The notch receptor and its ligands are selectively expressed during hematopoietic development in the mouse

Altered expression of Notch signaling, Tlr receptors, and surfactant protein expression after prostaglandin inhibition may be associated with the delayed labor in LPS-induced mice

PURPOSE

This study aims to investigate whether indomethacin (IND) delays preterm birth by regulating the Notch pathway, Tlr receptors, and Sp-A in the placenta in lipopolysaccharide (LPS)-induced preterm labor (PTL) model.

METHODS

CD-1 mice were distributed to the pregnant control (PC), Sham, PBS, IND (2 mg/kg; i.p.), LPS (25 μg/100 μl; intrauterine), and LPS + IND groups. The injections were performed on day 14.5 of pregnancy. Placentae were collected on day 15.5 of pregnancy, and immunohistochemical analyzes were performed. Differences in staining intensities between the Cox-1, Notch-1 (N1), Dll-1, Jagged-2 (Jag-2), Tlr-2, and Tlr-4 proteins were compared.

RESULTS

Preterm labor rates were 100% and 66% (preterm delivery delayed 5 h) in the LPS and LPS + IND groups, respectively. In LPS-treated mice, a general morphological deterioration was observed in the placenta. Total placental mid-sagittal measurement was significantly reduced in the LPS-treated group, while it was similar to the PC group in the LPS + IND group. Cox-1 expression in the LZ increased, and Sp-A expression decreased after LPS injection, and IND administration diminished this increase. N1 expression increased in the labyrinth zone (LZ) and the junctional zone (JZ). Dll-1 and Jag-2 expression increased in the JZ after LPS injection (p < 0.0001). IND administration diminished Tlr-2 expression in the LZ and Tlr-4 expression in the JZ after LPS injection.

CONCLUSION

In conclusion, PG (prostaglandin) inhibition may alter Notch signaling, Tlr, and Sp-A protein expression and may be associated with delayed labor in LPS-induced mice.

Regulatory Crosstalk between Physiological Low O2 Concentration and Notch Pathway in Early Erythropoiesis

Physiological low oxygen (O2) concentration (<5%) favors erythroid development ex vivo. It is known that low O2 concentration, via the stabilization of hypoxia-induced transcription factors (HIFs), intervenes with Notch signaling in the control of cell fate. In addition, Notch activation is implicated in the regulation of erythroid differentiation. We test here if the favorable effects of a physiological O2 concentration (3%) on the amplification of erythroid progenitors implies a cooperation between HIFs and the Notch pathway. To this end, we utilized a model of early erythropoiesis ex vivo generated from cord blood CD34+ cells transduced with shHIF1α and shHIF2α at 3% O2 and 20% O2 in the presence or absence of the Notch pathway inhibitor. We observed that Notch signalization was activated by Notch2R−Jagged1 ligand interaction among progenitors. The inhibition of the Notch pathway provoked a modest reduction in erythroid cell expansion and promoted erythroid differentiation. ShHIF1α and particularly shHIF2α strongly impaired erythroid progenitors’ amplification and differentiation. Additionally, HIF/NOTCH signaling intersects at the level of multipotent progenitor erythroid commitment and amplification of BFU-E. In that, both HIFs contribute to the expression of Notch2R and Notch target gene HES1. Our study shows that HIF, particularly HIF2, has a determining role in the early erythroid development program, which includes Notch signaling.

Spiperone Stimulates Regeneration in Pulmonary Endothelium Damaged by Cigarette Smoke and Lipopolysaccharide

Background

Endothelial dysfunction and destruction of the pulmonary microcirculation are important pathogenic factors in chronic obstructive pulmonary disease (COPD). In COPD, bronchial obstruction is associated with endothelial dysfunction. Thus, new pharmacological treatment options aimed at restoring the pulmonary endothelium represent a clinical need in COPD therapy. Notch1 has been shown to protect cells against apoptosis, inflammation, and oxidative stress caused by cigarette smoke extract (CSE). Therefore, drug which effect on Notch1 may be a potential therapeutic target for COPD in the future.

Methods

In this study, we assessed the potential of spiperone to mediate regeneration of pulmonary endothelium in model of pulmonary emphysema induced by a CSE and lipopolysaccharide (LPS) in female C57BL/6 mice.

Results

Spiperone increased the number of capillaries as well as the expression of the CD31 in the alveolar tissue compared to the controls. Moreover, application of spiperone prevented alveolar wall destruction (DI), and reduced the area of emphysema. Lastly, we demonstrated that spiperone positively influenced mobilization and migration of endothelial progenitor cells (EPC, CD45⁻CD34⁺CD31⁺), CD309⁺-endothelial cells, and angiogenesis precursors (CD45⁻CD117⁺CD309⁺) into the lung. Spiperone administration significantly reduced the number Notch1 positive CD309⁺-endothelial cells and Notch1+ EPCs.

Conclusion

Overall, our results suggest that spiperone mediates endothelial regeneration in an animal model of COPD. Thus, it could represent a novel therapeutic approach for treatment of emphysema associated with COPD.

The Notch signaling pathway involvement in innate lymphoid cell biology

The role of Notch in the immune system was first described in the late 90s. Reports revealed that Notch is one of the most conserved developmental pathways involved in diverse biological processes such as the development, differentiation, survival and functions of many immune populations. Here, we provide an extended view of the pleiotropic effects of the Notch signaling on the innate lymphoid cell (ILC) biology. We review the current knowledge on Notch signaling in the regulation of ILC differentiation, plasticity and functions in diverse tissue types and at both the fetal and adult developmental stages. ILCs are early responder cells that secrete a large panel of cytokines after stimulation. By controlling the abundance of ILCs and the specificity of their release, the Notch pathway is also implicated in the regulation of their functions. The Notch pathway is therefore an important player in both ILC cell fate decision and ILC immune response.

Notch signaling and the emergence of hematopoietic stem cells

The hematopoietic stem cell (HSC) is able to give rise to all blood cell lineages in vertebrates. HSCs are generated in the early embryo after two precedent waves of primitive hematopoiesis. Canonical Notch signaling is at the center of the complex mechanism that controls the development of the definitive HSC. The successful in vitro generation of hematopoietic cells from pluripotent stem cells with the capacity for multilineage hematopoietic reconstitution after transplantation requires the recapitulation of the most important process that takes place in the hemogenic endothelium during definitive hematopoiesis, that is the endothelial-to-hematopoietic transition (EHT). To meet this challenge, it is necessary to thoroughly understand the molecular mechanisms that modulate Notch signaling during the HSC differentiation process considering different temporal and spatial dimensions. In recent years, there have been important advances in this field. Here, we review relevant contributions describing different genes, factors, environmental cues, and signaling cascades that regulate the EHT through Notch interactions at multiple levels. The evolutionary conservation of the hematopoietic program has made possible the use of diverse model systems. We describe the contributions of the zebrafish model and the most relevant ones from transgenic mouse studies and from in vitro differentiated pluripotent cells.

Notch Downregulation and Extramedullary Erythrocytosis in Hypoxia-Inducible Factor Prolyl 4-Hydroxylase 2-Deficient Mice

Erythrocytosis is driven mainly by erythropoietin, which is regulated by hypoxia-inducible factor (HIF). Mutations in HIF prolyl 4-hydroxylase 2 (HIF-P4H-2) (PHD2/EGLN1), the major downregulator of HIFα subunits, are found in familiar erythrocytosis, and large-spectrum conditional inactivation of HIF-P4H-2 in mice leads to severe erythrocytosis. Although bone marrow is the primary site for erythropoiesis, spleen remains capable of extramedullary erythropoiesis. We studied HIF-P4H-2-deficient (Hif-p4h-2^gt/gt) mice, which show slightly induced erythropoiesis upon aging despite nonincreased erythropoietin levels, and identified spleen as the site of extramedullary erythropoiesis. Splenic hematopoietic stem cells (HSCs) of these mice exhibited increased erythroid burst-forming unit (BFU-E) growth, and the mice were protected against anemia. HIF-1α and HIF-2α were stabilized in the spleens, while the Notch ligand genes Jag1, Jag2, and Dll1 and target Hes1 became downregulated upon aging HIF-2α dependently. Inhibition of Notch signaling in wild-type spleen HSCs phenocopied the increased BFU-E growth. HIFα stabilization can thus mediate non-erythropoietin-driven splenic erythropoiesis via altered Notch signaling.

Jagged-1 Signaling in the Bone Marrow Microenvironment Promotes Endothelial Progenitor Cell Expansion and Commitment of CD133+ Human Cord Blood Cells for Postnatal Vasculogenesis

Notch signaling is involved in cell fate decisions during murine vascular development and hematopoiesis in the microenvironment of bone marrow. To investigate the close relationship between hematopoietic stem cells and human endothelial progenitor cells (EPCs) in the bone marrow niche, we examined the effects of Notch signals [Jagged-1 and Delta-like ligand (Dll)-1] on the proliferation and differentiation of human CD133+ cell-derived EPCs. We established stromal systems using HESS-5 murine bone marrow cells transfected with human Jagged-1 (hJagged-1) or human Dll-1 (hDll-1). CD133+ cord blood cells were co-cultured with the stromal cells for 7 days, and then their proliferation, differentiation, and EPC colony formation was evaluated. We found that hJagged-1 induced the proliferation and differentiation of CD133+ cord blood EPCs. In contrast, hDll-1 had little effect. CD133+ cells stimulated by hJagged-1 differentiated into CD31+/KDR+ cells, expressed vascular endothelial growth factor-A, and showed enhanced EPC colony formation compared with CD133+ cells stimulated by hDll-1. To evaluate the angiogenic properties of hJagged-1- and hDll-1-stimulated EPCs in vivo, we transplanted these cells into the ischemic hindlimbs of nude mice. Transplantation of EPCs stimulated by hJagged-1, but not hDll-1, increased regional blood flow and capillary density in ischemic hindlimb muscles. This is the first study to show that human Notch signaling influences EPC proliferation and differentiation in the bone marrow microenvironment. Human Jagged-1 induced the proliferation and differentiation of CD133+ cord blood progenitors compared with hDll-1. Thus, hJagged-1 signaling in the bone marrow niche may be used to expand EPCs for therapeutic angiogenesis.

TNF-alpha and Notch signaling regulates the expression of HOXB4 and GATA3 during early T lymphopoiesis

During the early thymus colonization, Notch signaling activation on hematopoietic progenitor cells (HPCs) drives proliferation and T cell commitment. Although these processes are driven by transcription factors such as HOXB4 and GATA3, there is no evidence that Notch directly regulates their transcription. To evaluate the role of NOTCH and TNF signaling in this process, human CD34⁺ HPCs were cocultured with OP9-DL1 cells, in the presence or absence of TNF. The use of a Notch signaling inhibitor and a protein synthesis inhibitor allowed us to distinguish primary effects, mediated by direct signaling downstream Notch and TNF, from secondary effects, mediated by de novo synthesized proteins. A low and physiologically relevant concentration of TNF promoted T lymphopoiesis in OP9-DL1 cocultures. TNF positively modulated the expression of both transcripts in a Notch-dependent manner; however, GATA3 induction was mediated by a direct mechanism, while HOXB4 induction was indirect. Induction of both transcripts was repressed by a GSK3β inhibitor, indicating that activation of canonical Wnt signaling inhibits rather than induces their expression. Our study provides novel evidences of the mechanisms integrating Notch and TNF-alpha signaling in the transcriptional induction of GATA3 and HOXB4. This mechanism has direct implications in the control of self-renewal, proliferation, commitment, and T cell differentiation.

Endothelium-targeted human Delta-like 1 enhances the regeneration and homing of human cord blood stem and progenitor cells

Background

Umbilical cord blood (UCB) is becoming an alternative cell source for hematopoietic stem cell transplantation (HSCT). However, umbilical cord blood transplantation (UCBT) has been severely limited by low and finite numbers of hematopoietic stem cells and their delayed engraftment. New strategies are needed to improve ex vivo expansion efficiency and in vivo haematopoietic recovery.

Methods

We produced an endothelium-targeted soluble Notch ligand, the Delta-Serrate-Lag-2 (DSL) domain of human Delta-like 1 fused with a RGD motif (hD1R), and tested the effects of this protein on human umbilical cord blood hematopoietic stem and progenitor cell (UCB-HSPC) ex vivo and in vivo.

Results

hD1R-mediated ex vivo expansion system was able to significantly increase the absolute number of UCB-HSPCs. The hD1R-expanded cells had the enhanced homing and maintained long-term hematopoietic stem cell repopulation capacity in the bone marrow of immunodeficient nonobese diabetic-severe combined immunodeficient (NOD/SCID) mice. Moreover, systemic administration of hD1R promoted the in vivo regeneration of donor cells in recipient mice and accelerated hematopoietic recovery, particularly in settings wherein the HSPCs dose was limiting.

Conclusions

Our results indicated that hD1R might be applied in improving hematopoietic recovery and HSC engraftment in human UCBT.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0761-0) contains supplementary material, which is available to authorized users.

The NOTCH signaling pathway in normal and malignant blood cell production

The NOTCH pathway is an evolutionarily conserved signalling network, which is fundamental in regulating developmental processes in invertebrates and vertebrates (Gazave et al. in BMC Evol Biol 9:249, 2009). It regulates self-renewal (Butler et al. in Cell Stem Cell 6:251-264, 2010), differentiation (Auderset et al. in Curr Top Microbiol Immunol 360:115-134, 2012), proliferation (VanDussen et al. in Development 139:488-497, 2012) and apoptosis (Cao et al. in APMIS 120:441-450, 2012) of diverse cell types at various stages of their development. NOTCH signalling governs cell-cell interactions and the outcome of such responses is highly context specific. This makes it impossible to generalize about NOTCH functions as it stimulates survival and differentiation of certain cell types, whereas inhibiting these processes in others (Meier-Stiegen et al. in PLoS One 5:e11481, 2010). NOTCH was first identified in 1914 in Drosophila and was named after the indentations (notches) present in the wings of the mutant flies (Bigas et al. in Int J Dev Biol 54:1175-1188, 2010). Homologs of NOTCH in vertebrates were initially identified in Xenopus (Coffman et al. in Science 249:1438-1441, 1990) and in humans NOTCH was first identified in T-Acute Lymphoblastic Leukaemia (T-ALL) (Ellisen et al. in Cell 66:649-61, 1991). NOTCH signalling is integral in neurogenesis (Mead and Yutzey in Dev Dyn 241:376-389, 2012), myogenesis (Schuster-Gossler et al. in Proc Natl Acad Sci U S A 104:537-542, 2007), haematopoiesis (Bigas et al. in Int J Dev Biol 54:1175-1188, 2010), oogenesis (Xu and Gridley in Genet Res Int 2012:648207, 2012), differentiation of intestinal cells (Okamoto et al. in Am J Physiol Gastrointest Liver Physiol 296:G23-35, 2009) and pancreatic cells (Apelqvist et al. in Nature 400:877-881, 1999). The current review will focus on NOTCH signalling in normal and malignant blood cell production or haematopoiesis.

Modeling murine yolk sac hematopoiesis with embryonic stem cell culture systems

The onset of hematopoiesis in mammals is defined by generation of primitive erythrocytes and macrophage progenitors in embryonic yolk sac. Laboratories have met the challenge of transient and swiftly changing specification events from ventral mesoderm through multipotent progenitors and maturing lineage-restricted hematopoietic subtypes, by developing powerful in vitro experimental models to interrogate hematopoietic ontogeny. Most importantly, studies of differentiating embryonic stem cell derivatives in embryoid body and stromal coculture systems have identified crucial roles for transcription factor networks (e.g. Gata1, Runx1, Scl) and signaling pathways (e.g. BMP, VEGF, WNT) in controlling stem and progenitor cell output. These and other relevant pathways have pleiotropic biological effects, and are often associated with early embryonic lethality in knockout mice. Further refinement in subsequent studies has allowed conditional expression of key regulatory genes, and isolation of progenitors via cell surface markers (e.g. FLK1) and reporter-tagged constructs, with the purpose of measuring their primitive and definitive hematopoietic potential. These observations continue to inform attempts to direct the differentiation, and augment the expansion, of progenitors in human cell culture systems that may prove useful in cell replacement therapies for hematopoietic deficiencies. The purpose of this review is to survey the extant literature on the use of differentiating murine embryonic stem cells in culture to model the developmental process of yolk sac hematopoiesis.

Notch1 regulates progenitor cell proliferation and differentiation during mouse yolk sac hematopoiesis

Loss-of-function studies have demonstrated the essential role of Notch in definitive embryonic mouse hematopoiesis. We report here the consequences of Notch gain-of-function in mouse embryo hematopoiesis, achieved by constitutive expression of Notch1 intracellular domain (N1ICD) in angiopoietin receptor tyrosine kinase receptor-2 (Tie2)-derived enhanced green fluorescence protein (EGFP(+)) hematovascular progenitors. At E9.5, N1ICD expression led to the absence of the dorsal aorta hematopoietic clusters and of definitive hematopoiesis. The EGFP(+) transient multipotent progenitors, purified from E9.5 to 10.5 Tie2-Cre;N1ICD yolk sac (YS) cells, had strongly reduced hematopoietic potential, whereas they had increased numbers of hemogenic endothelial cells. Late erythroid cell differentiation stages and mature myeloid cells (Gr1(+), MPO(+)) were also strongly decreased. In contrast, EGFP(+) erythro-myeloid progenitors, immature and intermediate differentiation stages of YS erythroid and myeloid cell lineages, were expanded. Tie2-Cre;N1ICD YS had reduced numbers of CD41(++) megakaryocytes, and these produced reduced below-normal numbers of immature colonies in vitro and their terminal differentiation was blocked. Cells from Tie2-Cre;N1ICD YS had a higher proliferation rate and lower apoptosis than wild-type (WT) YS cells. Quantitative gene expression analysis of FACS-purified EGFP(+) YS progenitors revealed upregulation of Notch1-related genes and alterations in genes involved in hematopoietic differentiation. These results represent the first in vivo evidence of a role for Notch signaling in YS transient definitive hematopoiesis. Our results show that constitutive Notch1 activation in Tie2(+) cells hampers YS hematopoiesis of E9.5 embryos and demonstrate that Notch signaling regulates this process by balancing the proliferation and differentiation dynamics of lineage-restricted intermediate progenitors.

Endothelium-targeted Delta-like 1 promotes hematopoietic stem cell expansion ex vivo and engraftment in hematopoietic tissues in vivo

BACKGROUND

Notch ligands enhance ex vivo expansion of hematopoietic stem cells (HSCs). But to use Notch ligands in HSC therapies of human diseases, efforts are required to improve ex vivo expansion efficiency and in vivo transplant engraftment.

DESIGN AND METHODS

We designed and produced an endothelium-targeted soluble Notch ligand, the DSL domain of Delta-like 1 fused with a RGD motif (D1R), and examined the effects of this protein on HSCs ex vivo and in vivo.

RESULTS

D1R efficiently promoted ex vivo expansion of both mouse bone marrow (BM) and human umbilical cord blood HSCs. HSCs expanded with D1R up-regulated many of the stemness-related genes, and showed high BM engraftment efficacy with long-term repopulation capacity after transplantation. Moreover, in vivo administration of D1R increased the number of BM HSCs in mice, and facilitated BM recovery of mice after irradiation. Injection of D1R significantly improved HSC engraftment and myeloid recovery after BM transplantation in irradiated mice. D1R enhanced HSC engraftment not only in BM, but also in the liver and spleen after BM transplantation in mice. D1R induced the formation of compact cell clusters containing the transplanted HSCs in close contact with endothelial cells, reminiscent of HSC niches, in the liver and spleen.

CONCLUSIONS

D1R might be applied in improving both HSC expansion ex vivo and HSC engraftment in vivo in transplantation.

β(2)-Integrin and Notch-1 differentially regulate CD34(+)CD31(+) cell plasticity in vascular niches

AIMS

The implication of circulating haematopoietic CD34(+) progenitors in the vasculature is unclear due to the lack of understanding of their characteristics and plasticity mediated by their cellular microenvironment. We investigated how vascular smooth muscle cells (SMCs) and their interactions with endothelial cells (ECs) affect the behaviour and plasticity of CD34(+)CD31(+) progenitors and the underlying mechanisms.

METHODS AND RESULTS

Human peripheral blood-derived CD34(+)CD31(+) cells were directly transplanted into injured arteries in vivo and co-cultured with ECs and SMCs in vitro. CD34(+)CD31(+) progenitors injected into wire-injured mouse arteries differentiate into ECs and macrophages in the neoendothelial layer and neointima, respectively. SMC-co-culture increases CD34(+)CD31(+) cell mobility and adhesion to and transmigration across ECs. Sorted CD34(+)CD31(+) progenitors that adhered to ECs co-cultured with SMCs have the capacity to form capillary-like structures in Matrigel and chimeric blood vessels in vivo. Sorted transmigrated progenitors give rise to macrophages with increased pro-angiogenic activity. These differentiations of CD34(+)CD31(+) progenitors into ECs and macrophages are mediated by β(2)-integrin and Notch-1, respectively. β(2)-Integrin and Notch-1 are activated by their counterligands, intercellular adhesion molecule-1 (ICAM-1) and jagged-1, which are highly expressed in the neoendothelium and neointima in injured arteries. Intra-arterial injection of β(2)-integrin-activated CD34(+)CD31(+) progenitors into wire-injured mouse arteries inhibits neointima formation.

CONCLUSION

Our findings indicate that the peripheral vascular niches composed of ECs and SMCs may predispose haematopoietic CD34(+)CD31(+) progenitors to differentiate into ECs and macrophages through the activations of the ICAM-1/β(2)-integrin and jagged-1/Notch-1 cascades, respectively.

Circadian system from conception till adulthood

In mammals, the circadian system is composed of the central clock in the hypothalamic suprachiasmatic nuclei and of peripheral clocks that are located in other neural structures and in cells of the peripheral tissues and organs. In adults, the system is hierarchically organized so that the central clock provides the other clocks in the body with information about the time of day. This information is needed for the adaptation of their functions to cyclically changing external conditions. During ontogenesis, the system undergoes substantial development and its sensitivity to external signals changes. Perinatally, maternal cues are responsible for setting the phase of the developing clock, while later postnatally, the LD cycle is dominant. The central clock attains its functional properties during a gradual and programmed process. Peripheral clocks begin to exhibit rhythmicity independent of each other at various developmental stages. During the early developmental stages, the peripheral clocks are set or driven by maternal feeding, but later the central clock becomes fully functional and begins to entrain the periphery. During the perinatal period, the central and peripheral clocks seem to be vulnerable to disturbances in external conditions. Further studies are needed to understand the processes of how the circadian system develops and what degree of plasticity and resilience it possesses during ontogenesis. These data may lead to an assessment of the contribution of disturbances of the circadian system during early ontogenesis to the occurrence of circadian diseases in adulthood.

Notch signaling and development of the hematopoietic system

Notch signaling exerts multiple important functions in the hematopoietic system. Notch1-mediated signals are essential to induce the onset of definitive hematopoiesis within specialized domains of hemogenic endothelium in the fetal dorsal aorta. In contrast, Notch is dispensable for the subsequent maintenance of hematopoietic stem cells in the adult bone marrow. Notch is a key regulator of early T-cell development in the thymus. An expanding number of hematopoietic and lymphoid cell types have been reported to receive context-dependent inputs from the Notch pathway that regulate their differentiation and function. Progress in the field will continue to bring fundamental information about hematopoiesis and practical insights into the potential to modulate Notch signaling for therapeutic purposes.

Decreased colony formation of high proliferative potential colony-forming cells and granulocyte-macrophage colony-forming units and increased Hes-1 expression in bone marrow mononuclear cells from patients with psoriasis

BACKGROUND

Psoriasis is a chronic inflammatory disease of the skin. The dysfunctional immunity experienced by patients with psoriasis is believed to influence the bone marrow haematopoietic cells and their surrounding microenvironment. Phagocytes derived from the bone marrow of patients with active psoriasis exhibit enhanced monocytopoietic activity and hyperplasia in vitro. However, direct evidence supporting the hypothesis that bone marrow is involved in the pathogenesis of psoriasis has yet to be established.

OBJECTIVES

To investigate the involvement of bone marrow in the pathogenesis of psoriasis.

METHODS

Bone marrow mononuclear cells (BMMNCs) were isolated from patients with psoriasis and healthy individuals. The high proliferative potential colony-forming cells (HPP-CFCs), granulocyte-macrophage colony-forming units (CFU-GM) and erythroid colony-forming units (CFU-E) were cultured in the presence of defined cytokines, and the effects of secreted factors from psoriatic peripheral blood mononuclear cells (PBMCs) on colony formation of normal haematopoietic cells were analysed. Furthermore, the telomere activity of psoriatic and normal BMMNCs was determined using the polymerase chain reaction (PCR)-based telomeric repeat amplification protocol, while the expression of human telomerase reverse transcriptase (hTERT) and HES1 mRNA was detected by reverse transcription-PCR assay.

RESULTS

The numbers of HPP-CFCs and CFU-GM, but not CFU-E, were significantly reduced in cultured haematopoietic cells from patients with psoriasis. The culture supernatant of PBMCs from patients with psoriasis was found to inhibit the colony formation capacity of HPP-CFCs, CFU-GM and CFU-E of normal haematopoietic cells. We also detected low levels of telomerase activity and hTERT gene expression in psoriatic and control BMMNCs that was statistically similar between the two groups. In contrast, the HES1 gene expression appeared to be significantly elevated in psoriatic BMMNCs (P < 0.05).

CONCLUSIONS

Together, our results indicate the involvement of bone marrow in the immunopathogenesis of psoriasis, and suggest a mechanism mediated by certain inflammatory or haematopoietic cytokines present in the bone marrow microenvironment. Elevated expression levels of HES1 mRNA suggest a potential role for the Notch signalling pathway in this process.

T-cell differentiation of multipotent hematopoietic cell line EML in the OP9-DL1 coculture system

OBJECTIVE

Multipotent hematopoietic cell line EML can differentiate into myeloid, erythroid, megakaryocytic, and B-lymphoid lineages, but it remained unknown whether EML cells have T-cell developmental potential as well. The goal of this study was to determine whether the coculture with OP9 stromal cells expressing Notch ligand Delta-like 1 (OP9-DL1) could induce differentiation of EML cells into T-cell lineage.

MATERIALS AND METHODS

EML cells were cocultured with control OP9 or OP9-DL1 stromal cells in the presence of cytokines (stem cell factor, interleukin-7, and Fms-like tyrosine kinase 3 ligand). Their T-cell lineage differentiation was assessed through flow cytometry and reverse transcription polymerase chain reaction expression analysis of cell surface markers and genes characterizing and associated with specific stages of T-cell development.

RESULTS

The phenotypic, molecular, and functional analysis has revealed that in EML/OP9-DL1 cocultures with cytokines, but not in control EML/OP9 cocultures, EML cell line undergoes T-cell lineage commitment and differentiation. In OP9-DL1 cocultures, EML cell line has differentiated into cells that 1) resembled double-negative, double-positive, and single-positive stages of T-cell development; 2) initiated expression of GATA-3, Pre-Talpha, RAG-1, and T-cell receptor-Vbeta genes; and 3) produced interferon-gamma in response to T-cell receptor stimulation.

CONCLUSIONS

These results support the notion that EML cell line has the capacity for T-cell differentiation. Remarkably, induction of T-lineage gene expression and differentiation of EML cells into distinct stages of T-cell development were very similar to previously described T-cell differentiation of adult hematopoietic stem cells and progenitors in OP9-DL1 cocultures. Thus, EML/OP9-DL1 coculture could be a useful experimental system to study the role of particular genes in T-cell lineage specification, commitment, and differentiation.

Diverse T-cell differentiation potentials of human fetal thymus, fetal liver, cord blood and adult bone marrow CD34 cells on lentiviral Delta-like-1-modified mouse stromal cells

Human haematopoietic progenitor/stem cells (HPCs) differentiate into functional T cells in the thymus through a series of checkpoints. A convenient in vitro system will greatly facilitate the understanding of T-cell development and future engineering of therapeutic T cells. In this report, we established a lentiviral vector-engineered stromal cell line (LSC) expressing the key lymphopoiesis regulator Notch ligand, Delta-like 1 (DL1), as feeder cells (LSC-mDL1) supplemented with Flt3 ligand (fms-like tyrosine kinase 3, Flt3L or FL) and interleukin-7 for the development of T cells from CD34(+) HPCs. We demonstrated T-cell development from human HPCs with various origins including fetal thymus (FT), fetal liver (FL), cord blood (CB) and adult bone marrow (BM). The CD34(+) HPCs from FT, FL and adult BM expanded more than 100-fold before reaching the beta-selection and CD4/CD8 double-positive T-cell stage. The CB HPCs, on the other hand, expanded more than 1000-fold before beta-selection. Furthermore, the time required to reach beta-selection differed for the various HPCs, 7 days for FT, 14 days for FL and CB, and 35 days for adult BM. Nevertheless, all of the T cells developed in vitro were stalled at the double-positive or immature single-positive stage with the exception that some CB-derived T cells arrived at a positive selection stage. Consequently, the LSC-mDL1 culture system illustrated diverse T-cell development potentials of pre- and post-natal and adult human BM HPCs. However, further modification of this in vitro T-cell development system is necessary to attain fully functional T cells.

Generation of pro-T cells in vitro: potential for immune reconstitution

Immunodeficient individuals are susceptible to opportunistic infection. While stem cell transplantation can restore a functional immune system, T cells are slow to recover and limited in eliciting adaptive immune responses. Approaches to selectively enhance T cell function have focused on boosting thymopoiesis to generate new T cells or expanding existing T cells. By taking advantage of the role of Notch signaling in T cell development, we have developed an in vitro system able to generate large numbers of progenitor T cells from human hematopoietic stem cells. Here, we discuss this in vitro system and its implications for the potential treatment of T cell immunodeficiency.

Effective erythropoiesis and HbF reactivation induced by kit ligand in beta-thalassemia

In human beta-thalassemia, the imbalance between alpha- and non-alpha-globin chains causes ineffective erythropoiesis, hemolysis, and anemia: this condition is effectively treated by an enhanced level of fetal hemoglobin (HbF). In spite of extensive studies on pharmacologic induction of HbF synthesis, clinical trials based on HbF reactivation in beta-thalassemia produced inconsistent results. Here, we investigated the in vitro response of beta-thalassemic erythroid progenitors to kit ligand (KL) in terms of HbF reactivation, stimulation of effective erythropoiesis, and inhibition of apoptosis. In unilineage erythroid cultures of 20 patients with intermedia or major beta-thalassemia, addition of KL, alone or combined with dexamethasone (Dex), remarkably stimulated cell proliferation (3-4 logs more than control cultures), while decreasing the percentage of apoptotic and dyserythropoietic cells (<5%). More important, in both thalassemic groups, addition of KL or KL plus Dex induced a marked increase of gamma-globin synthesis, thus reaching HbF levels 3-fold higher than in con-trol cultures (eg, from 27% to 75% or 81%, respectively, in beta-thalassemia major). These studies indicate that in beta-thalassemia, KL, alone or combined with Dex, induces an expansion of effective erythropoiesis and the reactivation of gamma-globin genes up to fetal levels and may hence be considered as a potential therapeutic agent for this disease.

Association evidence of schizophrenia with distal genomic region of NOTCH4 in Taiwanese families

Evidence for association with schizophrenia has been reported for NOTCH4, although results have been inconsistent. Previous studies have focused on polymorphisms in the 5' promoter region and first exon of NOTCH4. Our aim was to test the association of the entire genomic region of NOTCH4 in 218 families with at least two siblings affected by schizophrenia in Taiwan. We genotyped seven single nucleotide polymorphisms (SNPs) of this gene, with average intermarker distances of 5.3 kb. Intermarker linkage disequilibrium (LD) was calculated using gold software, and single-locus and haplotype association analyses were performed using transmit software. We found that the T allele of SNP rs2071285 (P= 0.035) and the G allele of SNP rs204993 (P= 0.0097) were significantly preferentially transmitted to the affected individuals in the single-locus association analysis. The two SNPs were in high LD (D' > 0.8). Trend for overtransmission was shown for the T-G haplotype of the two SNPs to affected individuals (P= 0.053), with the A-A haplotype significantly undertransmitted (P= 0.034). The associated region distributed across the distal portion of the NOTCH4 gene and overlapped with the genomic region of the G-protein signaling modulator 3 and pre-B-cell leukemia transcription factor 2. In summary, we found modest association evidence between schizophrenia and the distal genomic region of NOTCH4 in this Taiwanese family sample. Further replication for association with the distal genomic region of NOTCH4 is warranted.

Modeling Notch Signaling in Normal and Neoplastic Hematopoiesis: Global Gene Expression Profiling in Response to Activated Notch Expression

In normal hematopoiesis, proliferation is tightly linked to differentiation in ways that involve cell-cell interaction with stromal elements in the bone marrow stem cell niche. Numerous in vitro and in vivo studies strongly support a role for Notch signaling in the regulation of stem cell renewal and hematopoiesis. Not surprisingly, mutations in the Notch gene have been linked to a number of types of malignancies. To better define the function of Notch in both normal and neoplastic hematopoiesis, a tetracycline-inducible system regulating expression of a ligand-independent, constitutively active form of Notch1 was introduced into murine E14Tg2a embryonic stem cells. During coculture, OP9 stromal cells induce the embryonic stem cells to differentiate first to hemangioblasts and subsequently to hematopoietic stem cells. Our studies indicate that activation of Notch signaling in flk+ hemangioblasts dramatically reduces their survival and proliferative capacity and lowers the levels of hematopoietic stem cell markers CD34 and c-Kit and the myeloid marker CD11b. Global gene expression profiling of day 8 hematopoietic progenitors in the absence and presence of activated Notch yield candidate genes required for normal hematopoietic differentiation, as well as putative downstream targets of oncogenic forms of Notch including the noncanonical Wnts Wnt4 and 5A. Disclosure of potential conflicts of interest is found at the end of this article.

Physiology and pathology of notch signalling system

Notch proteins encode a family of transmembrane receptors that are part of a signalling transduction system known as Notch signalling, an extremely conserved and widely used mechanism regulating programs governing growth, apoptosis and differentiation in metazoans. Notch signalling begins when the Notch receptor binds ligands and ends when the Notch intracellular domain enters the nucleus and activates transcription of target genes. This core pathway is subjected to a wide array of regulatory influences and protein-protein interactions and is correlated with other signalling pathway. This review will summarize recent findings concerning the physiology and pathology of Notch signalling in vascular development and homeostasis. Moreover, the clinical phenotypes of Notch3 signalling system pathology will be described, with particular regard to CADASIL (Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy) for which the most recent pathogenetic hypotheses are reported.

Notch Signaling Requires GATA-2 to Inhibit Myelopoiesis from Embryonic Stem Cells and Primary Hemopoietic Progenitors

The bone marrow and thymus, although both hemopoietic environments, induce very distinct differentiation outcomes. The former supports hemopoietic stem cell self-renewal and multiple hemopoietic lineages, while the latter supports T lymphopoiesis almost exclusively. This distinction suggests that the thymic environment acts to restrict the hemopoietic fates available to thymic immigrants. In this study, we demonstrate that the addition of the Notch ligand Delta-like-1 (Dll-1) to an in vitro system that otherwise supports myelopoiesis, greatly reduces the myelopoietic potential of stem cells or uncommitted progenitors. In contrast, committed myeloid progenitors mature regardless of the presence of Dll-1. The block in myelopoiesis is the direct result of Notch signaling within the hemopoietic progenitor, and Dll-1-induced signals cause a rapid increase in the expression of the zinc finger transcription factor GATA-2. Importantly, in the absence of GATA-2, Dll-1-induced signals fail to inhibit commitment to the myeloid fate. Taken together, our results support a role for GATA-2 in allowing Dll-1 to restrict non-T cell lineage differentiation outcomes.

Regulation of lymphoid development, differentiation, and function by the Notch pathway

The Notch pathway is gaining increasing recognition as a key regulator of developmental choices, differentiation, and function throughout the hematolymphoid system. Notch controls the generation of hematopoietic stem cells during embryonic development and may affect their subsequent homeostasis. Commitment to the T cell lineage and subsequent stages of early thymopoiesis is critically regulated by Notch. Recent data indicate that Notch can also direct the differentiation and activity of peripheral T and B cells. Thus, the full spectrum of Notch effects is just beginning to be understood. In this review, we discuss this explosion of knowledge as well as current controversies and challenges in the field.

Differentiation of rat bone marrow cells cultured on artificial basement membrane containing extracellular matrix into a liver cell lineage

BACKGROUND/AIMS

Bone marrow (BM) cells have been shown to be capable of differentiating into a liver cell lineage in vitro. However, their differentiation and proliferation is poor, and the cell characteristics are poorly understood.

METHODS

We cultured rat BM cells on an artificial basement membrane containing extracellular matrix (ECM) with hepatocyte growth factor (HGF). The expression of mRNA for liver-specific genes was analyzed by reverse transcription PCR. The expression of albumin and Musashi-1 by cultured cells was analyzed using a fluorescence-activated cell sorter (FACS). The proportions of albumin-positive cells when culture was performed with different concentrations of HGF were analyzed by FACS.

RESULTS

On culture day 21, polygonal cells proliferated and formed cell colonies. These cells expressed mRNA for all the liver-specific genes analyzed, and showed heterogeneous differentiation, some cells expressing albumin, others expressing Musashi-1. Albumin-positive differentiated cells were large and rich in intracellular structures, while Musashi-1-positive undifferentiated cells had the opposite characteristics. Culturing cells with higher concentrations of HGF induced an increased proportion of albumin-positive cells.

CONCLUSIONS

The results suggest that cell culture on an ECM with a high concentration of HGF increases the extent to which BM cells differentiate into a liver cell lineage and proliferate in vitro.

Identification and characterization of genes involved in embryonic crystal cell formation during Drosophila hematopoiesis

Parallels between vertebrate and Drosophila hematopoiesis add to the value of flies as a model organism to gain insights into blood development. The Drosophila hematopoietic system is composed of at least three classes of terminally differentiated blood cells: plasmatocytes, crystal cells, and lamellocytes. Recent studies have identified transcriptional and signaling pathways in Drosophila involving proteins similar to those seen in human blood development. To identify additional genes involved in Drosophila hematopoiesis, we have conducted a P-element-based genetic screen to isolate mutations that affect embryonic crystal cell development. Using a marker of terminally differentiated crystal cells, we screened 1040 P-element-lethal lines located on the second and third chromosomes and identified 44 individual lines that affect crystal cell development. Identifying novel genes and pathways involved in Drosophila hematopoiesis is likely to provide further insights into mammalian hematopoietic development and disorders.

Induction of T-cell development from human cord blood hematopoietic stem cells by Delta-like 1 in vitro

The Notch signaling pathway plays a key role at several stages of T-lymphocyte differentiation. However, it remained unclear whether signals induced by the Notch ligand Delta-like 1 could support full T-cell differentiation from a defined source of human hematopoietic stem cells (HSCs) in vitro. Here, we show that human cord blood–derived HSCs cultured on Delta-like 1–expressing OP9 stromal cells undergo efficient T-cell lineage commitment and sustained T-cell differentiation. A normal stage-specific program of T-cell development was observed, including the generation of CD4 and CD8 αβ–T-cell receptor (TCR)–bearing cells. Induction of T-cell differentiation was dependent on the expression of Delta-like 1 by the OP9 cells. Stimulation of the in vitro–differentiated T cells by TCR engagement induced the expression of T-cell activation markers and costimulatory receptors. These results establish an efficient in vitro coculture system for the generation of T cells from human HSCs, providing a new avenue for the study of early T-cell differentiation and function.

A requirement for Notch1 distinguishes 2 phases of definitive hematopoiesis during development

Notch1 is known to play a critical role in regulating fates in numerous cell types, including those of the hematopoietic lineage. Multiple defects exhibited by Notch1-deficient embryos confound the determination of Notch1 function in early hematopoietic development in vivo. To overcome this limitation, we examined the developmental potential of Notch1(-/-) embryonic stem (ES) cells by in vitro differentiation and by in vivo chimera analysis. Notch1 was found to affect primitive erythropoiesis differentially during ES cell differentiation and in vivo, and this result reflected an important difference in the regulation of Notch1 expression during ES cell differentiation relative to the developing mouse embryo. Notch1 was dispensable for the onset of definitive hematopoiesis both in vitro and in vivo in that Notch1(-/-) definitive progenitors could be detected in differentiating ES cells as well as in the yolk sac and early fetal liver of chimeric mice. Despite the fact that Notch1(-/-) cells can give rise to multiple types of definitive progenitors in early development, Notch1(-/-) cells failed to contribute to long-term definitive hematopoiesis past the early fetal liver stage in the context of a wild-type environment in chimeric mice. Thus, Notch1 is required, in a cell-autonomous manner, for the establishment of long-term, definitive hematopoietic stem cells (HSCs).

Fanconi anemia C gene product regulates expression of genes involved in differentiation and inflammation

Loss of Fanconi anemia (FA) proteins activity by recessive inherited mutations in one of the FA genes leads to a disease characterized by bone marrow failure, myeloid leukemia and DNA damage hypersensitivity. The aim of this work was to improve our understanding of the FA syndrome defining the transcription profile of the FA complementation group C (FANCC)-deficient cells in comparison to their ectopically corrected counterpart using oligonucleotide microarrays. In this way, 49 RNAs have been isolated, which showed a consistent differential pattern of expression among FANCC mutated and corrected cells. The observed specific changes in gene expression suggest that FANCC regulates specifically myeloid differentiation and unmasks a previously unsuspected anti-inflammatory role for the FA proteins. In spite of the DNA damage hypersensitivity of the syndrome, no gene coding for a protein directly involved in DNA repair/damage response was found to be deregulated in our analysis. This observation suggests that FANCC does not directly control genes involved in DNA repair at the transcriptional level, but does not exclude a regulation at the translational or post-translational level, or by protein/protein interactions. The potential role of the differentially expressed genes in FA phenotype as well as a functional- and cellular-based clustering of the identified genes are presented and discussed.

Expression of constitutively active Notch4 (Int-3) modulates myeloid proliferation and differentiation and promotes expansion of hematopoietic progenitors

The Notch family of transmembrane receptors has been implicated in the regulation of many developmental processes. In this study, we evaluated the role of Notch4 in immature hematopoietic progenitors by inducing, with retroviral transduction, enforced expression of Int-3, the oncogenic and constitutively active form of mouse Notch4. Int-3-transduced human myeloid leukemia (HL-60) cells demonstrated significantly delayed expression of differentiation markers following retinoic acid and 12-0-tetradecanoylphorbol 13-acetate treatment. Furthermore, HL-60 cells expressing Int-3 displayed a slower growth rate than cells infected with void virus, and accumulation in the G0/G1 phases of cell cycle. Transduction with deletion mutants of Int-3 defined the importance of individual domains of the protein (in particular, the ANK domain and the C-terminal domain) in the inhibition of differentiation and growth arrest of HL-60 cells. When mouse bone marrow enriched for stem cells (5-fluorouracil-resistant, lineage negative) was transduced and cultured for two weeks, the Int-3-transduced population displayed a lower expression of differentiation markers and a three- to five-fold higher frequency of colony-forming cells (CFU-GM/BFU-E) than control cultures. These results strongly support the notion that Notch signaling inhibits differentiation and promotes expansion of hematopoietic stem/progenitor cells.

Notch regulation of lymphocyte development and function

Notch proteins regulate a broad spectrum of cell fate decisions and differentiation processes during fetal and postnatal development. Mammals have four Notch receptors that bind five different ligands. The function of Notch signaling during lymphopoiesis and T cell neoplasia, based on gain-of-function and conditional loss-of-function approaches for the Notch1 receptor, indicates Notch1 is essential in T cell lineage commitment. Recent studies have addressed the involvement of other Notch receptors and ligands as well as their downstream targets, demonstrating additional functions of Notch signaling in embryonic hematopoiesis, intrathymic T cell development, B cell development and peripheral T cell function.

Notch and the immune system

Notch proteins are used repeatedly to direct developmental cell fate decisions in multiple organs. During hematopoiesis and immune development, Notch is critical for T/B lineage specification and for generation of splenic marginal zone B cells. In early embryonic development, Notch is crucial for generating hematopoietic stem cells. Emerging data suggest that Notch may also modulate the differentiation and activity of peripheral T cells. Understanding the specific regulation of the Notch pathway in different contexts and its interaction with other signaling pathways remains an important challenge to comprehend the full spectrum of Notch effects. In this review, we critically assess recent findings regarding the function of Notch in the hematolymphoid system.

NOTCH4 gene haplotype is associated with schizophrenia in African Americans

BACKGROUND

The goal of this study was to investigate the relationship between the NOTCH4 gene and schizophrenia in African American (AA) and European American (EA) subjects.

METHODS

Two single nucleotide polymorphisms (SNPs) at the NOTCH4 locus were genotyped in 123 AA schizophrenia patients, 223 EA schizophrenia patients, 85 AA healthy control subjects, and 211 EA healthy control subjects. The specific markers studied were -1725T/G and -25T/C. Comparisons of allele and haplotype frequencies between patients and control subjects were performed with the chi-square test, the Fisher's Exact Test, and CLUMP software. Linkage disequilibrium (LD) between these two SNPs was calculated with the 3LOCUS program.

RESULTS

The haplotype -1725G/-25T associates to schizophrenia in AA subjects (p =.0008), but not in EA subjects. Alleles -1725G and allele -25T are in positive LD both in AAs and EAs. Allele and haplotype frequencies differ significantly between AAs and EAs.

CONCLUSIONS

The haplotype -1725G/-25T at the NOTCH4 locus, which results from SNPs of NOTCH4 that are in LD, may increase susceptibility to schizophrenia in AAs. Any effect of this locus on risk for schizophrenia is population-specific.

Thicker than blood: conserved mechanisms in Drosophila and vertebrate hematopoiesis

Blood development in Drosophila melanogaster shares several interesting features with hematopoiesis in vertebrates, including spatiotemporal regulation as well as the use of similar transcriptional regulators and signaling pathways. In this review, we describe what is known about hematopoietic development in Drosophila and the various cell types generated and their functions. Additionally, the molecular genetic mechanisms of hematopoietic cell fate determination and commitment within Drosophila blood cell lineages are discussed and compared to vertebrate mechanisms.

Activated Notch2 potentiates CD8 lineage maturation and promotes the selective development of B1 B cells

Although studies have shown that the Notch2 family member is critical for embryonic development, little is known concerning its role in hematopoiesis. In this study, we show that the effects of an activated form of Notch2 (N2IC) on the T-cell lineage are dosage related. High-level expression of N2IC results in the development of T-cell leukemias. In contrast, lower-level expression of N2IC does not lead to transformation but skews thymocyte development to the CD8 lineage. Underlying this skew is a dramatic enhancement in positive selection and CD8SP maturation. N2IC permits early B-cell development but blocks the maturation of conventional B2 cells at the pre-B stage, which is the limit of endogenous Notch2 protein expression in developing B cells. Most strikingly, while B2 B cell development is blocked at the pre-B-cell stage, N2IC promotes the selective development of LPS-responsive B1 B cells. This study implicates a role for Notch2 in the maturation of the CD8 lineage and suggests a novel function for Notch2 in the development of the B1 B-cell subset.

Involvement of Notch-1 signaling in bone marrow stroma-mediated de novo drug resistance of myeloma and other malignant lymphoid cell lines

The bone marrow (BM) microenvironment plays a critical role in malignant cell growth, patient survival, and response to chemotherapy in hematologic malignancies. However, mechanisms associated with this environmental influence remain unclear. In this study, we investigated the role of Notch family proteins in myeloma and other malignant lymphoid cell line growth and response to chemotherapeutic drugs. All 8 tested cell lines expressed Notch-3 and Notch-4; 7 cell lines expressed Notch-1; and 6 expressed Notch-2 proteins. Interaction with BM stroma (BMS) activated Notch signaling in tumor cells. However, activation of only Notch-1, but not Notch-2, resulted in protection of tumor cells from melphalan- and mitoxantrone-induced apoptosis. This protection was associated with up-regulation of p21(WAF/Cip) and growth inhibition of cells. Overexpression of Notch-1 in Notch-1(-) U266 myeloma cells up-regulated p21 and resulted in protection from drug-induced apoptosis. Thus, this is a first report demonstrating that Notch-1 signaling may be a primary mechanism mediating the BMS influence on hematologic malignant cell growth and survival.

Notch-regulated ankyrin-repeat protein inhibits Notch1 signaling: multiple Notch1 signaling pathways involved in T cell development

We have characterized the function of Notch-regulated ankyrin-repeat protein (Nrarp) in mouse cell lines and in hematopoietic stem cells (HSCs). Nrarp overexpression is able to block Notch-induced activation of CBF-1. In AKR1010 thymoma cells, Nrarp overexpression blocks CBF-1-dependent transcriptional activation of Notch-responsive genes and inhibits phenotypic changes associated with Notch activation. Enforced expression of Nrarp in mouse HSCs results in a profound block in T lineage commitment and progression through early stages of thymocyte maturation. In contrast, Deltex-1 overexpression in HSCs can also block T lineage commitment but not progression through the early double negative stages of thymocyte maturation. The different effects of Deltex-1 and Nrarp overexpression suggest that alternate Notch signaling pathways mediate T vs B lineage commitment and thymocyte maturation.

Differentiation of bone marrow cells into cells that express liver-specific genes in vitro: implication of the Notch signals in differentiation

Bone marrow (BM) stem cells have been shown to differentiate into liver cells. It remains difficult to sort and culture BM stem cells, and the gene expression of liver-specific proteins in these cells has not been fully investigated. We used a negative selective magnetic cell separation system to obtain stem cell-enriched BM cells. The cells obtained were cultured with hepatocytes or with hepatocyte growth factor (HGF), and the differentiation of BM cells into cells expressing liver-specific genes, hepatocyte nuclear factor (HNF) 1alpha, cytokeratin (CK) 8, alpha-fetoprotein (AFP), and albumin was investigated by the reverse transcription-polymerase chain reaction. We also investigated the gene expressions of Notch receptor-1 (Notch-1) and its ligand Jagged-1 in BM cell differentiation. Sorted BM cells showed positive for Sca-1 (Ataxin-1) by immunofluorescence staining. Fluorescence activated cell sorter analysis showed that 32.6% of sorted BM cells had a high level of expression of the hematopoietic stem cell marker CD90 (Thy-1). When cultured with hepatocytes, these cells expressed the liver-specific genes HNF1alpha and CK8 on culture day 3, AFP and albumin on culture day 7. When cultured with HGF (20ng/ml), the cells expressed HNF1alpha on day 3 and CK8 on day 7. Gene expressions of Notch-1 and Jagged-1 were detected in cultured BM cells on day 3. These results suggest that the negative selective magnetic cell separation system is useful for the rapid preparation of stem cell-enriched BM cells, and that the Notch signaling pathway plays a role in BM cell differentiation into a hepatocyte lineage in vitro.

Notch and lymphopoiesis: a view from the microenvironment

The differentiation of B- and T-cells in primary lymphoid organs depends on, or is strongly influenced by, signals provided by stromal cells, extracellular matrix components as well as by direct contacts between differentiating lymphocytes and distinct environmental cells. Notch receptors and their ligands mediate intercellular contacts and are crucially important for the development of T- and B-cell lineages. Here we start by reviewing current knowledge on the expression patterns of Notch receptors and their ligands in primary lymphoid organs and the effects induced by their functional interactions. Then we shall attempt to discuss how those interactions may regulate not only lymphopoiesis per se but also morphogenesis and the functional compartmentalization of lymphopoietic organs during development.

Microenvironmental regulation of Notch signalling in T cell development

T cells develop in the thymus from blood-borne progenitors derived from haematopoietic tissues. Amongst the mechanisms by which stromal cells in thymic and prethymic tissues influence lymphoid progenitors, recent attention has focussed on the importance of Notch signalling in early T cell development. Here, we review evidence that developing T cells and their progenitors receive signals through Notch receptors as a result of interactions with Notch ligands expressed by stromal cells. In particular, we focus on the role of Notch ligand-expressing stromal cells in regulating key control points during pre- and intrathymic phases of T cell development.

Multi-stage analysis of differential gene expression in BALB/C mouse liver development by high-density microarrays

The development of a complex organ such as the liver relies on precise temporal and spatial gene expression patterns during ontogenesis. The unique adult phenotype is a result of a cascade of transcriptional events that finally trigger gene expression in a liver-specific fashion. Development in mice starts at embryonic stage E8.5-9.5 with the expression of several genes typically associated with liver tissue. While the role of some genes and their expression is well studied, little is known about the complex expression pattern changes during embryonic and fetal liver development. High-density oligonucleotide microarrays, which allow simultaneous expression analysis of 12,488 mouse mRNA transcripts and EST sequences, were used to study the gene expression profiles in day 7.5 embryonic tissue, in micro-dissected fetal liver tissue from day 11.5 and day 13.5 embryos, and in adult liver. In pairwise comparisons of all stages, a total of 4242 distinct genes or ESTs were found to be differentially regulated. Cross-comparisons of data from all stages detected the highest number of differentially regulated genes in E11.5 fetal liver tissue versus adult liver (3063 genes) and the lowest number in E11.5 versus E13.5 fetal liver tissue (517 genes). Using adult liver as reference tissue, 212 genes were regulated exclusively in E7.5 embryonic tissue, 303 genes in E11.5 and 198 in E13.5 fetal liver tissue. Expression profiles of the 31 genes with significant regulation at all stages as well as of a number of known developmentally regulated genes were compared with published results and interpreted. The gene expression profiles detected by microarray hybridization were independently confirmed for selected genes by quantitative RT-PCR. Our data presented here suggest that a relatively small number of stage-specific genes exist, which may be of particular importance for liver development, growth and differentiation. Furthermore, the microarray approach led to the identification of a number of genes, which have not yet been associated with liver organogenesis and maturation.

Notch signaling in lymphocyte development

Cytokine and antigen receptor signals play well-characterized roles in promoting the survival and maturation of T and B lymphocyte progenitors through sequential developmental stages. Emerging studies suggest equally important roles for more ancient signaling pathways that evolved prior to the adaptive immune system in jawed vertebrates. In particular, there are at least two essential functions for the highly conserved Notch signaling pathway in lymphocyte development. First, Notch signals are essential for the development of T cell progenitors in the thymus and intestinal epithelium. Second, Notch signals are required to suppress B cell development in the thymus. This review will focus on focus on recent advances in our understanding of how Notch signaling regulates this developmental switch, as well as how Notch might regulate subsequent survival and cell fate decisions in developing T cells.

The notch pathway: modulation of cell fate decisions in hematopoiesis

The hematopoietic system is maintained by a rare population of hematopoietic stem cells (HSC) that are thought to undergo self-renewal as well as continuously produce progeny that differentiate into the various hematopoietic lineages. However, the mechanisms regulating cell fate choices by HSC and their progeny have not been understood. Results of most studies support a stochastic model of cell fate determination in which growth factors support only the survival or proliferation of the progeny specified along a particular lineage. In other developmental systems, however, Notch signaling has been shown to play a central role in regulating fate decisions of numerous types of precursors, often inhibiting a particular (default) pathway while permitting self-renewal or differentiation along an alternative pathway. There is also accumulating evidence that the Notch pathway affects survival, proliferation, and cell fate choices at various stages of hematopoietic cell development, including the decisions of HSC to self-renew or differentiate and of common lymphoid precursors to undergo T- or B-cell differentiation. These data suggest that the Notch pathway plays a fundamental role in the development and maintenance of the hematopoietic system.