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Objective: Notch signaling, re-activated in β cells from obese mice and causal to β cell dysfunction, is determined in part by transmembrane ligand availability in a neighboring cell. We hypothesized that β cell expression of Jagged1 determines the maladaptive Notch response and resultant insulin secretory defects in obese mice. Methods: We assessed expression of Notch pathway components in high-fat diet-fed (HFD) or leptin receptor-deficient (db/db) mice, and performed single-cell RNA sequencing (scRNA-Seq) in islets from patients with and without type 2 diabetes (T2D). We generated and performed glucose tolerance testing in inducible, β cell-specific Jagged1 gain-of- and loss-of-function mice. We also tested effects of monoclonal neutralizing antibodies to Jagged1 in glucose-stimulated insulin secretion (GSIS) assays in isolated islets. Results: Jag1 was the only Notch ligand that tracked with increased Notch activity in HFD-fed and db/db mice, as well as in metabolically-inflexible β cells enriched in patients with T2D. Neutralizing antibodies to block Jagged1 in islets isolated from HFD-fed and db/db mice potentiated GSIS ex vivo. To demonstrate if β cell Jagged1 is sufficient to cause glucose tolerance in vivo, we generated inducible β cell-specific Jag1 transgenic (β-Jag1TG) and loss-of-function (iβ-Jag1KO) mice. While forced Jagged1 impaired glucose intolerance due to reduced GSIS, loss of β cell Jagged1 did not protect against HFD-induced insulin secretory defects. Conclusions: Jagged1 is increased in islets from obese mice and in patients with T2D, and neutralizing Jagged1 antibodies lead to improved GSIS, suggesting that inhibition of Jagged1-Notch signaling may have therapeutic benefit. However, genetic loss-of-function experiments suggest that β cells are not a likely source of the Jagged1 signal.

Abstract Spontaneous bleeds are a leading cause of death in the pediatric JAG1‐related liver disease Alagille syndrome (ALGS). We asked whether there are sex differences in bleeding events in patients, whether Jag1Ndr/Ndr mice display bleeds or vascular defects, and whether discovered vascular pathology can be confirmed in patients non‐invasively. We performed a systematic review of patients with ALGS and vascular events following PRISMA guidelines, in the context of patient sex, and found significantly more girls than boys reported with spontaneous intracranial hemorrhage. We investigated vascular development, homeostasis, and bleeding in Jag1Ndr/Ndr mice, using retina as a model. Jag1Ndr/Ndr mice displayed sporadic brain bleeds, a thin skull, tortuous blood vessels, sparse arterial smooth muscle cell coverage in multiple organs, which could be aggravated by hypertension, and sex‐specific venous defects. Importantly, we demonstrated that retinographs from patients display similar characteristics with significantly increased vascular tortuosity. In conclusion, there are clinically important sex differences in vascular disease in ALGS, and retinography allows non‐invasive vascular analysis in patients. Finally, Jag1Ndr/Ndr mice represent a new model for vascular compromise in ALGS.

Spontaneous bleeds are a leading cause of death in the pediatric JAG1‐related liver disease Alagille syndrome (ALGS). We asked whether there are sex differences in bleeding events in patients, whether Jag1Ndr/Ndr mice display bleeds or vascular defects, and whether discovered vascular pathology can be confirmed in patients non‐invasively. We performed a systematic review of patients with ALGS and vascular events following PRISMA guidelines, in the context of patient sex, and found significantly more girls than boys reported with spontaneous intracranial hemorrhage. We investigated vascular development, homeostasis, and bleeding in Jag1Ndr/Ndr mice, using retina as a model. Jag1Ndr/Ndr mice displayed sporadic brain bleeds, a thin skull, tortuous blood vessels, sparse arterial smooth muscle cell coverage in multiple organs, which could be aggravated by hypertension, and sex‐specific venous defects. Importantly, we demonstrated that retinographs from patients display similar characteristics with significantly increased vascular tortuosity. In conclusion, there are clinically important sex differences in vascular disease in ALGS, and retinography allows non‐invasive vascular analysis in patients. Finally, Jag1Ndr/Ndr mice represent a new model for vascular compromise in ALGS. Synopsis: Spontaneous bleeds are a significant cause of death in the rare genetic disease Alagille syndrome, but little is known about the risk factors contributing to the bleeding events, or about vascular development and maintenance in the course of the disease. Alagille syndrome is modeled by Jag1Ndr/Ndr mice, including high mortality and sporadic bleeding.More female than male patients with Alagille syndrome are reported with intracranial bleeds, and certain vascular phenotypes are more severe in female Jag1Ndr/Ndr mice.Bleeding risk in Jag1Ndr/Ndr mice may be further modified by thin skull bones, fragile vascular smooth muscle cells, premature vascular aging, and increased venous tortuosity.Developmental and homeostatic vascular defects were detected in both endothelial cells and vascular smooth muscle cells in Jag1Ndr/Ndr mice.The vascular defects observed in Jag1Ndr/Ndr mice could be visualized, quantified, and validated in retinographs from patients, suggesting a non‐invasive method to assess vascular health. [ABSTRACT FROM AUTHOR]

Presenilins (Psen1 and Psen2 in mice) are polytopic transmembrane proteins that act in the γ-secretase complex to make intra-membrane cleavages of their substrates, including the well-studied Notch receptors. Such processing releases the Notch intracellular domain, allowing it to physically relocate from the cell membrane to the nucleus where it acts in a transcriptional activating complex to regulate downstream genes in the signal-receiving cell. Previous studies of Notch pathway mutants for Jagged1, Notch2, and Rbpj demonstrated that canonical signaling is a necessary component of normal mouse lens development. However, the central role of Psens within the γ-secretase complex has never been explored in any developing eye tissue or cell type. By directly comparing Psen single and double mutant phenotypes during mouse lens development, we found a stronger requirement for Psen1, although both genes are needed for progenitor cell growth and to prevent apoptosis. We also uncovered a novel genetic interaction between Psen1 and Jagged1. By quantifying protein and mRNA levels of key Notch pathway genes in Psen1/2 or Jagged1 mutant lenses, we identified multiple points in the overall signaling cascade where feedback regulation can occur. Our data are consistent with the loss of particular genes indirectly influencing the transcription level of another. However, we conclude that regulating Notch2 protein levels is particularly important during normal signaling, supporting the importance of post-translational regulatory mechanisms in this tissue.

Abstract Background Osteosarcoma is the most common primary bone cancer occurring in young adults and the 5-year survival rate of patients with metastatic osteosarcoma is less than 30% due to high metastatic recurrence and drug resistance. Notch is a highly conserved cell to cell signaling pathway in evolution, and Jagged1 is an important ligand of Notch. Although some studies have found that Notch receptors and ligands including Jagged1 were highly expressed in osteosarcoma tissues and osteosarcoma cells, the role of Jagged1 in osteosarcoma progression and metastasis are still not clear. Methods Tumor tissues were collected from 68 patients and immunohistochemical staining was employed to group these patients by expression of Jagged1. Real-time quantitative PCR and Western blotting were used to detect the expression of Jagged1. We used siRNA to knockdown the expression of Jagged1 in F5M2 cells. Colony formation assay and MTT were employed to detect and analyze the proliferation of F5M2 cells with or without knockdown of Jagged1. Transwell assay were used to detect the migration and invasion of F5M2 cells. Results In this study, we found that the high expression of Jagged1 is closely related to the metastasis and recurrence of osteosarcoma in 68 clinical specimens. The expression of Jagged1 in F5M2 cells with high metastasis was significantly higher than that in F4 cells with low metastasis. Knockdown of Jagged1 led to lower ability of proliferation, migration, and invasion in F5M2 cells. Conclusion The high expression of Jagged1 is closely related to the metastasis and recurrence of osteosarcoma. Knockdown of Jagged1 significantly reduced the proliferation, migration, and invasion of osteosarcoma cells. Our results suggested that knockdown of Jagged1 may be a potentially effective treatment for metastatic osteosarcoma.

Summary: Immune checkpoint inhibitor (ICI) therapy is generating remarkable responses in individuals with cancer, but only a small portion of individuals with breast cancer respond well. Here we report that tumor-derived Jagged1 is a key regulator of the tumor immune microenvironment. Jagged1 promotes tumorigenesis in multiple spontaneous mammary tumor models. Through Jagged1-induced Notch activation, tumor cells increase expression and secretion of multiple cytokines to help recruit macrophages into the tumor microenvironment. Educated macrophages crosstalk with tumor-infiltrating T cells to inhibit T cell proliferation and tumoricidal activity. In individuals with triple-negative breast cancer, a high expression level of Jagged1 correlates with increased macrophage infiltration and decreased T cell activity. Co-administration of an ICI PD-1 antibody with a Notch inhibitor significantly inhibits tumor growth in breast cancer models. Our findings establish a distinct signaling cascade by which Jagged1 promotes adaptive immune evasion of tumor cells and provide several possible therapeutic targets.

Abstract Background The therapeutic effects of adipose-derived mesenchymal stem cell (ADSC) transplantation have been demonstrated in several models of central nervous system (CNS) injury and are thought to involve the modulation of the inflammatory response. However, the exact underlying molecular mechanism is poorly understood. Activation of the Jagged1/Notch signaling pathway is thought to involve inflammatory and gliotic events in the CNS. Here, we elucidated the effect of ADSC transplantation on the inflammatory reaction after spinal cord injury (SCI) and the potential mechanism mediated by Jagged1/Notch signaling pathway suppression. Methods To evaluate the therapeutic effects of ADSC treatment and the potential inhibitory effects of ADSCs on Notch signaling, mice were subjected to contusion SCI, and GFP-labeled ADSCs were injected into the lesion site immediately after the injury. Locomotor function, spinal cord tissue morphology, and the levels of Notch-related proteins and proinflammatory transcripts were compared between groups. To validate the hypothesis that the therapeutic effects of ADSCs are partly due to Notch1 signaling inhibition, a Jagged1 small interfering RNA (siRNA) was injected into the spinal cord to knock down Jagged1/Notch signaling. Neuronal staining and analyses of microglia/macrophage activation and signaling pathways were performed. Results We demonstrated that ADSCs survived in the injured spinal cord for at least 28 days without differentiating into glial or neuronal elements. ADSC treatment resulted in significant downregulation of proinflammatory mediator expression and reduced ionized calcium-binding adapter molecule 1 (IBA1) and ED-1 staining in the injured spinal cord, eventually improving functional recovery. The augmentation of the Jagged1/Notch signaling pathway after SCI was suppressed by ADSC transplantation. The inhibition of the Jagged1/Notch signaling pathway by Jagged1 siRNA resulted in decreases in SCI-induced proinflammatory cytokines and the activation of microglia and an increase in the survival of neurons. Furthermore, Jagged1 knockdown suppressed the phosphorylation of JAK/STAT3 in astrocytes following SCI. Conclusion The results of this study demonstrated that the therapeutic effects of ADSCs in SCI mice were partly due to Jagged1/Notch signaling pathway inhibition and a subsequent reduction in JAK/STAT3 phosphorylation in astrocytes.

In the mammary gland, how alveolar progenitor cells are recruited to fuel tissue growth with each estrus cycle and pregnancy remains poorly understood. Here, we identify a regulatory pathway that controls alveolar progenitor differentiation and lactation by governing Notch activation in mouse. Loss of Robo1 in the mammary gland epithelium activates Notch signaling, which expands the alveolar progenitor cell population at the expense of alveolar differentiation, resulting in compromised lactation. ROBO1 is expressed in both luminal and basal cells, but loss of Robo1 in basal cells results in the luminal differentiation defect. In the basal compartment, ROBO1 inhibits the expression of Notch ligand Jag1 by regulating β-catenin (CTNNB1), which binds the Jag1 promoter. Together, our studies reveal how ROBO1/CTTNB1/JAG1 signaling in the basal compartment exerts paracrine control of Notch signaling in the luminal compartment to regulate alveolar differentiation during pregnancy. [ABSTRACT FROM AUTHOR]

Notch signaling, re-activated in β cells from obese mice and causal to β cell dysfunction, is determined in part by transmembrane ligand availability in a neighboring cell. We hypothesized that β cell expression of Jagged1 determines the maladaptive Notch response and resultant insulin secretory defects in obese mice. We assessed expression of Notch pathway components in high-fat diet-fed (HFD) or leptin receptor-deficient (db/db) mice, and performed single-cell RNA sequencing (scRNA-Seq) in islets from patients with and without type 2 diabetes (T2D). We generated and performed glucose tolerance testing in inducible, β cell-specific Jagged1 gain-of- and loss-of-function mice. We also tested effects of monoclonal neutralizing antibodies to Jagged1 in glucose-stimulated insulin secretion (GSIS) assays in isolated islets. Jag1 was the only Notch ligand that tracked with increased Notch activity in HFD-fed and db/db mice, as well as in metabolically-inflexible β cells enriched in patients with T2D. Neutralizing antibodies to block Jagged1 in islets isolated from HFD-fed and db/db mice potentiated GSIS ex vivo. To demonstrate if β cell Jagged1 is sufficient to cause glucose tolerance in vivo , we generated inducible β cell-specific Jag1 transgenic (β-Jag1TG) and loss-of-function (iβ-Jag1KO) mice. While forced Jagged1 impaired glucose intolerance due to reduced GSIS, loss of β cell Jagged1 did not protect against HFD-induced insulin secretory defects. Jagged1 is increased in islets from obese mice and in patients with T2D, and neutralizing Jagged1 antibodies lead to improved GSIS, suggesting that inhibition of Jagged1-Notch signaling may have therapeutic benefit. However, genetic loss-of-function experiments suggest that β cells are not a likely source of the Jagged1 signal. • Jag1 tracks with increased islet Notch activity in obese mice, and in metabolically inflexible β cells in patients with T2D. • Forced β cell Jagged1 is sufficient to induce glucose intolerance and impair glucose stimulated insulin secretion in mice. • Jagged1 neutralizing antibodies improve glucose stimulatd insulin secretion in islets from obese mice. • Genetic inhibition of β cell Jagged1 does not ameliorate HFD-induced glucose intolerance. [ABSTRACT FROM AUTHOR]

Background: Osteosarcoma is the most common primary bone cancer occurring in young adults and the 5-year survival rate of patients with metastatic osteosarcoma is less than 30% due to high metastatic recurrence and drug resistance. Notch is a highly conserved cell to cell signaling pathway in evolution, and Jagged1 is an important ligand of Notch. Although some studies have found that Notch receptors and ligands including Jagged1 were highly expressed in osteosarcoma tissues and osteosarcoma cells, the role of Jagged1 in osteosarcoma progression and metastasis are still not clear. Methods: Tumor tissues were collected from 68 patients and immunohistochemical staining was employed to group these patients by expression of Jagged1. Real-time quantitative PCR and Western blotting were used to detect the expression of Jagged1. We used siRNA to knockdown the expression of Jagged1 in F5M2 cells. Colony formation assay and MTT were employed to detect and analyze the proliferation of F5M2 cells with or without knockdown of Jagged1. Transwell assay were used to detect the migration and invasion of F5M2 cells. Results: In this study, we found that the high expression of Jagged1 is closely related to the metastasis and recurrence of osteosarcoma in 68 clinical specimens. The expression of Jagged1 in F5M2 cells with high metastasis was significantly higher than that in F4 cells with low metastasis. Knockdown of Jagged1 led to lower ability of proliferation, migration, and invasion in F5M2 cells. Conclusion: The high expression of Jagged1 is closely related to the metastasis and recurrence of osteosarcoma. Knockdown of Jagged1 significantly reduced the proliferation, migration, and invasion of osteosarcoma cells. Our results suggested that knockdown of Jagged1 may be a potentially effective treatment for metastatic osteosarcoma. [ABSTRACT FROM AUTHOR]

Background: Transdifferentiation of type II alveolar epithelial cells (AECII) into type I alveolar epithelial cells (AECI) is involved in neonatal respiratory distress syndrome (NRDS). Different ligands of the Notch pathway could have different effects on AECII transdifferentiation.Objective: To investigate the effects of Dlk1 and Jagged1 on the proliferation and transdifferentiation of AECII.Methods: Fetal AECIIs (19 days of gestation) were divided: control group, Dlk1 group, rhNF-κB group. Proliferation was tested using the MTT assay. Expression of surfactant protein C (SP-C) and aquaporin 5 (AQP5) was examined by immunofluorescence. mRNA and protein levels of SP-C, AQP5, Nortch1, Dlk1, Jagged1, and Hes1 were examined by RT-PCR and western blot.Results: In response to Dlk1, cell number and proliferation were increased (P < 0.05), and mRNA and protein levels of SP-C, Dlk1, Notch1, and Hes1 were up-regulated, while AQP and Jagged1 were decreased. In response to rhNF-κB, the cell number and proliferation were reduced, and mRNA and protein levels of Jagged1 and Notch1 were up-regulated, while Dlk1, and SP-C were downregulated. In the Dlk1 group, SP-C, and AQP5 expression patterns suggested that the cells were still transdifferentiating by 96 h, while in the rhNF-κB group, most cells had transdifferentiated by 72 h and were close to apoptosis by 96 h.Conclusion: These results suggest that Dlk1 promoted proliferation of AECIIs and inhibited cell transdifferentiation, while Jagged1 treatment inhibited proliferation of AECIIs and promoted transdifferentiation to AECIs. These results provide some clue for the eventual management of NDRS.

Background: The therapeutic effects of adipose-derived mesenchymal stem cell (ADSC) transplantation have been demonstrated in several models of central nervous system (CNS) injury and are thought to involve the modulation of the inflammatory response. However, the exact underlying molecular mechanism is poorly understood. Activation of the Jagged1/Notch signaling pathway is thought to involve inflammatory and gliotic events in the CNS. Here, we elucidated the effect of ADSC transplantation on the inflammatory reaction after spinal cord injury (SCI) and the potential mechanism mediated by Jagged1/Notch signaling pathway suppression. Methods: To evaluate the therapeutic effects of ADSC treatment and the potential inhibitory effects of ADSCs on Notch signaling, mice were subjected to contusion SCI, and GFP-labeled ADSCs were injected into the lesion site immediately after the injury. Locomotor function, spinal cord tissue morphology, and the levels of Notch-related proteins and proinflammatory transcripts were compared between groups. To validate the hypothesis that the therapeutic effects of ADSCs are partly due to Notch1 signaling inhibition, a Jagged1 small interfering RNA (siRNA) was injected into the spinal cord to knock down Jagged1/Notch signaling. Neuronal staining and analyses of microglia/macrophage activation and signaling pathways were performed. Results: We demonstrated that ADSCs survived in the injured spinal cord for at least 28 days without differentiating into glial or neuronal elements. ADSC treatment resulted in significant downregulation of proinflammatory mediator expression and reduced ionized calcium-binding adapter molecule 1 (IBA1) and ED-1 staining in the injured spinal cord, eventually improving functional recovery. The augmentation of the Jagged1/Notch signaling pathway after SCI was suppressed by ADSC transplantation. The inhibition of the Jagged1/Notch signaling pathway by Jagged1 siRNA resulted in decreases in SCI-induced proinflammatory cytokines and the activation of microglia and an increase in the survival of neurons. Furthermore, Jagged1 knockdown suppressed the phosphorylation of JAK/STAT3 in astrocytes following SCI. Conclusion: The results of this study demonstrated that the therapeutic effects of ADSCs in SCI mice were partly due to Jagged1/Notch signaling pathway inhibition and a subsequent reduction in JAK/STAT3 phosphorylation in astrocytes. [ABSTRACT FROM AUTHOR]

Surface immobilization of Jagged1 promotes odonto/osteogenic differentiation in human dental pulp cells. On the contrary, soluble Jagged1 fails to activate target gene expression of Notch signaling which is important for differentiation of human dental pulp cells. Hence, Jagged1 delivery system is indeed required for transportation of immobilized Jagged1 to promote odontogenic differentiation of human dental pulp cells in vivo. The present study described the preparation and characterization of Jagged1-bound fibrinogen-based microspheres. Water-in-oil emulsion technique was employed to prepare fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres. The average size of fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres was 213.9 ± 35.9 and 199.9 ± 41.9 µm, respectively. These microspheres did not alter the human dental pulp cells' cell viability. Human dental pulp cells were able to attach and spread on these microspheres. Jagged1 was conjugated on microspheres using 1-ethyl-3-(3-dimethylamino) propyl carbodiimide/N-hydroxysuccinimide. Binding capacity of Jagged1 on both fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres ranged from 25.8 ± 6.0 to 35.6 ± 9.1%. There was no significant difference in the size of microspheres between before and after Jagged1 conjugation process. In conclusion, fibrinogen microspheres and thrombin cross-linked fibrinogen microspheres could be utilized as the alternative biomaterials for Jagged1 delivery for future biomedical application. [ABSTRACT FROM AUTHOR]

Aim: The roles of hepatic progenitor cells (HPCs) in regeneration of a diseased liver are unclear. Hepatic stellate cells (HSCs) contribute to liver fibrosis but are also a component of the HPC niche. Hepatic progenitor cells expand along with HSC activation and liver fibrosis. However, little is known about the interplay of liver fibrosis and HPC‐mediated liver regeneration. This study aimed to investigate HSCs and HPCs in liver regeneration. Methods: Liver injury in mice was induced with 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine, and HPC expansion and fibrosis were assessed. An angiotensin II type 1 receptor blocker (ARB) was administered to assess its effect on fibrosis and regeneration. Results: Treatment with ARB attenuated fibrosis and expansion of α‐smooth muscle actin‐positive activated HSCs as indicated by increased liver weight and Ki‐67‐positive hepatocytes. Immunohistochemical staining suggested that HPC differentiation was shifted toward hepatocytes (HCs) when ARB treatment decreased HPC encapsulation by HSCs and extracellular matrix. Conditioned medium produced by culturing the human HSC LX‐2 line strongly augmented differentiation to biliary epithelial cells (BECs) but inhibited that to HCs. Activated HSCs expressed Jagged1, a NOTCH ligand, which plays a central role in differentiation of HPCs toward BECs. Conclusions: Hepatic stellate cells, the HPC niche cells, control differentiation of HPCs, directing them toward BECs rather than HCs in a diseased liver model. Antifibrosis treatment with an ARB preferentially redirects HPC differentiation toward HCs by blocking the NOTCH pathway in the HPC niche, resulting in more efficient HPC‐mediated liver regeneration. [ABSTRACT FROM AUTHOR]

Objective The aim of the present study was to develop a Jagged1-coated polycaprolactone (PCL) membrane and to evaluate the response of human periodontal ligament cells (hPDL) on this membrane in vitro. Methods Membranes were prepared from PCL and PCL-incorporated hydroxyapatite (PCL/HA). The membranes’ surface roughness, surface wettability, and mechanical properties were examined. An indirect affinity immobilization technique was used to coat the membranes with Jagged1. Membrane cytotoxicity was evaluated using LIVE/DEAD and MTT assays. The morphology of the cells on the membranes was observed using scanning electron microscopy. hPDL alkaline phosphatase (ALP) enzymatic activity and mineral deposition were examined using an ALP assay and Alizarin Red S staining, respectively. Notch target gene mRNA expression was determined using real-time polymerase chain reaction. Results The PCL/HA membranes exhibited a significantly reduced surface contact angle, decreased maximum tensile strain, and ultimate tensile stress. However, the surface roughness parameters were significantly increased. The PCL and PCL/HA membranes were not cytotoxic to hPDL in vitro . hPDLs attached and spread on both membrane types. Further, indirect affinity immobilized Jagged1 on the membranes upregulated hPDL Notch target gene expression. After culturing in osteogenic medium, Jagged1-immobilized PCL/HA membranes significantly enhanced hPDL ALP enzymatic activity. Conclusion Indirect immobilized Jagged1 PCL/HA membranes could be further developed as an alternative guided tissue regeneration membrane to promote osteogenic differentiation in periodontal defects. [ABSTRACT FROM AUTHOR]

Background & Aims Alagille syndrome is a genetic disorder characterized by cholestasis, ocular abnormalities, characteristic facial features, heart defects, and vertebral malformations. Most cases are associated with mutations in JAGGED1 ( JAG1 ), which encodes a Notch ligand, although it is not clear how these contribute to disease development. We aimed to develop a mouse model of Alagille syndrome to elucidate these mechanisms. Methods Mice with a missense mutation (H268Q) in Jag1 ( Jag1 +/Ndr mice) were outbred to a C3H/C57bl6 background to generate a mouse model for Alagille syndrome ( Jag1 Ndr/Ndr mice). Liver tissues were collected at different timepoints during development, analyzed by histology, and liver organoids were cultured and analyzed. We performed transcriptome analysis of Jag1 Ndr/Ndr livers and livers from patients with Alagille syndrome, cross-referenced to the Human Protein Atlas, to identify commonly dysregulated pathways and biliary markers. We used species-specific transcriptome separation and ligand-receptor interaction assays to measure Notch signaling and the ability of JAG1 Ndr to bind or activate Notch receptors. We studied signaling of JAG1 and JAG1 Ndr via NOTCH 1, NOTCH2, and NOTCH3 and resulting gene expression patterns in parental and NOTCH1-expressing C2C12 cell lines. Results Jag1 Ndr/Ndr mice had many features of Alagille syndrome, including eye, heart, and liver defects. Bile duct differentiation, morphogenesis, and function were dysregulated in newborn Jag1 Ndr/Ndr mice, with aberrations in cholangiocyte polarity, but these defects improved in adult mice. Jag1 Ndr/Ndr liver organoids collapsed in culture, indicating structural instability. Whole-transcriptome sequence analyses of liver tissues from mice and patients with Alagille syndrome identified dysregulated genes encoding proteins enriched at the apical side of cholangiocytes, including CFTR and SLC5A1 , as well as reduced expression of IGF1 . Exposure of Notch-expressing cells to JAG1 Ndr , compared with JAG1, led to hypomorphic Notch signaling, based on transcriptome analysis. JAG1-expressing cells, but not JAG1 Ndr -expressing cells, bound soluble Notch1 extracellular domain, quantified by flow cytometry. However, JAG1 and JAG1 Ndr cells each bound NOTCH2, and signaling from NOTCH2 signaling was reduced but not completely inhibited, in response to JAG1 Ndr compared with JAG1. Conclusions In mice, expression of a missense mutant of Jag1 ( Jag1 Ndr ) disrupts bile duct development and recapitulates Alagille syndrome phenotypes in heart, eye, and craniofacial dysmorphology. JAG1 Ndr does not bind NOTCH1, but binds NOTCH2, and elicits hypomorphic signaling. This mouse model can be used to study other features of Alagille syndrome and organ development. [ABSTRACT FROM AUTHOR]

Osteoblast commitment and differentiation are controlled by multiple growth factors including members of the Notch signaling pathway. JAGGED1 is a cell surface ligand of the Notch pathway that is necessary for murine bone formation. The delivery of JAGGED1 to induce bone formation is complicated by its need to be presented in a bound form to allow for proper Notch receptor signaling. In this study, we investigate whether the sustained release of JAGGED1 stimulates human mesenchymal cells to commit to osteoblast cell fate using polyethylene glycol malemeide (PEG-MAL) hydrogel delivery system. Our data demonstrated that PEG-MAL hydrogel constructs are stable in culture for at least three weeks and maintain human mesenchymal cell viability with little cytotoxicity in vitro. JAGGED1 loaded on PEG-MAL hydrogel (JAGGED1-PEG-MAL) showed continuous release from the gel for up to three weeks, with induction of Notch signaling using a CHO cell line with a Notch1 reporter construct, and qPCR gene expression analysis in vitro. Importantly, JAGGED1-PEG-MAL hydrogel induced mesenchymal cells towards osteogenic differentiation based on increased Alkaline phosphatase activity and osteoblast genes expression including RUNX2, ALP, COL1, and BSP. These results thus indicated that JAGGED1 delivery in vitro using PEG-MAL hydrogel induced osteoblast commitment, suggesting that this may be a viable in vivo approach to bone regeneration. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 552-560, 2018. [ABSTRACT FROM AUTHOR]

The objective of this study was to observe the effect of Jagged1/Notch pathway-mediated angiogenesis on the in vitro proliferation of hepatocellular carcinoma cells, and the effect and possible mechanism of the spleen-invigorating and blood stasis-removing recipe. Spleen-invigorating and blood stasis-removing recipe serum from SPF grade nude mice was prepared, and the fingerprint of the drugs of the spleen-invigorating and blood stasis-removing recipe and drug serum were identified by HPLC. SMMC-7721 human hepatocellular carcinoma cells were divided into the normal control group, DAPT inhibitor control group, and drug serum group according to the different treatments. The Cell Counting Kit-8 (CCK-8) method was used to determine cell proliferation ability, and angiogenesis was observed under an inverted microscope. The expression of Jagged1, Notch1, and VEGF was measured by qPCR and western blot analysis. The interaction of Jagged1 and Notch1 was detected by Co-IP. The CCK-8 assay indicated that cell proliferation was inhibited in response to drug treatment (P<0.01). The expression of Jagged1, Notch1, and VEGF in the drug serum group was significantly lower than in the normal control group (P<0.01). Compared with the control group, the new vascular area of the DAPT inhibitor control group and drug serum group was smaller, and the blood vessels of the DAPT inhibitor control group and drug serum group were more sparse. The levels of Jagged1, Notch1, VEGF protein and the interaction between Jagged1 and Notch1 in the DAPT inhibitor control group and drug serum group were significantly lower than in the control serum group (P<0.01). In conclusion, the spleen-invigorating and blood stasis-removing recipe can inhibit the proliferation of hepatocellular carcinoma cells, and tumor angiogenesis in vitro. The function is related to the reduced expression of Jagged1, reduced interaction between Jagged1 and Notch1, and the reduced expression and activity of VEGF. [ABSTRACT FROM AUTHOR]

Muscular dystrophies are genetic conditions leading to muscle degeneration and often, impaired regeneration. Duchenne Muscular Dystrophy is a prototypical form of muscular dystrophy, and like other forms of genetically inherited muscle diseases, pathological progression is variable. Variability in muscular dystrophy can arise from differences in the manner in which the primary mutation impacts the affected protein's function; however, clinical heterogeneity also derives from secondary mutations in other genes that can enhance or reduce pathogenic features of disease. These genes, called genetic modifiers, regulate the pathophysiological context of dystrophic degeneration and regeneration. Understanding the mechanistic links between genetic modifiers and dystrophic progression sheds light on pathologic remodeling, and provides novel avenues to therapeutically intervene to reduce muscle degeneration. Based on targeted genetic approaches and unbiased genomewide screens, several modifiers have been identified for muscular dystrophy, including extracellular agonists of signaling cascades. This review will focus on identification and possible mechanisms of recently identified modifiers for muscular dystrophy, including osteopontin, latent TGFβ binding protein 4 (LTBP4) and Jagged1. Moreover, we will review the investigational approaches that aim to target modifier pathways and thereby counteract dystrophic muscle wasting. [ABSTRACT FROM AUTHOR]

Spinal muscular atrophy (SMA) is a neurodegenerative disease produced by low levels of Survival Motor Neuron (SMN) protein that affects alpha motoneurons in the spinal cord. Notch signaling is a cell-cell communication system well known as a master regulator of neural development, but also with important roles in the adult central nervous system. Aberrant Notch function is associated with several developmental neurological disorders; however, the potential implication of the Notch pathway in SMA pathogenesis has not been studied yet. We report here that SMN deficiency, induced in the astroglioma cell line U87MG after lentiviral transduction with a shSMN construct, was associated with an increase in the expression of the main components of Notch signaling pathway, namely its ligands, Jagged1 and Delta1, the Notch receptor and its active intracellular form (NICD). In the SMNΔ7 mouse model of SMA we also found increased astrocyte processes positive for Jagged1 and Delta1 in intimate contact with lumbar spinal cord motoneurons. In these motoneurons an increased Notch signaling was found, as denoted by increased NICD levels and reduced expression of the proneural gene neurogenin 3, whose transcription is negatively regulated by Notch. Together, these findings may be relevant to understand some pathologic attributes of SMA motoneurons.

The Notch signaling pathway is required to maintain renin expression within juxtaglomerular (JG) cells. However, the specific ligand which activates Notch signaling in renin-expressing cells remains undefined. In this study, we found that among all Notch ligands, Jagged1 is differentially expressed in renin cells with higher expression during neonatal life. We therefore hypothesized that Jagged1 was involved in renin expression and/or vascular integrity. We used a conditional knockout approach to delete Jagged1 in cells of the renin lineage. Deletion of Jagged1 specifically within renin cells did not result in decreased renin production within the kidney. However, animals with conditional deletion of Jagged1 did develop focal kidney fibrosis and elevated blood urea nitrogen. Our data demonstrate that Jagged1-mediated Notch signaling is dispensable in renin cells of the kidney in regard to renin expression. However, deletion of Jagged1 in renin cells descendants affects perivascular-interstitial integrity leading to focal fibrosis and diminished renal function. [ABSTRACT FROM AUTHOR]

Neurofibromatosis type 1 (NF1) is a common neurodevelopmental disorder caused by impaired function of the neurofibromin RAS regulator. Using a combination of Nf1 genetically engineered mice and pharmacological/genetic inhibition approaches, we report that neurofibromin differentially controls neural stem cell (NSC) proliferation and multilineage differentiation through the selective use of the PI3K/AKT and RAF/MEK pathways. While PI3K/AKT governs neurofibromin-regulated NSC proliferation, multilineage differentiation is MEK-dependent. Moreover, whereas MEK-regulated multilineage differentiation requires Smad3-induced Jagged-1 expression and Notch activation, MEK/Smad3-regulated Hes1 induction is only responsible for astrocyte and neuronal differentiation. Collectively, these findings establish distinct roles for the RAS effector pathways in regulating brain NSC function. [ABSTRACT FROM AUTHOR]

Immune checkpoint inhibitor (ICI) therapy is generating remarkable responses in individuals with cancer, but only a small portion of individuals with breast cancer respond well. Here we report that tumor-derived Jagged1 is a key regulator of the tumor immune microenvironment. Jagged1 promotes tumorigenesis in multiple spontaneous mammary tumor models. Through Jagged1-induced Notch activation, tumor cells increase expression and secretion of multiple cytokines to help recruit macrophages into the tumor microenvironment. Educated macrophages crosstalk with tumor-infiltrating T cells to inhibit T cell proliferation and tumoricidal activity. In individuals with triple-negative breast cancer, a high expression level of Jagged1 correlates with increased macrophage infiltration and decreased T cell activity. Co-administration of an ICI PD-1 antibody with a Notch inhibitor significantly inhibits tumor growth in breast cancer models. Our findings establish a distinct signaling cascade by which Jagged1 promotes adaptive immune evasion of tumor cells and provide several possible therapeutic targets. [Display omitted] • Tumor-derived Jagged1 promotes breast cancer progression • Notch activation in tumor cells leads to cytokine production and macrophage recruitment • Tumor education macrophages suppress CD8+ T cell proliferation and tumoricidal activity • Co-administration of PD-1 antibody and Notch inhibitor restrains tumor growth in vivo Meng et al. report that tumor-derived Jagged1 helps recruit macrophages and blocks tumor-killing T cell functions to promote tumor immune evasion during breast cancer progression. Co-administration of an immune checkpoint inhibitor and Jagged1-Notch pathway inhibitor restrains tumor growth in vivo. [ABSTRACT FROM AUTHOR]

Highlights: [•] Notch signaling is important in brain development and implicated in adult synaptic plasticity and memory. [•] Roles of Notch ligands (e.g., Delta-like, Dll1, Jagged, Jag1), modulators (Lunatic fringe, Lfng) in memory are unknown. [•] We examined memory and other behaviors in adult mice with reduced expression of Dll1, Jag1, Lfng and Dll1+Lfng. [•] Mice with reduced Jag1 expression showed impaired spatial memory formation but normal behavior in all other tests. [•] These results provide the first in vivo evidence that Jag1–Notch signaling is critical for memory formation in adults. [ABSTRACT FROM AUTHOR]

Highlights: [•] Notch signaling is important in brain development and implicated in adult synaptic plasticity and memory. [•] Roles of Notch ligands (e.g., Delta-like, Dll1, Jagged, Jag1), modulators (Lunatic fringe, Lfng) in memory are unknown. [•] We examined memory and other behaviors in adult mice with reduced expression of Dll1, Jag1, Lfng and Dll1+Lfng. [•] Mice with reduced Jag1 expression showed impaired spatial memory formation but normal behavior in all other tests. [•] These results provide the first in vivo evidence that Jag1–Notch signaling is critical for memory formation in adults. [ABSTRACT FROM AUTHOR]

Spinal muscular atrophy (SMA) is a neurodegenerative disease produced by low levels of Survival Motor Neuron (SMN) protein that affects alpha motoneurons in the spinal cord. Notch signaling is a cell-cell communication system well known as a master regulator of neural development, but also with important roles in the adult central nervous system. Aberrant Notch function is associated with several developmental neurological disorders; however, the potential implication of the Notch pathway in SMA pathogenesis has not been studied yet. We report here that SMN deficiency, induced in the astroglioma cell line U87MG after lentiviral transduction with a shSMN construct, was associated with an increase in the expression of the main components of Notch signaling pathway, namely its ligands, Jagged1 and Delta1, the Notch receptor and its active intracellular form (NICD). In the SMN?7 mouse model of SMA we also found increased astrocyte processes positive for Jagged1 and Delta1 in intimate contact with lumbar spinal cord motoneurons. In these motoneurons an increased Notch signaling was found, as denoted by increased NICD levels and reduced expression of the proneural gene neurogenin 3, whose transcription is negatively regulated by Notch. Together, these findings may be relevant to understand some pathologic attributes of SMA motoneurons. [ABSTRACT FROM AUTHOR]

Objective To explore the expression of Notch signaling receptors Notchi, Notch3 and its ligand Jaggedl, Jagged2 in tongue squamous cell carcinoma (TSCC). Methods mRNA and protein expression levels of tissue samples from 74 cases of tongue cancer patients and human tongue cell line Cal-27 were detected by reverse transcriptase-polymerase chain reaction (RT-PCR), immunohistochemistry and Western blot. Its relationship with cell proliferation and clinical pathology was analyzed. Results mRNA and protein expression were detected in tongue cancer tissues, adjacent tissues and cell lines. Notch1 and Notch3 protein expression in tongue cancer was higher than the adjacent tissues. Jagged! and Jagged2 protein expression in tongue cancer and adjacent tissues had no difference. Notch1 and Notch3 protein had correlation with tongue cancer clinical staging. Pathway protein expression had no correlation with pathological grade, age, gender. Notch1 protein expression in lymph node metastasis-positive cases was higher than in lymph node metastasis-negative cases. The expression of Notch3 and Jagged2 had correlation. Jagged1 expression grade in metastasis-positive cases was higher than in negative cases. Conclusion Notch sigualing molecules have active expression in TSCC and may play important roles in tongue cancer development. [ABSTRACT FROM AUTHOR]

ABSTRACT Background: The Notch signaling pathway plays complex roles in developing lungs, including regulation of proximodistal fates, airway cell specification and differentiation. However, the specific Notch-mediated signals involved in lung development remain unclear. Results: Here we report that Jagged1 is expressed in a subset of bronchial and bronchiolar epithelial cells, where it controls proximal airway cell fate and differentiation. In agreement with previous studies involving disruption of all Notch signaling, we found that deletion of Jagged1 in airway epithelium increased the number of ciliated cells at the expense of Clara cells, a phenotype associated with downregulation of Hes1. Deletion of Jagged1 also led to an increased number of pulmonary neuroendocrine cells (PNEC), suggesting that Jagged1/Notch signaling inhibits PNEC cell fate. As expected, Jagged1 deletion did not affect alveolar cell differentiation, although alveolar septation was impaired, likely an indirect effect of proximal airway defects. Finally, in the postnatal lung, Jagged1 deletion induced mucous metaplasia, accompanied by downregulation of Hes1 and Hes5. Conclusions: Our results demonstrate that Jagged1-mediated Notch signaling regulates multiple cell fate decisions as well as differentiation in the respiratory system to coordinate lung development and to maintain a balance of airway cell types in adult life. Developmental Dynamics 242:678-686, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Background The changes in Notch signaling are closely related to the occurrence and development of many cancers. We have investigated Notch signaling receptor and its ligand expressions in TSCC cell lines, tissues and its significance. We clarified Notch signaling pathway in TSCC and its mechanism. We regulated Notch signaling pathway of tumor cells, thereby inhibiting tumor cell proliferation and differentiation. Methods We detected Jagged1 protein and mRNA expression levels in specimens (tongue cancer and adjacent tissues) from 74 patients with tongue cancer and in TSCC cell line. The Jagged1-targeted lentiviral vector RNAi system was constructed, and its suppressive effects on the proliferation and invasion of tongue carcinoma cells in in vivo and ex vivo were determined. Results Jagged1 was expressed in tongue squamous cell cancer tissues and cell line, but there were differences in its expression. Jagged1 was knocked down and the tumor growth was inhibited accompanying cell cycle changes. Animal studies also showed that the tumor growth was inhibited. Conclusions Jagged1 may be involved in the differentiation and proliferation of tongue cancer. Targeting Jagged1 RNA interference lentiviral vector can effectively lower Jagged1 mRNA and protein expression levels of Tca8113 cells, thereby preventing the proliferation of TSCC cells. Jagged1 is expected to be a promising new target for curing tongue cancer. In-depth study of the interaction between Jagged1 and other molecules of Notch signaling pathway in the process of carcinogenesis has important theoretical guidance and clinical significance in revealing the mechanism of Jagged1 and its application in the therapy for tongue cancer. [ABSTRACT FROM AUTHOR]

Patterning of the upper versus lower face involves generating distinct pre-skeletal identities along the dorsoventral (DV) axes of the pharyngeal arches. Whereas previous studies have shown roles for BMPs, Endothelin 1 (Edn1) and Jagged1b-Notch2 in DV patterning of the facial skeleton, how these pathways are integrated to generate different skeletal fates has remained unclear. Here, we show that BMP and Edn1 signaling have distinct roles in development of the ventral and intermediate skeletons, respectively, of the zebrafish face. Using transgenic gain-of-function approaches and cell-autonomy experiments, we find that BMPs strongly promote hand2 and msxe expression in ventral skeletal precursors, while Edn1 promotes the expression of nkx3.2 and three Dlx genes (dlx3b, dlx5a and dlx6a) in intermediate precursors. Furthermore, Edn1 and Jagged1b pattern the intermediate and dorsal facial skeletons in part by inducing the BMP antagonist Gremlin 2 (Grem2), which restricts BMP activity to the ventral-most face. We therefore propose a model in which later cross-inhibitory interactions between BMP and Edn1 signaling, in part mediated by Grem2, separate an initially homogenous ventral region into distinct ventral and intermediate skeletal precursor domains. [ABSTRACT FROM AUTHOR]

Abstract: During pancreas development, endocrine and exocrine cells arise from a common multipotent progenitor pool. How these cell fate decisions are coordinated with tissue morphogenesis is poorly understood. Here we have examined ductal morphology, endocrine progenitor cell fate and Notch signaling in Ngn3−/− mice, which do not produce islet cells. Ngn3 deficiency results in reduced branching and enlarged pancreatic duct-like structures, concomitant with Ngn3 promoter activation throughout the ductal epithelium and reduced Notch signaling. Conversely, forced generation of surplus endocrine progenitor cells causes reduced duct caliber and an excessive number of tip cells. Thus, endocrine progenitor cells normally provide a feedback signal to adjacent multipotent ductal progenitor cells that activates Notch signaling, inhibits further endocrine differentiation and promotes proper morphogenesis. These results uncover a novel layer of regulation coordinating pancreas morphogenesis and endocrine/exocrine differentiation, and suggest ways to enhance the yield of beta cells from stem cells. [Copyright &y& Elsevier]

Abstract: The Notch pathway is crucial for a wide variety of developmental processes including the formation of tissue boundaries. That it may function in calvarial suture development and figure in the pathophysiology of craniosynostosis was suggested by the demonstration that heterozygous loss of function of JAGGED1 in humans can cause Alagille syndrome, which has craniosynostosis as a feature. We used conditional gene targeting to examine the role of Jagged1 in the development of the skull vault. We demonstrate that Jagged1 is expressed in a layer of mesoderm-derived sutural cells that lie along the osteogenic–non-osteogenic boundary. We show that inactivation of Jagged1 in the mesodermal compartment of the coronal suture, but not in the neural crest compartment, results in craniosynostosis. Mesodermal inactivation of Jagged1 also results in changes in the identity of sutural cells prior to overt osteogenic differentiation, as well as defects in the boundary between osteogenic and non-osteogenic compartments at the coronal suture. These changes, surprisingly, are associated with increased expression of Notch2 and the Notch effector, Hes1, in the sutural mesenchyme. They are also associated with an increase in nuclear β-catenin. In Twist1 mutants, Jagged1 expression in the suture is reduced substantially, suggesting an epistatic relationship between Twist1 and Jagged1. Consistent with such a relationship, Twist1-Jagged1 double heterozygotes exhibit a substantial increase in the severity of craniosynostosis over individual heterozygotes. Our results thus suggest that Jagged1 is an effector of Twist1 in coronal suture development. [ABSTRACT FROM AUTHOR]

The Notch signaling pathway has been implicated in the development of several leukemia and lymphoma. In order to investigate the relationship between Notch signaling and acute myeloid leukemia (AML), in this study, we expressed a recombinant Notch ligand protein, the DSL domain of the human Jagged1 fused with GST (GST-Jag1). GST-Jag1 could activate Notch signaling in the human promyelocytic leukemia cell line HL60, as shown by a reporter assay and the induced expression of Notch effector gene Hes1 and Hes5. However, GST-Jag1 had no effect on the proliferation and survival of HL60 cells. HL60 cells expressed both Notch ligands and receptors, and had a potential of reciprocal stimulation of Notch signaling between cells. We, therefore, blocked Notch signaling in cultured HL60 cells using a γ-secretase inhibitor (GSI). We found that GSI inhibited the proliferation of HL60 cells significantly by blocking the cell-cycle progression in the G1 phase. Furthermore, GSI induced remarkably apoptosis of HL60 cells. These changes in GSI-treated HL60 cells correlated with the down-regulation of c-Myc and Bcl2, and the low phosphorylation of the Rb protein. These results suggested that reciprocal Notch signaling might be necessary for the proliferation and survival of AML cells, possibly through the maintenance of the expression of c-Myc and Bcl2, as well as the phosphorylation of the Rb protein. [ABSTRACT FROM AUTHOR]

The Notch signaling pathway is fundamental to proper cardiovascular development and is now recognized as an important player in tumor angiogenesis. Two key Notch ligands have been implicated in tumor angiogenesis, Delta-like 4 and Jagged1. We introduce the proteins and how they work in normal developing vasculature and then discuss differing models describing the action of these Notch ligands in tumor angiogenesis. Endothelial Dll4 expression activates Notch resulting in restriction of new sprout development; for instance, in growing retinal vessels. In agreement with this activity, inhibition of Dll4-mediated Notch signaling in tumors results in hypersprouting of nonfunctional vasculature. This Dll4 inhibition may paradoxically lead to increased angiogenesis but poor tumor growth because the newly growing vessels are not functional. In contrast, Jagged1 has been described as a Notch ligand expressed in tumor cells that can have a positive influence on tumor angiogenesis, possibly by activating Notch on tumor endothelium. A novel Notch inhibitor, the Notch1 decoy, which blocks both Dll4 and Jagged1 has been recently shown to restrict tumor vessel growth. We discuss these models and speculate on therapeutic approaches.Oncogene (2008) 27, 5132–5137; doi:10.1038/onc.2008.227 [ABSTRACT FROM AUTHOR]

Specific deletion of Notch1 and RBPjκ in the mouse results in abrogation of definitive haematopoiesis concomitant with the loss of arterial identity at embryonic stage. As prior arterial determination is likely to be required for the generation of embryonic haematopoiesis, it is difficult to establish the specific haematopoietic role of Notch in these mutants. By analysing different Notch-ligand-null embryos, we now show that Jagged1 is not required for the establishment of the arterial fate but it is required for the correct execution of the definitive haematopoietic programme, including expression of GATA2 in the dorsal aorta. Moreover, successful haematopoietic rescue of the Jagged1-null AGM cells was obtained by culturing them with Jagged1-expressing stromal cells or by lentiviral-mediated transduction of the GATA2 gene. Taken together, our results indicate that Jagged1-mediated activation of Notch1 is responsible for regulating GATA2 expression in the AGM, which in turn is essential for definitive haematopoiesis in the mouse. [ABSTRACT FROM AUTHOR]

Hematopoietic stem cells (HSC) are rare primitive cells capable of reconstituting all blood cell lineages throughout the life of an individual. The microenvironment in which stem cells reside is essential for their survival, self-renewal, and differentiation. This microenvironment, or HSC niche, has been difficult to define in bone and bone marrow, but recent studies from our laboratory and others have shown that osteoblasts, the bone-forming cells, are an essential regulatory component of this complex cellular network. We established that parathyroid hormone (PTH), through activation of the PTH/PTHrP receptor (PTH1R) in osteoblastic cells, could alter the HSC niche resulting in HSC expansion in vivo and in vitro and improving dramatically the survival of mice receiving bone marrow transplants. These findings are of great clinical appeal, because they suggest that a strategy aimed at modifying supportive cells in a stem cell niche can expand HSC. While a number of molecules have been found to be important for hematopoietic/osteoblastic interactions, we have focused on the Jagged1/Notch signaling pathway, which was necessary for the PTH-dependent HSC expansion. Since the Jagged1/Notch signaling pathway has been implicated in the microenvironmental control of stem cell self-renewal in several organ systems, definition of Jagged1 modulation, which is currently poorly understood, should provide additional molecular targets for stem cell regulation and advance the understanding of stem cell-microenvironmental interactions. [ABSTRACT FROM AUTHOR]

Abstract: A requirement for β4galactosyltransferase-1 (β4GalT-1) activity in the modulation of Notch signaling by the glycosyltransferase Fringe was previously identified in a mammalian co-culture assay. Notch signaling is necessary for the formation of somites in mammals. We therefore investigated the expression of eleven Notch pathway and somitogenic genes in E9.5 mouse embryos lacking β4GalT-1. Four of these genes were altered in expression pattern or expression level. The Notch target genes Hes5 and Mesp2 were affected to some degree in all mutant embryos. The Notch ligand genes Dll1 and Dll3 were reduced or altered in expression in a significant proportion of mutants. While there were no differences in the number or morphology of somites in E9.5 B4galt1 null embryos, the number of lumbar vertebrae in mutant embryos differed from control littermates (P≤0.01). The subtlety of the in vivo phenotype may be due to redundancy since several B4galt genes related to B4galt1 are expressed during embryogenesis. [Copyright &y& Elsevier]