A rare human syndrome provides genetic evidence that WNT signaling is required for reprogramming of fibroblasts to induced pluripotent stem cells

Perinuclear mitochondrial clustering for mesenchymal-to-epithelial transition in pluripotency induction

Remodeled mitochondria are characteristic of pluripotent stem cells. However, a role for mitochondrial movement and distribution in pluripotency remains unknown. Here, we show that mitochondrial retrograde transport-mediated perinuclear clustering via dynein complex occurs at the early phase of pluripotency induction. Interestingly, this mitochondrial redistribution is regulated by Yamanaka factor OCT4 but not SOX2 or KLF4. This mitochondrial redistribution, which has effect on the efficiency of somatic cell reprogramming, also depends on DRP1-mediated mitochondrial fission. Importantly, perinuclear mitochondrial clustering is required for mesenchymal-to-epithelial transition (MET), an early step in reprogramming, during which β-catenin regulates the MET process. Furthermore, sufficient amount of β-catenin plays a key role in maintaining stabilization of E-CADHERIN. Taken together, these studies show that perinuclear mitochondrial clustering is an essential organellar step for MET process of pluripotency induction, which may shed light on the subcellular relationship between mitochondrial dynamics, pluripotency, and cellular morphology.

Chromosome-level genome assembly and single-cell analysis unveil molecular mechanisms of arm regeneration in the ophiuroid Ophiura sarsii vadicola

BACKGROUND

Ophiuroids, belonging to Ophiuroidea in Echinodermata, possess remarkable regenerative capacities in their arms, relying on cellular recruitment and de-differentiation. However, limited high-quality genomic resources have hindered the investigation of the underlying molecular mechanisms of ophiuroid regeneration.

RESULTS

Here, we report a chromosome-level genome of Ophiura sarsii vadicola, 259.28 Mbp in length with a scaffold N50 length of 66.91 Mbp. We then perform bulk and single-cell RNA sequencing analysis to investigate gene expression and cellular dynamics during arm regeneration. We identify five distinct cellular clusters involved in the arm regeneration and infer the dynamic transformations from sensory stimulation to injury response, wound healing, and tissue regeneration. We find that progenitor cells derived from connective tissue cells differentiate into muscle, cartilage, endothelial, and epithelial cells. Pseudotime analysis indicates that muscle differentiation occurs early in the regeneration process.

CONCLUSIONS

Our genomic resource and single-cell atlas shed light on the mechanisms of organ regeneration in ophiuroids.

Developmental signals control chromosome segregation fidelity during pluripotency and neurogenesis by modulating replicative stress

Human development relies on the correct replication, maintenance and segregation of our genetic blueprints. How these processes are monitored across embryonic lineages, and why genomic mosaicism varies during development remain unknown. Using pluripotent stem cells, we identify that several patterning signals-including WNT, BMP, and FGF-converge into the modulation of DNA replication stress and damage during S-phase, which in turn controls chromosome segregation fidelity in mitosis. We show that the WNT and BMP signals protect from excessive origin firing, DNA damage and chromosome missegregation derived from stalled forks in pluripotency. Cell signalling control of chromosome segregation declines during lineage specification into the three germ layers, but re-emerges in neural progenitors. In particular, we find that the neurogenic factor FGF2 induces DNA replication stress-mediated chromosome missegregation during the onset of neurogenesis, which could provide a rationale for the elevated chromosomal mosaicism of the developing brain. Our results highlight roles for morphogens and cellular identity in genome maintenance that contribute to somatic mosaicism during mammalian development.

Emerging roles of mitochondrial functions and epigenetic changes in the modulation of stem cell fate

Mitochondria serve as essential organelles that play a key role in regulating stem cell fate. Mitochondrial dysfunction and stem cell exhaustion are two of the nine distinct hallmarks of aging. Emerging research suggests that epigenetic modification of mitochondria-encoded genes and the regulation of epigenetics by mitochondrial metabolites have an impact on stem cell aging or differentiation. Here, we review how key mitochondrial metabolites and behaviors regulate stem cell fate through an epigenetic approach. Gaining insight into how mitochondria regulate stem cell fate will help us manufacture and preserve clinical-grade stem cells under strict quality control standards, contributing to the development of aging-associated organ dysfunction and disease.

Wnt signaling and the regulation of pluripotency

The role of Wnt signaling in stem cells has been mired in seemingly contradictory findings. On one hand, Wnt has been heralded as a self-renewal factor. On the other hand, Wnt's association with differentiation and lineage commitment is indisputable. This apparent contradiction is particularly evident in pluripotent stem cells, where Wnt promotes self-renewal as well as differentiation. To resolve this discrepancy one must delve into fundamental principles of pluripotency and gain an appreciation for the concept of pluripotency states, which exist in a continuum with intermediate metastable states, some of which have been stabilized in vitro. Wnt signaling is a critical regulator of transitions between pluripotent states. Here, we will discuss Wnt's roles in maintaining pluripotency, promoting differentiation, as well as stimulating reprogramming of somatic cells to an induced pluripotent state.

Cancer cells as a new source of induced pluripotent stem cells

Over the last 2 decades, induced pluripotent stem cells (iPSCs) have had various potential applications in various medical research areas, from personalized medicine to disease treatment. Different cellular resources are accessible for iPSC generation, such as keratinocytes, skin fibroblasts, and blood or urine cells. However, all these sources are somatic cells, and we must make several changes in a somatic cell's transcriptome and chromatin state to become a pluripotent cell. It has recently been revealed that cancer cells can be a new source of iPSCs production. Cancer cells show similarities with iPSCs in self-renewal capacity, reprogramming potency, and signaling pathways. Although genetic abnormalities and potential tumor formation in cancer cells pose a severe risk, reprogrammed cancer-induced pluripotent stem cells (cancer-iPSCs) indicate that pluripotency can transiently overcome the cancer phenotype. This review discusses whether cancer cells can be a preferable source to generate iPSCs.

Enrichment and Detection of Wnt Proteins from Cell Culture Media

Wnt proteins are secreted, lipid-modified growth factors with a wide range of activities across all metazoan species. Their production, secretion, and signaling range are under tight cellular control such that detection of Wnt proteins in biological samples is often extremely difficult. In this chapter, we describe a protocol to detect secreted Wnt proteins in the culture medium of cell lines that ectopically or endogenously express Wnt genes. This protocol uses an affinity resin, called Blue Sepharose, that binds and thereby enriches Wnt proteins, followed by immunoblotting for the Wnt protein of interest. This method for detecting Wnt proteins will aid in the isolation of biologically active Wnt proteins, provide an assay to study the molecular basis of Wnt secretion, and potentially offer a means to detect trace amounts of Wnt proteins associated with pathological states.

Selective activation of FZD7 promotes mesendodermal differentiation of human pluripotent stem cells

WNT proteins are secreted symmetry breaking signals that interact with cell surface receptors of the FZD family to regulate a multitude of developmental processes. Studying selectivity between WNTs and FZDs has been hampered by the paucity of purified WNT proteins and by their apparent non-selective interactions with the FZD receptors. Here, we describe an engineered protein, called F7L6, comprised of antibody-derived single-chain variable fragments, that selectively binds to human FZD7 and the co-receptor LRP6. F7L6 potently activates WNT/β-catenin signaling in a manner similar to Wnt3a. In contrast to Wnt3a, F7L6 engages only FZD7 and none of the other FZD proteins. Treatment of human pluripotent stem (hPS) cells with F7L6 initiates transcriptional programs similar to those observed during primitive streak formation and subsequent gastrulation in the mammalian embryo. This demonstrates that selective engagement and activation of FZD7 signaling is sufficient to promote mesendodermal differentiation of hPS cells.

CBP-mediated Wnt3a/β-catenin signaling promotes cervical oncogenesis initiated by Piwil2

Our previous work demonstrated that Piwil2 reactivated by the human papillomavirus oncoproteins E6 and E7 may reprogram somatic cells into tumor-initiating cells (TICs), which contribute to cervical neoplasia lesions. Maintaining the stemness of TICs is critical for the progression of cervical lesions. Here, we determined that canonical Wnt signaling was aberrantly activated in HaCaT cells transfected with lentivirus expressing Piwil2 and in cervical lesion specimens of low-grade squamous intraepithelial lesion, high-grade squamous intraepithelial lesion, and invasive carcinoma. Blocking the β-catenin and CREB binding protein interaction with ICG-001 significantly downregulated the reprogramming factors c-Myc, Nanog, Oct4, Sox2, and Klf4, thus leading to cell differentiation and preventing tumorigenicity in Piwil2-overexpressing HaCaT cells. Similarly, Piwil2 also critically regulated the canonical Wnt signaling pathway in cervical cancer. We further demonstrated that ICG-001 increased cisplatin sensitivity and significantly suppressed tumor growth of cervical cancer alone or in combination with cisplatin both in vitro and in vivo. The β-catenin/ CREB binding protein-mediated transcription activated by Piwil2 is essential for the maintenance of TICs, therefore contributing to the progression of cervical oncogenesis.

Secreted Frizzled-Related Protein 4 (SFRP4) Is an Independent Prognostic Marker in Prostate Cancers Lacking TMPRSS2: ERG Fusions

Secreted frizzled-related protein 4 (SFRP4) controls WNT signaling and is thought to play a role for tumor aggressiveness. Here, we analyzed a tissue microarray containing 11,152 prostate cancers with pathological, clinical and molecular data by immunohistochemistry. SFRP4 expression was higher in cancer than in non-neoplastic acinar cells. SFRP4 staining was seen in 64.9% of tumors and classified as weak in 33.2%, moderate in 23.9% and strong in 7.8% of cancers. SFRP4 overexpression was linked to advanced tumor stage, high classical/quantitative Gleason grade (p < 0.0001 each), lymph node metastasis (p = 0.0002), and a positive surgical margin (p = 0.0017). SFRP4 positivity was markedly more frequent in ERG positive (77.4%) than in ERG negative cancers (57.4% p < 0.0001). Subset analyses in 2725 cancers with and 3592 cancers without TMPRSS2:ERG fusion revealed that associations with tumor phenotype and patient outcome were largely driven by the subset of ERG negative tumors. In a multivariate analysis including various postoperative and prognostic clinico-pathological features, SFRP4 protein expression emerged as an independent prognostic parameter in ERG negative cancers. SFRP4 immunostaining was significantly linked with 10 of 11 previously analyzed chromosomal deletions (p < 0.05 each). In conclusion, high SFRP4 immunostaining is associated with poor prognosis and genomic instability in ERG negative prostate cancers.

Application of porcupine inhibitors in stem cell fate determination

Porcupine (Porcn), a membrane-bound O-acyltransferase, is an endoplasmic reticulum-located protein that has catalytic activity. Porcn is involved in post-translational lipid modification of wingless-Int (Wnt) proteins and serves as an indispensable step in the Wnt proper secretion and signaling. Small-molecule inhibitors targeting Porcn catalytic function in vitro and in vivo are of great interest not only for treating cancer and fibrotic disorders but also in the field of regenerative medicine. Although a number of studies have been conducted, the exact role of Porcn in stem cell fate is not entirely clear. In some cases, Porcn inhibition declined differentiation rate, and in others, it induced stem cell differentiation toward specific lineages. In this review, we first elaborated the Porcn catalytic activity and its inhibitors. Then, we discussed about the recently reported results of Porcn inhibitors in stem cells self-renewal and differentiation.

NANOG and LIN28 dramatically improve human cell reprogramming by modulating LIN41 and canonical WNT activities

Human cell reprogramming remains extremely inefficient and the underlying mechanisms by different reprogramming factors are elusive. We found that NANOG and LIN28 (NL) synergize to improve OCT4, SOX2, KLF4 and MYC (OSKM)-mediated reprogramming by ∼76-fold and shorten reprogramming latency by at least 1 week. This synergy is inhibited by GLIS1 but reinforced by an inhibitor of the histone methyltransferase DOT1L (iDOT1L) to a ∼127-fold increase in TRA-1-60-positive (+) iPSC colonies. Mechanistically, NL serve as the main drivers of reprogramming in cell epithelialization, the expression of Let-7 miRNA target LIN41, and the activation of canonical WNT/β-CATENIN signaling, which can be further enhanced by iDOT1L treatment. LIN41 overexpression in addition to OSKM similarly promoted cell epithelialization and WNT activation in reprogramming, and a dominant-negative LIN41 mutation significantly blocked NL- and iDOT1L-enhanced reprogramming. We also found that NL- and iDOT1L-induced canonical WNT activation facilitates the initial development kinetics of iPSCs. However, a substantial increase in more mature, homogeneous TRA-1-60+ colony formation was achieved by inhibiting WNT activity at the middle-to-late-reprogramming stage. We further found that LIN41 can replace LIN28 to synergize with NANOG, and that the coexpression of LIN41 with NL further enhanced the formation of mature iPSCs under WNT inhibition. Our study established LIN41 and canonical WNT signaling as the key downstream effectors of NL for the dramatic improvement in reprogramming efficiency and kinetics, and optimized a condition for the robust formation of mature human iPSC colonies from primary cells.This article has an associated First Person interview with the first author of the paper.

Fragmented Elastic Fibers in Focal Dermal Hypoplasia (Goltz-Gorlin Syndrome) Without Focal Dermal Hypoplasia: Report of a Male Case and Review of the Literature

Goltz-Gorlin syndrome (GGS) (focal dermal hypoplasia) is a very rare developmental disorder affecting ectodermal and mesodermal structures. The syndrome is inherited in an X-linked manner, with the majority of affected individuals being female. We report the case of a 51-year-old man presenting with congenital skin lesions, syndactyly, facial and thoracic asymmetry, inguinal and laryngeal papillomas, cryptorchidism, polythelia, and dental anomalies. Molecular genetic analysis confirmed the clinically suspected diagnosis of GGS by detecting a known pathogenic mutation in the PORCN gene, c.502G>A [p.(Gly168Arg)] in the mosaic state. Histopathological examinations of skin biopsies of affected individuals typically show focal dermal hypoplasia and fat herniation; despite numerous skin biopsies, these characteristics were not found in the patient involved. Instead, we observed a notable reduction and fragmentation of the elastic fibers in the upper dermis. A systematic literature review regarding the histopathological presence or absence of dermal hypoplasia and/or information on elastic fibers revealed 240 histopathological descriptions of 173 individuals. Absence of dermal hypoplasia was found in 21 biopsies (8.8%). Information on elastic fibers was given in 47 cases (19.6%), showing decrease/absence in 31 cases and fragmentation of elastic fibers in 11 cases. Therefore, the histopathological absence of dermal hypoplasia does not exclude the diagnosis of the GGS. Decrease and fragmentation of elastic fibers may represent new histopathological clues to the diagnosis of this rare syndrome. At the same time, GGS should be included in the histopathological differential diagnoses of elastolytic disorders.

Mechanisms of Wnt signaling and control

The Wnt signaling pathway is a highly conserved system that regulates complex biological processes across all metazoan species. At the cellular level, secreted Wnt proteins serve to break symmetry and provide cells with positional information that is critical to the patterning of the entire body plan. At the organismal level, Wnt signals are employed to orchestrate fundamental developmental processes, including the specification of the anterior-posterior body axis, induction of the primitive streak and ensuing gastrulation movements, and the generation of cell and tissue diversity. Wnt functions extend into adulthood where they regulate stem cell behavior, tissue homeostasis, and damage repair. Disruption of Wnt signaling activity during embryonic development or in adults results in a spectrum of abnormalities and diseases, including cancer. The molecular mechanisms that underlie the myriad of Wnt-regulated biological effects have been the subject of intense research for over three decades. This review is intended to summarize our current understanding of how Wnt signals are generated and interpreted. This article is categorized under: Biological Mechanisms > Cell Signaling Developmental Biology > Stem Cell Biology and Regeneration.

Wnt/β-Catenin/TCF Pathway Is a Phase-Dependent Promoter of Colony Formation and Mesendodermal Differentiation During Human Somatic Cell Reprogramming

Somatic cell reprogramming is a biphasic phenomenon that goes through a mesenchymal-to-epithelial transition, called initiation phase, followed by a maturation phase wherein reprogramming cells acquire pluripotency. Here, we show that these phases display a differential response to Wnt signaling activation. Wnt signaling increases colony formation by promoting cellular epithelialization during the initiation phase in a TCF7-dependent manner. However, during maturation phase, it is also responsible for inducing mesendodermal differentiation, which is negatively regulated by TCF7L1. Thus, Wnt signaling inhibition or TCF7L1 overexpression downregulates mesendodermal gene expression without perturbing pluripotency. Together, our results demonstrate that a phase-specific modulation of Wnt signaling leads to an improved reprogramming efficiency in terms of colony output and pluripotency acquisition. This work provides new insights into the cell context-dependent roles of Wnt signaling during human somatic cell reprogramming.

The Pleiotropic Effects of the Canonical Wnt Pathway in Early Development and Pluripotency

The technology to derive embryonic and induced pluripotent stem cells from early embryonic stages and adult somatic cells, respectively, emerged as a powerful resource to enable the establishment of new in vitro models, which recapitulate early developmental processes and disease. Additionally, pluripotent stem cells (PSCs) represent an invaluable source of relevant differentiated cell types with immense potential for regenerative medicine and cell replacement therapies. Pluripotent stem cells support self-renewal, potency and proliferation for extensive periods of culture in vitro. However, the core pathways that rule each of these cellular features specific to PSCs only recently began to be clarified. The Wnt signaling pathway is pivotal during early embryogenesis and is central for the induction and maintenance of the pluripotency of PSCs. Signaling by the Wnt family of ligands is conveyed intracellularly by the stabilization of β-catenin in the cytoplasm and in the nucleus, where it elicits the transcriptional activity of T-cell factor (TCF)/lymphoid enhancer factor (LEF) family of transcription factors. Interestingly, in PSCs, the Wnt/β-catenin–TCF/LEF axis has several unrelated and sometimes opposite cellular functions such as self-renewal, stemness, lineage commitment and cell cycle regulation. In addition, tight control of the Wnt signaling pathway enhances reprogramming of somatic cells to induced pluripotency. Several recent research efforts emphasize the pleiotropic functions of the Wnt signaling pathway in the pluripotent state. Nonetheless, conflicting results and unanswered questions still linger. In this review, we will focus on the diverse functions of the canonical Wnt signaling pathway on the developmental processes preceding embryo implantation, as well as on its roles in pluripotent stem cell biology such as self-renewal and cell cycle regulation and somatic cell reprogramming.

ERAD-dependent control of the Wnt secretory factor Evi

Active regulation of protein abundance is an essential strategy to modulate cellular signaling pathways. Within the Wnt signaling cascade, regulated degradation of β-catenin by the ubiquitin-proteasome system (UPS) affects the outcome of canonical Wnt signaling. Here, we found that abundance of the Wnt cargo receptor Evi (Wls/GPR177), which is required for Wnt protein secretion, is also regulated by the UPS through endoplasmic reticulum (ER)-associated degradation (ERAD). In the absence of Wnt ligands, Evi is ubiquitinated and targeted for ERAD in a VCP-dependent manner. Ubiquitination of Evi involves the E2-conjugating enzyme UBE2J2 and the E3-ligase CGRRF1. Furthermore, we show that a triaging complex of Porcn and VCP determines whether Evi enters the secretory or the ERAD pathway. In this way, ERAD-dependent control of Evi availability impacts the scale of Wnt protein secretion by adjusting the amount of Evi to meet the requirement of Wnt protein export. As Wnt and Evi protein levels are often dysregulated in cancer, targeting regulatory ERAD components might be a useful approach for therapeutic interventions.

Comparative gene expression study and pathway analysis of the human iris- and the retinal pigment epithelium

Background

The retinal pigment epithelium (RPE) is a neural monolayer lining the back of the eye.

Degeneration of the RPE leads to severe vision loss in, so far incurable, diseases such as age-related macular degeneration and some forms of retinitis pigmentosa. A promising future replacement therapy may be autologous iris epithelial cell transdifferentiation into RPE in vitro and, subsequently, transplantation. In this study we compared the gene expression profiles of the iris epithelium (IE) and the RPE.

Methods

We collected both primary RPE- and IE cells from 5 freshly frozen human donor eyes, using respectively laser dissection microscopy and excision. We performed whole-genome expression profiling using 44k Agilent human microarrays. We investigated the gene expression profiles on both gene and functional network level, using R and the knowledge database Ingenuity.

Results

The major molecular pathways related to the RPE and IE were quite similar and yielded basic neuro-epithelial cell functions. Nonetheless, we also found major specific differences: For example, genes and molecular pathways, related to the visual cycle and retinol biosynthesis are significantly higher expressed in the RPE than in the IE. Interestingly, Wnt and aryl hydrocarbon receptor (AhR-) signaling pathways are much higher expressed in the IE than in the RPE, suggesting, respectively, a possible pluripotent and high detoxification state of the IE.

Conclusions

This study provides a valuation of the similarities and differences between the expression profiles of the RPE and IE. Our data combined with that of the literature, represent a most comprehensive perspective on transcriptional variation, which may support future research in the development of therapeutic transplantation of IE.

Identification and characterization of secreted factors that are upregulated during somatic cell reprogramming

The process of cell reprogramming has been characterized considerably since the successful generation of induced pluripotent stem cells. However, the importance of cell-cell communications for cellular reprogramming remains largely unknown. Secreted factors, which are expressed and secreted during reprogramming, may influence the reprogramming efficiency. Here, we have identified Sostdc1, Glb1l2, Fetub, Dpp4, Gdf3, Trh, and Tdgf1 as prominently upregulated secreted factors during reprogramming. Our detailed analysis reveals that these seven factors may be categorized into four groups based on their expression patterns in relation to the reprogramming stages. Remarkably, knockdown of Sostdc1, which is the most prominently upregulated factor and which is expressed earlier than the other six factors, results in reduced reprogramming efficiency, suggesting its involvement in the reprogramming process.

Transient Expression of WNT2 Promotes Somatic Cell Reprogramming by Inducing β-Catenin Nuclear Accumulation

Treatment with several Wnt/β-catenin signaling pathway regulators can change the cellular reprogramming efficiency; however, the dynamics and role of endogenous Wnt/β-catenin signaling in reprogramming remain largely unanswered. Here we identify the upregulation of WNT2 and subsequent β-catenin nuclear accumulation as key events in reprogramming. Transient nuclear accumulation of β-catenin occurs early in MEF reprogramming. Wnt2 is strongly expressed in the early stage of reprogramming. Wnt2 knockdown suppresses the nuclear accumulation of β-catenin and reduces the reprogramming efficiency. WNT2 overexpression promotes β-catenin nuclear accumulation and enhances the reprogramming efficiency. WNT2 contributes to the promotion of cell proliferation. Experiments with several drugs that control the Wnt pathway also indicate the importance of β-catenin nuclear accumulation in reprogramming. Our findings reveal the role of WNT2/β-catenin signaling in reprogramming.

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Nuclear accumulation of β-catenin occurs in the early stage of MEF reprogramming

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Wnt2 expression is transiently increased during MEF reprogramming

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WNT2 promotes both the β-catenin nuclear accumulation and the reprogramming process

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Nuclear accumulation of β-catenin is important for MEF reprogramming

hiPSC-derived iMSCs: NextGen MSCs as an advanced therapeutically active cell resource for regenerative medicine

Mesenchymal stem cells (MSCs) are being assessed for ameliorating the severity of graft‐versus‐host disease, autoimmune conditions, musculoskeletal injuries and cardiovascular diseases. While most of these clinical therapeutic applications require substantial cell quantities, the number of MSCs that can be obtained initially from a single donor remains limited. The utility of MSCs derived from human‐induced pluripotent stem cells (hiPSCs) has been shown in recent pre‐clinical studies. Since adult MSCs have limited capability regarding proliferation, the quantum of bioactive factor secretion and immunomodulation ability may be constrained. Hence, the alternate source of MSCs is being considered to replace the commonly used adult tissue‐derived MSCs. The MSCs have been obtained from various adult and foetal tissues. The hiPSC‐derived MSCs (iMSCs) are transpiring as an attractive source of MSCs because during reprogramming process, cells undergo rejuvination, exhibiting better cellular vitality such as survival, proliferation and differentiations potentials. The autologous iMSCs could be considered as an inexhaustible source of MSCs that could be used to meet the unmet clinical needs. Human‐induced PSC‐derived MSCs are reported to be superior when compared to the adult MSCs regarding cell proliferation, immunomodulation, cytokines profiles, microenvironment modulating exosomes and bioactive paracrine factors secretion. Strategies such as derivation and propagation of iMSCs in chemically defined culture conditions and use of footprint‐free safer reprogramming strategies have contributed towards the development of clinically relevant cell types. In this review, the role of iPSC‐derived mesenchymal stromal cells (iMSCs) as an alternate source of therapeutically active MSCs has been described. Additionally, we also describe the role of iMSCs in regenerative medical applications, the necessary strategies, and the regulatory policies that have to be enforced to render iMSC's effectiveness in translational medicine.

Anti-cancer drug 3,3'-diindolylmethane activates Wnt4 signaling to enhance gastric cancer cell stemness and tumorigenesis

As a natural health supplement, 3,3'-diindolylmethane (DIM) is proposed as a preventive and chemotherapeutic agent for cancer by inhibiting cell proliferation and inducing cell apoptosis. However, we found that in contrary to high level of DIM (30 μM), low level of DIM (1 μM and 10 μM) obviously promoted gastric cancer cell growth and migration. In addition, we found that low level of DIM increased the expression of stemness factors and enhanced the pluripotency of gastric cancer cells. Low level of DIM promoted gastric cancer progression by inducing the PORCN-dependent secretion of Wnt4 and the activation of β-catenin signaling. Wnt4 knockdown reversed the effects of low level of DIM on gastric cancer cells. The results of in vivo studies showed that gastric cancer cells treated with low level of DIM (1 μM) grew faster and expressed higher level of Wnt4 than control cells. Taken together, our findings indicate that low level of DIM activates autocrine Wnt4 signaling to enhance the progression of gastric cancer, which may suggest an adverse aspect of DIM in cancer therapy. Our findings will provide a new aspect for the safety of DIM in its clinical application.

Biochemical Methods to Analyze Wnt Protein Secretion

Wnt proteins act as potent morphogens in various aspects of embryonic development and adult tissue homeostasis. However, in addition to its physiological importance, aberrant Wnt signaling has been linked to the onset and progression of different types of cancer. On the cellular level, the secretion of Wnt proteins involves trafficking of lipid-modified Wnts from the endoplasmic reticulum (ER) to Golgi and further compartments via the Wnt cargo receptor evenness interrupted. Others and we have recently shown that Wnt proteins are secreted on extracellular vesicles (EVs) such as microvesicles and exosomes. Although more details about specific regulation of Wnt secretion steps are emerging, it remains largely unknown how Wnt proteins are channeled into different release pathways such as lipoprotein particles, EVs and cytonemes. Here, we describe protocols to purify and quantify Wnts from the supernatant of cells by either assessing total Wnt proteins in the supernatant or monitoring Wnt proteins on EVs. Purified Wnts from the supernatant as well as total cellular protein content can be investigated by immunoblotting. Additionally, the relative activity of canonical Wnts in the supernatant can be assessed by a dual-luciferase Wnt reporter assay. Quantifying the amount of secreted Wnt proteins and their activity in the supernatant of cells allows the investigation of intracellular trafficking events that regulate Wnt secretion and the role of extracellular modulators of Wnt spreading.

Methods to Manipulate and Monitor Wnt Signaling in Human Pluripotent Stem Cells

Human pluripotent stem cells (hPSCs) may revolutionize medical practice by providing: (a) a renewable source of cells for tissue replacement therapies, (b) a powerful system to model human diseases in a dish, and (c) a platform for examining efficacy and safety of novel drugs. Furthermore, these cells offer a unique opportunity to study early human development in vitro, in particular, the process by which a seemingly uniform cell population interacts to give rise to the three main embryonic lineages: ectoderm, endoderm. and mesoderm. This process of lineage allocation is regulated by a number of inductive signals that are mediated by growth factors, including FGF, TGFβ, and Wnt. In this book chapter, we introduce a set of tools, methods, and protocols to specifically manipulate the Wnt signaling pathway with the intention of altering the cell fate outcome of hPSCs.

Signaling involved in stem cell reprogramming and differentiation

Stem cell differentiation is regulated by multiple signaling events. Recent technical advances have revealed that differentiated cells can be reprogrammed into stem cells. The signals involved in stem cell programming are of major interest in stem cell research. The signaling mechanisms involved in regulating stem cell reprogramming and differentiation are the subject of intense study in the field of life sciences. In this review, the molecular interactions and signaling pathways related to stem cell differentiation are discussed.

From "directed differentiation" to "neuronal induction": modeling neuropsychiatric disease

Aberrant behavior and function of neurons are believed to be the primary causes of most neurological diseases and psychiatric disorders. Human postmortem samples have limited availability and, while they provide clues to the state of the brain after a prolonged illness, they offer limited insight into the factors contributing to disease onset. Conversely, animal models cannot recapitulate the polygenic origins of neuropsychiatric disease. Novel methods, such as somatic cell reprogramming, deliver nearly limitless numbers of pathogenic human neurons for the study of the mechanism of neuropsychiatric disease initiation and progression. First, this article reviews the advent of human induced pluripotent stem cell (hiPSC) technology and introduces two major methods, “directed differentiation” and “neuronal induction,” by which it is now possible to generate neurons for modeling neuropsychiatric disease. Second, it discusses the recent applications, and the limitations, of these technologies to in vitro studies of psychiatric disorders.