Paternal and maternal genomes confer opposite effects on proliferation, cell-cycle length, senescence, and tumor formation

Challenges in the clinical advancement of cell therapies for Parkinson's disease

Cell therapies as potential treatments for Parkinson's disease first gained traction in the 1980s, owing to the clinical success of trials that used transplants of foetal midbrain dopaminergic tissue. However, the poor standardization of the tissue for grafting, and constraints on its availability and ethical use, have hindered this treatment strategy. Recent advances in stem-cell technologies and in the understanding of the development of dopaminergic neurons have enabled preclinical advancements of promising stem-cell therapies. To move these therapies to the clinic, appropriate levels of safety screening, as well as optimization of the cell products and the scalability of their manufacturing, will be required. In this Review, we discuss how challenges pertaining to cell sources, functional and safety testing, manufacturing and storage, and clinical-trial design are being addressed to advance the translational and clinical development of cell therapies for Parkinson's disease.

Lower expression of the equine maternally imprinted gene IGF2R is related to the slow proliferation of hinny embryonic fibroblast in vitro

BACKGROUND

Proliferation of embryonic fibroblasts under the same cell culture conditions, hinny embryonic fibroblasts (HiEFs) was slower than horse embryonic fibroblast (HEFs), donkey embryonic fibroblasts (DEFs) and mule embryonic fibroblasts (MuEFs). The imprinted genes IGF2 and IGF2R are important for cell proliferation. Therefore, we investigated whether the slower proliferation of HiEFs is related to an aberrant gene expression of IGF2 or its receptors or genes influencing the expression of the IGF2 system.

METHODS AND RESULTS

Real-time polymerase chain reaction, immunofluorescence and cell starving experiment in HEFs, DEFs, MuEFs and HiEFs revealed that the slower proliferation of HiEF in vitro was related to its lower expression of IGF2R (P < 0.001). Moreover, quantification of allele-specific expression and bisulfate assay confirmed that in both MuEFs and HiEFs, IGF2R had normal maternal imprinting, implying that the imprint aberrant was not involved in the lower IGF2R expression in HiEFs.

CONCLUSIONS

The reduction of IGF2R expression in HiEFs is associated with its slower proliferation in vitro.

Epigenetic integrity of paternal imprints enhances the developmental potential of androgenetic haploid embryonic stem cells

The use of two inhibitors of Mek1/2 and Gsk3β (2i) promotes the generation of mouse diploid and haploid embryonic stem cells (ESCs) from the inner cell mass of biparental and uniparental blastocysts, respectively. However, a system enabling long-term maintenance of imprints in ESCs has proven challenging. Here, we report that the use of a two-step a2i (alternative two inhibitors of Src and Gsk3β, TSa2i) derivation/culture protocol results in the establishment of androgenetic haploid ESCs (AG-haESCs) with stable DNA methylation at paternal DMRs (differentially DNA methylated regions) up to passage 60 that can efficiently support generating mice upon oocyte injection. We also show coexistence of H3K9me3 marks and ZFP57 bindings with intact DMR methylations. Furthermore, we demonstrate that TSa2i-treated AG-haESCs are a heterogeneous cell population regarding paternal DMR methylation. Strikingly, AG-haESCs with late passages display increased paternal-DMR methylations and improved developmental potential compared to early-passage cells, in part through the enhanced proliferation of H19-DMR hypermethylated cells. Together, we establish AG-haESCs that can long-term maintain paternal imprints.

Loss of p57KIP2 expression confers resistance to contact inhibition in human androgenetic trophoblast stem cells

Complete hydatidiform moles (CHMs) develop from androgenetic conceptuses and are characterized by enhanced proliferation of trophoblast cells and a significantly higher risk of trophoblast tumors. Loss of the maternal genome and duplication of the paternal genome are considered to be responsible for the phenotype, but the detailed mechanism remains unclear. Here, we report the derivation of trophoblast stem (TS) cells from CHMs. These cells have reduced sensitivity to contact inhibition of cell proliferation and exhibit aberrant expression of imprinted genes, which are expressed from only 1 parental allele. We also reveal that the maternally expressed imprinted gene p57^KIP2 would be responsible for the enhanced proliferation of CHM-derived TS cells. Our findings provide an insight into the pathogenesis of CHMs.

A complete hydatidiform mole (CHM) is androgenetic in origin and characterized by enhanced trophoblastic proliferation and the absence of fetal tissue. In 15 to 20% of cases, CHMs are followed by malignant gestational trophoblastic neoplasms including choriocarcinoma. Aberrant genomic imprinting may be responsible for trophoblast hypertrophy in CHMs, but the detailed mechanisms are still elusive, partly due to the lack of suitable animal or in vitro models. We recently developed a culture system of human trophoblast stem (TS) cells. In this study, we apply this system to CHMs for a better understanding of their molecular pathology. CHM-derived TS cells, designated as TS^mole cells, are morphologically similar to biparental TS (TS^bip) cells and express TS-specific markers such as GATA3, KRT7, and TFAP2C. Interestingly, TS^mole cells have a growth advantage over TS^bip cells only after they reach confluence. We found that p57^KIP2, a maternally expressed gene encoding a cyclin-dependent kinase inhibitor, is strongly induced by increased cell density in TS^bip cells, but not in TS^mole cells. Knockout and overexpression studies suggest that loss of p57^KIP2 expression would be the major cause of the reduced sensitivity to contact inhibition in CHMs. Our findings shed light on the molecular mechanism underlying the pathogenesis of CHMs and could have broad implications in tumorigenesis beyond CHMs because silencing of p57^KIP2 is frequently observed in a variety of human tumors.

Mouse Parthenogenetic Embryonic Stem Cells with Biparental-Like Expression of Imprinted Genes Generate Cortical-Like Neurons That Integrate into the Injured Adult Cerebral Cortex

One strategy for stem cell-based therapy of the cerebral cortex involves the generation and transplantation of functional, histocompatible cortical-like neurons from embryonic stem cells (ESCs). Diploid parthenogenetic Pg-ESCs have recently emerged as a promising source of histocompatible ESC derivatives for organ regeneration but their utility for cerebral cortex therapy is unknown. A major concern with Pg-ESCs is genomic imprinting. In contrast with biparental Bp-ESCs derived from fertilized oocytes, Pg-ESCs harbor two maternal genomes but no sperm-derived genome. Pg-ESCs are therefore expected to have aberrant expression levels of maternally expressed (MEGs) and paternally expressed (PEGs) imprinted genes. Given the roles of imprinted genes in brain development, tissue homeostasis and cancer, their deregulation in Pg-ESCs might be incompatible with therapy. Here, we report that, unexpectedly, only one gene out of 7 MEGs and 12 PEGs was differentially expressed between Pg-ESCs and Bp-ESCs while 13 were differentially expressed between androgenetic Ag-ESCs and Bp-ESCs, indicating that Pg-ESCs but not Ag-ESCs, have a Bp-like imprinting compatible with therapy. In vitro, Pg-ESCs generated cortical-like progenitors and electrophysiologically active glutamatergic neurons that maintained the Bp-like expression levels for most imprinted genes. In vivo, Pg-ESCs participated to the cortical lineage in fetal chimeras. Finally, transplanted Pg-ESC derivatives integrated into the injured adult cortex and sent axonal projections in the host brain. In conclusion, mouse Pg-ESCs generate functional cortical-like neurons with Bp-like imprinting and their derivatives properly integrate into both the embryonic cortex and the injured adult cortex. Collectively, our data support the utility of Pg-ESCs for cortical therapy. Stem Cells 2018;36:192-205.

Epigenetic analysis of bovine parthenogenetic embryonic fibroblasts

Although more than 100 imprinted genes have already been identified in the mouse and human genomes, little is known about genomic imprinting in cattle. For a better understanding of these genes in cattle, parthenogenetically activated bovine blastocysts were transferred to recipient cows to obtain parthenotes, and fibroblasts derived from a Day 40 (Day 0 being the day of parthenogenetic activation) parthenogenetic embryo (BpEFs) were successfully obtained. Bovine embryonic fibroblasts (BEFs) were also isolated from a normal fertilized embryo obtained from an artificially inseminated cow. The expression of imprinted genes was analyzed by RT-PCR. Paternally expressed genes (PEGs) in mouse (viz., IGF2, PEG3, ZAC1, NDN, DLK1, SGCE, and PEG10) were expressed in BEFs, but not in BpEFs, suggesting that these genes are also imprinted in cattle. However, other PEGs in mouse (viz., IMPACT, MAGEL2, SNRPN, and PEG1/MEST) were expressed in both BEFs and BpEFs. These genes may not be imprinted in BEFs. The expression of seven maternally expressed genes in mouse was also analyzed, and only CDKN1C was not expressed in BpEFs. The DNA methylation patterns of repetitive elements (Satellite I, Satellite II, alpha-satellite, and Art2) were not different between the BEFs and BpEFs; however, the differentially methylated region (DMR) of paternally methylated H19 was hypomethylated, whereas those of maternally methylated PEG3 and PEG10 were hypermethylated in BpEFs, as expected. The methylation of the SNRPN DMR was not different between the BEFs and BpEFs, in accordance with the SNRPN expression levels in both cell types. The XIST gene, which is essential for X chromosome inactivation in females, was expressed in BpEFs, whereas its DMR was half-methylated, suggesting that X chromosome inactivation is normal in these cells. Microarray analysis was also applied to identify novel PEGs that should be expressed only in BEFs but not in BpEFs. More than 300 PEG candidate genes, including IGF2, PEG3, and PEG10, were obtained. These results illustrate the epigenetic characteristic of bovine parthenogenetic embryos and contribute to the identification of novel imprinted genes in cattle.

Are Stem Cell-Based Therapies for Parkinson's Disease Ready for the Clinic in 2016?

Recent news of an impending clinical cell transplantation trial in Parkinson’s disease using parthenogenetic stem cells as a source of donor tissue have raised hopes in the patient community and sparked discussion in the research community. Based on discussions held by a global collaborative initiative on translation of stem cell therapy in Parkinson’s disease, we have identified a set of key questions that we believe should be addressed ahead of every clinical stem cell-based transplantation trial in this disorder. In this article, we first provide a short history of cell therapy in Parkinson’s disease and briefly describe the current state-of-art regarding human stem cell-derived dopamine neurons for use in any patient trial. With this background information as a foundation, we then discuss each of the key questions in relation to the upcoming therapeutic trial and critically assess if the time is ripe for clinical translation of parthenogenetic stem cell technology in Parkinson’s disease.

Paternal Insulin-like Growth Factor 2 (Igf2) Regulates Stem Cell Activity During Adulthood

Insulin-like Growth Factor 2 (IGF2) belongs to the IGF/Insulin pathway, a highly conserved evolutionarily network that regulates growth, aging and lifespan. Igf2 is highly expressed in the embryo and in cancer cells. During mouse development, Igf2 is expressed in all sites where hematopoietic stem cells (HSC) successively expand, then its expression drops at weaning and becomes undetectable when adult HSC have reached their niches in bones and start to self-renew. In the present study, we aim to discover the role of IGF2 during adulthood. We show that Igf2 is specifically expressed in adult HSC and we analyze HSC from adult mice deficient in Igf2 transcripts. We demonstrate that Igf2 deficiency avoids the age-related attrition of the HSC pool and that Igf2 is necessary for tissue homeostasis and regeneration. Our study reveals that the expression level of Igf2 is critical to maintain the balance between stem cell self-renewal and differentiation, presumably by regulating the interaction between HSC and their niche. Our data have major clinical interest for transplantation: understanding the changes in adult stem cells and their environments will improve the efficacy of regenerative medicine and impact health- and life-span.

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The imprinted gene Igf2 is expressed in adult tissue stem cells.

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Igf2 deficiency increases HSC (hematopoietic stem cells) self-renewal and avoids age-related attrition of the HSC pool.

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Igf2 deficiency decreases HSC differentiation and mobilization.

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Igf2 deficiency modifies the interaction between HSC and their environment.

IGF2 belongs to the IGF/Insulin family that regulates growth, aging and lifespan. This role is evolutionarily conserved from worms to mammals. IGF2 favors cell proliferation during embryonic development but its role in adulthood is unknown. To decipher its function we undertook a lifelong analysis of the consequences of Igf2 deficiency on hematopoiesis, in steady-state conditions and during bone marrow transplantation. We demonstrate that lowering Igf2 levels increases the pool of stem cells, without uncontrolled proliferation and migration of immature cells that would lead to cancer. This is a promising way to enhance the stem cells pool during aging that has major interest for transplantation.

Clinical potential of human-induced pluripotent stem cells : Perspectives of induced pluripotent stem cells

The recent establishment of induced pluripotent stem (iPS) cells promises the development of autologous cell therapies for degenerative diseases, without the ethical concerns associated with human embryonic stem (ES) cells. Initially, iPS cells were generated by retroviral transduction of somatic cells with core reprogramming genes. To avoid potential genotoxic effects associated with retroviral transfection, more recently, alternative non-viral gene transfer approaches were developed. Before a potential clinical application of iPS cell-derived therapies can be planned, it must be ensured that the reprogramming to pluripotency is not associated with genome mutagenesis or epigenetic aberrations. This may include direct effects of the reprogramming method or "off-target" effects associated with the reprogramming or the culture conditions. Thus, a rigorous safety testing of iPS or iPS-derived cells is imperative, including long-term studies in model animals. This will include not only rodents but also larger mammalian model species to allow for assessing long-term stability of the transplanted cells, functional integration into the host tissue, and freedom from undifferentiated iPS cells. Determination of the necessary cell dose is also critical; it is assumed that a minimum of 1 billion transplantable cells is required to achieve a therapeutic effect. This will request medium to long-term in vitro cultivation and dozens of cell divisions, bearing the risk of accumulating replication errors. Here, we review the clinical potential of human iPS cells and evaluate which are the most suitable approaches to overcome or minimize risks associated with the application of iPS cell-derived cell therapies.

Directing the Differentiation of Parthenogenetic Stem Cells into Tenocytes for Tissue-Engineered Tendon Regeneration

Uniparental parthenogenesis yields pluripotent stem cells without the political and ethical concerns surrounding the use of embryonic stem cells (ESCs) for biomedical applications. In the current study, we hypothesized that parthenogenetic stem cells (pSCs) could be directed to differentiate into tenocytes and applied for tissue‐engineered tendon. We showed that pSCs displayed fundamental properties similar to those of ESCs, including pluripotency, clonogenicity, and self‐renewal capacity. pSCs spontaneously differentiated into parthenogenetic mesenchymal stem cells (pMSCs), which were positive for mesenchymal stem cell surface markers and possessed osteogenic, chondrogenic, and adipogenic potential. Then, mechanical stretch was applied to improve the tenogenic differentiation of pMSCs, as indicated by the expression of tenogenic‐specific markers and an increasing COL1A1:3A1 ratio. The pSC‐derived tenocytes could proliferate and secrete extracellular matrix on the surface of poly(lactic‐co‐glycolic) acid scaffolds. Finally, engineered tendon‐like tissue was successfully generated after in vivo heterotopic implantation of a tenocyte‐scaffold composite. In conclusion, our experiment introduced an effective and practical strategy for applying pSCs for tendon regeneration. Stem Cells Translational Medicine2017;6:196–208

Regulation of the imprinted Dlk1-Dio3 locus by allele-specific enhancer activity

In this study, Luo et al. find that the AFF family protein AFF3 can specifically bind both gametic differentially DNA-methylated regions (gDMRs) and enhancers within imprinted loci in an allele-specific manner. These results provide the mechanistic details of the control of dosage-critical imprinted gene expression through the regulated binding of the transcription elongation factor AFF3 between a DMR and an enhancer.

Genomic imprinting is a critical developmental process characteristic of parent of origin-specific gene expression. It is well accepted that differentially DNA-methylated regions (DMRs) and enhancers are two major classes of cis-elements determining parent of origin-specific gene expression, with each recruiting different sets of transcription factors. Previously, we identified the AF4/FMR2 (AFF) family protein AFF3 within the transcription elongation complex SEC-L3. Here, we report that AFF3 can specifically bind both gametic DMRs (gDMRs) and enhancers within imprinted loci in an allele-specific manner. We identify the molecular regulators involved in the recruitment of AFF3 to gDMRs and provide mechanistic insight into the requirement of AFF3 at an enhancer for the expression of an ∼200-kb polycistronic transcript within the imprinted Dlk1-Dio3 locus. Our data suggest that the heterochromatic environment at the gDMR reinforces silencing of its related enhancer by controlling the binding and activity of AFF3 in an allele-specific manner. In summary, this study provides molecular details about the regulation of dosage-critical imprinted gene expression through the regulated binding of the transcription elongation factor AFF3 between a DMR and an enhancer.

An integrative view on sex differences in brain tumors

Sex differences in human health and disease can range from undetectable to profound. Differences in brain tumor rates and outcome are evident in males and females throughout the world and regardless of age. These observations indicate that fundamental aspects of sex determination can impact the biology of brain tumors. It is likely that optimal personalized approaches to the treatment of male and female brain tumor patients will require recognizing and understanding the ways in which the biology of their tumors can differ. It is our view that sex-specific approaches to brain tumor screening and care will be enhanced by rigorously documenting differences in brain tumor rates and outcomes in males and females, and understanding the developmental and evolutionary origins of sex differences. Here we offer such an integrative perspective on brain tumors. It is our intent to encourage the consideration of sex differences in clinical and basic scientific investigations.

Brief report: Parthenogenetic embryonic stem cells are an effective cell source for therapeutic liver repopulation

Parthenogenesis is the development of an oocyte without fertilization. Mammalian parthenogenetic (PG) embryos are not viable, but can develop into blastocysts from which embryonic stem cells (ESCs) have been derived in mouse and human. PG ESCs are frequently homozygous for alleles encoding major histocompatibility complex (MHC) molecules. MHC homozygosity permits much more efficient immune matching than MHC heterozygosity found in conventional ESCs, making PG ESCs a promising cell source for cell therapies requiring no or little immune suppression. However, findings of restricted differentiation and proliferation of PG cells in developmental chimeras have cast doubt on the potential of PG ESC derivatives for organ regeneration. To address this uncertainty, we determined whether PG ESC derivatives are effective in rescuing mice with lethal liver failure due to deficiency of fumarylacetoacetate hydrolase (Fah). In developmental chimeras generated by injecting wild-type PG ESCs into Fah-deficient blastocysts, PG ESCs differentiated into hepatocytes that could repopulate the liver, provide normal liver function, and facilitate long-term survival of adult mice. Moreover, after transplantation into adult Fah-deficient mice, PG ESC-derived hepatocytes efficiently engrafted and proliferated, leading to high-level liver repopulation. Our results show that--despite the absence of a paternal genome--PG ESCs can form therapeutically effective hepatocytes.

Inducing human parthenogenetic embryonic stem cells into islet‑like clusters

In order to determine whether human parthenogenetic embryonic stem (hpES) cells have the potential to differentiate into functional cells, a modified four-step protocol was used to induce the hpES cells into islet-like clusters (ILCs) in vitro. Growth factors activin A, retinoic acid, nicotinamide, Exendin-4 and betacellulin were added sequentially to the hpES cells at each step. The terminally differentiated cells were shown to gather into ILCs. Immunohistochemistry and semi quantitative polymerase chain reaction analyses demonstrated that the ILCs expressed islet specific hormones and functional markers. Furthermore, an insulin release test indicated that the clusters had the same physiological function as islets. The ILCs derived from hpES cells shared similar characteristics with islets. These results indicate that hpES cell-derived ILCs may be used as reliable material for the treatment of type I diabetes mellitus.

Knockdown of IGF2R suppresses proliferation and induces apoptosis in hemangioma cells in vitro and in vivo

Insulin-like growth factor-II (IGF-II)/IGF2R signaling plays a pivotal role in cell growth, migration and differentiation in many malignancies. An individual with high IGF-II expression levels has a high risk of developing cancer, but IGF2R is often considered to be a tumor suppressor. To date, little has been reported about the role of IGF-II/IGF2R signaling in hemangiomas (HAs). Thus, uncovering the mechanisms of IGF-II/IGF2R signaling is very important to understanding the development of HAs. In the present study, the expression of IGF-II and IGF2R was investigated in 27 cases of HAs of different phases by immunohistochemistry. Through lentivirus-mediated IGF2R siRNA (Lv-siIGF2R) in HA-derived endothelial cells (HDECs), we observed the effects of IGF2R knockdown on the biological behavior of HA cells. We found that the expression of IGF-II and IGF2R was significantly increased in proliferating phase HAs, but decreased in involuting phase HAs. Furthermore, knockdown of IGF2R in vitro significantly diminished the proliferative activity and induced apoptosis and cycle arrest with decreased expression of PCNA, Ki-67, Bcl-2, Cyclin D1 and E and increased the expression of Bax in the proliferative phase HAs (HDEC and CRL-2586 EOMA cells). In addition, the tumor volumes in a subcutaneous HDEC nude mouse model treated with Lv-siIGF2R were significantly smaller than those of the control group. Taken together, our findings indicate that the expression of IGF-II and IGF2R is increased in proliferating phase HAs, and knockdown of IGF2R suppresses proliferation and induces apoptosis in HA cells in vitro and in vivo, suggesting that IGF2R may represent a novel therapeutic target for the treatment of human HAs.

Autophagy and apoptosis: parent-of-origin genome-dependent mechanisms of cellular self-destruction

Functional genomic imprinting is necessary for the transfer of maternal resources to mammalian embryos. Imprint-free embryos are unable to establish a viable placental vascular network necessary for the transfer of resources such as nutrients and oxygen. How the parental origin of inherited genes influences cellular response to resource limitation is currently not well understood. Because such limitations are initially realized by the placenta, we studied how maternal and paternal genomes influence the cellular self-destruction responses of this organ specifically. Here, we show that cellular autophagy is prevalent in androgenetic (i.e. having only a paternal genome) placentae, while apoptosis is prevalent in parthenogenetic (i.e. having only a maternal genome) placentae. Our findings indicate that the parental origin of inherited genes determines the placenta's cellular death pathway: autophagy for androgenotes and apoptosis for parthenogenotes. The difference in time of arrest between androgenotes and parthenogenotes can be attributed, at least in part, to their placentae's selective use of these two cell death pathways. We anticipate our findings to be a starting point for general studies on the parent-of-origin regulation of autophagy. Furthermore, our work opens the door to new studies on the involvement of autophagy in pathologies of pregnancy in which the restricted transfer of maternal resources is diagnosed.

Effects of histone deacetylase inhibitors on the early development of bovine androgenetic embryos

Histone acetylation is one of the most important posttranslational modifications that contribute to transcriptional initiation and chromatin remodeling. In our previous study, we enhanced sperm chromatin remodeling within the bovine sperm injection-derived androgenentic (SpI-AG) embryos by sperm pretreatment, and thereby improved their early developmental competence. In this study, we found that blastocyst development of SpI-AG embryos could be elevated by the histone deacetylase inhibitor (HDACi). First, we optimized the efficacy of two histone deacetylase inhibitors [trichostatin A (TSA) and Scriptaid (SCR)] in a dose (0, 5, 10, 20, 50, and 100 nM for TSA; 0, 50, 100, 200, 300, and 500 nM for SCR, respectively) and time-dependent (0, 10, 15, 20, and 25 h) manner on the developmental capacity of these embryos. Furthermore, we quantitatively assessed the alterations in histone H3 and H4 overall acetylation levels and blastocyst quality of SpI-AG embryos by immunofluorescence staining. We found a significantly improved morula and blastocyst development rate of SpI-AG embryos at a mild dose of TSA (20 nM) or SCR (200 nM) for 15 h after embryo activation. Furthermore, both HDACi noticeably increased the levels of acetylated histone H3 and H4 in SpI-AG blastocyst embryos, whereas, SCR treatment improved the quality of blastocysts when compared with control group. In conclusion, HDACi is beneficial for early development of bovine SpI-AG embryos and can be used to improve the efficiency of its in vitro production.

IL-6-STAT3 signaling and premature senescence

Cytokines play several roles in developing and/or reinforcing premature cellular senescence of young cells. One such cytokine, interleukin-6 (IL-6), regulates senescence in some systems in addition to its known functions of immune regulation and promotion of tumorigenesis. In this review, we describe recent advances in studies on the roles of IL-6 and its downstream signal transducer and activator of transcription 3 (STAT3) in regulating premature cellular senescence. IL-6/sIL-6Rα stimulation forms a senescence-inducing circuit involving the STAT3-insulin-like growth factor-binding protein 5 (IGFBP5) as a key axis triggering and reinforcing component in human fibroblasts. We describe how cytokines regulate the process of senescence by activating STAT3 in one system and anti-senescence or tumorigenesis in other systems. The roles of other STAT members in premature senescence also will be discussed to show the multiple mechanisms leading to cytokine-induced senescence.

Phenotype and Stability of Neural Differentiation of Androgenetic Murine ES Cell-Derived Neural Progenitor Cells

Uniparental zygotes with two paternal (androgenetic, AG) or two maternal genomes (gynogenetic, GG) cannot develop into viable offsprings but form blastocysts from which pluripotent embryonic stem (ES) cells can be derived. For most organs, it is unclear whether uniparental ES cells can give rise to stably expandable somatic stem cells that can repair injured tissues. Even if previous reports indicated that the capacity of AG ES cells to differentiate in vitro into pan-neural progenitor cells (pNPCs) and into cells expressing neural markers is similar to biparental [normal fertilized (N)] ES cells, their potential for functional neurogenesis is not known. Here we show that murine AG pNPCs give rise to neuron-like cells, which then generate sodium-driven action potentials while maintaining fidelity of imprinted gene expression. Neural engraftment after intracerebral transplantation was achieved only by late (22 days) AG and N pNPCs with in vitro low colony-forming cell (CFC) capacity. However, persisting CFC formation seen, in particular, in early (13 or 16 days) differentiation cultures of N and AG pNPCs correlated with a high incidence of trigerm layer teratomas. As AG ES cells display functional neurogenesis and in vivo stability similar to N ES cells, they represent a unique model system to study the roles of paternal and maternal genomes on neural development and on the development of imprinting-associated brain diseases.

In vivo and in vitro differentiation of uniparental embryonic stem cells into hematopoietic and neural cell types

The biological role of genomic imprinting in adult tissue is central to the consideration of transplanting uniparental embryonic stem (ES) cell-derived tissues. We have recently shown that both maternal (parthenogenetic/gynogenetic) and paternal (androgenetic) uniparental ES cells can differentiate, both in vivo in chimeras and in vitro, into adult-repopulating hematopoietic stem and progenitor cells. This suggests that, at least in some tissues, the presence of two maternal or two paternal genomes does not interfere with stem cell function and tissue homeostasis in the adult. Here, we consider implications of the contribution of uniparental cells to hematopoiesis and to development of other organ systems, notably neural tissue for which consequences of genomic imprinting are associated with a known bias in development and behavioral disorders. Our findings so far indicate that there is little or no limit to the differentiation potential of uniparental ES cells outside the normal developmental paradigm. As a potentially donor MHC-matching source of tissue, uniparental transplants may provide not only a clinical resource but also a unique tool to investigate aspects of genomic imprinting in adults.

Higher copy number variation and diverse X chromosome inactivation in parthenote-derived human embryonic stem cells

Parthenote-derived human embryonic stem cells (phESCs) have many advantages over conventionally derived human embryonic stem cells (hESCs), but a more thorough investigation of these cells is needed before they can be implemented in cell therapies. In this work, we used a Cytogenetics Whole-Genome Array to study the copy number variation (CNV) status in phESCs and hESCs. We also investigated X chromosome inactivation (XCI) and expression levels of marker genes in these cells. More CNVs were found in phESCs than in hESCs in the present study, and gene expression appeared to be associated with the gain or loss of CNVs. In addition, a variable XCI status and different expression pattern of paternally expressed imprinted gene were also found in phESCs. In conclusion, although phESCs had a similar pluripotent profile to conventionally derived hESCs, these cells differed in imprinted gene expression, XCI status and number of CNVs. Our work highlights the need for a deeper investigation to elucidate the genetic and epigenetic characteristics of these 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. We first derived pSC from activated MII oocytes, and differentiated them to parthenogenetic mesenchymal stem cells (pMSC). We then proceeded to induce pluripotency in pMSC by over expression of the four transcription factors Oct4, Sox2, Klf4 and c-Myc. pMSC-derived iPS (piPS) were further differentiated into secondary pMSC (pMSC-II). At every potency change, we characterized the obtained lines both molecularly and by functional differentiation, and performed an extensive genome-wide expression study by microarray analysis. Although overall gene expression of parthenogenetic cells resembled that of potency-matched biparental lines, significantly broader changes were brought about upon secondary differentiation of piPS to pMSC-II compared with matched biparental controls; our results highlight the effect of the interplay of epigenetic reprogramming on a monoparental background, as well as the importance of heterozygosis and biparental imprinting for stable epigenetic reprogramming.

Autism and cancer risk

A literature review was conducted on the genetic and developmental bases of autism in relation to genes and pathways associated with cancer risk. Convergent lines of evidence from four types of analysis: (1) recent theoretical studies on the causes of autism, (2) epidemiological studies, (3) genetic analyses linking autism with mutations in tumor suppressor genes and other cancer-associated genes and pathways, and (4) contrasts with schizophrenia, Parkinson's, and Alzheimer's disease indicate that autism may involve altered cancer risk. This evidence should motivate further epidemiological studies, and it provides useful insights into the nature of the genetic, epigenetic, and environmental factors underlying the etiologies of autism, other neurological conditions, and carcinogenesis.

Selection of stable reference genes for quantitative rt-PCR comparisons of mouse embryonic and extra-embryonic stem cells

Isolation and culture of both embryonic and tissue specific stem cells provide an enormous opportunity to study the molecular processes driving development. To gain insight into the initial events underpinning mammalian embryogenesis, pluripotent stem cells from each of the three distinct lineages present within the preimplantation blastocyst have been derived. Embryonic (ES), trophectoderm (TS) and extraembryonic endoderm (XEN) stem cells possess the developmental potential of their founding lineages and seemingly utilize distinct epigenetic modalities to program gene expression. However, the basis for these differing cellular identities and epigenetic properties remain poorly defined.

Quantitative reverse transcription-polymerase chain reaction (qPCR) is a powerful and efficient means of rapidly comparing patterns of gene expression between different developmental stages and experimental conditions. However, careful, empirical selection of appropriate reference genes is essential to accurately measuring transcriptional differences. Here we report the quantitation and evaluation of fourteen commonly used references genes between ES, TS and XEN stem cells. These included: Actb, B2m, Hsp70, Gapdh, Gusb, H2afz, Hk2, Hprt, Pgk1, Ppia, Rn7sk, Sdha, Tbp and Ywhaz. Utilizing three independent statistical analysis, we identify Pgk1, Sdha and Tbp as the most stable reference genes between each of these stem cell types. Furthermore, we identify Sdha, Tbp and Ywhaz as well as Ywhaz, Pgk1 and Hk2 as the three most stable reference genes through the in vitro differentiation of embryonic and trophectoderm stem cells respectively.

Understanding the transcriptional and epigenetic regulatory mechanisms controlling cellular identity within these distinct stem cell types provides essential insight into cellular processes controlling both embryogenesis and stem cell biology. Normalizing quantitative RT-PCR measurements using the geometric mean CT values obtained for the identified mRNAs, offers a reliable method to assess differing patterns of gene expression between the three founding stem cell lineages present within the mammalian preimplantation embryo.

Imprinted genes that regulate early mammalian growth are coexpressed in somatic stem cells

Lifelong, many somatic tissues are replenished by specialized adult stem cells. These stem cells are generally rare, infrequently dividing, occupy a unique niche, and can rapidly respond to injury to maintain a steady tissue size. Despite these commonalities, few shared regulatory mechanisms have been identified. Here, we scrutinized data comparing genes expressed in murine long-term hematopoietic stem cells with their differentiated counterparts and observed that a disproportionate number were members of the developmentally-important, monoallelically expressed imprinted genes. Studying a subset, which are members of a purported imprinted gene network (IGN), we found their expression in HSCs rapidly altered upon hematopoietic perturbations. These imprinted genes were also predominantly expressed in stem/progenitor cells of the adult epidermis and skeletal muscle in mice, relative to their differentiated counterparts. The parallel down-regulation of these genes postnatally in response to proliferation and differentiation suggests that the IGN could play a mechanistic role in both cell growth and tissue homeostasis.

Mouse chimeras as a system to investigate development, cell and tissue function, disease mechanisms and organ regeneration

Chimeras are organisms composed of at least two genetically distinct cell lineages originating from different zygotes. In the laboratory, mouse chimeras can be produced experimentally; various techniques allow combining different early stage mouse embryos with each other or with pluripotent stem cells. Identification of the progeny of the different lineages in chimeras permits to follow cell fate and function, enabling correlation of genotype with phenotype. Mouse chimeras have become a tool to investigate critical developmental processes, including cell specification, differentiation, patterning, and the function of specific genes. In addition, chimeras can also be generated to address biological processes in the adult, including mechanisms underlying diseases or tissue repair and regeneration. This review summarizes the different types of chimeras and how they have been generated and provides examples of how mouse chimeras offer a unique and powerful system to investigate questions pertaining to cell and tissue function in the developing and adult organism.

Germline competency of parthenogenetic embryonic stem cells from immature oocytes of adult mouse ovary

Parthenogenetic embryonic stem cells (pESCs) have been generated in several mammalian species from parthenogenetic embryos that would otherwise die around mid-gestation. However, previous reports suggest that pESCs derived from in vivo ovulated (IVO) mature oocytes show limited pluripotency, as evidenced by low chimera production, high tissue preference and especially deficiency in germline competence, a critical test for genetic integrity and pluripotency of ESCs. Here, we report efficient generation of germline-competent pESC lines (named as IVM pESCs) from parthenogenetic embryos developed from immature oocytes of adult mouse ovaries following in vitro maturation (IVM) and artificial activation. In contrast, pESCs derived from IVO oocytes show defective germline competence, consistent with previous reports. Further, IVM pESCs resemble more ESCs from fertilized embryos (fESCs) than do IVO pESCs on genome-wide DNA methylation and global protein profiles. In addition, IVM pESCs express higher levels of Blimp1, Lin28 and Stella, relative to fESCs, and in their embryoid bodies following differentiation. This may indicate differences in differentiation potentially to the germline. The mechanisms for acquisition of pluripotency and germline competency of IVM pESCs from immature oocytes remain to be determined.

The effects of culture on genomic imprinting profiles in human embryonic and fetal mesenchymal stem cells

Human embryonic stem (hES) cells and fetal mesenchymal stem cells (fMSC) offer great potential for regenerative therapy strategies. It is therefore important to characterise the properties of these cells in vitro. One major way the environment impacts on cellular physiology is through changes to epigenetic mechanisms. Genes subject to epigenetic regulation via genomic imprinting have been characterised extensively. The integrity of imprinted gene expression therefore provides a measurable index for epigenetic stability. Allelic expression of 26 imprinted genes and DNA methylation at associated differentially methylated regions (DMRs) was measured in fMSC and hES cell lines. Both cell types exhibited monoallelic expression of 13 imprinted genes, biallelic expression of six imprinted genes, and there were seven genes that differed in allelic expression between cell lines. fMSCs exhibited the differential DNA methylation patterns associated with imprinted expression. This was unexpected given that gene expression of several imprinted genes was biallelic. However, in hES cells, differential methylation was perturbed. These atypical methylation patterns did not correlate with allelic expression. Our results suggest that regardless of stem cell origin, in vitro culture affects the integrity of imprinted gene expression in human cells. We identify biallelic and variably expressed genes that may inform on overall epigenetic stability. As differential methylation did not correlate with imprinted expression changes we propose that other epigenetic effectors are adversely influenced by the in vitro environment. Since DMR integrity was maintained in fMSC but not hES cells, we postulate that specific hES cell derivation and culturing practices result in changes in methylation at DMRs.

p57KIP2: "Kip"ing the cell under control

p57(KIP2) is an imprinted gene located at the chromosomal locus 11p15.5. It is a cyclin-dependent kinase inhibitor belonging to the CIP/KIP family, which includes additionally p21(CIP1/WAF1) and p27(KIP1). It is the least studied CIP/KIP member and has a unique role in embryogenesis. p57(KIP2) regulates the cell cycle, although novel functions have been attributed to this protein including cytoskeletal organization. Molecular analysis of animal models and patients with Beckwith-Wiedemann Syndrome have shown its nodal implication in the pathogenesis of this syndrome. p57(KIP2) is frequently down-regulated in many common human malignancies through several mechanisms, denoting its anti-oncogenic function. This review is a thorough analysis of data available on p57(KIP2), in relation to p21(CIP1/WAF1) and p27(KIP1), on gene and protein structure, its transcriptional and translational regulation, and its role in human physiology and pathology, focusing on cancer development.

H19 gene is epigenetically stable in mouse multipotent germline stem cells

Testis-derived germline stem (GS) cells can undergo re-programming to acquire multipotency when cultured under appropriate culture conditions. These multipotent GS (mGS) cells have been known to differ from GS cells in their DNA methylation pattern. In this study, we examined the DNA methylation status of the H19 imprinting control region (ICR) in multipotent adult germline stem (maGS) cells to elucidate how epigenetic imprints are altered by culture conditions. DNA methylation was analyzed by bisulfite sequencing PCR of established maGS cells cultured in the presence of glial cell line-derived neurotrophic factor (GDNF) alone or both GDNF and leukemia inhibitory factor (LIF). The results showed that the H19 ICR in maGS cells of both groups was hypermethylated and had an androgenetic pattern similar to that of GS cells. In line with these data, the relative abundance of the Igf2 mRNA transcript was two-fold higher and that of H19 was three fold lower than in control embryonic stem cells. The androgenetic DNA methylation pattern of the H19 ICR was maintained even after 54 passages. Furthermore, differentiating maGS cells from retinoic acid-treated embryoid bodies maintained the androgenetic imprinting pattern of the H19 ICR. Taken together these data suggest that our maGS cells are epigenetically stable for the H19 gene during in vitro modifications. Further studies on the epigenetic regulation and chromatin structure of maGS cells are therefore necessary before their full potential can be utilized in regenerative medicine.

Correlation of expression and methylation of imprinted genes with pluripotency of parthenogenetic embryonic stem cells

Mammalian parthenogenetic embryos (pE) are not viable due to placental deficiency, presumably resulting from lack of paternally expressed imprinted genes. Pluripotent parthenogenetic embryonic stem (pES) cells derived from pE could advance regenerative medicine by avoiding immuno-rejection and ethical roadblocks. We attempted to explore the epigenetic status of imprinted genes in the generation of pES cells from parthenogenetic blastocysts, and its relationship to pluripotency of pES cells. Pluripotency was evaluated for developmental and differentiation potential in vivo, based on contributions of pES cells to chimeras and development to day 9.5 of pES fetuses complemented by tetraploid embryos (TEC). Consistently, pE and fetuses failed to express paternally expressed imprinted genes, but pES cells expressed those genes in a pattern resembling that of fertilized embryos (fE) and fertilized embryonic stem (fES) cells derived from fE. Like fE and fES cells, but unlike pE or fetuses, pES cells and pES cell-fetuses complemented by TEC exhibited balanced methylation of Snrpn, Peg1 and U2af1-rs1. Coincidently, global methylation increased in pE but decreased in pES cells, further suggesting dramatic epigenetic reprogramming occurred during isolation and culture of pES cells. Moreover, we identified decreased methylation of Igf2r, Snrpn, and especially U2af1-rs1, in association with increased contributions of pES cells to chimeras. Our data show that in vitro culture changes epigenetic status of imprinted genes during isolation of pES cells from their progenitor embryos and that increased expression of U2af1-rs1 and Snrpn and decreased expression of Igf2r correlate with pluripotency of pES cells.

Mouse androgenetic embryonic stem cells differentiated to multiple cell lineages in three embryonic germ layers in vitro

The embryos of some rodents and primates can precede early development without the process of fertilization; however, they cease to develop after implantation because of restricted expressions of imprinting genes. Asexually developed embryos are classified into parthenote/gynogenote and androgenote by their genomic origins. Embryonic stem cells (ESCs) derived from asexual origins have also been reported. To date, ESCs derived from parthenogenetic embryos (PgESCs) have been established in some species, including humans, and the possibility to be alternative sources for autologous cell transplantation in regenerative medicine has been proposed. However, some developmental characteristics, which might be important for therapeutic applications, such as multiple differentiation capacity and transplantability of the ESCs of androgenetic origin (AgESCs) are uncertain. Here, we induced differentiation of mouse AgESCs and observed derivation of neural cells, cardiomyocytes and hepatocytes in vitro. Following differentiated embryoid body (EB) transplantation in various mouse strains including the strain of origin, we found that the EBs could engraft in theoretically MHC-matched strains. Our results indicate that AgESCs possess at least two important characteristics, multiple differentiation properties in vitro and transplantability after differentiation, and suggest that they can also serve as a source of histocompatible tissues for transplantation.

Senescence-messaging secretome: SMS-ing cellular stress

Oncogene-induced cellular senescence constitutes a strong anti-proliferative response, which can be set in motion following either oncogene activation or loss of tumour suppressor signalling. It serves to limit the expansion of early neoplastic cells and as such is a potent cancer-protective response to oncogenic events. Recently emerging evidence points to a crucial role in oncogene-induced cellular senescence for the 'senescence-messaging secretome' or SMS, setting the stage for cross-talk between senescent cells and their environment. How are such signals integrated into a coordinated response and what are the implications of this unexpected finding?

Strategies and new developments in the generation of patient-specific pluripotent stem cells

Generating pluripotent stem cells directly from cells obtained from patients is one of the ultimate goals in regenerative medicine. Two "reprogramming" strategies for the generation of pluripotent stem cells from somatic cells have been studied extensively: nuclear transfer to oocytes and fusion with ES cells. The recent demonstration that, in mouse, nuclear transfer into zygotes can also be effective if the recipient cells are arrested in mitosis provides an exciting new avenue for this type of approach. Patient-specific pluripotent cells could potentially also be generated by the spontaneous reprogramming of bone marrow cells, spermatogonial cells, and parthenogenetic embryos. A third overall type of strategy arose from the demonstration that pluripotent stem (iPS) cells can be generated from mouse fibroblasts by the introduction of four transcription factors (Oct-3/4, Sox2, c-Myc, and KLF4). Recent work has underlined the potential of this strategy by improving the efficiency of the process and demonstrating that iPS cells can contribute to many different tissues in vivo, including the germline. Taken together, these studies underscore the crucial roles of transcription factors and chromatin remodeling in nuclear reprogramming.

Derivation of human embryonic stem cell lines from parthenogenetic blastocysts

Parthenogenesis is one of the main, and most useful, methods to derive embryonic stem cells (ESCs), which may be an important source of histocompatible cells and tissues for cell therapy. Here we describe the derivation and characterization of two ESC lines (hPES-1 and hPES-2) from in vitro developed blastocysts following parthenogenetic activation of human oocytes. Typical ESC morphology was seen, and the expression of ESC markers was as expected for alkaline phosphatase, octamer-binding transcription factor 4, stage-specific embryonic antigen 3, stage-specific embryonic antigen 4, TRA-1-60, and TRA-1-81, and there was absence of expression of negative markers such as stage-specific embryonic antigen 1. Expression of genes specific for different embryonic germ layers was detected from the embryoid bodies (EBs) of both hESC lines, suggesting their differentiation potential in vitro. However, in vivo, only hPES-1 formed teratoma consisting of all three embryonic germ layers (hPES-2 did not). Interestingly, after continuous proliferation for more than 100 passages, hPES-1 cells still maintained a normal 46 XX karyotype; hPES-2 displayed abnormalities such as chromosome translocation after long term passages. Short Tandem Repeat (STR) results demonstrated that the hPES lines were genetic matches with the egg donors, and gene imprinting data confirmed the parthenogenetic origin of these ES cells. Genome-wide SNP analysis showed a pattern typical of parthenogenesis. All of these results demonstrated the feasibility to isolate and establish human parthenogenetic ESC lines, which provides an important tool for studying epigenetic effects in ESCs as well as for future therapeutic interventions in a clinical setting.

When genomes collide: aberrant seed development following maize interploidy crosses

BACKGROUND AND AIMS

The results of wide- or interploidy crosses in angiosperms are unpredictable and often lead to seed abortion. The consequences of reciprocal interploidy crosses have been explored in maize in detail, focusing on alterations to tissue domains in the maize endosperm, and changes in endosperm-specific gene expression.

METHODS

Following reciprocal interploidy crosses between diploid and tetraploid maize lines, development of endosperm domains was studied using GUS reporter lines, and gene expression in resulting kernels was investigated using semi-quantitative RT-PCR on endosperms isolated at different stages of development.

KEY RESULTS

Reciprocal interploidy crosses result in very small, largely infertile seeds with defective endosperms. Seeds with maternal genomic excess are smaller than those with paternal genomic excess, their endosperms cellularize earlier and they accumulate significant quantities of starch. Endosperms from the reciprocal cross undergo an extended period of cell proliferation, and accumulate little starch. Analysis of reporter lines and gene expression studies confirm that functional domains of the endosperm are severely disrupted, and are modified differently according to the direction of the interploidy cross.

CONCLUSIONS

Interploidy crosses affect factors which regulate the balance between cell proliferation and cell differentiation within the endosperm. In particular, unbalanced crosses in maize affect transfer cell differentiation, and lead to the temporal deregulation of the ontogenic programme of endosperm development.

Gene-specific vulnerability to imprinting variability in human embryonic stem cell lines

Disregulation of imprinted genes can be associated with tumorigenesis and altered cell differentiation capacity and so could provide adverse outcomes for stem cell applications. Although the maintenance of mouse and primate embryonic stem cells in a pluripotent state has been reported to disrupt the monoallelic expression of several imprinted genes, available data have suggested relatively higher imprint stability in the human equivalents. Identification of 202 heterozygous loci allowed us to examine the allelic expression of 22 imprinted genes in 22 human embryonic stem cell lines. Half of the genes examined (IPW, H19, MEG3, MEST isoforms 1 and 2, PEG10, MESTIT1, NESP55, ATP10A, PHLDA2, IGF2) showed variable allelic expression between lines, indicating vulnerability to disrupted imprinting. However, seven genes showed consistent monoallelic expression (NDN, MAGEL2, SNRPN, PEG3, KCNQ1, KCNQ1OT1, CDKN1C). Furthermore, four genes known to be monoallelic or to exhibit polymorphic imprinting in later-developing human tissues (TP73, IGF2R, WT1, SLC22A18) were always biallelic in hESCs. MEST isoform 1, PEG10, and NESP55 showed an association between the variability observed in interline allelic expression status and the DNA methylation of previously identified regulatory regions. Our results demonstrate gene-specific differences in the stability of imprinted loci in human embryonic stem cells and identify disrupted DNA methylation as one potential mechanism. We conclude the prudence of including comprehensive imprinting analysis in the continued characterization of human embryonic stem cell lines.

Loss of genomic imprinting in mouse parthenogenetic embryonic stem cells

In mammals, complementary contributions of both the maternal and the paternal genomes are required for normal development because of the parental-allele-specific modification of the genome, called genomic imprinting. Therefore, parthenogenetic embryos (PG) with two maternal genomes cannot develop to term, and PG chimeras show a restricted cell contribution of donor cells and reduced weight, although they can develop to term. On the other hand, parthenogenetic embryonic stem cells (PGES) chimeras are more normal in their tissue contribution of donor cells and body weight compared with PG chimeras. To elucidate the epigenetic mechanisms underlying this, we analyzed the imprint status in donor cells of PGES and PG chimeras. In somatic lineages, genomic imprinting was lost in some PGES chimeras, whereas those in PG chimeras were almost totally maintained. Moreover, loss of imprints correlated to the gene expression pattern of imprinted genes. Therefore, this loss of imprinting in PGES chimeras could improve the tissue contribution and body weight to a normal level. On the other hand, in germ lineages, both PGES and PG in chimeras showed normal erasure of imprints, indicating that the reprogramming in germ lineages is an inevitable event, regardless of the imprint status of primordial germ cells.

Insulin is imprinted in the placenta of the marsupial, Macropus eugenii

Therian mammals (marsupials and eutherians) rely on a placenta for embryo survival. All mammals have a yolk sac, but while both chorio-allantoic and chorio-vitelline (yolk sac) placentation can occur, most marsupials only develop a yolk sac placenta. Insulin (INS) is unusual in that it is the only gene that is imprinted exclusively in the yolk sac placenta. Marsupials, therefore, provide a unique opportunity to examine the conservation of INS imprinting in mammalian yolk sac placentation. Marsupial INS was cloned and its imprint status in the yolk sac placenta of the tammar wallaby, Macropus eugenii, examined. In two informative individuals of the eight that showed imprinting, INS was paternally expressed. INS protein was restricted to the yolk sac endoderm, while insulin receptor, IR, protein was additionally expressed in the trophoblast. INS protein increased during late gestation up to 2 days before birth, but was low the day before and on the day of birth. The conservation of imprinted expression of insulin in the yolk sac placenta of divergent mammalian species suggests that it is of critical importance in the yolk sac placenta. The restriction of imprinting to the yolk sac suggests that imprinting of INS evolved in the chorio-vitelline placenta independently of other tissues in the therian ancestor of marsupials and eutherians.

Recombination signatures distinguish embryonic stem cells derived by parthenogenesis and somatic cell nuclear transfer

Parthenogenesis and somatic cell nuclear transfer (SCNT) are two methods for deriving embryonic stem (ES) cells that are genetically matched to the oocyte donor or somatic cell donor, respectively. Using genome-wide single nucleotide polymorphism (SNP) analysis, we demonstrate distinct signatures of genetic recombination that distinguish parthenogenetic ES cells from those generated by SCNT. We applied SNP analysis to the human ES cell line SCNT-hES-1, previously claimed to have been derived by SCNT, and present evidence that it represents a human parthenogenetic ES cell line. Genome-wide SNP analysis represents a means to validate the genetic provenance of an ES cell line.

Imprinting Status of IGF2 in Cord Blood Cells of Han Chinese Newborns

Loss of imprinting (LOI) of insulin-like growth factor II gene (IGF2) is an epigenetic abnormality associated with human diseases. However, little is known about the characteristics of IGF2 imprinting in newborn cord blood cells. METHODS: A total of 923 cord blood samples from term singletons and related clinical data were collected; IGF2 imprinting status in 273 specimens were successfully analyzed using RT-PCR and restriction fragment length polymorphism. RESULTS: LOI of IGF2 was detected in 20.9% of informative samples. The mean birth weights (BW) in the LOI and the normal imprinting groups were 3462.7 ± 460.2 g and 3363.7 ± 427.7 g, respectively. The abdominal perimeters in the LOI group tended to be larger than that in the normal imprinting group. Pregnancy complications, delivery modes, newborn diseases, occurrences of malignant tumors in grandparents, and other maternal factors were not associated with LOI of IGF2. 22.2% of the infants with IGF2 LOI also showed LOI in their father’s lymphocytes while 21.4% in their mother’s lymphocytes. CONCLUSIONS: About 20% of Han Chinese newborns indicated LOI of IGF2 in their cord blood lymphocytes that may represent the epigenetic characteristics in this ethnic group. While IGF2 LOI tends to be weakly inherited between parents and offspring, abnormal imprinting seems to be statistically unrelated with phenotypes of newborns, although it might have an association with later phenotypes of infants.

Biological functions of DNA methyltransferase 1 require its methyltransferase activity

DNA methyltransferase 1 (DNMT1) has been reported to interact with a wide variety of factors and to contain intrinsic transcriptional repressor activity. When a conservative point mutation was introduced at the key catalytic residue, mutant DNMT1 failed to rescue any of the phenotypes of Dnmt1-null embryonic stem (ES) cells, which indicated that the biological functions of DNMT1 are exerted through the methylation of DNA. ES cells that expressed the mutant protein did not survive differentiation. Intracisternal A-particle family retrotransposons were no longer methylated and were transcribed at high levels. The proper localization of DNMT1 depended on normal genomic methylation, and we discuss the implications of this finding for epigenetic dysregulation in cancer.

Hematopoietic reconstitution with androgenetic and gynogenetic stem cells

Parthenogenetic embryonic stem (ES) cells with two oocyte-derived genomes (uniparental) have been proposed as a source of autologous tissue for transplantation. The therapeutic applicability of any uniparental cell type is uncertain due to the consequences of genomic imprinting that in mammalian uniparental tissues causes unbalanced expression of imprinted genes. We transplanted uniparental fetal liver cells into lethally irradiated adult mice to test their capacity to replace adult hematopoietic tissue. Both maternal (gynogenetic) and paternal (androgenetic) derived cells conveyed long-term, multilineage reconstitution of hematopoiesis in recipients, with no associated pathologies. We also establish that uniparental ES cells can differentiate into transplantable hematopoietic progenitors in vitro that contribute to long-term hematopoiesis in recipients. Hematopoietic tissue in recipients maintained fidelity of parent-of-origin methylation marks at the Igf2/H19 locus; however, variability occurred in the maintenance of parental-specific methylation marks at other loci. In summary, despite genomic imprinting and its consequences on development that are particularly evident in the androgenetic phenotype, uniparental cells of both parental origins can form adult-transplantable stem cells and can repopulate an adult organ.

Histocompatible Embryonic Stem Cells by Parthenogenesis

Genetically matched pluripotent embryonic stem (ES) cells generated via nuclear transfer or parthenogenesis (pES cells) are a potential source of histocompatible cells and tissues for transplantation. After parthenogenetic activation of murine oocytes and interruption of meiosis I or II, we isolated and genotyped pES cells and characterized those that carried the full complement of major histocompatibility complex (MHC) antigens of the oocyte donor. Differentiated tissues from these pES cells engrafted in immunocompetent MHC-matched mouse recipients, demonstrating that selected pES cells can serve as a source of histocompatible tissues for transplantation.