LEF-1, a gene encoding a lymphoid-specific protein with an HMG domain, regulates T-cell receptor alpha enhancer function [corrected]

Intestinal Development and Gut Disease: Contributions From the Caenorhabditis elegans Model

The mammalian intestine is a highly organized and complex system essential for nutrient absorption, immune response, and homeostasis. Disruptions in its development can lead to various gut diseases, ranging from congenital anomalies to inflammatory and neoplastic disorders. Caenorhabditis elegans (C elegans) has emerged as a valuable model organism for studying intestinal development and gut diseases due to its genetic tractability and transparent body. This review explores the significant contributions of C elegans research to our understanding of intestinal biology, examining historical milestones, anatomical and physiological insights, and its utility in modeling gut diseases and drug discovery. We also draw comparative insights into mammalian systems and propose future research directions. The findings highlight the potential of C elegans as an essential model system for advancing our knowledge of intestinal development and its implications for human health.

Enhancers in T Cell development and malignant lesions

Enhancers constitute a vital category of cis-regulatory elements with a Mediator complex within DNA sequences, orchestrating gene expression by activating promoters. In the development of T cells, some enhancers regulate the critical genes, which might also regulate T cell malignant lesions. This review is to comprehensively elucidate the contributions of enhancers in both normal T cell development and its malignant pathogenesis, proposing the idea that the precise subunits of the Mediator complex are the potential drug target for disrupting the specific gene enhancer for T cell malignant diseases.

A Single Interfacial Point Mutation Rescues Solution Structure Determination of the Complex of HMG-D with a DNA Bulge

Broadening of signals from atoms at interfaces can often be a limiting factor in applying solution NMR to the structure determination of complexes. Common contributors to such problems include exchange between free and bound states and the increased molecular weight of complexes relative to the free components, but another cause that can be more difficult to deal with occurs when conformational dynamics within the interface takes place at an intermediate rate on the chemical shift timescale. In this work we show how a carefully chosen mutation in the protein HMG-D rescued such a situation, making possible high-resolution structure determination of its complex with a dA2 bulge DNA ligand designed to mimic a natural DNA bend, and thereby revealing a new spatial organization of the complex.

The role of thymic epithelium in thymus development and age-related thymic involution

The establishment of an adaptive immune system is critical for protecting our bodies from neoplastic cancers and invading pathogens such as viruses and bacteria. As a primary lymphoid organ, the thymus generates lymphoid T cells that play a major role in the adaptive immune system. T cell generation in the thymus is controlled by interactions between thymocytes and other thymic cells, primarily thymic epithelial cells. Thus, the normal development and function of thymic epithelial cells are important for the generation of immunocompetent and self-tolerant T cells. On the other hand, the degeneration of the thymic epithelium due to thymic aging causes thymic involution, which is associated with the decline of adaptive immune function. Herein we summarize basic and current knowledge of the development and function of thymic epithelial cells and the mechanism of thymic involution. J. Med. Invest. 71 : 29-39, February, 2024.

Acute myeloid leukemia with mixed phenotype is characterized by stemness transcriptomic signatures and limited lineage plasticity

Mixed phenotype (MP) in acute leukemias poses unique classification and management dilemmas and can be seen in entities other than de novo mixed phenotype acute leukemia (MPAL). Although WHO classification empirically recommends excluding AML with myelodysplasia related changes (AML-MRC) and therapy related AML (t-AML) with mixed phenotype (AML-MP) from MPAL, there is lack of studies investigating the clinical, genetic, and biologic features of AML-MP. We report the first cohort of AML-MRC and t-AML with MP integrating their clinical, immunophenotypic, genomic and transcriptomic features with comparison to MPAL and AML-MRC/t-AML without MP. Both AML cohorts with and without MP shared similar clinical features including adverse outcomes but were different from MPAL. The genomic landscape of AML-MP overlaps with AML without MP but differs from MPAL. AML-MP harbors more frequent RUNX1 mutations than AML without MP and MPAL. RUNX1 mutations did not impact the survival of patients with MPAL. Unsupervised hierarchal clustering based on immunophenotype identified biologically distinct clusters with phenotype/genotype correlation and outcome differences. Furthermore, transcriptomic analysis showed an enrichment for stemness signature in AML-MP and AML without MP as compared to MPAL. Lastly, MPAL but not AML-MP often switched to lymphoid only immunophenotype after treatment. Expression of transcription factors critical for lymphoid differentiation were upregulated only in MPAL, but not in AML-MP. Our study for the first time demonstrates that AML-MP clinically and biologically resembles its AML counterpart without MP and differs from MPAL, supporting the recommendation to exclude these patients from the diagnosis of MPAL. Future studies are needed to elucidate the molecular mechanism of mixed phenotype in AML.

Key points

AML-MP clinically and biologically resembles AML but differs from MPAL. AML-MP shows RUNX1 mutations, stemness signatures and limited lymphoid lineage plasticity.

ISG20L2: an RNA nuclease regulating T cell activation

ISG20L2, a 3' to 5' exoribonuclease previously associated with ribosome biogenesis, is identified here in activated T cells as an enzyme with a preferential affinity for uridylated miRNA substrates. This enzyme is upregulated in T lymphocytes upon TCR and IFN type I stimulation and appears to be involved in regulating T cell function. ISG20L2 silencing leads to an increased basal expression of CD69 and induces greater IL2 secretion. However, ISG20L2 absence impairs CD25 upregulation, CD3 synaptic accumulation and MTOC translocation towards the antigen-presenting cell during immune synapsis. Remarkably, ISG20L2 controls the expression of immunoregulatory molecules, such as AHR, NKG2D, CTLA-4, CD137, TIM-3, PD-L1 or PD-1, which show increased levels in ISG20L2 knockout T cells. The dysregulation observed in these key molecules for T cell responses support a role for this exonuclease as a novel RNA-based regulator of T cell function.

Visualizing WNT signaling in mammalian systems

WNT/CTNNB1 signaling plays a critical role in the development of all multicellular animals. Here, we include both the embryonic stages, during which tissue morphogenesis takes place, and the postnatal stages of development, during which tissue homeostasis occurs. Thus, embryonic development concerns lineage development and cell fate specification, while postnatal development involves tissue maintenance and regeneration. Multiple tools are available to researchers who want to investigate, and ideally visualize, the dynamic and pleiotropic involvement of WNT/CTNNB1 signaling in these processes. Here, we discuss and evaluate the decisions that researchers need to make in identifying the experimental system and appropriate tools for the specific question they want to address, covering different types of WNT/CTNNB1 reporters in cells and mice. At a molecular level, advanced quantitative imaging techniques can provide spatio-temporal information that cannot be provided by traditional biochemical assays. We therefore also highlight some recent studies to show their potential in deciphering the complex and dynamic mechanisms that drive WNT/CTNNB1 signaling.

Stepwise progression of β-selection during T cell development involves histone deacetylation

During T cell development, the first step in creating a unique T cell receptor (TCR) is genetic recombination of the TCRβ chain. The quality of the new TCRβ is assessed at the β-selection checkpoint. Most cells fail this checkpoint and die, but the coordination of fate at the β-selection checkpoint is not yet understood. We shed new light on fate determination during β-selection using a selective inhibitor of histone deacetylase 6, ACY1215. ACY1215 disrupted the β-selection checkpoint. Characterising the basis for this disruption revealed a new, pivotal stage in β-selection, bookended by up-regulation of TCR co-receptors, CD28 and CD2, respectively. Within this "DN3b^Pre" stage, CD5 and Lef1 are up-regulated to reflect pre-TCR signalling, and their expression correlates with proliferation. These findings suggest a refined model of β-selection in which a coordinated increase in expression of pre-TCR, CD28, CD5 and Lef1 allows for modulating TCR signalling strength and culminates in the expression of CD2 to enable exit from the β-selection checkpoint.

HMGN2 represses gene transcription via interaction with transcription factors Lef-1 and Pitx2 during amelogenesis

The chromatin-associated high mobility group protein N2 (HMGN2) cofactor regulates transcription factor activity through both chromatin and protein interactions. Hmgn2 expression is known to be developmentally regulated, but the post-transcriptional mechanisms that regulate Hmgn2 expression and its precise roles in tooth development remain unclear. Here, we demonstrate that HMGN2 inhibits the activity of multiple transcription factors as a general mechanism to regulate early development. Bimolecular fluorescence complementation, pull-down, and coimmunoprecipitation assays show that HMGN2 interacts with the transcription factor Lef-1 through its HMG-box domain as well as with other early development transcription factors, Dlx2, FoxJ1, and Pitx2. Furthermore, EMSAs demonstrate that HMGN2 binding to Lef-1 inhibits its DNA-binding activity. We found that Pitx2 and Hmgn2 associate with H4K5ac and H3K4me2 chromatin marks in the proximal Dlx2 promoter, demonstrating Hmgn2 association with open chromatin. In addition, we demonstrate that microRNAs (miRs) mir-23a and miR-23b directly target Hmgn2, promoting transcriptional activation at several gene promoters, including the amelogenin promoter. In vivo, we found that decreased Hmgn2 expression correlates with increased miR-23 expression in craniofacial tissues as the murine embryo develops. Finally, we show that ablation of Hmgn2 in mice results in increased amelogenin expression because of increased Pitx2, Dlx2, Lef-1, and FoxJ1 transcriptional activity. Taken together, our results demonstrate both post-transcriptional regulation of Hmgn2 by miR-23a/b and post-translational regulation of gene expression by Hmgn2–transcription factor interactions. We conclude that HMGN2 regulates tooth development through its interaction with multiple transcription factors.

The DNA-Binding High-Mobility Group Box Domain of Sox Family Proteins Directly Interacts with RNA In Vitro

There is a growing body of evidence that a substantial number of protein domains identified as DNA-binding also interact with RNA to regulate biological processes. Several recent studies have revealed that the Sox2 transcription factor binds RNA through its high-mobility group box (HMGB) domain in vitro and in vivo. A high degree of conservation of this domain among members of the Sox family of transcription factors suggests that RNA-binding activity may be a general feature of these proteins. To address this hypothesis, we examined a subset of HMGB domains from human Sox family of proteins for their ability to bind both DNA and RNA in vitro. We observed selective, high-affinity interactions between Sox family HMGB domains and various model RNA elements, including a four-way junction RNA, a hairpin RNA with an internal bulge, G-quadruplex RNA, and a fragment of long noncoding RNA ES2, which is known to directly interact with Sox2. Importantly, the HMGB domains bind these RNA ligands significantly tighter than nonconsensus dsDNA and in some cases with affinities rivaling those of their consensus dsDNA sequences. These data suggest that RNA binding is a conserved feature of the Sox family of transcription factors with the potential to modulate unappreciated biological functions.

Fine-tuning of β-catenin in mouse thymic epithelial cells is required for postnatal T-cell development

In the thymus, the thymic epithelium provides a microenvironment essential for the development of functionally competent and self-tolerant T cells. Previous findings showed that modulation of Wnt/β-catenin signaling in mouse thymic epithelial cells (TECs) disrupts embryonic thymus organogenesis. However, the role of β-catenin in TECs for postnatal T-cell development remains to be elucidated. Here, we analyzed gain-of-function (GOF) and loss-of-function (LOF) of β-catenin highly specific in mouse TECs. We found that GOF of β-catenin in TECs results in severe thymic dysplasia and T-cell deficiency beginning from the embryonic period. By contrast, LOF of β-catenin in TECs reduces the number of cortical TECs and thymocytes modestly and only postnatally. These results indicate that fine-tuning of β-catenin expression within a permissive range is required for TECs to generate an optimal microenvironment to support postnatal T-cell development.

T-Cell Factors as Transcriptional Inhibitors: Activities and Regulations in Vertebrate Head Development

Since its first discovery in the late 90s, Wnt canonical signaling has been demonstrated to affect a large variety of neural developmental processes, including, but not limited to, embryonic axis formation, neural proliferation, fate determination, and maintenance of neural stem cells. For decades, studies have focused on the mechanisms controlling the activity of β-catenin, the sole mediator of Wnt transcriptional response. More recently, the spotlight of research is directed towards the last cascade component, the T-cell factor (TCF)/Lymphoid-Enhancer binding Factor (LEF), and more specifically, the TCF/LEF-mediated switch from transcriptional activation to repression, which in both embryonic blastomeres and mouse embryonic stem cells pushes the balance from pluri/multipotency towards differentiation. It has been long known that Groucho/Transducin-Like Enhancer of split (Gro/TLE) is the main co-repressor partner of TCF/LEF. More recently, other TCF/LEF-interacting partners have been identified, including the pro-neural BarH-Like 2 (BARHL2), which belongs to the evolutionary highly conserved family of homeodomain-containing transcription factors. This review describes the activities and regulatory modes of TCF/LEF as transcriptional repressors, with a specific focus on the functions of Barhl2 in vertebrate brain development. Specific attention is given to the transcriptional events leading to formation of the Organizer, as well as the roles and regulations of Wnt/β-catenin pathway in growth of the caudal forebrain. We present TCF/LEF activities in both embryonic and neural stem cells and discuss how alterations of this pathway could lead to tumors.

Prognostic signatures and potential pathogenesis of eRNAs-related genes in colon adenocarcinoma

Enhancer RNAs (eRNAs) are a subclass of long noncoding RNAs (lncRNAs) that have a wide effect in human tumors. However, the systematic analysis of potential functions of eRNAs-related genes (eRGs) in colon cancer (CC) remains unexplored. In this study, a total of 8231 eRGs including 6236 protein-coding genes and 1995 lncRNAs were identified in CC based on the multiple resources. These eRGs showed higher expression level and stability compared to other genes. What's more, the functions of these eRGs were closely related to cancer. Then a prognostic prediction model with 12 eRGs signatures were obtained for colon adenocarcinoma (COAD) patients. ROC curves showed the AUCs were 0.81, 0.77, and 0.78 for 1-, 3-, and 5-year survival prediction, respectively. And the prognostic model also manifested good performance in the validation datasets. Besides, the expression levels of two prognostic signatures, TMEM220 and LRRN2, were verified to be significantly lower in CC tissues than in adjacent noncancerous tissues (p < .05). Finally, the distinct molecular features were characterized between the high- and low-risk group through multiomics analysis including DNA mutation and methylation. Our results show eRGs signatures based prognostic model has high accuracy and may provide innovative biomarkers in COAD.

Expression of TCF3 in Wilms' tumor and its regulatory role in kidney tumor cell viability, migration and apoptosis in vitro

Wilms' tumor (WT) is a major type of kidney cancer in children; however, the therapeutic measures for control of tumor metastasis, recurrence and death for this type of cancer remain unsatisfactory. The present study aimed to verify the expression of T-cell factor 3 (TCF3) in WT, and to explore its role in regulating the viability, migration and apoptosis of kidney tumor cells. Tumor tissues were collected from 10 patients with WT, and adjacent tissues were collected as normal controls. The expression levels of TCF3 were detected in WT tissues and adjacent tissues by reverse transcription-quantitative PCR (RT-qPCR), western blotting and immunohistochemistry. In addition, TCF3 expression was silenced in G401 kidney tumor cells via small interfering RNA transfection. Cell viability, cell cycle progression and cell apoptosis were assessed using the MTT assay and flow cytometry; the migration and invasion of kidney tumor cells were examined using Transwell and wound-healing assays; and the expression levels of Wnt signaling pathway-related genes (Wnt1, β-catenin and c-myc) were detected by RT-qPCR and western blotting. The results revealed that the expression levels of TCF3 were high in WT tissues from patients. Silencing TCF3 expression in G401 kidney tumor cells in vitro significantly inhibited cell viability and migration, and promoted cell apoptosis. Moreover, silencing TCF3 expression in G401 cells inhibited the expression levels of Wnt signaling pathway-related genes. Overall, these data indicated that TCF3 may be involved in WT development through regulation of Wnt signaling pathways. The findings of the present study provide a novel potential marker for the treatment and prognostic evaluation of WT.

Dynamics of alternative splicing during somatic cell reprogramming reveals functions for RNA-binding proteins CPSF3, hnRNP UL1, and TIA1

BACKGROUND

Somatic cell reprogramming is the process that allows differentiated cells to revert to a pluripotent state. In contrast to the extensively studied rewiring of epigenetic and transcriptional programs required for reprogramming, the dynamics of post-transcriptional changes and their associated regulatory mechanisms remain poorly understood. Here we study the dynamics of alternative splicing changes occurring during efficient reprogramming of mouse B cells into induced pluripotent stem (iPS) cells and compare them to those occurring during reprogramming of mouse embryonic fibroblasts.

RESULTS

We observe a significant overlap between alternative splicing changes detected in the two reprogramming systems, which are generally uncoupled from changes in transcriptional levels. Correlation between gene expression of potential regulators and specific clusters of alternative splicing changes enables the identification and subsequent validation of CPSF3 and hnRNP UL1 as facilitators, and TIA1 as repressor of mouse embryonic fibroblasts reprogramming. We further find that these RNA-binding proteins control partially overlapping programs of splicing regulation, involving genes relevant for developmental and morphogenetic processes.

CONCLUSIONS

Our results reveal common programs of splicing regulation during reprogramming of different cell types and identify three novel regulators of this process and their targets.

High expression of LEF1 correlates with poor prognosis in solid tumors, but not blood tumors: a meta-analysis

BACKGROUND

Previously published studies have indicated that lymphoid enhancer-binding factor 1 (LEF1) expression could be recognized as a valuable biomarker to evaluate clinical outcome for various types of malignant cancer, but the results remained controversial. Therefore, we conducted this meta-analysis to pool the published estimates and discuss the relationship of LEF1 expression with cancer prognosis.

METHODS

Five electronic databases Pubmed, Web of Science, Embase, CNKI, and Wanfang were systematically searched for eligible literatures. Hazard ratios (HRs) and 95% confidence intervals (CIs) from the included studies were combined to estimate the effect of LEF1 expression on cancer patients' survival.

RESULTS

Eleven original studies met the criteria and were enrolled for analysis. The results indicated that compared with patients in low LEF1 expression group, patients in high LEF1 expression group tended to have shorter overall survival (HR = 1.74, 95% CI: 1.06-2.86, P=0.029), especially for patients with solid tumors (HR = 2.39, 95% CI: 1.86-3.08, P=0.000).

CONCLUSIONS

Individual evidence about the prognostic value of LEF1 expression in human cancers was limited. Our meta-analysis supported the suggestion that elevated LEF1 expression could function as a promising biomarker to predict the clinical outcomes for malignant cancers, especially solid tumors. More high-quality clinical studies are warranted to highlight the prognostic value of LEF1 expression in human cancers.

Prioritizing transcriptional factors in gene regulatory networks with PageRank

Biological states are controlled by orchestrated transcriptional factors (TFs) within gene regulatory networks. Here we show TFs responsible for the dynamic changes of biological states can be prioritized with temporal PageRank. We further show such TF prioritization can be extended by integrating gene regulatory networks reverse engineered from multi-omics profiles, e.g. gene expression, chromatin accessibility, and chromosome conformation assays, using multiplex PageRank.

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Temporal PageRank prioritizes TFs controlling cellular state dynamics

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Multiplex PageRank prioritizes TFs by integrating multi-omics GRNs

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Temporal and multiplex PageRank can be used in combination for TF prioritization

Negative regulation of IL-8 in human astrocytes depends on β-catenin while positive regulation is mediated by TCFs/LEF/ATF2 interaction

Expression of cytokines/chemokines is tightly regulated at the transcription level. This is crucial in the central nervous system to maintain neuroimmune homeostasis. IL-8 a chemoattractant, which recruits neutrophils, T cells, and basophils into the brain in response to inflammation and/or injury is secreted predominantly by neurons, microglia, and astrocytes. Here, we investigated the mechanism by which astrocytes regulate IL-8 expression. We demonstrate that while β-catenin negatively regulated IL-8 transcription, its canonical transcriptional partners, members of the TCF/LEF transcription factors (TCF1, TCF3, TCF4 and LEF1) and Activating transcription factor 2 (ATF2) positively regulated IL-8 transcription. We further identified a putative TCF/LEF binding site at -175nt close to the minimal transcription region on the IL-8 promoter, mutation of which caused a significant reduction in IL-8 promoter activity. Chromatin immunoprecipitation demonstrated binding of TCF1, TCF4, LEF1 and ATF2 on the IL-8 promoter suggesting that TCFs/LEF partner with ATF2 to induce IL-8 transcription. These findings demonstrate a novel role for β-catenin in suppression of IL-8 expression and for TCFs/LEF/ATF2 in inducing IL-8. These findings reveal a unique mechanism by which astrocytes tightly regulate IL-8 expression.

LEF1 mediates osteoarthritis progression through circRNF121/miR-665/MYD88 axis via NF-кB signaling pathway

Osteoarthritis (OA) is a joint disease that causes great pain to patients and imposes a tremendous burden on the world’s medical resources. Regulatory noncoding RNAs, including circular RNAs (circRNAs) and microRNAs (miRNAs), play an important role in OA progression. Here, we identified differential expression of transcription factor LEF1 that increased circRNA circRNF121 levels in normal and OA cartilage tissues. The expression of LEF1 and circRNF121 was positively associated with Mankin’s scores. Alteration of circRNF121 mediated the degradation of extracellular mechanisms (ECM), apoptosis, and proliferation of chondrocytes. MiR-665 was identified as a direct regulatory target of circRNF121 and MYD88. Functional analysis showed that circRNF121 and MYD88 modulated ECM degradation, apoptosis, and proliferation of chondrocytes, which could be reversed by miR-665. MYD88 regulated the activity of the NF-кB signaling pathway by circRNF121 via sponging miR-665. Collectively, these data indicated that LEF1 impacted OA progression by modulating the circRNF121/miR-665/MYD88 axis via NF-кB pathway. Our research proposed a new molecular mechanism for the development of OA, and provided a prospective therapeutic target for OA.

Ectodermal Organ Development Is Regulated by a microRNA-26b-Lef-1-Wnt Signaling Axis

The developmental role of Lef-1 in ectodermal organs has been characterized using Lef-1 murine knockout models. We generated a Lef-1 conditional over-expression (COEL) mouse to determine the role of Lef-1 expression in epithelial structures at later stages of development after endogenous expression switches to the mesenchyme. Lef-1 over expression (OE) in the oral epithelium creates a new dental epithelial stem cell niche that significantly increases incisor growth. These data indicate that Lef-1 expression is switched off in the dental epithelial at early stages to maintain the stem cell niche and regulate incisor growth. Bioinformatics analyses indicated that miR-26b expression increased coinciding with decreased Lef-1 expression in the dental epithelium. We generated a murine model over-expressing miR-26b that targets endogenous Lef-1 expression and Lef-1-related developmental mechanisms. miR-26b OE mice have ectodermal organ defects including a lack of incisors, molars, and hair similar to the Lef-1 null mice. miR-26b OE rescues the Lef-1 OE phenotype demonstrating a critical genetic and developmental role for miR-26b in the temporal and spatial expression of Lef-1 in epithelial tissues. Lef-1 expression regulates Wnt signaling and Wnt target genes as well as cell proliferation mechanisms, while miR-26b OE reduced the levels of Wnt target gene expression. The extra stem cell compartment in the COEL mice expressed Lef-1 suggesting that Lef-1 is a stem cell factor, which was absent in the miR-26b OE/COEL rescue mice. This is the first demonstration of a microRNA OE mouse model that has ectodermal organ defects. These findings demonstrate that the levels of Lef-1 are critical for development and establish a role for miR-26b in the regulation of ectodermal organ development through the control of Lef-1 expression and an endogenous stem cell niche.

DOCK2 couples with LEF-1 to regulate B cell metabolism and memory response

Dedicator of cytokinesis 2 (DOCK2) is essential for the B cell differentiation, BCR signaling and humoral immune response. However, the role of DOCK2 in the memory response of B cell is unknown. By using two DOCK2 deficient patients, we found that the memory B cells were decreased and the early activation of DOCK2 deficient memory B cells was abolished to the degree of naïve B cells due to the decreased expression of CD19 and CD21 mechanistically. Interestingly the expression of LEF-1, a negative regulator of CD21, was increased in DOCK2 deficient B cells. This was linked to the increased expression of HIF-1α and cell metabolism, which in turn affected the ER structure. Finally, the reduction of memory B cells in DOCK2 patients was due to the increased apoptosis, which might be related with the increased metabolism.

β-Catenin and TCFs/LEF signaling discordantly regulate IL-6 expression in astrocytes

Background

The Wnt/β-catenin signaling pathway is a prolific regulator of cell-to-cell communication and gene expression. Canonical Wnt/β-catenin signaling involves partnering of β-catenin with members of the TCF/LEF family of transcription factors (TCF1, TCF3, TCF4, LEF1) to regulate gene expression. IL-6 is a key cytokine involved in inflammation and is particularly a hallmark of inflammation in the brain. Astrocytes, specialized glial cells in the brain, secrete IL-6. How astrocytes regulate IL-6 expression is not entirely clear, although in other cells NFκB and C/EBP pathways play a role. We evaluated here the interface between β-catenin, TCFs/LEF and C/EBP and NF-κB in relation to IL-6 gene regulation in astrocytes.

Methods

We performed molecular loss and/or gain of function studies of β-catenin, TCF/LEF, NFκB, and C/EBP to assess IL-6 regulation in human astrocytes. Specifically, siRNA mediated target gene knockdown, cDNA over expression of target gene, and pharmacological agents for regulation of target proteins were used. IL-6 levels was evaluated by real time quantitative PCR and ELISA. We also cloned the IL-6 promoter under a firefly luciferase reporter and used bioinformatics, site directed mutagenesis, and chromatin immunoprecipitation to probe the interaction between β-catenin/TCFs/LEFs and IL-6 promoter activity.

Results

β-catenin binds to TCF/LEF to inhibits IL-6 while TCFs/LEF induce IL-6 transcription through interaction with ATF-2/SMADs. β-catenin independent of TCFs/LEF positively regulates C/EBP and NF-κB, which in turn activate IL-6 expression. The IL-6 promoter has two putative regions for TCFs/LEF binding, a proximal site located at -91 nt and a distal site at -948 nt from the transcription start site, both required for TCF/LEF induction of IL-6 independent of β-catenin.

Conclusion

IL-6 regulation in human astrocytes engages a discordant interaction between β-catenin and TCF/LEF. These findings are intriguing given that no role for β-catenin nor TCFs/LEF to date is associated with IL-6 regulation and suggest that β-catenin expression in astrocytes is a critical regulator of anti-inflammatory responses and its disruption can potentially mediate persistent neuroinflammation.

Exploring a Drosophila Transcription Factor Interaction Network to Identify Cis-Regulatory Modules

Multiple transcription factors (TFs) bind to specific sites in the genome and interact among themselves to form the cis-regulatory modules (CRMs). They are essential in modulating the expression of genes, and it is important to study this interplay to understand gene regulation. In the present study, we integrated experimentally identified TF binding sites collected from published studies with computationally predicted TF binding sites to identify Drosophila CRMs. Along with the detection of the previously known CRMs, this approach identified novel protein combinations. We determined high-occupancy target sites, where a large number of TFs bind. Investigating these sites revealed that Giant, Dichaete, and Knirp are highly enriched in these locations. A common TAG team motif was observed at these sites, which might play a role in recruiting other TFs. While comparing the binding sites at distal and proximal promoters, we found that certain regulatory TFs, such as Zelda, were highly enriched in enhancers. Our study has shown that, from the information available concerning the TF binding sites, the real CRMs could be predicted accurately and efficiently. Although we only may claim co-occurrence of these proteins in this study, it may actually point to their interaction (as known interaction proteins typically co-occur together). Such an integrative approach can, therefore, help us to provide a better understanding of the interplay among the factors, even though further experimental verification is required.

Transforming growth factor-β1 enhances proliferative and metastatic potential by up-regulating lymphoid enhancer-binding factor 1/integrin αMβ2 in human renal cell carcinoma

Renal cell carcinoma (RCC) is a kind of malignant tumor with high recurrence, and it is urgent to find molecular markers for diagnosis and prognosis of RCC. Our study investigated the expression and function of integrin αMβ2 in RCC cells, aiming to understand the role of integrin αMβ2 in RCC and develop new therapeutic target for RCC. Overexpression and knockdown of lymphoid enhancer-binding factor 1 (LEF1) were performed using vector containing full-length cDNA and via siRNA technology, respectively. The expressions of mRNA and protein were detected by RT-PCR and Western blot, respectively. Proliferation of RCC cell was analyzed using WST-1 assay, and metastasis of RCC cell was evaluated using the transwell system. Our results demonstrated that LEF1 and integrin αMβ2 were up-regulated in RCC cells via TGF-β1-dependent mechanism, and LEF1 together with β-catenin directly increased integrin αMβ2 level. On the other hand, TGF-β1-induced proliferation, migration and invasion were suppressed by function-blocking antibody against integrin αMβ2 in RCC cells. In addition, integrin αMβ2 is crucial for LEF1 mediated cell invasion by regulating MMP-2, MMP-9 and calpain-2 secretion in RCC cells. LEF1/integrin αMβ2 expression was regulated by TGF-β1, and LEF1/integrin αMβ2 was involved in TGF-β1's improvement effects on the proliferation and metastasis of RCC. Blocking integrin αMβ2 activity could be a therapeutic option for patients with advanced RCC.

Dedicator of cytokinesis protein 2 couples with lymphoid enhancer-binding factor 1 to regulate expression of CD21 and B-cell differentiation

BACKGROUND

B-cell receptor (BCR) signaling, combined with CD19 and CD21 signals, imparts specific control of B-cell responses. Dedicator of cytokinesis protein 2 (DOCK2) is critical for the migration and motility of lymphocytes. Although absence of DOCK2 leads to lymphopenia, little is known about the signaling mechanisms and physiologic functions of DOCK2 in B cells.

OBJECTIVE

We sought to determine the underlying molecular mechanism of how DOCK2 regulates BCR signaling and peripheral B-cell differentiation.

METHODS

In this study we used genetic models for DOCK2, Wiskott-Aldrich syndrome protein (WASP), and lymphoid enhancer-binding factor 1 deficiency to study their interplay in BCR signaling and B-cell differentiation.

RESULTS

We found that the absence of DOCK2 led to downregulation of proximal and distal BCR signaling molecules, including CD19, but upregulation of SH2-containing inositol 5 phosphatase 1, a negative signaling molecule. Interestingly, DOCK2 deficiency reduced CD19 and CD21 expression at the mRNA and/or protein levels and was associated with reduced numbers of marginal zone B cells. Additionally, loss of DOCK2 reduced activation of WASP and accelerated degradation of WASP, resulting into reduced actin accumulation and early activation of B cells. Mechanistically, the absence of DOCK2 upregulates the expression of lymphoid enhancer-binding factor 1. These differences were associated with altered humoral responses in the absence of DOCK2.

CONCLUSIONS

Overall, our study has provided a novel underlying molecular mechanism of how DOCK2 deficiency regulates surface expression of CD21, which leads to downregulation of CD19-mediated BCR signaling and marginal zone B-cell differentiation.

Opposing roles of TCF7/LEF1 and TCF7L2 in cyclin D2 and Bmp4 expression and cardiomyocyte cell cycle control during late heart development

Bone morphogenetic protein (BMP) and Wnt pathways regulate cell proliferation and differentiation, but how these two pathways interact and mediate their nuclear actions in the heart, especially during late cardiac development, remains poorly defined. T-cell factor (TCF) and lymphoid enhancer factor (LEF) family transcriptional factors, including Lef1, Tcf7, Tcf7l1, and Tcf7l2, are important nuclear mediators of canonical Wnt/β-catenin signaling throughout cardiac development. We reveal that these TCF/LEF family members direct heart maturation through distinct temporal and spatial control. TCF7 and LEF1 decrease while TCF7L1 and TCF7L2 remain relatively stable during heart development. LEF1 is mainly expressed in mesenchymal cells in valvular regions. TCF7 and TCF7L1 are detected in the nucleus of mesothelial and endothelial cells, but not in cardiomyocytes or mesenchymal cells. Tcf7l2 is the primary TCF/LEF family member in cardiomyocytes and undergoes alternative splicing during heart development. A TCF7L2 intensity gradient opposite to that of β-catenin and cardiomyocyte proliferative activity is present in fetal hearts. Wnt activation by cardiac deletion of APC, a negative Wnt regulator, dramatically increases Cyclin D2 and Bmp4 expression. BMP signal transducing transcription factors, the mothers against decapentaplegic homologs (SMADs) are increasingly phosphorylated upon Wnt activation. LEF1/TCF7 displaces TCF7L2 and cooperates with pSMAD 1/5/8 in the regulatory elements of Cyclin D2 and Bmp4 promoters to promote β-catenin recruitment and transcriptional activation. Finally, we demonstrate that TCF7L2 is a transcriptional suppressor of Cyclin D2 and Bmp 4 in a cardiac cell line by overexpression and knockdown experiments.

Cloning and characterization of the LEF/TCF gene family in grass carp (Ctenopharyngodon idella) and their expression profiles in response to grass carp reovirus infection

T-cell factor/lymphoid enhancer-binding factor (TCF/LEF) proteins from the High Mobility Group (HMG) box family act as the main downstream effectors of the Wnt signaling pathway. HMGB proteins play multifaceted roles in the immune system of mammals. To clarify the immunological characteristics of LEF/TCF genes in grass carp (Ctenopharyngodon idella), five LEF/TCF genes (TCF7, LEF1, TCF7L1A, TCF7L1B, and TCF7L2) were identified and characterized. All five LEF/TCF proteins contained two characteristic domains: a HMG-BOX domain and a CTNNB1_binding region. Phylogenetic tree analysis revealed that the LEF/TCF proteins were represented different lineages. These results of subcellular localization showed that four of the LEF/TCF genes were localized exclusively within the nucleus, while TCF7L2 was localized in the cytoplasm and nucleus. The mRNA expression profiles of these LEF/TCF family genes differed across different tissues. The mRNA expression levels of TCF7, TCF7L1A, and TCF7L2 changed significantly in liver after grass carp reovirus (GCRV) challenge; TCF7 and TCF7L1A responded early while TCF7L2 responded late. This suggests that these genes may participate in GCRV-related immune responses. Moreover, TCF7 promoted Bcl6 transcription in response to the GCRV challenge. These findings further our understanding of the function of LEF/TCF genes in teleosts.

HIV-1 Escape from Small-Molecule Antagonism of Vif

Although antiretroviral therapy can suppress HIV-1 replication effectively, virus reservoirs persist in infected individuals and virus replication rapidly rebounds if therapy is interrupted. Currently, there is a need for therapeutic approaches that eliminate, reduce, or control persistent viral reservoirs if a cure is to be realized. This work focuses on the preclinical development of novel, small-molecule inhibitors of the HIV-1 Vif protein. Vif inhibitors represent a new class of antiretroviral drugs that may expand treatment options to more effectively suppress virus replication or to drive HIV-1 reservoirs to a nonfunctional state by harnessing the activity of the DNA-editing cytidine deaminase A3G, a potent, intrinsic restriction factor expressed in macrophage and CD4⁺ T cells. In this study, we derived inhibitor escape variants to characterize the mechanism by which these novel agents inhibit virus replication and to provide evidence for target validation.

The HIV-1 accessory protein Vif, which counteracts the antiviral action of the DNA-editing cytidine deaminase APOBEC3G (A3G), is an attractive and yet unexploited therapeutic target. Vif reduces the virion incorporation of A3G by targeting the restriction factor for proteasomal degradation in the virus-producing cell. Compounds that inhibit Vif-mediated degradation of A3G in cells targeted by HIV-1 would represent a novel antiviral therapeutic. We previously described small molecules with activity consistent with Vif antagonism. In this study, we derived inhibitor escape HIV-1 variants to characterize the mechanism by which these novel agents inhibit virus replication. Here we show that resistance to these agents is dependent on an amino acid substitution in Vif (V142I) and on a point mutation that likely upregulates transcription by modifying the lymphocyte enhancing factor 1 (LEF-1) binding site. Molecular modeling demonstrated a docking site in the Vif-Elongin C complex that is disrupted by these inhibitors. This docking site is lost when Vif acquires the V142I mutation that leads to inhibitor resistance. Competitive fitness experiments indicated that the V142I Vif and LEF-1 binding site mutations created a virus that is better adapted to growing in the presence of A3G than the wild-type virus.

Role of β-Catenin Activation Levels and Fluctuations in Controlling Cell Fate

Cells have developed numerous adaptation mechanisms to external cues by controlling signaling-pathway activity, both qualitatively and quantitatively. The Wnt/β-catenin pathway is a highly conserved signaling pathway involved in many biological processes, including cell proliferation, differentiation, somatic cell reprogramming, development, and cancer. The activity of the Wnt/β-catenin pathway and the temporal dynamics of its effector β-catenin are tightly controlled by complex regulations. The latter encompass feedback loops within the pathway (e.g., a negative feedback loop involving Axin2, a β-catenin transcriptional target) and crosstalk interactions with other signaling pathways. Here, we provide a review shedding light on the coupling between Wnt/β-catenin activation levels and fluctuations across processes and cellular systems; in particular, we focus on development, in vitro pluripotency maintenance, and cancer. Possible mechanisms originating Wnt/β-catenin dynamic behaviors and consequently driving different cellular responses are also reviewed, and new avenues for future research are suggested.

Lymphoid Enhancer Factor 1 Contributes to Hepatocellular Carcinoma Progression Through Transcriptional Regulation of Epithelial-Mesenchymal Transition Regulators and Stemness Genes

Lymphoid enhancer factor 1 (LEF1) activity is associated with progression of several types of cancers. The role of LEF1 in progression of hepatocellular carcinoma (HCC) remains poorly known. We investigated LEF1 expression in HCC and its interactions with epithelial-mesenchymal transition (EMT) regulators (e.g., Snail, Slug, Twist) and stemness genes (e.g., octamer-binding transcription factor 4 [Oct4], sex determining region Y-box 2 [Sox2], Nanog homeobox [Nanog]). Microarray analysis was performed on resected tumor samples from patients with HCC with or without postoperative recurrence. LEF1 expression was associated with postoperative recurrence as validated by immunohistochemical staining in another HCC cohort. Among 74 patients, 44 displayed a relatively high percentage of LEF1 staining (>30% of HCC cells), which was associated with a reduced recurrence-free interval (P < 0.001) and overall survival (P = 0.009). In multivariate analysis, a high percentage of LEF1 staining was significantly associated with low albumin level (P = 0.035), Twist overexpression (P = 0.018), Snail overexpression (P = 0.064), co-expression of Twist and Snail (P = 0.054), and multinodular tumors (P = 0.025). Down-regulation of LEF1 by short hairpin RNA decreased tumor sphere formation, soft agar colony formation, and transwell invasiveness of HCC cell lines Mahlavu and PLC. Xenotransplant and tail vein injection experiments revealed that LEF1 down-regulation in Mahlavu reduced tumor size and metastasis. LEF1 up-regulation in Huh7 increased sphere formation, soft agar colony formation, and transwell invasiveness. LEF1 was shown to physically interact with and transcriptionally activate promoter regions of Oct4, Snail, Slug, and Twist. Furthermore, Oct4, Snail, and Twist transactivated LEF1 to form a regulatory positive-feedback loop. Conclusion: LEF1 plays a pivotal role in HCC progression through transcriptional regulation of Oct4 and EMT regulators.

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.

Identification of LEF1 as a Susceptibility Locus for Kawasaki Disease in Patients Younger than 6 Months of Age

Kawasaki disease (KD) is an acute febrile vasculitis predominately affecting infants and children. The dominant incidence age of KD is from 6 months to 5 years of age, and the incidence is unusual in those younger than 6 months and older than 5 years of age. We tried to identify genetic variants specifically associated with KD in patients younger than 6 months or older than 5 years of age. We performed an age-stratified genome-wide association study using the Illumina HumanOmni1-Quad BeadChip data (296 cases vs. 1,000 controls) and a replication study (1,360 cases vs. 3,553 controls) in the Korean population. Among 26 candidate single nucleotide polymorphisms (SNPs) tested in replication study, only a rare nonsynonymous SNP (rs4365796: c.1106C＞T, p.Thr369Met) in the lymphoid enhancer binding factor 1 (LEF1) gene was very significantly associated with KD in patients younger than 6 months of age (odds ratio [OR], 3.07; p_combined = 1.10 × 10^-5), whereas no association of the same SNP was observed in any other age group of KD patients. The same SNP (rs4365796) in the LEF1 gene showed the same direction of risk effect in Japanese KD patients younger than 6 months of age, although the effect was not statistically significant (OR, 1.42; p = 0.397). This result indicates that the LEF1 gene may play an important role as a susceptibility gene specifically affecting KD patients younger than 6 months of age.

Wnt signalling: conquering complexity

The history of the Wnt pathway is an adventure that takes us from mice and flies to frogs, zebrafish and beyond, sketching the outlines of a molecular signalling cascade along the way. Here, we specifically highlight the instrumental role that developmental biology has played throughout. We take the reader on a journey, starting with developmental genetics studies that identified some of the main molecular players, through developmental model organisms that helped unravel their biochemical function and cell biological activities. Culminating in complex analyses of stem cell fate and dynamic tissue growth, these efforts beautifully illustrate how different disciplines provided missing pieces of a puzzle. Together, they have shaped our mechanistic understanding of the Wnt pathway as a conserved signalling process in development and disease. Today, researchers are still uncovering additional roles for Wnts and other members of this multifaceted signal transduction pathway, opening up promising new avenues for clinical applications.

Wnt/β-catenin signalling is necessary for gut differentiation in a marine annelid, Platynereis dumerilii

Background

Wnt/β-catenin (or canonical) signalling pathway activity is necessary and used independently several times for specification of vegetal fate and endoderm, gut differentiation, maintenance of epithelium in adult intestine and the development of gut-derived organs in various vertebrate and non-vertebrate organisms. However, its conservation in later stages of digestive tract development still remains questionable due to the lack of detailed data, mainly from Spiralia.

Results

Here we characterize the Pdu-Tcf gene, a Tcf/LEF orthologue and a component of Wnt/β-catenin pathway from Platynereis dumerilii, a spiralian, marine annelid worm. Pdu-Tcf undergoes extensive alternative splicing in the C-terminal region of the gene generating as many as eight mRNA isoforms some of which differ in the presence or absence of a C-clamp domain which suggests a distinct DNA binding activity of individual protein variants. Pdu-Tcf is broadly expressed throughout development which is indicative of many functions. One of the most prominent domains that exhibits rather strong Pdu-Tcf expression is in the putative precursors of endodermal gut cells which are detected after 72 h post-fertilization (hpf). At day 5 post-fertilization (dpf), Pdu-Tcf is expressed in the hindgut and pharynx (foregut), whereas at 7 dpf stage, it is strongly transcribed in the now-cellularized midgut for the first time. In order to gain insight into the role of Wnt/β-catenin signalling, we disrupted its activity using pharmacological inhibitors between day 5 and 7 of development. The inhibition of Wnt/β-catenin signalling led to the loss of midgut marker genes Subtilisin-1, Subtilisin-2, α-Amylase and Otx along with a drop in β-catenin protein levels, Axin expression in the gut and nearly the complete loss of proliferative activity throughout the body of larva. At the same time, a hindgut marker gene Legumain was expanded to the midgut compartment under the same conditions.

Conclusions

Our findings suggest that high Wnt/β-catenin signalling in the midgut might be necessary for proper differentiation of the endoderm to an epithelium capable of secreting digestive enzymes. Together, our data provide evidence for the role of Wnt/β-catenin signalling in gut differentiation in Platynereis.

Gene expression profiling of hematologic malignant cell lines resistant to oncolytic virus treatment

Pexa-Vec (pexastimogene devacirpvec; JX-594) has emerged as an attractive tool in oncolytic virotherapy. Pexa-Vec demonstrates oncolytic and immunotherapeutic mechanisms of action. But the determinants of resistance to Pexa-Vec are mostly unknown. We treated hemoatologic malignant cells with Pexa-Vec and examined the gene-expression pattern of sensitive and resistant cells. Human myeloid malignant cell lines (RPMI-8226, IM-9, K562, THP-1) and lymphoid cancer cell lines (MOLT4, CCRF-CEM, Ramos, U937) were treated with Pexa-Vec. Pexa-Vec was cytotoxic on myeloid cell lines in a dose-dependent manner, and fluorescent imaging and qPCR revealed that Pexa-Vec expression was low in RAMOS than IM-9 after 24 hrs and 48 hrs of infection. Gene expression profiles between two groups were analyzed by microarray. Genes with at least 2-fold increase or decrease in their expression were identified. A total of 660 genes were up-regulated and 776 genes were down-regulated in lymphoid cancer cell lines. The up- and down-regulated genes were categorized into 319 functional gene clusters. We identified the top 10 up-regulated genes in lymphoid cells. Among them three human genes (LEF1, STAMBPL1, and SLFN11) strongly correlated with viral replication. Up-regulation of PVRIG, LPP, CECR1, Arhgef6, IRX3, IGFBP2, CD1d were related to resistant to Pexa-Vec. In conclusion, lymphoid malignant cells are resistant to Pexa-Vec and displayed up-regulated genes associated with resistance to oncolytic viral therapy. These data provide potential targets to overcome resistance, and suggest that molecular assays may be useful in selecting patients for further clinical trials with Pexa-Vec.

Mesenchymal Wnt/β-catenin signaling limits tooth number

Tooth agenesis is one of the predominant developmental anomalies in humans, usually affecting the permanent dentition generated by sequential tooth formation and, in most cases, caused by mutations perturbing epithelial Wnt/β-catenin signaling. In addition, loss-of-function mutations in the Wnt feedback inhibitor AXIN2 lead to human tooth agenesis. We have investigated the functions of Wnt/β-catenin signaling during sequential formation of molar teeth using mouse models. Continuous initiation of new teeth, which is observed after genetic activation of Wnt/β-catenin signaling in the oral epithelium, was accompanied by enhanced expression of Wnt antagonists and a downregulation of Wnt/β-catenin signaling in the dental mesenchyme. Genetic and pharmacological activation of mesenchymal Wnt/β-catenin signaling negatively regulated sequential tooth formation, an effect partly mediated by Bmp4. Runx2, a gene whose loss-of-function mutations result in sequential formation of supernumerary teeth in the human cleidocranial dysplasia syndrome, suppressed the expression of Wnt inhibitors Axin2 and Drapc1 in dental mesenchyme. Our data indicate that increased mesenchymal Wnt signaling inhibits the sequential formation of teeth, and suggest that Axin2/Runx2 antagonistic interactions modulate the level of mesenchymal Wnt/β-catenin signaling, underlying the contrasting dental phenotypes caused by human AXIN2 and RUNX2 mutations.

Expression and functional analysis of TCF4 isoforms in human glioma cells

Transcription factor 4 (TCF4) is a member of the T-cell factor/lymphoid enhancer factor (TCF/LEF) transcription factor family in the Wnt/β‑catenin signaling pathway. The alternative splicing of TCF4 has been reported to exhibit potential carcinogenic properties in various cancer types. In the present study, TCF4 isoforms were cloned and identified in three human glioma cell lines, with the majority of splicing regions being exons 4, 5, 14, 15, and 16. Using MTT assays, it was demonstrated that the overexpression of TCF4 isoforms inhibits the proliferation of U251 cells. Flow cytometry and wound healing analyses revealed that the overexpression of TCF4 isoforms induced cell apoptosis and migration. Taken together, the β‑catenin binding domain of the TCF4 isoforms inhibited cell proliferation, and induced cell apoptosis and migration in glioma. Furthermore, all the isoforms identified contained the N‑terminal part of TCF4 including the β‑catenin binding domain. This implied that a high expression of TCF4 isoforms may lead to Wnt/β‑catenin signal activation and potentially promote malignant glioma development.

How One Thing Led to Another

I started research in high school, experimenting on immunological tolerance to transplantation antigens. This led to studies of the thymus as the site of maturation of T cells, which led to the discovery, isolation, and clinical transplantation of purified hematopoietic stem cells (HSCs). The induction of immune tolerance with HSCs has led to isolation of other tissue-specific stem cells for regenerative medicine. Our studies of circulating competing germline stem cells in colonial protochordates led us to document competing HSCs. In human acute myelogenous leukemia we showed that all preleukemic mutations occur in HSCs, and determined their order; the final mutations occur in a multipotent progenitor derived from the preleukemic HSC clone. With these, we discovered that CD47 is an upregulated gene in all human cancers and is a "don't eat me" signal; blocking it with antibodies leads to cancer cell phagocytosis. CD47 is the first known gene common to all cancers and is a target for cancer immunotherapy.

Waldenström's macroglobulinemia: Two malignant clones in a monoclonal disease? Molecular background and clinical reflection

Waldenström's macroglobulinemia (WM) is a complex disease characterized by apparent morphological heterogeneity within the malignant clonal cells representing a continuum of small lymphocytes, plasmacytoid lymphocytes, and plasma cells. At the molecular level, the neoplastic B cell-derived clone has undergone somatic hypermutation, but not isotype switching, and retains the capability of plasmacytic differentiation. Although by classical definition, WM is formed by monoclonal expansion, long-lived clonal B lymphocytes are of heterogeneous origin. Even more, according to current opinion, plasma cells also conform certain population with pathogenic and clinical significance. In this article, we review the recent advances in the WM clonal architecture, briefly describe B-cell development during which the molecular changes lead to the malignant transformation and mainly focus on differences between two principal B-lineage clones, including analysis of their genome and transcriptome profiles, as well as immunophenotype features. We assume that the correct identification of a number of specific immunophenotypic molecular and expression alterations leading to proper aberrant clone detection can help to guide patient monitoring throughout treatment and successfully implement therapy strategies directed against both B- and plasma cell tumor WM clones.

Of sex and determination: marking 25 years of Randy, the sex-reversed mouse

On Thursday 9 May 1991, the world awoke to front-page news of a breakthrough in biological research. From Washington to Wollongong, newspapers, radio and TV were abuzz with the story of a transgenic mouse in London called Randy. Why was this mouse so special? The mouse in question was a chromosomal female (XX) made male by the presence of a transgene containing the Y chromosome gene Sry This sex-reversal provided clear experimental proof that Sry was the elusive mammalian sex-determining gene. Twenty-five years on, we reflect on what this discovery meant for our understanding of how males and females arise and what remains to be understood.

Clinical and Biological Insights from the University of California San Francisco Prospective and Longitudinal Cohort

INTRODUCTION

Sarcoidosis is a systemic inflammatory disease characterized by non-necrotizing granulomas in involved organs, most commonly the lung. Description of patient characteristics in the Western United States is limited. Furthermore, blood-based measures that relate to clinical sarcoidosis phenotypes are lacking. We present an analysis of a prospective, longitudinal sarcoidosis cohort at a Northern Californian academic medical center.

METHODS

We enrolled 126 sarcoidosis subjects and 64 healthy controls and recorded baseline demographic and clinical characteristics. We used regression models to identify factors independently associated with pulmonary physiology. We tested whether blood transcript levels at study entry could relate to longitudinal changes in pulmonary physiology.

RESULTS

White, non-Hispanics composed ~70% of subjects. Hispanics and Blacks had a diagnostic biopsy at an age ~7 years younger than whites. Obstructive, but not restrictive, physiology characterized Scadding Stage IV patients. Subjects reporting use of immunosuppression had worse FEV1%p, FVC%p, and DLCO%p compared to subjects never treated, regardless of Scadding stage. We defined sarcoidosis disease activity by a drop in pulmonary function over 36 months and found that subjects meeting this definition had significant repression of blood gene transcripts related to T cell receptor signaling pathways, referred to as the "TCR factor."

CONCLUSION

Obstructive pulmonary physiology defined Stage IV patients which were mostly white, non-Hispanics. Genes comprising the composite gene expression score, TCR factor, may represent a blood-derived measure of T-cell activity and an indirect measure of active sarcoidosis inflammation. Validation of this measure could translate into individualized treatment for sarcoidosis patients.

Differentiation of mesenchymal stem cells into cardiomyocytes is regulated by miRNA-1-2 via WNT signaling pathway

BACKGROUND

Bone marrow derived stem cells (BMSCs) have the potential to differentiate into cardiomyocytes, but the rate of differentiation is low and the mechanism of differentiation is unclear completely. Here, we aimed to investigate the role of miR1-2 in differentiation of mouse BMSCs into cardiomyocyte-like cells and reveal the involved signaling pathways in the procedure.

METHODS

Mouse BMSCs were treated with miR1-2 and 5-azacytine (5-aza). The expression of cardiac cell markers: NKx2.5, cTnI and GATA4 in BMSCs were examined by qPCR. The apoptosis rate was detected by flow cytometry and the activity of the Wnt/β-catenin signaling pathway was evaluated by measuring the upstream protein of this signaling pathway.

RESULTS

After over-expression of miR1-2 in mouse BMSCs, the apoptosis rate was significantly lower than the 5-aza group, while the expressions of cardiac-specific genes: such as Nkx2.5, cTnI and GATA4 were significantly increased compared to the control group and the 5-aza group. Meanwhile, over-expression of miR1-2 in mouse BMSCs enhanced the expression of wnt11, JNK, β-catenin and TCF in the Wnt/β-catenin signaling pathway. Use of LGK-974, an inhibitor of Wnt/β-catenin signaling pathway, significantly reduced the expression of cardiac-specific genes and partially blocked the role of the miR1-2.

CONCLUSION

Over-expression of miR1-2 in mouse BMSCs can induce them toward promoted cardiomyocyte differentiation via the activation of the Wnt/β-catenin signaling pathway. Compared to 5-aza, miR1-2 can induce differentiation of BMSCs into cardiomyocytes more effectively with a less cytotoxicity.

Analyzing gene expression profiles in dilated cardiomyopathy via bioinformatics methods

Dilated cardiomyopathy (DCM) is characterized by ventricular dilatation, and it is a common cause of heart failure and cardiac transplantation. This study aimed to explore potential DCM-related genes and their underlying regulatory mechanism using methods of bioinformatics. The gene expression profiles of GSE3586 were downloaded from Gene Expression Omnibus database, including 15 normal samples and 13 DCM samples. The differentially expressed genes (DEGs) were identified between normal and DCM samples using Limma package in R language. Pathway enrichment analysis of DEGs was then performed. Meanwhile, the potential transcription factors (TFs) and microRNAs (miRNAs) of these DEGs were predicted based on their binding sequences. In addition, DEGs were mapped to the cMap database to find the potential small molecule drugs. A total of 4777 genes were identified as DEGs by comparing gene expression profiles between DCM and control samples. DEGs were significantly enriched in 26 pathways, such as lymphocyte TarBase pathway and androgen receptor signaling pathway. Furthermore, potential TFs (SP1, LEF1, and NFAT) were identified, as well as potential miRNAs (miR-9, miR-200 family, and miR-30 family). Additionally, small molecules like isoflupredone and trihexyphenidyl were found to be potential therapeutic drugs for DCM. The identified DEGs (PRSS12 and FOXG1), potential TFs, as well as potential miRNAs, might be involved in DCM.

TCF/LEF Transcription Factors: An Update from the Internet Resources

T-cell factor/lymphoid enhancer-binding factor (TCF/LEF) proteins (TCFs) from the High Mobility Group (HMG) box family act as the main downstream effectors of the Wnt signaling pathway. The mammalian TCF/LEF family comprises four nuclear factors designated TCF7, LEF1, TCF7L1, and TCF7L2 (also known as TCF1, LEF1, TCF3, and TCF4, respectively). The proteins display common structural features and are often expressed in overlapping patterns implying their redundancy. Such redundancy was indeed observed in gene targeting studies; however, individual family members also exhibit unique features that are not recapitulated by the related proteins. In the present viewpoint, we summarized our current knowledge about the specific features of individual TCFs, namely structural-functional studies, posttranslational modifications, interacting partners, and phenotypes obtained upon gene targeting in the mouse. In addition, we employed several publicly available databases and web tools to evaluate the expression patterns and production of gene-specific isoforms of the TCF/LEF family members in human cells and tissues.

Tcf7l1 protects the anterior neural fold from adopting the neural crest fate

The neural crest (NC) is crucial for the evolutionary diversification of vertebrates. NC cells are induced at the neural plate border by the coordinated action of several signaling pathways, including Wnt/β-catenin. NC cells are normally generated in the posterior neural plate border, whereas the anterior neural fold is devoid of NC cells. Using the mouse model, we show here that active repression of Wnt/β-catenin signaling is required for maintenance of neuroepithelial identity in the anterior neural fold and for inhibition of NC induction. Conditional inactivation of Tcf7l1, a transcriptional repressor of Wnt target genes, leads to aberrant activation of Wnt/β-catenin signaling in the anterior neuroectoderm and its conversion into NC. This reduces the developing prosencephalon without affecting the anterior-posterior neural character. Thus, Tcf7l1 defines the border between the NC and the prospective forebrain via restriction of the Wnt/β-catenin signaling gradient.

Transcription Factor 7-like 2 Mediates Canonical Wnt/β-Catenin Signaling and c-Myc Upregulation in Heart Failure

BACKGROUND

How canonical Wnt/β-catenin signals in adult hearts, especially in different diseased states, remains unclear. The proto-oncogene, c-Myc, is a Wnt target and an early response gene during cardiac stress. It is not clear whether c-Myc is activated or how it is regulated during heart failure.

METHODS AND RESULTS

We investigated canonical Wnt/β-catenin signaling and how it regulated c-Myc expression in failing hearts of human ischemic heart disease, idiopathic dilated cardiomyopathy, and murine desmin-related cardiomyopathy. Our data demonstrated that canonical Wnt/β-catenin signaling was activated through nuclear accumulation of β-catenin in idiopathic dilated cardiomyopathy, ischemic heart disease, and murine desmin-related cardiomyopathy when compared with nonfailing controls and transcription factor 7-like 2 (TCF7L2) was the main β-catenin partner of the T-cell factor (TCF) family in adult hearts. We further revealed that c-Myc mRNA and protein levels were significantly elevated in failing hearts by real-time reverse transcription polymerase chain reaction, Western blotting, and immunohistochemical staining. Immunoprecipitation and confocal microscopy further showed that β-catenin interacted and colocalized with TCF7L2. More importantly, chromatin immunoprecipitation confirmed that β-catenin and TCF7L2 were recruited to the regulatory elements of c-Myc. This recruitment was associated with increased histone H3 acetylation and transcriptional upregulation of c-Myc. With lentiviral infection, TCF7L2 overexpression increased c-Myc expression and cardiomyocyte size, whereas shRNA-mediated knockdown of TCF7L2 suppressed c-Myc expression and cardiomyocyte growth in cultured neonatal rat cardiomyocytes.

CONCLUSIONS

This study indicates that TCF7L2 mediates canonic Wnt/β-catenin signaling and c-Myc upregulation during abnormal cardiac remodeling in heart failure and suppression of Wnt/β-catenin to c-Myc axis can be explored for preventing and treating heart failure.

Fusion genes in malignant neoplastic disorders of haematopoietic system

OBJECTIVES

The new World Health Organization's (WHO) classification of haematopoietic and lymphoid tissue neoplasms incorporating the recurrent fusion genes as the defining criteria for different haematopoietic malignant phenotypes is reviewed. The recurrent fusion genes incorporated in the new WHO's classification and other chromosomal rearrangements of haematopoietic and lymphoid tissue neoplasms are reviewed.

METHODOLOGY

Cytokines and transcription factors in haematopoiesis and leukaemic mechanisms are described. Genetic features and clinical implications due to the encoded chimeric neoproteins causing malignant haematopoietic disorders are reviewed.

RESULTS AND DISCUSSION

Multiple translocation partner genes are well known for leukaemia such as MYC, MLL, RARA, ALK, and RUNX1. With the advent of more sophisticated diagnostic tools and bioinformatics algorithms, an exponential growth in fusion genes discoveries is likely to increase.

CONCLUSION

Demonstration of fusion genes and their specific translocation breakpoints in malignant haematological disorders are crucial for understanding the molecular pathogenesis and clinical phenotype of cancer, determining prognostic indexes and therapeutic responses, and monitoring residual disease and relapse status.