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Epidermal growth factor receptors increase during the differentiation of embryonal carcinoma cells.

Mouse teratocarcinoma stem cells (embryonal carcinoma, or EC cells) bind very small amounts of mouse epidermal growth factor (EGF) and the latter hormone seems to have no stimulatory effect on the growth of two cloned lines of EC cells. However, when EC cells are induced to differentiate into large flat endodern-like cells (END cells), EGF receptors increase in number reaching a plateau in 6 to 8 days. At 8 to 10 days after induction, END cells multiply very slowly, but when EGF is added (3 x 10(-10) M) to the medium, cell division is stimulated and a further change in morphology occurs. This letter describes the binding characteristics and numbers of the EGF receptors on EC and END cells and shows that exogenous retinoic acid increases the numbers of EGF receptors on END cells. We were unable to find endogenous competing factors produced by EC cells. Such factors could account for the lack of detectable binding of EGF on these cells. As EC cells differentiate to END cells, so the ability of the cells to form tumours is reduced. Since this change is accompanied by an increase in the number of EGF receptors there may be a relationship between these two events.

Animals

Overcoming gene dosage barriers in mammalian development: An imprinting balancing act.

Genomic imprinting ensures parent-of-origin gene expression and prevents uniparental development. In this issue of Cell Stem Cell, Li et al.1 extensively engineered androgenic haploid embryonic stem cells to overcome imprinting barriers, producing adult bi-paternal mice, albeit with low efficiency, and providing insights into roles of imprinted genes in development.

Genomic Imprinting

mRNA turnover dynamics are affected by cell differentiation and loss of the cytosine methyltransferase Nsun2.

Nsun2 catalyzes 5-methylcytosine (m5C) formation in several types of RNA, including messenger RNAs (mRNAs), transfer RNAs, and other non-coding RNAs. In mRNA, m5C was reported to influence transcript stability. However, it is unclear if it has stabilizing or destabilizing effects. To address the role of Nsun2 in mRNA stability, we characterized the landscape of mRNA turnover dynamics during embryonic stem cell (ESC) differentiation in wild-type and Nsun2-mutant cells. By using an RNA labeling approach combined with thiouridine-to-cytidine-sequencing (TUC-seq), we demonstrate that mRNA synthesis and stability undergo extensive changes during normal cellular differentiation. Remarkably, a large proportion of these changes did not result in altered mRNA abundance, providing evidence for robust transcript buffering during ESC differentiation. Importantly, also the loss of Nsun2 affected mRNA turnover dynamics but not the steady-state levels of transcripts. Furthermore, our data indicate that the effect of Nsun2 on mRNA turnover was not mediated by m5C deposition in mRNA, which is corroborated by catalysis-independent effects of Nsun2 on translation in early ESC differentiation. In conclusion, this study demonstrates that differentiation as well as loss of Nsun2 can induce changes in mRNA turnover dynamics that are independent of mRNA methylation but consistent with a buffering mechanism to maintain constant RNA levels.

Cell Differentiation

Functional impact of cancer-associated cohesin variants on gene expression and cellular identity.

Cohesin is a ring-shaped protein complex that controls dynamic chromosome structure. Cohesin activity is important for a variety of biological processes, including formation of DNA loops that regulate gene expression. The precise mechanisms by which cohesin shapes local chromosome structure and gene expression are not fully understood. Recurrent mutations in cohesin complex members have been reported in various cancers, though it is not clear whether many cohesin sequence variants have phenotypes and contribute to disease. Here, we utilized CRISPR/Cas9 genome editing to introduce a variety of cohesin sequence variants into murine embryonic stem cells and investigate their molecular and cellular consequences. Some of the cohesin variants tested caused changes to transcription, including altered expression of gene encoding lineage-specifying developmental regulators. Altered gene expression was also observed at insulated neighborhoods, where cohesin-mediated DNA loops constrain potential interactions between genes and enhancers. Furthermore, some cohesin variants altered the proliferation rate and differentiation potential of murine embryonic stem cells. This study provides a functional comparison of cohesin variants found in cancer within an isogenic system, revealing the relative roles of various cohesin perturbations on gene expression and maintenance of cellular identity.

Animals

Application of BrdU/Hoechst-ethidium bromide two parameter flow cytometry in studying synchronous and non-synchronous mouse cells.

BrdU/Hoechst-EB bivariate flow cytometry has a wide application in the study of factors controlling cell cycle for asynchronous cells such as embryonic stem cells (ES), and for synchronous cells such as stimulated resting B cells (Bo). The technique allows one to calculate the average cell cycle duration time. ES cells are found to cycle every 8-10 h, and most B cells are 11-12 h, but there is a small subset of B cells with a cycle time of only 6-7 h. Using this technique, we also study the roles of different T lymphocytes on B cell activation when B cells are stimulated with anti-IgM antibodies (commonly used, anti-mu). Exposure to anti-mu recruits small B cells into the cell cycle, but arrests them in the G1 phase of the second cycle. Interleukin (IL) 4 is a costimulator of anti-mu. In addition, IL-4 is an S-phase progression factor. Contrary to that seen when B cells are stimulated by other mitogens, very few cells are in the G2 compartments after anti-mu plus IL-4 stimulation. This phenomenon is reminiscent of embryonic cells. Our findings provide strong evidence to propose that there are two restriction points for B cell activation: at the transition from G0 to G1 and at the transition from G1 to S phase.

Adjuvants, Immunologic

Comparison of cancer cell surfaces of the lower reproductive tract by scanning electron microscopy.

The squamous cells of the cervix simulate those of the vagina and vulva both histologically and by scanning electron microscopy. However, in areas of the cervix undergoing active metaplasia, there are cells which share some of the characteristics demonstrated by scanning electron microscopy of both squamous and columnar epithelium. In these cells there is a wide range of characteristics of each cell type, suggesting a possible gradual transition from columnar to squamous epithelium. Furthermore, the cells of severe dysplasia and of intraepithelial and invasive squamous cancers of the cervix, though histologically similar to those of vaginal and vulvar cancers, are distinctly different when examined by scanning electron microscopy. These findings suggest that both metaplastic and neoplastic squamous cells are derived from the same progenitor columnar cells of the cervix, by orderly transition in the former and by atypical transformation in the latter. Second, the distinctiveness from the vaginal and vulvar cells indicates different embryonic stem cell lines.

Carcinoma in Situ

Inferring metabolic objectives and trade-offs in single cells during embryogenesis.

While proliferating cells optimize their metabolism to produce biomass, the metabolic objectives of cells that perform non-proliferative tasks are unclear. The opposing requirements for optimizing each objective result in a trade-off that forces single cells to prioritize their metabolic needs and optimally allocate limited resources. Here, we present single-cell optimization objective and trade-off inference (SCOOTI), which infers metabolic objectives and trade-offs in biological systems by integrating bulk and single-cell omics data, using metabolic modeling and machine learning. We validated SCOOTI by identifying essential genes from CRISPR-Cas9 screens in embryonic stem cells, and by inferring the metabolic objectives of quiescent cells, during different cell-cycle phases. Applying this to embryonic cell states, we observed a decrease in metabolic entropy upon development. We further uncovered a trade-off between glutathione and biosynthetic precursors in one-cell zygote, two-cell embryo, and blastocyst cells, potentially representing a trade-off between pluripotency and proliferation. A record of this paper's transparent peer review process is included in the supplemental information.

Single-Cell Analysis

Donor MHC-specific thymus vaccination allows for immunocompatible allotransplantation.

Organ transplantation is the last-resort option to treat organ failure. However, less than 10% of patients benefit from this only option due to lack of major histocompatibility complex (MHC)-matched donor organs and 25%-80% of donated organs could not find MHC-matched recipients. T cell allorecognition is the principal mechanism for allogeneic graft rejection. We herein present a "donor MHC-specific thymus vaccination" (DMTV) strategy to induce T cell tolerance to both autologous and allogeneic donor MHC. Allogeneic MHC molecules were expressed in the recipient thymus through adeno-associated virus-mediated delivery, which led to stable expression of allogeneic MHC together with the autologous MHC in the engineered thymus. During local T cell education, those T cells recognizing either autologous MHC or allogeneic MHC were equally depleted. We constructed C57BL/6-MHC and BALB/c-MHC dual immunocompatible mice via thymus vaccination of C57BL/6-MHC into the BALB/c thymus and observed long-term graft tolerance after transplantation of C57BL/6 skin and C57BL/6 mouse embryonic stem cells into the vaccinated BALB/c mice. We also validated our DMTV strategy in a bone marrow, liver, thymus (BLT)-humanized mouse model for immunocompatible allotransplantation of human embryonic stem cells. Our study suggests that the DMTV strategy is a potent avenue to introduce a donor compatible immune system in recipients, which overcomes the clinical dilemma of the extreme shortage of MHC-matched donor organs for treating patients with end-stage organ failure.

Animals

Somatic cell origin of teratocarcinomas.

Malignant teratocarcinomas arise from developmentally totipotent normal stem cells. Whether the targets are embryonal somatic cells or germinal cells has long been a matter of controversy. Past experiments on teratocarcinoma induction by ectopic grafting of early rodent embryos or fetal germinal ridges have remained ambiguous because embryos ordinarily soon form germ cells, and parthenogenetic germ cells form "embryos." In order to interrupt the developmental cycle at its most telling point, day 6 (egg-cylinder stage) mouse embryos of genetically sterile types were grafted; in such grafts, only a terminal residue of totipotent embryonal somatic ("ectoderm") cells is available, and subsequent germ cell development is severely impaired. One graft series, from S1(J)/+ matings, comprised 25% S1(J)/S1(J) presumptive sterile embryos; these grafts formed tumors containing embryonal carcinoma cells as often (47%) as did control +/+ grafts (41%) on the same genetic background. In another series, from W/+ matings, tumors of the sterile W/W genotype were individually identified by means of a closely linked marker, phosphoglucomutase (PGM, EC 2.7.5.1; Pgm-1 locus), coding for electrophoretic enzyme variants and incorporated into the stock. Four tumors were obtained (out of 16) that had the PGM-1D phenotype diagnostic for W/W, and that also contained embryonal carcinoma cells. Therefore, the malignancy arises here in susceptible somatic embryonal stem cells at the terminal stage of their capacity for totipotency. Other teratocarcinomas-whether induced or spontaneous-of ostensible germ-cell origin by parthenogenesis may also depend upon development of the same somatic target cells before neoplastic conversion can occur. A general model based on these experiments is proposed for all malignancies: Malignant transformation of a particular kind of normal stem cell may be possible only when that stem cell has progressed to the threshold of further differentiation.

Animals

From genes to geometry: Controlling embryo models by programming genomic activation.

Embryo-like models derived from stem cells have emerged as powerful tools to study early development. In this issue, Lodewijk et al.1 demonstrate that activating just two enhancers via CRISPR activation (CRISPRa) in mouse embryonic stem cells (ESCs) can drive self-organization into structured embryo-like models, offering a genome-driven approach in stem cell and developmental biology.

Animals

Rewiring Cellular Context as A Central Mechanism Governing Cancer Stem Cell Survival: Insights from ESC Comparisons.

Cancer stem cells (CSCs) drive tumor initiation, metastasis, and therapy resistance, yet their remarkable persistence remains poorly understood. While CSCs share stemness attributes with embryonic stem cells (ESCs), including self-renewal, transcriptional plasticity, and permissive chromatin, they exhibit a fundamentally divergent regulatory logic that prioritizes survival over developmental fidelity. ESCs maintain globally open chromatin that supports transcriptional hyperactivity but predisposes them to apoptosis under genotoxic stress, whereas CSCs maintain dynamically inducible, permissive chromatin at survival loci while repressing differentiation programs, enabling adaptive stress responses. We advance the hypothesis that CSC persistence emerges not from any single factor, but from the integrative rewiring of signaling cascades (Wnt/β-catenin, Notch, Hedgehog, PI3K/AKT/mTOR), stress-responsive transcription factors (HIFs, NF-κB, STAT3), and core pluripotency networks (OCT4, SOX2, NANOG) within a survival-centric context, reinforced by dynamic chromatin remodeling, inducible super-enhancer landscapes, and microenvironmental cues (hypoxia, inflammation, matrix stiffness). Within this framework, the E2F family serves as a key contextual integrator: in ESCs, constitutive E2F activity triggers p53-mediated apoptosis upon DNA damage, preserving genomic integrity; in CSCs, deregulated E2F activity redirects transcription toward DNA repair, antioxidant defenses, and anti-apoptotic programs. This functional divergence underscores that phenotypic outcome is determined by the broader cellular and epigenetic landscape rather than any single factor. We conclude that CSC persistence is an emergent property of this integrated, survival-centric program, fundamentally distinct from the developmental imperative of ESCs. Effective therapeutic strategies must therefore move beyond targeting individual pathways to dismantle the interconnected regulatory networks that define the CSC survival context, offering a more robust approach to overcome therapy resistance and prevent tumor relapse.

Cancer Stem Cells (CSCs)

The scramblases VMP1 and TMEM41B are required for primitive endoderm specification by targeting WNT signaling.

The ER-resident proteins VMP1 and TMEM41B share a conserved DedA domain, which confers lipid scramblase activity. Loss of either gene results in embryonic lethality in mice and defects in autophagy and lipid droplet metabolism. To investigate their role in pluripotency and lineage specification, we generated Vmp1 and Tmem41b mutations in mouse embryonic stem cells (ESCs). We observed that ESCs carrying mutations in Vmp1 and Tmem41b show robust self-renewal and an unperturbed pluripotent expression profile but accumulate LC3-positive autophagosomes and lipid droplets consistent with defects in autophagy and lipid metabolism. ESCs carrying combined mutations in Vmp1 and Tmem41b can differentiate into a wide range of embryonic cell types. However, differentiation into primitive endoderm-like cells in culture is impaired, and the establishment of extra-embryonic endoderm stem (XEN) cells is delayed. Mechanistically, we show the deregulation of genes that are associated with WNT signaling. This is further confirmed by cell surface proteome profiling, which identified a significant reduction of the WNT-receptor FZD2 at the plasma membrane in Vmp1 and Tmem41b double mutant ESCs. Importantly, we show that transgenic expression of Fzd2 rescues XEN differentiation. Our findings identify the role of the lipid scramblases VMP1 and TMEM41B in WNT signaling during extra-embryonic endoderm development and characterize their distinct and overlapping functions.

Animals

Establishment and longitudinal characterisation of a feeder-free embryonic stem-like cell line (ATES1) derived from blastomeres of the climbing perch, Anabas testudineus.

Embryonic stem (ES) cell-based platforms in non-model teleosts remain scarce, which may constrain in vitro studies in functional genomics and developmental biology in aquaculture-relevant species. Here, we report the derivation and characterisation of ATES1, an ES-like cell line derived from Anabas testudineus, a commercially important freshwater fish. ATES1 has been maintained for over 250 passages (> 1500 days) under feeder-free conditions in Leibovitz-15 medium supplemented with foetal bovine serum, fish serum, embryo extract, and human basic fibroblast growth factor (hbFGF). Proliferation was optimal at 28 °C, with both fish serum and hbFGF significantly enhancing cell growth. The cell line exhibited multiple characteristics associated with ES-like cells in vitro during early passages (approximately up to passages 25-35), including ES cell-like morphology, high self-renewal capacity (5-bromo-2'-deoxyuridine incorporation > 90% and a doubling time of 39.9 h), alkaline phosphatase activity, responsiveness to differentiation induction conditions, and expression of stemness-associated genes (sox2, klf4, sall4, nanog, myc). Immunocytochemistry confirmed Sox2 protein expression. However, real-time PCR revealed a significant decline in klf4 and sall4 expression, along with a lack of responsiveness to differentiation cues, increased heterogeneity, and the emergence of chromosomal abnormalities, suggesting compromised maintenance of ES-like properties during extended passaging. Despite these limitations, ATES1 remained continuously proliferative under feeder-free conditions and supported moderate to high (~ 45.8 ± 4.26%) non-viral transgene delivery efficiency via lipofection, suggesting its potential utility as a genetically manipulable in vitro system for future cellular and biotechnological applications in Anabas testudineus.

Animals

Adult bi-paternal offspring generated through direct modification of imprinted genes in mammals.

Imprinting abnormalities pose a significant challenge in applications involving embryonic stem cells, induced pluripotent stem cells, and animal cloning, with no universal correction method owing to their complexity and stochastic nature. In this study, we targeted these defects at their source-embryos from same-sex parents-aiming to establish a stable, maintainable imprinting pattern de novo in mammalian cells. Using bi-paternal mouse embryos, which exhibit severe imprinting defects and are typically non-viable, we introduced frameshift mutations, gene deletions, and regulatory edits at 20 key imprinted loci, ultimately achieving the development of fully adult animals, albeit with a relatively low survival rate. The findings provide strong evidence that imprinting abnormalities are a primary barrier to unisexual reproduction in mammals. Moreover, this approach can significantly improve developmental outcomes for embryonic stem cells and cloned animals, opening promising avenues for advancements in regenerative medicine.

Animals

Replication timing networks reveal a link between transcription regulatory circuits and replication timing control.

DNA replication occurs in a defined temporal order known as the replication timing (RT) program and is regulated during development, coordinated with 3D genome organization and transcriptional activity. However, transcription and RT are not sufficiently coordinated to predict each other, suggesting an indirect relationship. Here, we exploit genome-wide RT profiles from 15 human cell types and intermediate differentiation stages derived from human embryonic stem cells to construct different types of RT regulatory networks. First, we constructed networks based on the coordinated RT changes during cell fate commitment to create highly complex RT networks composed of thousands of interactions that form specific functional subnetwork communities. We also constructed directional regulatory networks based on the order of RT changes within cell lineages, and identified master regulators of differentiation pathways. Finally, we explored relationships between RT networks and transcriptional regulatory networks (TRNs) by combining them into more complex circuitries of composite and bipartite networks. Results identified novel trans interactions linking transcription factors that are core to the regulatory circuitry of each cell type to RT changes occurring in those cell types. These core transcription factors were found to bind cooperatively to sites in the affected replication domains, providing provocative evidence that they constitute biologically significant directional interactions. Our findings suggest a regulatory link between the establishment of cell-type-specific TRNs and RT control during lineage specification.

Cell Differentiation

[Effect of syngenic lymphocytes on allogenic inhibition of hematopoietic stem cells of embryonic liver].

The transplantation of liver from the embryos and newborn C57BL-6 mice to the lethally irradiated hybrids (CBA X C57BL/6) F1resulted in 90% allogenic inhibition of the colony-forming activity of the donor elements. The degree of allogenic inhibition of liver cells of 19 days old embryos and newborn mice may be changed with the help of syngenic lymphocytes of adult mice or delayed transplantation of cells 72 hrs following the irradiation of recipients but these procedures proved to be ineffective with the liver cells of 13 and 16 days old embryos. A suggestion is put forward to the effect that the allogenic inhibition is based on the active reaction of recipient hybrids (CBAXXC57BL/6) F1 to the stem hemopoietic cells of C57BL/6 mice.

Animals

Origin of hemopoietic stem cells in embryonic bursa of Fabricius and bone marrow studied through interspecific chimeras.

The histogenesis of the bursa of Fabricius and of bone marrow was studied by a biological cell marking technique based on differences in the nuclear structure of two species of birds, Japanese quail (Coturnix coturnix japonica) and chick (Gallus gallus). In quail cells the nucleus contains a large amount of heterochromatin associated with the nucleolus. That makes it possible to distinguish them from chick cells after Feulgen-Rossenbeck staining and by electron microscopy. By grafting bursal rudiments and limb buds of quail into chick and inversely it was possible to demonstrate that the whole hemopoietic population of the bursa of Fabricius and of bone marrow is derived from bloodborne extrinsic stem cells. Neither endoderm nor mesoderm of the bursal rudiments is capable of differentiating into lymphoid cells. Combinations of quail bursal endoderm with chick homologous mesenchyme showed that the reticular cells of the follicles are the only endodermal derivatives of the bursa. The mesenchymal bursal component gives rise to the interfollicular connective cells. The contribution to bone marrow histogenesis of cells of vascular and blood origin, on one hand, and of the elements of the cartilaginous model, on the other hand, was analyzed. It appeared that osteoblasts, osteocytes, and stromal cells of marrow are derived from the perichondrium. In contrast, the endothelium of the vascular buds and the hemopoietic cells which invade the diaphysal cartilage during the endochondral ossification process do not belong to the mesenchymal bone primordium but have a fully extrinsic origin.

Animals

The development of the olfactory mucosa in the mouse: electron microscopy.

The development of the olfactory epithelium from the 10th day of gestation of postnatal life has been examined electron miscroscopically in the mouse. At 10 days' gestation the epithelium is already differentiated into dark and pale cells, the former representing embryonic stem cells and the latter the developing receptors. Axons are also visible at this stage. At 11 days the first signs of dendrite formation appear, and at 12 days spheroidal terminal swellings containing numerous microtubules are present at the apices of receptor dendrites. Centriole clusters also appear in the receptor cell bodies and dendrites. From the 12th to the 16th day of gestation a few cilia are formed on the receptor endings. Final steps in the maturation of differentiating receptors begin on the 17th day of gestation, when membranous organelles and lysosomes increase greatly in numbers. However, immature receptors can still be found in the base of the epithelium in postnatal life. Supporting cells are first recognizable on the 17th day of gestation, derived apparently from the remaining stem cells. At the same time differentiated basal cells and glands of Bowman begin to appear. In the early develoment of the olfactory nerve bundles the axons have large and varying diameters, but later on axonal sizes are progressively reduced and the adult size range is achieved at about 18 days of gestation. The significance of these findings is discussed.

Age Factors