Tissue and cancer-specific expression of DIEXF is epigenetically mediated by an Alu repeat.

Alu repeats constitute a major fraction of human genome and for a small subset of them a role in gene regulation has been described. The number of studies focused on the functional characterization of particular Alu elements is very limited. Most Alu elements are DNA methylated and then assumed to lie in repressed chromatin domains.

Acute Myeloid Leukemia: Aging and Epigenetics.

Acute myeloid leukemia (AML) is an aggressive hematological disorder mainly affecting people of older age. AML initiation is primarily attributed to mutations in crucial cellular regulators such as epigenetic factors, transcription factors, and signaling genes. AML's aggressiveness and responsiveness to treatment depends on the specific cell type where leukemia first arose.

Understanding intrinsic hematopoietic stem cell aging.

Hematopoietic stem cells (HSC) sustain blood production over the entire life-span of an organism. It is of extreme importance that these cells maintain self-renewal and differentiation potential over time in order to preserve homeostasis of the hematopoietic system. Many of the intrinsic aspects of HSC are affected by the aging process resulting in a deterioration in their potential, independently of their microenvironment.

Haematopoietic stem cells in perisinusoidal niches are protected from ageing.

With ageing, intrinsic haematopoietic stem cell (HSC) activity decreases, resulting in impaired tissue homeostasis, reduced engraftment following transplantation and increased susceptibility to diseases. However, whether ageing also affects the HSC niche, and thereby impairs its capacity to support HSC function, is still widely debated. Here, by using in-vivo long-term label-retention assays we demonstrate that aged label-retaining HSCs, which are, in old mice, the most quiescent HSC subpopulation with the highest regenerative capacity and cellular polarity, reside predominantly in perisinusoidal niches.

Hematopoietic Stem Cell Dynamics Are Regulated by Progenitor Demand: Lessons from a Quantitative Modeling Approach.

The prevailing view on murine hematopoiesis and on hematopoietic stem cells (HSCs) in particular derives from experiments that are related to regeneration after irradiation and HSC transplantation. However, over the past years, different experimental techniques have been developed to investigate hematopoiesis under homeostatic conditions, thereby providing access to proliferation and differentiation rates of hematopoietic stem and progenitor cells in the unperturbed situation. Moreover, it has become clear that hematopoiesis undergoes distinct changes during aging with large effects on HSC abundance, lineage contribution, asymmetry of division, and self-renewal potential.

Fast and Efficient Neural Conversion of Human Hematopoietic Cells.

A major challenge in regenerative medicine is the generation of functionally effective target cells to replace or repair damaged tissues. The finding that most somatic cells can be directly converted into cells of another lineage by the expression of specific transcription factors has paved the way to novel applications. Induced neurons (iNs) represent an alternative source of neurons for disease modeling, drug screening, and potentially, for cell replacement therapy.

Proinflammatory signals are insufficient to drive definitive hematopoietic specification of human HSCs in vitro.

Recent studies in zebrafish and mice have revealed that proinflammatory signaling is a positive regulator of definitive hematopoietic development. Whether proinflammatory signaling also regulates human hematopoietic specification remains unknown. Here, we explored the impact of the proinflammatory cytokines tumor necrosis factor-α (TNFα), interferon-γ (IFNγ), and interleukin-1β (IL1β) on in vitro hematopoietic differentiation using human pluripotent stem cells.

Genome engineering through CRISPR/Cas9 technology in the human germline and pluripotent stem cells.

Background: With the recent development of CRISPR (clustered regularly interspaced short palindromic repeats)/Cas9 genome editing technology, the possibility to genetically manipulate the human germline (gametes and embryos) has become a distinct technical possibility. Although many technical challenges still need to be overcome in order to achieve adequate efficiency and precision of the technology in human embryos, the path leading to genome editing has never been simpler, more affordable, and widespread.

Objective And Rationale: In this narrative review we seek to understand the possible impact of CRISR/Cas9 technology on human reproduction from the technical and ethical point of view, and suggest a course of action for the scientific community.

SETD7 Regulates the Differentiation of Human Embryonic Stem Cells.

The successful use of specialized cells in regenerative medicine requires an optimization in the differentiation protocols that are currently used. Understanding the molecular events that take place during the differentiation of human pluripotent cells is essential for the improvement of these protocols and the generation of high quality differentiated cells. In an effort to understand the molecular mechanisms that govern differentiation we identify the methyltransferase SETD7 as highly induced during the differentiation of human embryonic stem cells and differentially expressed between induced pluripotent cells and somatic cells.

Female human pluripotent stem cells rapidly lose X chromosome inactivation marks and progress to a skewed methylation pattern during culture.

Study Hypothesis: Does a preferential X chromosome inactivation (XCI) pattern exist in female human pluripotent stem cells (hPSCs) and does the pattern change during long-term culture or upon differentiation?

Study Finding: We identified two independent phenomena that lead to aberrant XCI patterns in female hPSC: a rapid loss of histone H3 lysine 27 trimethylation (H3K27me3) and long non-coding X-inactive specific transcript (XIST) expression during culture, often accompanied by erosion of XCI-specific methylation, and a frequent loss of random XCI in the cultures.

What Is Known Already: Variable XCI patterns have been reported in female hPSC, not only between different hPSC lines, but also between sub-passages of the same cell line, however the reasons for this variability remain unknown. Moreover, while non-random XCI-linked DNA methylation patterns have been previously reported, their origin and extent have not been investigated.

Modelling Fanconi anemia pathogenesis and therapeutics using integration-free patient-derived iPSCs.

Fanconi anaemia (FA) is a recessive disorder characterized by genomic instability, congenital abnormalities, cancer predisposition and bone marrow (BM) failure. However, the pathogenesis of FA is not fully understood partly due to the limitations of current disease models. Here, we derive integration free-induced pluripotent stem cells (iPSCs) from an FA patient without genetic complementation and report in situ gene correction in FA-iPSCs as well as the generation of isogenic FANCA-deficient human embryonic stem cell (ESC) lines.

The lysine-specific demethylase 1 is a novel substrate of protein kinase CK2.

Protein kinase CK2 is a pleiotropic serine/threonine kinase responsible for the generation of a substantial proportion of the human phosphoproteome. CK2 is generally found as a tetramer with two catalytic, α and α' and two non catalytic β subunits. CK2α C-terminal tail phosphorylation is regulated during the mitotic events and the absence of these phosphosites in α' suggests an isoform specialization.

Regenerative medicine: transdifferentiation in vivo.

A major challenge in regenerative medicine is the generation of functionally effective target cells to replace or repair damaged tissues. Transdifferentiation in vivo is a novel strategy to achieve cell fate conversion within the native physiological niche; this technology may provide a time- and cost-effective alternative for applications in regenerative medicine and may also minimize the concerns associated with in vitro culture and cell transplantation.

MicroRNAs contribute to induced pluripotent stem cell somatic donor memory.

Induced pluripotent stem cells (iPSCs) maintain during the first few culture passages a set of epigenetic marks and metabolites characteristic of their somatic cell of origin, a concept defined as epigenetic donor memory. These residual somatic features are lost over time after extensive culture passaging. Therefore, epigenetic donor memory may be responsible for the higher differentiation efficiency toward the tissue of origin observed in low passage iPSCs versus high passage iPSC or iPSCs derived from a different tissue source.

Gating pluripotency via nuclear pores.

In recent years, growing evidence has pointed to the interesting idea that pluripotency might be regulated by a nuclear-pore-coordinated network that controls the level of pluripotency factors in the nucleus. A thorough understanding of this process might improve our comprehension of cell pluripotency and differentiation during embryogenesis, as well as aiding the development of novel models for studying human diseases.

SMYD2 is induced during cell differentiation and participates in early development.

Histone modifying enzymes play critical roles in cell differentiation and development. In this study, we report that SMYD2 (SET and MYND domain containing protein 2), a histone lysine methyltransferase, is induced during human embryonic stem (ES) cell differentiation and it is preferentially expressed in somatic cells versus pluripotent cells. Knockdown of SMYD2 in human ES cells promotes the induction of endodermal markers during differentiation, while overexpression has opposite effects.

Macro histone variants are critical for the differentiation of human pluripotent cells.

We have previously shown that macro histone variants (macroH2A) are expressed at low levels in stem cells and are up-regulated during differentiation. Here we show that the knockdown of macro histone variants impaired the in vitro and in vivo differentiation of human pluripotent cells, likely through defects in the silencing of pluripotency-related genes. ChIP experiments showed that during differentiation macro histone variants are recruited to the regulatory regions of pluripotency and developmental genes marked with H3K27me3 contributing to the silencing of these genes.

Macrohistone variants preserve cell identity by preventing the gain of H3K4me2 during reprogramming to pluripotency.

Transcription-factor-induced reprogramming of somatic cells to pluripotency is a very inefficient process, probably due to the existence of important epigenetic barriers that are imposed during differentiation and that contribute to preserving cell identity. In an effort to decipher the molecular nature of these barriers, we followed a genome-wide approach, in which we identified macrohistone variants (macroH2A) as highly expressed in human somatic cells but downregulated after reprogramming to pluripotency, as well as strongly induced during differentiation. Knockdown of macrohistone variants in human keratinocytes increased the efficiency of reprogramming to pluripotency, whereas overexpression had opposite effects.

Dedifferentiation, transdifferentiation, and reprogramming: future directions in regenerative medicine.

The main goal of regenerative medicine is to replace damaged tissue. To do this it is necessary to understand in detail the whole regeneration process including differentiated cells that can be converted into progenitor cells (dedifferentiation), cells that can switch into another cell type (transdifferentiation), and somatic cells that can be induced to become pluripotent cells (reprogramming). By studying the regenerative processes in both nonmammal and mammal models, natural or artificial processes could underscore the molecular and cellular mechanisms behind these phenomena and be used to create future regenerative strategies for humans.

Vitrified blastocysts from Preimplantation Genetic Diagnosis (PGD) as a source for human Embryonic Stem Cell (hESC) derivation.

Embryos diagnosed as abnormal in Preimplantation Genetic Diagnosis (PGD) cycles are useful for the establishment of human Embryonic Stem Cells (hESC) lines with genetic disorders. These lines can be helpful for drug screening and for the development of new treatments. Vitrification has proved to be an efficient method to preserve human blastocysts.

DNA hypermethylation in somatic cells correlates with higher reprogramming efficiency.

The efficiency of somatic cell reprogramming to pluripotency using defined factors is dramatically affected by the cell type of origin. Here, we show that human keratinocytes, which can be reprogrammed at a higher efficiency than fibroblast [Nat Biotechnol 2008;26:1276-1284], share more genes hypermethylated at CpGs with human embryonic stem cells (ESCs) than other somatic cells frequently used for reprogramming. Moreover, pluripotent cells reprogrammed from keratinocytes (KiPS) are more similar to ESCs than those reprogrammed from fibroblasts (FiPS) in regard to DNA methylation levels, mostly due to the presence of genes that fail to acquire high levels of DNA methylation in FiPS cells.

Accumulation of instability in serial differentiation and reprogramming of parthenogenetic human cells.

Human leukocyte antigen-homozygous parthenogenetic stem cells (pSC) could provide a source of progenitors for regenerative medicine, lowering the need for immune suppression in patients. However, the high level of homozygosis and the lack of a paternal genome might pose a safety challenge for their therapeutic use, and no study so far has evaluated the spread and significance of gene expression changes across serial potency changes in these cells. We performed serial rounds of differentiation and reprogramming to assess pSC gene expression stability, likely of epigenetic source.

Identification of phosphorylase kinase as a novel therapeutic target through high-throughput screening for anti-angiogenesis compounds in zebrafish.

Angiogenesis is essential for development and tumor progression. With the aim of identifying new compound inhibitors of the angiogenesis process, we used an established enhanced green fluorescent protein-transgenic zebrafish line to develop an automated assay that enables high-throughput screening of compound libraries in a whole-organism setting. Using this system, we have identified novel kinase inhibitor compounds that show anti-angiogenic properties in both zebrafish in-vivo system and in human endothelial cell in-vitro angiogenesis models.

Increased dosage of tumor suppressors limits the tumorigenicity of iPS cells without affecting their pluripotency.

Embryonic stem (ES) cells and induced pluripotent stem (iPS) cells represent a promising therapeutic tool for many diseases, including aged tissues and organs at high risk of failure. However, the intrinsic self-renewal and pluripotency of ES and iPS cells make them tumorigenic, and hence, the risk of tumor development hinders their clinical application. Here, we present a novel approach to limit their tumorigenicity and increase their safety through increased copy number of tumor suppressors.