cell (hPSC)-derived pancreatic β cells are an attractive cell source for treating diabetes. However, current derivation methods remain inefficient, heterogeneous, and cell line dependent. To address these issues, we first devised a strategy to efficiently cluster hPSC-derived pancreatic progenitors into 3D structures.

Expanding the Toolbox and Targets for Gene Editing.

Genome editing holds great promise for treating a range of human genetic diseases. While emerging clustered regularly interspaced short-palindromic repeats (CRISPR) technologies allow editing of the nuclear genome, it is still not possible to precisely manipulate mitochondrial DNA (mtDNA). Here, we summarize past developments and recent advances in nuclear and mitochondrial genome editing.

The Arginine Methyltransferase PRMT6 Regulates DNA Methylation and Contributes to Global DNA Hypomethylation in Cancer.

DNA methylation plays crucial roles in chromatin structure and gene expression. Aberrant DNA methylation patterns, including global hypomethylation and regional hypermethylation, are associated with cancer and implicated in oncogenic events. How DNA methylation is regulated in developmental and cellular processes and dysregulated in cancer is poorly understood.

Zscan4 Inhibits Maintenance DNA Methylation to Facilitate Telomere Elongation in Mouse Embryonic Stem Cells.

Proper telomere length is essential for embryonic stem cell (ESC) self-renewal and pluripotency. Mouse ESCs (mESCs) sporadically convert to a transient totipotent state similar to that of two-cell (2C) embryos to recover shortened telomeres. Zscan4, which exhibits a burst of expression in 2C-like mESCs, is required for telomere extension in these cells.

Genetic Studies on Mammalian DNA Methyltransferases.

Cytosine methylation at the C5-position, generating 5-methylcytosine (5mC), is a DNA modification found in many eukaryotic organisms, including fungi, plants, invertebrates, and vertebrates, albeit its levels vary greatly in different organisms. In mammals, cytosine methylation occurs predominantly in the context of CpG dinucleotides, with the majority (60-80 %) of CpG sites in their genomes being methylated. DNA methylation plays crucial roles in the regulation of chromatin structure and gene expression and is essential for mammalian development.

Tet Enzymes Regulate Telomere Maintenance and Chromosomal Stability of Mouse ESCs.

Ten-eleven translocation (Tet) family proteins convert 5-methylcytosine to 5-hydroxymethylcytosine. We show that mouse embryonic stem cells (ESCs) depleted of Tet1 and/or Tet2 by RNAi exhibit short telomeres and chromosomal instability, concomitant with reduced telomere recombination. Tet1 and Tet2 double-knockout ESCs also display short telomeres but to a lesser extent.

Maternal Setdb1 Is Required for Meiotic Progression and Preimplantation Development in Mouse.

Oocyte meiotic progression and maternal-to-zygote transition are accompanied by dynamic epigenetic changes. The functional significance of these changes and the key epigenetic regulators involved are largely unknown. Here we show that Setdb1, a lysine methyltransferase, controls the global level of histone H3 lysine 9 di-methyl (H3K9me2) mark in growing oocytes.

Tcstv1 and Tcstv3 elongate telomeres of mouse ES cells.

Mouse embryonic stem cell (ESC) cultures exhibit a heterogeneous mixture of metastable cells sporadically entering the 2-cell (2C)-embryo-like state, critical for ESC potency. One of 2-cell genes, Zscan4, has been shown to be responsible for telomere maintenance, genomic stability and pluripotency of mouse ESCs. Functions of other 2C-genes in ESCs remain elusive.

Roles for Histone Acetylation in Regulation of Telomere Elongation and Two-cell State in Mouse ES Cells.

Mammalian telomeres and subtelomeres are marked by heterochromatic epigenetic modifications, including repressive DNA methylation and histone methylation (e.g., H3K9me3 and H4K20me3).

Drp1 is dispensable for mitochondria biogenesis in induction to pluripotency but required for differentiation of embryonic stem cells.

Mature mitochondria with high oxidative phosphorylation undergo fission and fusion and morphogenesis to become immature mitochondria during induced pluripotent stem (iPS) induction from somatic cells. Dynamin-related protein 1 (Drp1) is involved in mitochondria fission and biogenesis in somatic cells. We tested the role of Drp1 in the induction and maintenance of pluripotency.

Rif1 maintains telomere length homeostasis of ESCs by mediating heterochromatin silencing.

Telomere length homeostasis is essential for genomic stability and unlimited self-renewal of embryonic stem cells (ESCs). We show that telomere-associated protein Rif1 is required to maintain telomere length homeostasis by negatively regulating Zscan4 expression, a critical factor for telomere elongation by recombination. Depletion of Rif1 results in terminal hyperrecombination, telomere length heterogeneity, and chromosomal fusions.

Roles for Tbx3 in regulation of two-cell state and telomere elongation in mouse ES cells.

Mouse embryonic stem (ES) cell cultures exhibit heterogeneity and recently are discovered to sporadically enter the 2-cell (2C)-embryo state, critical for ES potency. Zscan4 could mark the sporadic 2C-state of ES cells. However, factors that regulate the Zscan4(+)/2C state remain to be elucidated.

Reprogramming- and pluripotency-associated membrane proteins in mouse stem cells revealed by label-free quantitative proteomics.

Unlabelled: Induced pluripotent stem cells (iPSCs), derived from somatic cells and functionally very similar to embryonic stem cells (ESCs), are at the center stage of intense research in regenerative medicine. We carried out the first membrane proteomic profiling of mouse iPSCs, in comparison with ESCs and adult mouse tail tip fibroblasts (TTFs) from which iPSCs were generated. Using a proteomic workflow combining membrane fractionation, SDS-PAGE separation and nanoUPLC-MS(E) technology, we identified 673, 679 and 682 non-redundant proteins from mouse iPSC, ESC and TTF membrane fractions, respectively.

Influences of lamin A levels on induction of pluripotent stem cells.

Lamin A is an inner nuclear membrane protein that maintains nuclear structure integrity, is involved in transcription, DNA damage response and genomic stability, and also links to cell differentiation, senescence, premature aging and associated diseases. Induced pluripotent stem (iPS) cells have been successfully generated from various types of cells and used to model human diseases. It remains unclear whether levels of lamin A influence reprogramming of somatic cells to pluripotent states during iPS induction.

Molecular insights into the heterogeneity of telomere reprogramming in induced pluripotent stem cells.

Rejuvenation of telomeres with various lengths has been found in induced pluripotent stem cells (iPSCs). Mechanisms of telomere length regulation during induction and proliferation of iPSCs remain elusive. We show that telomere dynamics are variable in mouse iPSCs during reprogramming and passage, and suggest that these differences likely result from multiple potential factors, including the telomerase machinery, telomerase-independent mechanisms and clonal influences including reexpression of exogenous reprogramming factors.