Notch signaling at a glance

The Cross-Talk between Epigenetic Gene Regulation and Signaling Pathways Regulates Cancer Pathogenesis

Cancer begins due to uncontrolled cell division. Cancer cells are insensitive to the signals that control normal cell proliferation. This uncontrolled cell division is due to the accumulation of abnormalities in different factors associated with the cell division, including different cyclins, cell cycle checkpoint inhibitors, and cellular signaling. Cellular signaling pathways are aberrantly activated in cancer mainly due to epigenetic regulation and post-translational regulation. In this chapter, the role of epigenetic regulation in aberrant activation of PI3K/AKT, Ras, Wnt, Hedgehog, Notch, JAK/STAT, and mTOR signaling pathways in cancer progression is discussed. The role of epigenetic regulators in controlling the upstream regulatory proteins and downstream effector proteins responsible for abnormal cellular signaling-mediated cancer progression is covered in this chapter. Similarly, the role of signaling pathways in controlling epigenetic gene regulation-mediated cancer progression is also discussed. We have tried to ascertain the current status of potential epigenetic drugs targeting several epigenetic regulators to prevent different cancers.

Employing the CRISPR Technology for Studying Notch Signaling in the Male Gonad of Drosophila melanogaster

The Notch (N) signaling pathway plays versatile roles in development and disease of many model organisms (Andersson et al., Development 138, 3593-3612, 2011; Hori et al., J Cell Sci, 126, 2135-2140, 2013). However, studying a role for N in adult tissue of Drosophila melanogaster is challenging, because the gene is located on the X-chromosome. To reduce the expression of N specifically in either the germline or the somatic cells of the adult gonad, we used the CRISPR technology in combination with the UAS/Gal4 expression system. After generation of the flies, gonads were investigated for germline survival. Here, we outline our detailed protocol.

Analysis of Pattern Formation by Colored Petri Nets With Quantitative Regulation of Gene Expression Level

Modeling and simulation are becoming indispensable tools for studying multicellular events such as pattern formation during embryonic development. In this paper, we propose a new approach for analyzing multicellular biological phenomena by combining colored hybrid Petri nets (ColHPNs) with newly devised biological experiments that can control level of a gene quantitatively. With this approach, we analyzed patterning of the boundary cells in the Drosophila large intestine, where one-cell-wide domain of boundary cells differentiate through Delta-Notch signaling. Biological experiments regulating the level of Delta resulted in six distinct patterns of boundary cells correlating with the level of Delta. All these patterns were successfully reproduced by simulation based on ColHPN modeling only by changing the parameter related to the level of Delta. By monitoring the concentration of the active form of Notch in each cell during simulation, it was revealed that these distinct modes of patterning correlate with the fluctuation range of active Notch. Combination of simulation and quantitative manipulation of a gene activity described here is a reliable and powerful approach for analyzing and understanding the patterning process regulated by Notch signaling. This approach can be easily adapted to address other similar pattern formation issues in the systems biology area.

A Comprehensive Bioinformatic Analysis of NOTCH Pathway Involvement in Stomach Adenocarcinoma

Background

Activation of NOTCH signaling pathways, which are key regulators of multiple cellular functions, has been frequently implicated in cancer pathogenesis, and NOTCH inhibitors have received much recent focus in the context of cancer therapeutics. However, the role and possible involvement of NOTCH pathways in stomach adenocarcinoma (STAD) are unclear. Here, putative regulatory mechanisms and functions of NOTCH pathways in STAD were investigated.

Methods

Publicly available data from the TCGA-STAD database were utilized to explore the involvement of canonical NOTCH pathways in STAD by analyzing RNA expression levels of NOTCH receptors, ligands, and downstream genes. Statistical analysis of the data pertaining to cancer and noncancerous samples was performed using R software packages and public databases/webservers.

Results

Significant differential gene expression between control and STAD samples was noted for all NOTCH receptors (NOTCH1, 2, 3, and 4), the delta-like NOTCH ligands (DLL-3 and 4), and typical downstream genes (HES1 and HEY1). Four genes (NOTCH1, NOTCH2, NOTCH3, and HEY1) presented prognostic values for the STAD outcome in terms of overall survival. Functional enrichment analysis indicated that NOTCH family genes-strongly correlated genes were mainly enriched in several KEGG signaling pathways such as the PI3K-Akt signaling pathway, human papillomavirus infection, focal adhesion, Rap1 signaling pathway, and ECM-receptor interaction. Gene set enrichment analysis (GSEA) results showed that NOTCH family genes-significantly correlated genes were mainly enriched in four signaling pathways, ECM (extracellular matrix), tumor angiogenesis, inflammatory response, and immune regulation.

Conclusions

NOTCH family genes may play an essential role in the progression of STAD by modulating immune cells and mediating ECM synthesis, angiogenesis, focal adhesion, and PI3K-Akt signaling. Multiple NOTCH family genes are valuable candidate biomarkers or therapeutic targets for the management of STAD.

Terminal 6q deletions cause brain malformations, a phenotype mimicking heterozygous DLL1 pathogenic variants: A multicenter retrospective case series

OBJECTIVE

Terminal 6q deletion is a rare genetic condition associated with a neurodevelopmental disorder characterized by intellectual disability and structural brain anomalies. Interestingly, a similar phenotype is observed in patients harboring pathogenic variants in the DLL1 gene. Our study aimed to further characterize the prenatal phenotype of this syndrome as well as to attempt to establish phenotype-genotype correlations.

METHOD

We collected ultrasound findings from 22 fetuses diagnosed with a pure 6qter deletion. We reviewed the literature and compared our 22 cases with 14 fetuses previously reported as well as with patients with heterozygous DLL1 pathogenic variants.

RESULTS

Brain structural alterations were observed in all fetuses. The most common findings (>70%) were cerebellar hypoplasia, ventriculomegaly, and corpus callosum abnormalities. Gyration abnormalities were observed in 46% of cases. Occasional findings included cerebral heterotopia, aqueductal stenosis, vertebral malformations, dysmorphic features, and kidney abnormalities.

CONCLUSION

This is the first series of fetuses diagnosed with pure terminal 6q deletion. Based on our findings, we emphasize the prenatal sonographic anomalies, which may suggest the syndrome. Furthermore, this study highlights the importance of chromosomal microarray analysis to search for submicroscopic deletions of the 6q27 region involving the DLL1 gene in fetuses with these malformations.

TM2D genes regulate Notch signaling and neuronal function in Drosophila

TM2 domain containing (TM2D) proteins are conserved in metazoans and encoded by three separate genes in each model organism species that has been sequenced. Rare variants in TM2D3 are associated with Alzheimer's disease (AD) and its fly ortholog almondex is required for embryonic Notch signaling. However, the functions of this gene family remain elusive. We knocked-out all three TM2D genes (almondex, CG11103/amaretto, CG10795/biscotti) in Drosophila and found that they share the same maternal-effect neurogenic defect. Triple null animals are not phenotypically worse than single nulls, suggesting these genes function together. Overexpression of the most conserved region of the TM2D proteins acts as a potent inhibitor of Notch signaling at the γ-secretase cleavage step. Lastly, Almondex is detected in the brain and its loss causes shortened lifespan accompanied by progressive motor and electrophysiological defects. The functional links between all three TM2D genes are likely to be evolutionarily conserved, suggesting that this entire gene family may be involved in AD.

Current Thoughts of Notch's Role in Myoblast Regulation and Muscle-Associated Disease

The evolutionarily conserved signaling pathway Notch is unequivocally essential for embryogenesis. Notch’s contribution to the muscle repair process in adult tissue is complex and obscure but necessary. Notch integrates with other signals in a functional antagonist manner to direct myoblast activity and ultimately complete muscle repair. There is profound recent evidence describing plausible mechanisms of Notch in muscle repair. However, the story is not definitive as evidence is slowly emerging that negates Notch’s importance in myoblast proliferation. The purpose of this review article is to examine the prominent evidence and associated mechanisms of Notch’s contribution to the myogenic repair phases. In addition, we discuss the emerging roles of Notch in diseases associated with muscle atrophy. Understanding the mechanisms of Notch’s orchestration is useful for developing therapeutic targets for disease.

Diversity of Nuclear Lamin A/C Action as a Key to Tissue-Specific Regulation of Cellular Identity in Health and Disease

A-type lamins are the main structural components of the nucleus, which are mainly localized at the nucleus periphery. First of all, A-type lamins, together with B-type lamins and proteins of the inner nuclear membrane, form a stiff structure-the nuclear lamina. Besides maintaining the nucleus cell shape, A-type lamins play a critical role in many cellular events, such as gene transcription and epigenetic regulation. Nowadays it is clear that lamins play a very important role in determining cell fate decisions. Various mutations in genes encoding A-type lamins lead to damages of different types of tissues in humans, collectively known as laminopathies, and it is clear that A-type lamins are involved in the regulation of cell differentiation and stemness. However, the mechanisms of this regulation remain unclear. In this review, we discuss how A-type lamins can execute their regulatory role in determining the differentiation status of a cell. We have summarized recent data focused on lamin A/C action mechanisms in regulation of cell differentiation and identity development of stem cells of different origin. We also discuss how this knowledge can promote further research toward a deeper understanding of the role of lamin A/C mutations in laminopathies.

Cell-cell communication through FGF4 generates and maintains robust proportions of differentiated cell types in embryonic stem cells

During embryonic development and tissue homeostasis, reproducible proportions of differentiated cell types are specified from populations of multipotent precursor cells. Molecular mechanisms that enable both robust cell-type proportioning despite variable initial conditions in the precursor cells, and the re-establishment of these proportions upon perturbations in a developing tissue remain to be characterized. Here, we report that the differentiation of robust proportions of epiblast-like and primitive endoderm-like cells in mouse embryonic stem cell cultures emerges at the population level through cell-cell communication via a short-range fibroblast growth factor 4 (FGF4) signal. We characterize the molecular and dynamical properties of the communication mechanism and show how it controls both robust cell-type proportioning from a wide range of experimentally controlled initial conditions, as well as the autonomous re-establishment of these proportions following the isolation of one cell type. The generation and maintenance of reproducible proportions of discrete cell types is a new function for FGF signaling that might operate in a range of developing tissues.

The recruitment mechanisms and potential therapeutic targets of podocytes from parietal epithelial cells

Podocytes are differentiated postmitotic cells which cannot be replaced after podocyte injury. The mechanism of podocyte repopulation after injury has aroused wide concern. Parietal epithelial cells (PECs) are heterogeneous and only a specific subpopulation of PECs has the capacity to replace podocytes. Major progress has been achieved in recent years regarding the role and function of a subset of PECs which could transdifferentiate toward podocytes. Additionally, several factors, such as Notch, Wnt/ß-catenin, Wilms’ tumor-1, miR-193a and growth arrest-specific protein 1, have been shown to be involved in these processes. Finally, PECs serve as a potential therapeutic target in the conditions of podocyte loss. In this review, we discuss the latest observations and concepts about the recruitment of podocytes from PECs in glomerular diseases as well as newly identified mechanisms and the most recent treatments for this process.

Targeting Notch to Maximize Chemotherapeutic Benefits: Rationale, Advanced Strategies, and Future Perspectives

Simple Summary

The Notch signaling pathway regulates cell proliferation, apoptosis, stem cell self-renewal, and differentiation in a context-dependent fashion both during embryonic development and in adult tissue homeostasis. Consistent with its pleiotropic physiological role, unproper activation of the signaling promotes or counteracts tumor pathogenesis and therapy response in distinct tissues. In the last twenty years, a wide number of studies have highlighted the anti-cancer potential of Notch-modulating agents as single treatment and in combination with the existent therapies. However, most of these strategies have failed in the clinical exploration due to dose-limiting toxicity and low efficacy, encouraging the development of novel agents and the design of more appropriate combinations between Notch signaling inhibitors and chemotherapeutic drugs with improved safety and effectiveness for distinct types of cancer.

Abstract

Notch signaling guides cell fate decisions by affecting proliferation, apoptosis, stem cell self-renewal, and differentiation depending on cell and tissue context. Given its multifaceted function during tissue development, both overactivation and loss of Notch signaling have been linked to tumorigenesis in ways that are either oncogenic or oncosuppressive, but always context-dependent. Notch signaling is critical for several mechanisms of chemoresistance including cancer stem cell maintenance, epithelial-mesenchymal transition, tumor-stroma interaction, and malignant neovascularization that makes its targeting an appealing strategy against tumor growth and recurrence. During the last decades, numerous Notch-interfering agents have been developed, and the abundant preclinical evidence has been transformed in orphan drug approval for few rare diseases. However, the majority of Notch-dependent malignancies remain untargeted, even if the application of Notch inhibitors alone or in combination with common chemotherapeutic drugs is being evaluated in clinical trials. The modest clinical success of current Notch-targeting strategies is mostly due to their limited efficacy and severe on-target toxicity in Notch-controlled healthy tissues. Here, we review the available preclinical and clinical evidence on combinatorial treatment between different Notch signaling inhibitors and existent chemotherapeutic drugs, providing a comprehensive picture of molecular mechanisms explaining the potential or lacking success of these combinations.

Mathematical modeling of Notch dynamics in Drosophila neural development

Notch signalling is a well-conserved signalling pathway that regulates cell fate through cell-cell communication. A typical feature of Notch signalling is ‘lateral inhibition’, whereby two neighbouring cells of equivalent state of differentiation acquire different cell fates. Recently, mathematical and computational approaches have addressed the Notch dynamics in Drosophila neural development. Typical examples of lateral inhibition are observed in the specification of neural stem cells in the embryo and sensory organ precursors in the thorax. In eye disc development, Notch signalling cooperates with other signalling pathways to define the evenly spaced positioning of the photoreceptor cells. The interplay between Notch and epidermal growth factor receptor signalling regulates the timing of neural stem cell differentiation in the optic lobe. In this review, we summarize the theoretical studies that have been conducted to elucidate the Notch dynamics in these systems and discuss the advantages of combining mathematical models with biological experiments.

Autophagy, Mesenchymal Stem Cell Differentiation, and Secretion

Mesenchymal stem cells (MSC) are multipotent cells capable to differentiate into adipogenic, osteogenic, and chondrogenic directions, possessing immunomodulatory activity and a capability to stimulate angiogenesis. A scope of these features and capabilities makes MSC a significant factor of tissue homeostasis and repair. Among factors determining the fate of MSC, a prominent place belongs to autophagy, which is activated under different conditions including cell starvation, inflammation, oxidative stress, and some others. In addition to supporting cell homeostasis by elimination of protein aggregates, and non-functional and damaged proteins, autophagy is a necessary factor of change in cell phenotype on the process of cell differentiation. In present review, some mechanisms providing participation of autophagy in cell differentiation are discussed

Criss-crossing autism spectrum disorder and adult neurogenesis

Autism spectrum disorder (ASD) comprises a group of multifactorial neurodevelopmental disorders primarily characterized by deficits in social interaction and repetitive behavior. Although the onset is typically in early childhood, ASD poses a lifelong challenge for both patients and caretakers. Adult neurogenesis (AN) is the process by which new functional neurons are created from neural stem cells existing in the post-natal brain. The entire event is based on a sequence of cellular processes, such as proliferation, specification of cell fate, maturation, and ultimately, synaptic integration into the existing neural circuits. Hence, AN is implicated in structural and functional brain plasticity throughout life. Accumulating evidence shows that impaired AN may underlie some of the abnormal behavioral phenotypes seen in ASD. In this review, we approach the interconnections between the molecular pathways related to AN and ASD. We also discuss existing therapeutic approaches targeting such pathways both in preclinical and clinical studies. A deeper understanding of how ASD and AN reciprocally affect one another could reveal important converging pathways leading to the emergence of psychiatric disorders.

The developmental origins of Notch-driven intrahepatic bile duct disorders

The Notch signaling pathway is an evolutionarily conserved mechanism of cell-cell communication that mediates cellular proliferation, cell fate specification, and maintenance of stem and progenitor cell populations. In the vertebrate liver, an absence of Notch signaling results in failure to form bile ducts, a complex tubular network that radiates throughout the liver, which, in healthy individuals, transports bile from the liver into the bowel. Loss of a functional biliary network through congenital malformations during development results in cholestasis and necessitates liver transplantation. Here, we examine to what extent Notch signaling is necessary throughout embryonic life to initiate the proliferation and specification of biliary cells and concentrate on the animal and human models that have been used to define how perturbations in this signaling pathway result in developmental liver disorders.

Notch1 haploinsufficiency in mice accelerates adipogenesis

Notch signaling has been recognized recently as a key regulator of metabolism. Here, we determined the role of Notch1 in adipogenesis in wild-type (WT) and Notch1 hetero-mutant (N1+/-) mice provided with 12-week normal or high-fat diet. Haploinsufficiency of Notch1 was associated with adipose tissue accumulation despite similar food intake. White adipose tissue (WAT) of N1+/- showed accumulation of adipogenic cells (CD34+CD68+ cells), crown-like structures, and upregulation of cell proliferation markers (cyclin D1 and Ki67). Notch1 expression in WAT reached peak levels in 8-week-old WT mice in parallel with fat accumulation, especially under HF/HS-feeding, whereas such increment was blunted in N1+/- mice. Downstream of Notch1 haploinsufficiency, over-expression of adipogenic factors PPARγ and C/EBPα was noted following down-regulation of downstream transcriptional factors of Notch signaling (Hes-1, Pref-1, and Sox9). Both pharmacological Notch signal inhibition and Notch1 knockdown enhanced adipogenesis of 3T3-L1 preadipocytes. N1+/- mice showed impaired glucose and insulin tolerance with downregulation of IRS-1 and GLUT4 in WAT after high-fat diet. Taken together, our results suggest that haploinsufficiency of Notch1 promotes fat accumulation and adipogenesis and provides a mechanistic link between Notch signaling and development of metabolic syndrome.

The role of NUMB/NUMB isoforms in cancer stem cells

Cancer stem cells (CSCs) are a subpopulation of cancer that can self-renew and differentiate into large tumor masses. Evidence accumulated to date shows that CSCs affect tumor proliferation, recurrence, and resistance to chemotherapy. Recent studies have shown that, like stem cells, CSCs maintain cells with self-renewal capacity by means of asymmetric division and promote cell proliferation by means of symmetric division. This cell division is regulated by fate determinants, such as the NUMB protein, which recently has also been confirmed as a tumor suppressor. Loss of NUMB expression leads to uncontrolled proliferation and amplification of the CSC pool, which promotes the Notch signaling pathway and reduces the expression of the p53 protein. NUMB genes are alternatively spliced to produce six functionally distinct isoforms. An interesting recent discovery is that the protein NUMB isoform produced by alternative splicing of NUMB plays an important role in promoting carcinogenesis. In this review, we summarize the known functions of NUMB and NUMB isoforms related to the proliferation and generation of CSCs.

Targeted Drug Therapy to Overcome Chemoresistance in Triple-negative Breast Cancer

Triple-negative Breast Cancer (TNBC) is the most aggressive and prevailing breast cancer subtype. The chemotherapeutics used in the treatment of TNBC suffer from chemoresistance, dose-limiting toxicities and off-target side effects. As a result, conventional chemotherapeutics are unable to prevent tumor growth, metastasis and result in failure of therapy. Various new targets such as BCSCs surface markers (CD44, CD133, ALDH1), signaling pathways (IL-6/JAK/STAT3, notch), pro and anti-apoptotic proteins (Bcl-2, Bcl-xL, DR4, DR5), hypoxic factors (HIF-1α, HIF-2α) and drug efflux transporters (ABCC1, ABCG2 and ABCB1) have been exploited to treat TNBC. Further, to improve the efficacy and safety of conventional chemotherapeutics, researchers have tried to deliver anticancer agents specifically to the TNBCs using nanocarrier based drug delivery. In this review, an effort has been made to highlight the various factors responsible for the chemoresistance in TNBC, novel molecular targets of TNBC and nano-delivery systems employed to achieve sitespecific drug delivery to improve efficacy and reduce off-target side effects.

POFUT1 acts as a tumor promoter in glioblastoma by enhancing the activation of Notch signaling

Dysregulation of protein O-fucosyl transferase 1 (POFUT1) contributes to the occurrence and progression of multiple cancers. However, whether POFUT1 has a relationship with the pathogenesis of glioblastoma (GBM) is unknown. This work was aimed at evaluating the detailed relevance of POFUT1 in GBM. Here, we demonstrated high levels of POFUT1 in GBM tissue and elucidated that GBM patients with high levels of POFUT1 had a shorter survival rate than those with low levels of POFUT1. POFUT1 knockdown in GBM cells markedly downregulated the ability to proliferate and invade, while overexpression of POFUT1 potentiated the proliferative and invasive ability of GBM cells. Further mechanistic studies indicated that silencing POFUT1 prohibited the activation of Notch signaling, leading to a reduction in the expression of HES1 and HEY1. On the contrary, overexpression of POFUT1 enhanced the activation of Notch signaling. Notably, inhibition of Notch signaling markedly reversed POFUT1-overexpression-induced tumor promotion effects in GBM cells. In addition, POFUT1 silencing markedly repressed the potential of GBM cells to form tumors in vivo. In conclusion, the data of this work indicates that POFUT1 serves a tumor promotion role in GBM by enhancing the activation of Notch signaling. This study underlines the potential role of the POFUT1/Notch axis in GBM progression and proposes POFUT1 as a promising anticancer target for GBM.

Effect of the Notch4/Dll4 signaling pathway in early gestational intrauterine infection on lung development

Intrauterine infection is an important risk factor for bronchopulmonary dysplasia (BPD). BPD is characterized by arrested lung alveolarization and impaired pulmonary vascularization. The Notch4 signaling pathway is a key regulator of vascular remodeling and angiogenesis. Therefore, the presents study investigated the expression of Notch4, delta-like canonical Notch ligand 4 (Dll4) and related factors in an in vivo rat model and in rat pulmonary microvascular endothelial cells (PMVECs) in vitro, to study the mechanisms by which intrauterine infection affects rat lung development. A rat model of intrauterine infection was established by endocervical inoculation with Escherichia scoli on embryonic day 15. The date of birth was counted as postnatal day 0 (P0). Then, the lung tissues were collected from pups at days P3-P14. The expression of Notch4, Dll4 and related factors was measured by reverse transcription-quantitative PCR and western blotting. In addition, the γ-secretase inhibitor DAPT was used to examine the effect of Notch4 signaling on PMVECs. Intrauterine E. coli infection impaired normal lung development, as indicated by decreased microvessel density, fewer alveoli, fewer secondary septa, and larger alveoli compared with the control group. Furthermore, Notch4, Dll4 and NF-κB levels were significantly increased in the E. coli-infected group at P3 compared with the control group. Similarly, the mRNA expression levels of fetal liver kinase 1 (Flk-1, a VEGF receptor) were significantly increased in the E. coli-infected group at P3 and P7. In PMVECs, the inhibition of Notch4 signaling contributed to decreases in lipopolysaccharide (LPS)-induced expression of VEGF and its receptors. Furthermore, the inhibition of Notch4/Dll4 signaling accelerated cell proliferation and decreased the apoptosis rate of LPS-induced PMVECs. LPS-induced NF-κB expression in PMVECs was also attenuated by the Notch4/Dll4 inhibitor. In conclusion, intrauterine E. coli infection impaired normal lung development, possibly through Notch4/Dll4 signaling and effects on VEGF and its receptors.

Notch Signalling in Breast Development and Cancer

The Notch signalling pathway is a highly conserved developmental signalling pathway, with vital roles in determining cell fate during embryonic development and tissue homeostasis. Aberrant Notch signalling has been implicated in many disease pathologies, including cancer. In this review, we will outline the mechanism and regulation of the Notch signalling pathway. We will also outline the role Notch signalling plays in normal mammary gland development and how Notch signalling is implicated in breast cancer tumorigenesis and progression. We will cover how Notch signalling controls several different hallmarks of cancer within epithelial cells with sections focussed on its roles in proliferation, apoptosis, invasion, and metastasis. We will provide evidence for Notch signalling in the breast cancer stem cell phenotype, which also has implications for therapy resistance and disease relapse in breast cancer patients. Finally, we will summarise the developments in therapeutic targeting of Notch signalling, and the pros and cons of this approach for the treatment of breast cancer.

The role of NUMB/NUMB isoforms in cancer stem cells

Cancer stem cells (CSCs) are a subpopulation of cancer that can self-renew and differentiate into large tumor masses. Evidence accumulated to date shows that CSCs affect tumor proliferation, recurrence, and resistance to chemotherapy. Recent studies have shown that, like stem cells, CSCs maintain cells with self-renewal capacity by means of asymmetric division and promote cell proliferation by means of symmetric division. This cell division is regulated by fate determinants, such as the NUMB protein, which recently has also been confirmed as a tumor suppressor. Loss of NUMB expression leads to uncontrolled proliferation and amplification of the CSC pool, which promotes the Notch signaling pathway and reduces the expression of the p53 protein. NUMB genes are alternatively spliced to produce six functionally distinct isoforms. An interesting recent discovery is that the protein NUMB isoform produced by alternative splicing of NUMB plays an important role in promoting carcinogenesis. In this review, we summarize the known functions of NUMB and NUMB isoforms related to the proliferation and generation of CSCs. [BMB Reports 2021; 54(7): 335-343].

Lens regeneration: scientific discoveries and clinical possibilities

In the process of exploring new methods for cataract treatment, lens regeneration is an ideal strategy for effectively restoring accommodative vision and avoiding postoperative complications and has great clinical potential. Lens regeneration, which is not a simple repetition of lens development, depends on the complex regulatory network comprising the FGF, BMP/TGF-β, Notch, and Wnt signaling pathways. Current research mainly focuses on in situ and in vitro lens regeneration. On the one hand, the possibility of the autologous stem cell in situ regeneration of functional lenses has been confirmed; on the other hand, both embryonic stem cells and induced pluripotent stem cells have been induced into lentoid bodies in vitro which are similar to the natural lens to a certain extent. This article will briefly summarize the regulatory mechanisms of lens development, describe the recent progress of lens regeneration, explore the key molecular signaling pathways, and, more importantly, discuss the prospects and challenges of their clinical applications to provide reference for clinical transformations.

The many facets of Notch signaling in breast cancer: toward overcoming therapeutic resistance

In this review, Nandi et al. revisit the mechanisms by which Notch receptors and ligands contribute to normal mammary gland development and breast tumor progression. The authors also discuss combinatorial approaches aimed at disrupting Notch- and TME-mediated resistance that may improve prognosis in breast cancer patients.

Breast cancer is the second leading cause of cancer-related death in women and is a complex disease with high intratumoral and intertumoral heterogeneity. Such heterogeneity is a major driving force behind failure of current therapies and development of resistance. Due to the limitations of conventional therapies and inevitable emergence of acquired drug resistance (chemo and endocrine) as well as radio resistance, it is essential to design novel therapeutic strategies to improve the prognosis for breast cancer patients. Deregulated Notch signaling within the breast tumor and its tumor microenvironment (TME) is linked to poor clinical outcomes in treatment of resistant breast cancer. Notch receptors and ligands are also important for normal mammary development, suggesting the potential for conserved signaling pathways between normal mammary gland development and breast cancer. In this review, we focus on mechanisms by which Notch receptors and ligands contribute to normal mammary gland development and breast tumor progression. We also discuss how complex interactions between cancer cells and the TME may reduce treatment efficacy and ultimately lead to acquired drug or radio resistance. Potential combinatorial approaches aimed at disrupting Notch- and TME-mediated resistance that may aid in achieving in an improved patient prognosis are also highlighted.

LncRNA HOXA-AS2 Activates the Notch Pathway to Promote Cervical Cancer Cell Proliferation and Migration

Long non-coding RNAs (lncRNAs) are crucial participants in cancer development. HOXA cluster antisense RNA 2 (HOXA-AS2) plays a tumor promoter role in bladder cancer. However, the functional role of HOXA-AS2 in cervical cancer remains unclear. Our study first found that HOXA-AS2 expression was up-regulated in cervical cancer cells. Then functional analysis including cell counting kit-8 (CCK-8), colony formation, transwell, and wound healing uncovered that reduction of HOXA-AS2 remarkably impeded cell proliferation and migration in cervical cancer. Additionally, luciferase reporter assays were performed to confirm that HOXA-AS2 activated Notch signaling pathway via the mediation of independent recombination signal binding protein for JK (RBP-JK) activity. As we know, Notch intracellular domain (NICD) is associated with RBP-JK in the nucleus to promote target genes in the Notch pathway. Through RNA immunoprecipitation (RIP), RNA pull down, and fluorescent in situ hybridization (FISH) assays, we observed that HOXA-AS2 combined with NICD. Moreover, the data from Co-IP assays indicated that HOXA-AS2 reduction weakened the interaction of NICD and RBP-JK. Collectively, HOXA-AS2 played a cancer-promoting role in cervical cancer development by modulating the Notch pathway, which might become a novel target for cervical cancer treatment.

Disruption of myofibroblastic Notch signaling attenuates liver fibrosis by modulating fibrosis progression and regression

The phenotypic transformation of hepatic myofibroblasts (MFs) is involved in the whole process of the progression and regression of liver fibrosis. Notch signaling has been demonstrated to modulate the fibrosis. In this study, we found that Notch signaling in MFs was overactivated and suppressed with the progression and regression of hepatic fibrosis respectively, by detecting Notch signaling readouts in MFs. Moreover, we inactivated Notch signaling specifically in MFs with Sm22α^CreER-RBPj^flox/flox mice (RBPj^MF-KO), and identified that MFs-specific down-regulation of Notch signaling significantly alleviated CCl₄-induced liver fibrosis during the progression and regression. During the progression of liver fibrosis, MFs-specific blockade of Notch signaling inhibited the activation of HSCs to MFs and increases the expression of MMPs to reduce the deposition of ECM. During the regression of fibrosis, blocking Notch signaling in MFs increased the expression of HGF to promote proliferation in hepatocytes and up-regulated the expression of pro-apoptotic factors, Ngfr and Septin4, to induce apoptosis of MFs, thereby accelerating the reversal of fibrosis. Collectively, the MFs-specific disruption of Notch signaling attenuates liver fibrosis by modulating fibrosis progression and regression, which suggests a promising therapeutic strategy for liver fibrosis.

Cell proliferation control by Notch signalling during imaginal discs development in Drosophila

The Notch signalling pathway is evolutionary conserved and participates in numerous developmental processes, including the control of cell proliferation. However, Notch signalling can promote or restrain cell division depending on the developmental context, as has been observed in human cancer where Notch can function as a tumor suppressor or an oncogene. Thus, the outcome of Notch signalling can be influenced by the cross-talk between Notch and other signalling pathways. The use of model organisms such as Drosophila has been proven to be very valuable to understand the developmental role of the Notch pathway in different tissues and its relationship with other signalling pathways during cell proliferation control. Here we review recent studies in Drosophila that shed light in the developmental control of cell proliferation by the Notch pathway in different contexts such as the eye, wing and leg imaginal discs. We also discuss the autonomous and non-autonomous effects of the Notch pathway on cell proliferation and its interactions with different signalling pathways.

Role of Notch in endothelial biology

The Notch signalling pathway is one of the main regulators of endothelial biology. In the last 20 years the critical function of Notch has been uncovered in the context of angiogenesis, participating in tip-stalk specification, arterial-venous differentiation, vessel stabilization, and maturation processes. Importantly, pharmacological compounds targeting distinct members of the Notch signalling pathway have been used in the clinics for cancer therapy. However, the underlying mechanisms that support the variety of outcomes triggered by Notch in apparently opposite contexts such as angiogenesis and vascular homeostasis remain unknown. In recent years, advances in -omics technologies together with mosaic analysis and high molecular, cellular and temporal resolution studies have allowed a better understanding of the mechanisms driven by the Notch signalling pathway in different endothelial contexts. In this review we will focus on the main findings that revisit the role of Notch signalling in vascular biology. We will also discuss potential future directions and technologies that will shed light on the puzzling role of Notch during endothelial growth and homeostasis. Addressing these open questions may allow the improvement and development of therapeutic strategies based on modulation of the Notch signalling pathway.

Ehrlichia TRP effectors: moonlighting, mimicry and infection

Intracellular bacteria have evolved various strategies to evade host defense mechanisms. Remarkably, the obligately intracellular bacterium, Ehrlichia chaffeensis, hijacks host cell processes of the mononuclear phagocyte to evade host defenses through mechanisms executed in part by tandem repeat protein (TRP) effectors secreted by the type 1 secretion system. In the past decade, TRP120 has emerged as a model moonlighting effector, acting as a ligand mimetic, nucleomodulin and ubiquitin ligase. These defined functions illuminate the diverse roles TRP120 plays in exploiting and manipulating host cell processes, including cytoskeletal organization, vesicle trafficking, cell signaling, transcriptional regulation, post-translational modifications, autophagy and apoptosis. This review will focus on TRP effectors and their expanding roles in infection and provide perspective on Ehrlichia chaffeensis as an invaluable model organism for understanding infection strategies of obligately intracellular bacteria.

Dual-Specificity Phosphatase 15 (DUSP15) Modulates Notch Signaling by Enhancing the Stability of Notch Protein

Dual-specificity phosphatases (DUSPs) comprise a unique group of enzymes that dephosphorylate signaling proteins at both phospho-serine/threonine and phospho-tyrosine residues. Since Notch signaling is an essential pathway for neuronal cell fate determination and development that is also upregulated in Alzheimer's disease tissues, we sought to explore whether and how DUSPs may impact Notch processing. Our results show that overexpression of DUSP15 concomitantly and dose-dependently increased the steady-state levels of recombinant Notch (extracellular domain-truncated Notch, NotchΔE) protein and its cleaved product, Notch intracellular domain (NICD). The overall ratio of NotchΔE to NICD was unchanged by overexpression of DUSP15, suggesting that the effect is independent of γ-secretase. Interestingly, overexpression of DUSP15 also dose-dependently increased phosphorylated ERK1/2. Phosphorylated ERK1/2 is known to be positively correlated with Notch protein level, and we found that DUSP15-mediated regulation of Notch was dependent on ERK1/2 activity. Together, our findings reveal the existence of a previously unidentified DUSP15-ERK1/2-Notch signaling axis, which could potentially play a role in neuronal differentiation and neurological disease.

The Role of Notch, Hedgehog, and Wnt Signaling Pathways in the Resistance of Tumors to Anticancer Therapies

Resistance to therapy is the major hurdle in the current cancer management. Cancer cells often rewire their cellular process to alternate mechanisms to resist the deleterious effect mounted by different therapeutic approaches. The major signaling pathways involved in the developmental process, such as Notch, Hedgehog, and Wnt, play a vital role in development, tumorigenesis, and also in the resistance to the various anticancer therapies. Understanding how cancer utilizes these developmental pathways in acquiring the resistance to the multi-therapeutic approach cancer can give rise to a new insight of the anti-therapy resistance mechanisms, which can be explored for the development of a novel therapeutic approach. We present a brief overview of Notch, Hedgehog, and Wnt signaling pathways in cancer and its role in providing resistance to various cancer treatment modalities such as chemotherapy, radiotherapy, molecular targeted therapy, and immunotherapy. Understanding the importance of these molecular networks will provide a rational basis for novel and safer combined anticancer therapeutic approaches for the improvement of cancer treatment by overcoming drug resistance.

Targeting the Notch Signaling Pathway in Chronic Inflammatory Diseases

The Notch signaling pathway regulates developmental cell-fate decisions and has recently also been linked to inflammatory diseases. Although therapies targeting Notch signaling in inflammation in theory are attractive, their design and implementation have proven difficult, at least partly due to the broad involvement of Notch signaling in regenerative and homeostatic processes. In this review, we summarize the supporting role of Notch signaling in various inflammation-driven diseases, and highlight efforts to intervene with this pathway by targeting Notch ligands and/or receptors with distinct therapeutic strategies, including antibody designs. We discuss this in light of lessons learned from Notch targeting in cancer treatment. Finally, we elaborate on the impact of individual Notch members in inflammation, which may lay the foundation for development of therapeutic strategies in chronic inflammatory diseases.

Therapeutic aspects of cell signaling and communication in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is a devastating chromosome X-linked disease that manifests predominantly in progressive skeletal muscle wasting and dysfunctions in the heart and diaphragm. Approximately 1/5000 boys and 1/50,000,000 girls suffer from DMD, and to date, the disease is incurable and leads to premature death. This phenotypic severity is due to mutations in the DMD gene, which result in the absence of functional dystrophin protein. Initially, dystrophin was thought to be a force transducer; however, it is now considered an essential component of the dystrophin-associated protein complex (DAPC), viewed as a multicomponent mechanical scaffold and a signal transduction hub. Modulating signal pathway activation or gene expression through epigenetic modifications has emerged at the forefront of therapeutic approaches as either an adjunct or stand-alone strategy. In this review, we propose a broader perspective by considering DMD to be a disease that affects myofibers and muscle stem (satellite) cells, as well as a disorder in which abrogated communication between different cell types occurs. We believe that by taking this systemic view, we can achieve safe and holistic treatments that can restore correct signal transmission and gene expression in diseased DMD tissues.

Obesity and intestinal stem cell susceptibility to carcinogenesis

Background

Obesity is a top public health problem associated with an increase in colorectal cancer incidence. Stem cells are the chief cells in tissue homeostasis that self-renew and differentiate into other cells to regenerate the organ. It is speculated that an increase in stem cell pool makes cells susceptible to carcinogenesis. In this review, we looked at the recent investigations linking obesity/high-fat diet-induced obesity to intestinal carcinogenesis with regard to intestinal stem cells and their niche.

Findings

High-fat diet-induced obesity may rise intestinal carcinogenesis by increased Intestinal stem cells (ISC)/progenitor’s population, stemness, and niche independence through activation of PPAR-δ with fatty acids, hormonal alterations related to obesity, and low-grade inflammation. However, these effects may possibly relate to the interaction between fats and carbohydrates, and not a fatty acid per se. Nonetheless, literature studies are inconsistency in their results, probably due to the differences in the diet components and limitations of genetic models used.

Conclusion

High-fat diet-induced obesity affects carcinogenesis by changing ISC proliferation and function. However, a well-matched diet and the reliable colorectal cancer models that mimic human carcinogenesis is necessary to clearly elucidate the influence of high-fat diet-induced obesity on ISC behavior.

Zfh-2 facilitates Notch-induced apoptosis in the CNS and appendages of Drosophila melanogaster

Apoptosis is a fundamental remodeling process for most tissues during development. In this manuscript we examine a pro-apoptotic function for the Drosophila DNA binding protein Zfh-2 during development of the central nervous system (CNS) and appendages. In the CNS we find that a loss-of-function zfh-2 allele gives an overall reduction of apoptotic cells in the CNS, and an altered pattern of expression for the axonal markers 22C10 and FasII. This same loss-of-function zfh-2 allele causes specific cells in the NB7-3 lineage of the CNS that would normally undergo apoptosis to be inappropriately maintained, whereas a gain-of-function zfh-2 allele has the opposite effect, resulting in a loss of normal NB 7-3 progeny. We also demonstrate that Zfh-2 and Hunchback reciprocally repress each other's gene expression which limits apoptosis to later born progeny of the NB7-3 lineage. Apoptosis is also required for proper segmentation of the fly appendages. We find that Zfh-2 co-localizes with apoptotic cells in the folds of the imaginal discs and presumptive cuticular joints. A reduction of Zfh-2 levels with RNAi inhibits expression of the pro-apoptotic gene reaper, and produces abnormal joints in the leg, antenna and haltere. Apoptosis has previously been shown to be activated by Notch signaling in both the NB7-3 CNS lineage and the appendage joints. Our results indicate that Zfh-2 facilitates Notch-induced apoptosis in these structures.

Reg4 and its downstream transcriptional activator CD44ICD in stage II and III colorectal cancer

Reg4 is highly expressed in gastrointestinal malignancies and acts as a mitogenic and pro-invasive factor. Our recent works suggest that Reg4 binds with CD44 and induces its proteolytic cleavage to release intra-cytoplasmic domain of CD44 (CD44ICD). The goal of this study is to demonstrate clinical significance of the Reg4-CD44/CD44ICD pathway in stage II/III colon cancer and its association with clinical parameters of aggression. We constructed a tissue microarray (TMA) of 93 stage II/III matched colon adenocarcinoma patients, 23 with recurrent disease. The TMA was immunohistochemically stained for Reg4, CD44, and CD44ICD proteins and analyzed to identify associations with tumor characteristics, recurrence and overall survival. The TMA data analysis showed a significant correlation between Reg4 and CD44 (r² = 0.23, P = 0.028), CD44 and CD44ICD (r² = 0.36, p = 0.0004), and Reg4 and CD44ICD (r² = 0.45, p ≤ 0.0001). Reg4 expression was associated with larger tumor size (r² = 0.23, p = 0.026). Although, no association was observed between Reg4, CD44, or CD44ICD expression and disease recurrence, Reg4-positive patients had a median survival of 4 years vs. 7 years for Reg4-negative patients (p = 0.04) in patients who recurred. Inhibition of the Reg4-CD44/CD44ICD pathway may be a future therapeutic target for colon cancer patients.

Analysis of the Conditions That Affect the Selective Processing of Endogenous Notch1 by ADAM10 and ADAM17

Notch signaling is critical for controlling a variety of cell fate decisions during metazoan development and homeostasis. This unique, highly conserved signaling pathway relies on cell-to-cell contact, which triggers the proteolytic release of the cytoplasmic domain of the membrane-anchored transcription factor Notch from the membrane. A disintegrin and metalloproteinase (ADAM) proteins are crucial for Notch activation by processing its S2 site. While ADAM10 cleaves Notch1 under physiological, ligand-dependent conditions, ADAM17 mainly cleaves Notch1 under ligand-independent conditions. However, the mechanism(s) that regulate the distinct contributions of these ADAMs in Notch processing remain unclear. Using cell-based assays in mouse embryonic fibroblasts (mEFs) lacking ADAM10 and/or ADAM17, we aimed to clarify what determines the relative contributions of ADAM10 and ADAM17 to ligand-dependent or ligand-independent Notch processing. We found that EDTA-stimulated ADAM17-dependent Notch1 processing is rapid and requires the ADAM17-regulators iRhom1 and iRhom2, whereas the Delta-like 4-induced ligand-dependent Notch1 processing is slower and requires ADAM10. The selectivity of ADAM17 for EDTA-induced Notch1 processing can most likely be explained by a preference for ADAM17 over ADAM10 for the Notch1 cleavage site and by the stronger inhibition of ADAM10 by EDTA. The physiological ADAM10-dependent processing of Notch1 cannot be compensated for by ADAM17 in Adam10-/- mEFs, or by other ADAMs shown here to be able to cleave the Notch1 cleavage site, such as ADAMs9, 12, and 19. Collectively, these results provide new insights into the mechanisms underlying the substrate selectivity of ADAM10 and ADAM17 towards Notch1.

Xenopus to the rescue: A model to validate and characterize candidate ciliopathy genes

Cilia are present on most vertebrate cells and play a central role in development, growth, and homeostasis. Thus, cilia dysfunction can manifest into an array of diseases, collectively termed ciliopathies, affecting millions of lives worldwide. Yet, our understanding of the gene regulatory networks that control cilia assembly and functions remain incomplete. With the advances in next-generation sequencing technologies, we can now rapidly predict pathogenic variants from hundreds of ciliopathy patients. While the pace of candidate gene discovery is exciting, most of these genes have never been previously implicated in cilia assembly or function. This makes assigning the disease causality difficult. This review discusses how Xenopus, a genetically tractable and high-throughput vertebrate model, has played a central role in identifying, validating, and characterizing candidate ciliopathy genes. The review is focused on multiciliated cells (MCCs) and diseases associated with MCC dysfunction. MCCs harbor multiple motile cilia on their apical surface to generate extracellular fluid flow inside the airway, the brain ventricles, and the oviduct. In Xenopus, these cells are external and present on the embryonic epidermal epithelia, facilitating candidate genes analysis in MCC development in vivo. The ability to introduce patient variants to study their effects on disease progression makes Xenopus a powerful model to improve our understanding of the underlying disease mechanisms and explain the patient phenotype.

Cross-talk of Signaling Pathways in the Pathogenesis of Allergic Asthma and Cataract

Allergic asthma is a chronic inflammatory disease, which involves many cellular and cellular components. Cataract is a condition that affects the transparency of the lens, which the opacity of the lens caused by any innate or acquired factor degrades its transparency or changes in color. Both of them belong to diseases induced by immune disorders or inflammation. We want to confirm the signaling pathways involved in the regulation of asthma and cataract simultaneously, and provide reference for the later related experiments. So we conducted a scoping review of many databases and searched for studies (Academic research published in Wiley, Springer and Bentham from 2000 to 2019) about the possible relationship between asthma and cataract. It was found that during the onset of asthma and cataract, Rho/Rock signaling pathway, Notch signaling pathway, Wnt/β-catenin signaling pathway, PI3K/AKT signaling pathway, JAK/STAT signaling pathway, MAPK signaling pathway, TGF-β1/Smad signaling pathway and NF-κB signaling pathway are all active, so they may have a certain correlation in pathogenesis. Asthma may be associated with cataract through the eight signaling pathways, causing inflammation or immune imbalance based on allergy that can lead to cataract. According to these studies, we speculated that the three most likely signaling pathways are PI3K/AKT, MAPK and NF-κB signaling pathway.

The roles and activation of endocardial Notch signaling in heart regeneration

As a highly conserved signaling pathway in metazoans, the Notch pathway plays important roles in embryonic development and tissue regeneration. Recently, cardiac injury and regeneration have become an increasingly popular topic for biomedical research, and Notch signaling has been shown to exert crucial functions during heart regeneration as well. In this review, we briefly summarize the molecular functions of the endocardial Notch pathway in several cardiac injury and stress models. Although there is an increase in appreciating the importance of endocardial Notch signaling in heart regeneration, the mechanism of its activation is not fully understood. This review highlights recent findings on the activation of the endocardial Notch pathway by hemodynamic blood flow change in larval zebrafish ventricle after partial ablation, a process involving primary cilia, mechanosensitive ion channel Trpv4 and mechanosensitive transcription factor Klf2.

JAGGED1 stimulates cranial neural crest cell osteoblast commitment pathways and bone regeneration independent of canonical NOTCH signaling

Craniofacial bone loss is a complex clinical problem with limited regenerative solutions. Currently, BMP2 is used as a bone-regenerative therapy in adults, but in pediatric cases of bone loss, it is not FDA-approved due to concerns of life-threatening inflammation and cancer. Development of a bone-regenerative therapy for children will transform our ability to reduce the morbidity associated with current autologous bone grafting techniques. We discovered that JAGGED1 (JAG1) induces cranial neural crest (CNC) cell osteoblast commitment during craniofacial intramembranous ossification, suggesting that exogenous JAG1 delivery is a potential craniofacial bone-regenerative approach. In this study, we found that JAG1 delivery using synthetic hydrogels containing O9-1 cells, a CNC cell line, into critical-sized calvarial defects in C57BL/6 mice provided robust bone-regeneration. Since JAG1 signals through canonical (Hes1/Hey1) and non-canonical (JAK2) NOTCH pathways in CNC cells, we used RNAseq to analyze transcriptional pathways activated in CNC cells treated with JAG1 ± DAPT, a NOTCH-canonical pathway inhibitor. JAG1 upregulated expression of multiple NOTCH canonical pathway genes (Hes1), which were downregulated in the presence of DAPT. JAG1 also induced bone chemokines (Cxcl1), regulators of cytoskeletal organization and cell migration (Rhou), signaling targets (STAT5), promoters of early osteoblast cell proliferation (Prl2c2, Smurf1 and Esrra), and, inhibitors of osteoclasts (Id1). In the presence of DAPT, expression levels of Hes1 and Cxcl1 were decreased, whereas, Prl2c2, Smurf1, Esrra, Rhou and Id1 remain elevated, suggesting that JAG1 induces osteoblast proliferation through these non-canonical genes. Pathway analysis of JAG1 + DAPT-treated CNC cells revealed significant upregulation of multiple non-canonical pathways, including the cell cycle, tubulin pathway, regulators of Runx2 initiation and phosphorylation of STAT5 pathway. In total, our data show that JAG1 upregulates multiple pathways involved in osteogenesis, independent of the NOTCH canonical pathway. Moreover, our findings suggest that JAG1 delivery using a synthetic hydrogel, is a bone-regenerative approach with powerful translational potential.

Relevance of Notch Signaling for Bone Metabolism and Regeneration

Notch1-4 receptors and their signaling pathways are expressed in almost all organ systems and play a pivotal role in cell fate decision by coordinating cell proliferation, differentiation and apoptosis. Differential expression and activation of Notch signaling pathways has been observed in a variety of organs and tissues under physiological and pathological conditions. Bone tissue represents a dynamic system, which is constantly remodeled throughout life. In bone, Notch receptors have been shown to control remodeling and regeneration. Numerous functions have been assigned to Notch receptors and ligands, including osteoblast differentiation and matrix mineralization, osteoclast recruitment and cell fusion and osteoblast/osteoclast progenitor cell proliferation. The expression and function of Notch1-4 in the skeleton are distinct and closely depend on the temporal expression at different differentiation stages. This review addresses the current knowledge on Notch signaling in adult bone with emphasis on metabolism, bone regeneration and degenerative skeletal disorders, as well as congenital disorders associated with mutant Notch genes. Moreover, the crosstalk between Notch signaling and other important pathways involved in bone turnover, including Wnt/β-catenin, BMP and RANKL/OPG, are outlined.

Comparative hematopoiesis and signal transduction in model organisms

Hematopoiesis is a continuous phenomenon involving the formation of hematopoietic stem cells (HSCs) giving rise to diverse functional blood cells. This developmental process of hematopoiesis is evolutionarily conserved, yet comparably different in various model organisms. Vertebrate HSCs give rise to all types of mature cells of both the myeloid and the lymphoid lineages sequentially colonizing in different anatomical tissues. Signal transduction in HSCs facilitates their potency and specifies branching of lineages. Understanding the hematopoietic signaling pathways is crucial to gain insights into their deregulation in several blood-related disorders. The focus of the review is on hematopoiesis corresponding to different model organisms and pivotal role of indispensable hematopoietic pathways. We summarize and discuss the fundamentals of blood formation in both invertebrate and vertebrates, examining the requirement of key signaling nexus in hematopoiesis. Knowledge obtained from such comparative studies associated with developmental dynamics of hematopoiesis is beneficial to explore the therapeutic options for hematopoietic diseases.

Rare Earth Elements Lanthanum and Praseodymium Adversely Affect Neural and Cardiovascular Development in Zebrafish (Danio rerio)

Increasing rare earth element (REE) mining and refining activities have led to a considerable release of these substances into aquatic environment, yet the knowledge of their impacts on aquatic organisms is still limited. Here, we explored the developmental effects of 16 REEs (concentration ranged from 0.46 to 1000 mg/L) to zebrafish embryos and highlighted the adverse effects of lanthanum (La) and praseodymium (Pr). Among the multiple developmental parameters measured, the significant effects on swimming behavior and cardiac physiology were the most prominent. Transcriptomic analysis of La and Pr at concentrations of 1.1 to 10 mg/L revealed their rather uniform effects at molecular levels. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways analysis revealed that among others, notch, glutamate, and serotonin signaling, as well as cardiac hypertrophy and cardiac muscle contraction, were significantly affected. These changes of neural signaling were consistent with behavior effects observed and supported by neurotransmitter changes and thus provide a reasonable molecular mechanistic explanation. Furthermore, increased DNA damage and apoptotic activity at high concentrations were observed, especially in the heart. They may contribute to explain the observed adverse morphological and physiological outcomes, such as pericardial edema. The effect concentrations observed in the present study were comparable to the concentrations of REE residues at highly contaminated sites (several mg/L), indicating ecotoxicological effects at environmentally relevant concentrations. Overall, the present data help to clarify the potential developmental toxicity of REEs that was not yet fully recognized and thus contribute to their environmental risk assessment.

Ubiquitin Ligases at the Heart of Skeletal Muscle Atrophy Control

Skeletal muscle loss is a detrimental side-effect of numerous chronic diseases that dramatically increases mortality and morbidity. The alteration of protein homeostasis is generally due to increased protein breakdown while, protein synthesis may also be down-regulated. The ubiquitin proteasome system (UPS) is a master regulator of skeletal muscle that impacts muscle contractile properties and metabolism through multiple levers like signaling pathways, contractile apparatus degradation, etc. Among the different actors of the UPS, the E3 ubiquitin ligases specifically target key proteins for either degradation or activity modulation, thus controlling both pro-anabolic or pro-catabolic factors. The atrogenes MuRF1/TRIM63 and MAFbx/Atrogin-1 encode for key E3 ligases that target contractile proteins and key actors of protein synthesis respectively. However, several other E3 ligases are involved upstream in the atrophy program, from signal transduction control to modulation of energy balance. Controlling E3 ligases activity is thus a tempting approach for preserving muscle mass. While indirect modulation of E3 ligases may prove beneficial in some situations of muscle atrophy, some drugs directly inhibiting their activity have started to appear. This review summarizes the main signaling pathways involved in muscle atrophy and the E3 ligases implicated, but also the molecules potentially usable for future therapies.

Multiscale Regulation of the Intervertebral Disc: Achievements in Experimental, In Silico, and Regenerative Research

Intervertebral disc (IVD) degeneration is a major risk factor of low back pain. It is defined by a progressive loss of the IVD structure and functionality, leading to severe impairments with restricted treatment options due to the highly demanding mechanical exposure of the IVD. Degenerative changes in the IVD usually increase with age but at an accelerated rate in some individuals. To understand the initiation and progression of this disease, it is crucial to identify key top-down and bottom-up regulations' processes, across the cell, tissue, and organ levels, in health and disease. Owing to unremitting investigation of experimental research, the comprehension of detailed cell signaling pathways and their effect on matrix turnover significantly rose. Likewise, in silico research substantially contributed to a holistic understanding of spatiotemporal effects and complex, multifactorial interactions within the IVD. Together with important achievements in the research of biomaterials, manifold promising approaches for regenerative treatment options were presented over the last years. This review provides an integrative analysis of the current knowledge about (1) the multiscale function and regulation of the IVD in health and disease, (2) the possible regenerative strategies, and (3) the in silico models that shall eventually support the development of advanced therapies.

Functional Gene Expression Differentiation of the Notch Signaling Pathway in Female Reproductive Tract Tissues-A Comprehensive Review With Analysis

The Notch pathway involves evolutionarily conserved signaling regulating the development of the female tract organs such as breast, ovary, cervix, and uterine endometrium. A great number of studies revealed Notch aberrancies in association with their carcinogenesis and disease progression, the management of which is still challenging. The present study is a comprehensive review of the available literature on Notch signaling during the normal development and carcinogenesis of the female tract organs. The review has been enriched with our analyses of the TCGA data including breast, cervical, ovarian, and endometrial carcinomas concerning the effects of Notch signaling at two levels: the core components and downstream effectors, hence filling the lack of global overview of Notch-driven carcinogenesis and disease progression. Phenotype heterogeneity regarding Notch signaling was projected in two uniform manifold approximation and projection algorithm dimensions, preceded by the principal component analysis step reducing the data burden. Additionally, overall and disease-free survival analyses were performed with the optimal cutpoint determination by Evaluate Cutpoints software to establish the character of particular Notch components in tumorigenesis. In addition to the review, we demonstrated separate models of the examined cancers of the Notch pathway and its targets, although expression profiles of all normal tissues were much more similar to each other than to its cancerous compartments. Such Notch-driven cancerous differentiation resulted in a case of opposite association with DFS and OS. As a consequence, target genes also show very distinct profiles including genes associated with cell proliferation and differentiation, energy metabolism, or the EMT. In conclusion, the observed Notch associations with the female tract malignancies resulted from differential expression of target genes. This may influence a future analysis to search for new therapeutic targets based on specific Notch pathway profiles.

NOTCH1-driven UBR7 stimulates nucleotide biosynthesis to promote T cell acute lymphoblastic leukemia

Ubiquitin protein ligase E3 component N-recognin 7 (UBR7) is the most divergent member of UBR box-containing E3 ubiquitin ligases/recognins that mediate the proteasomal degradation of its substrates through the N-end rule. Here, we used a proteomic approach and found phosphoribosyl pyrophosphate synthetases (PRPSs), the essential enzymes for nucleotide biosynthesis, as strong interacting partners of UBR7. UBR7 stabilizes PRPS catalytic subunits by mediating the polyubiquitination-directed degradation of PRPS-associated protein (PRPSAP), the negative regulator of PRPS. Loss of UBR7 leads to nucleotide biosynthesis defects. We define UBR7 as a transcriptional target of NOTCH1 and show that UBR7 is overexpressed in NOTCH1-driven T cell acute lymphoblastic leukemia (T-ALL). Impaired nucleotide biosynthesis caused by UBR7 depletion was concomitant with the attenuated cell proliferation and oncogenic potential of T-ALL. Collectively, these results establish UBR7 as a critical regulator of nucleotide metabolism through the regulation of the PRPS enzyme complex and uncover a metabolic vulnerability in NOTCH1-driven T-ALL.

Complex crosstalk of Notch and Hedgehog signalling during the development of the central nervous system

The development of the vertebrate central nervous system (CNS) is tightly regulated by many highly conserved cell signalling pathways. These pathways ensure that differentiation and migration events occur in a specific and spatiotemporally restricted manner. Two of these pathways, Notch and Hedgehog (Hh) signalling, have been shown to form a complex web of interaction throughout different stages of CNS development. Strikingly, some processes employ Notch signalling to regulate Hh response, while others utilise Hh signalling to modulate Notch response. Notch signalling functions upstream of Hh response through controlling the trafficking of integral pathway components as well as through modulating protein levels and transcription of downstream transcriptional factors. In contrast, Hh signalling regulates Notch response by either indirectly controlling expression of key Notch ligands and regulatory proteins or directly through transcriptional control of canonical Notch target genes. Here, we review these interactions and demonstrate the level of interconnectivity between the pathways, highlighting context-dependent modes of crosstalk. Since many other developmental signalling pathways are active in these tissues, it is likely that the interplay between Notch and Hh signalling is not only an example of signalling crosstalk but also functions as a component of a wider, multi-pathway signalling network.

Epigenetics of glioblastoma multiforme: From molecular mechanisms to therapeutic approaches

Glioblastoma multiforme (GBM) is the most common form of brain cancer and one of the most aggressive cancers found in humans. Most of the signs and symptoms of GBM can be mild and slowly aggravated, although other symptoms might demonstrate it as an acute ailment. However, the precise mechanisms of the development of GBM remain unknown. Due to the improvement of molecular pathology, current researches have reported that glioma progression is strongly connected with different types of epigenetic phenomena, such as histone modifications, DNA methylation, chromatin remodeling, and aberrant microRNA. Furthermore, the genes and the proteins that control these alterations have become novel targets for treating glioma because of the reversibility of epigenetic modifications. In some cases, gene mutations including P16, TP53, and EGFR, have been observed in GBM. In contrast, monosomies, including removals of chromosome 10, particularly q23 and q25-26, are considered the standard markers for determining the development and aggressiveness of GBM. Recently, amid the epigenetic therapies, histone deacetylase inhibitors (HDACIs) and DNA methyltransferase inhibitors have been used for treating tumors, either single or combined. Specifically, HDACIs are served as a good choice and deliver a novel pathway to treat GBM. In this review, we focus on the epigenetics of GBM and the consequence of its mutations. We also highlight various treatment approaches, namely gene editing, epigenetic drugs, and microRNAs to combat GBM.