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Developmental expression of the Notch signaling pathway genes during mouse preimplantation development.

Notch signaling is an evolutionary conserved pathway involved in intercellular signaling and essential for proper cell fate choices during development. Thus, it could be involved in mouse preimplantation development where intercellular signaling plays a crucial role, particularly between the inner cell mass and the trophectoderm of the blastocyst. At their face value, the phenotypes observed when disrupting each of the four Notch genes known in the mouse do not support this view as none of them involves perturbation of preimplantation development. However this could be due to functional redundancy and/or maternal expression. As a first step to address this issue, we decided to examine the expression in early development of various genes known to participate in Notch signaling. Here, we report on the expression pattern of Notch1-4, Jagged1 (Jag1), Jag2, Delta-like1 (Dll-1), Dll-3, Dll-4, Rbpsuh, Deltex1(Dtx1)and Dtx2 genes during preimplantation development from unfertilized eggs until late blastocyst stage using a RT-PCR strategy. We show that Notch1, 2, Jag1-2, Dll-3, Rbpsuh and Dtx2 transcripts are expressed at all stages. Notch4 and Dll-4 mRNAs are synthesized from the 2-cell through to the hatched blastocyst stage. Notch3, Dll-1 and Dtx1exhibit a stage dependent expression as their mRNAs are detected in 2-cell embryos and in hatched blastocysts, but are absent or weakly detected at the morula stage. Finally, we show that all the above genes are expressed both in Embryonic and Trophoblast Stem cells (ES and TS cells, respectively). Our results suggest that the Notch pathway may be active during mouse preimplantation development.

Animals↗

Notch1 and Notch3 instructively restrict bFGF-responsive multipotent neural progenitor cells to an astroglial fate.

Notch1 has been shown to induce glia in the peripheral nervous system. However, it has not been known whether Notch can direct commitment to glia from multipotent progenitors of the central nervous system. Here we present evidence that activated Notch1 and Notch3 promotes the differentiation of astroglia from the rat adult hippocampus-derived multipotent progenitors (AHPs). Quantitative clonal analysis indicates that the action of Notch is likely to be instructive. Transient activation of Notch can direct commitment of AHPs irreversibly to astroglia. Astroglial induction by Notch signaling was shown to be independent of STAT3, which is a key regulatory transcriptional factor when ciliary neurotrophic factor (CNTF) induces astroglia. These data suggest that Notch provides a CNTF-independent instructive signal of astroglia differentiation in CNS multipotent progenitor cells.

Animals↗

Basic helix-loop-helix transcription factors regulate the neuroendocrine differentiation of fetal mouse pulmonary epithelium.

To clarify the mechanisms that regulate neuroendocrine differentiation of fetal lung epithelia, we have studied the expression of the mammalian homologs of achaete-scute complex (Mash1) (Ascl1 - Mouse Genome Informatics); hairy and enhancer of split1 (Hes1); and the expression of Notch/Notch-ligand system in the fetal and adult mouse lungs, and in the lungs of Mash1- or Hes1-deficient mice. Immunohistochemical studies revealed that Mash1-positive cells seemed to belong to pulmonary neuroendocrine cells (PNEC) and their precursors. In mice deficient for Mash1, no PNEC were detected. Hes1-positive cells belong to non-neuroendocrine cells. In the mice deficient in Hes1, in which Mash1 mRNA was upregulated, PNEC appeared precociously, and the number of PNEC was markedly increased. NeuroD (Neurod1 - Mouse Genome Informatics) expression in the lung was detected in the adult, and was enhanced in the fetal lungs of Hes1-null mice. Expression of Notch1, Notch2, Notch3 and Notch4 mRNAs in the mouse lung increased with age, and Notch1 mRNA was expressed in a Hes1-dependent manner. Notch1, Notch2 and Notch3 were immunohistochemically detected in non-neuroendocrine cells. Moreover, analyses of the lungs from the gene-targeted mice suggested that expression of Delta-like 1 (Dll1 - Mouse Genome Informatics) mRNA depends on Mash1. Thus, the neuroendocrine differentiation depends on basic helix-loop-helix factors, and Notch/Notch-ligand pathways may be involved in determining the cell differentiation fate in fetal airway epithelium.

Aging↗

Coexistence of CADASIL and Alzheimer's disease.

Cerebral autosomal dominant arteriopathy with subcortical infarcts and leucoencephalopathy (CADASIL) is caused by point mutations in the Notch3 gene. Presenilins are proteins involved in the cleaving of both Notch and the amyloid precursor protein (APP). In cases of early onset Alzheimer's disease mutations of the presenilin genes (PSEN 1 and PSEN 2) and APP can be found. A 64 year old patient with CADASIL (R169C-mutation) is reported, who, in addition to subcortical infarcts and granular osmiophilic deposits, had numerous senile plaques and neurofibrillary tangles on pathological examination. Mutations in the APP, PSEN1, and PSEN2 genes were not identified. Neuropathological findings of Alzheimer's disease may be found in CADASIL patients.

Alzheimer Disease↗

Evolutionary analysis of vertebrate Notch genes.

We have conducted an evolutionary analysis of Notch genes of the vertebrates Danio rerio and Mus musculus to examine the expansion and diversification of the Notch family during vertebrate evolution. The existence of multiple Notch genes in vertebrate genomes suggests that the increase in Notch signaling pathways may be necessary for the additional complexity observed in the vertebrate body plan. However, orthology relationships within the vertebrate Notch family indicate that biological functions are not fixed within orthologous groups. Phylogenetic reconstruction of the vertebrate Notch family suggests that the zebrafish notch1a and 1b genes resulted from a duplication occurring around the time of the teleost/mammalian divergence. There is also evidence that the mouse Notch4 gene is the result of a rapid divergence from a Notch3-like gene. Investigation of the ankyrin repeat region sequences showed there to be little evidence for gene conversion events between repeat units. However, relationships between repeats 2-5 suggest that these repeats are the result of a tandem duplication of a dual repeat unit. Selective pressure on maintenance of ankyrin repeat sequences indicated by relationships between the repeats suggests that specific repeats are responsible for particular biological activities, a finding consistent with mutational studies of the Caenorhabditis elegans gene glp-1. Sequence similarities between the ankyrin repeats and the region immediately C-terminal of the repeats further suggests that this region may be involved in the modulation of ankyrin repeat function.

Amino Acid Sequence↗

Jagged2-expressing hematopoietic progenitors promote regulatory T cell expansion in the periphery through notch signaling.

Cellular interactions promoting the in vivo expansion of CD4(+)CD25(+)Foxp3(+) regulatory T (Treg) cells for maintenance of immune tolerance remain poorly defined. Here we report that mobilized Lin(-)Sca-1(+)c-kit(+) (LSK) hematopoietic progenitor cells (HPCs), unlike medullary hematopoietic stem cells (HSCs), selectively drove the direct, immediate expansion of functional host-derived Treg cells, thereby preventing the progression to overt spontaneous autoimmune diabetes in nonobese diabetic mice. Treg cell expansion required cell-to-cell contact and Notch3 signaling, which was mediated selectively through the Notch ligand Jagged2 expressed by the multipotent HPC subset, as assessed by small interfering RNA (siRNA) silencing. Conversely, notwithstanding their similar multilineage microchimerism, neither sorted Jagged2(-) HPCs nor Jagged2(lo) medullary HSCs were able to expand Treg cells. These data provide evidence for a productive Notch-mediated interaction between a unique subset of mobilized hematopoietic progenitors and Treg cells. They open therapeutic perspectives for autologous transplantation of Jagged2(+) LSK progenitors to promote Treg cell expansion in T cell-mediated diseases.

Adoptive Transfer↗

Target selectivity of vertebrate notch proteins. Collaboration between discrete domains and CSL-binding site architecture determines activation probability.

All four mammalian Notch proteins interact with a single DNA-binding protein (RBP-jkappa), yet they are not equivalent in activating target genes. Parallel assays of three Notch-responsive promoters in several cell lines revealed that relative activation strength is dependent on protein module and promoter context more than the cellular context. Each Notch protein reads binding site orientation and distribution on the promoter differently; Notch1 performs extremely well on paired sites, and Notch3 prefers single sites in conjunction with a proximal zinc finger transcription factor. Although head-head sites can elicit a Notch response on their own, use of CBS (CSL binding site) in tail-tail orientation is context-dependent. Bias for specific DNA elements is achieved by interplay between the N-terminal RAM (RBP-jkappa-associated molecule/ankyrin region), which interprets CBS proximity and orientation, and the C-terminal transactivation domain that interacts specifically with the transcription machinery or nearby factors. To confirm the prediction that modular design underscores the evolution of functional divergence between Notch proteins, we generated a synthetic Notch protein (Notch1 ankyrin with Notch3 transactivation domain) that displayed superior signaling strength on the hes5 promoter. Consistent with the prediction that "preferred" targets (Hes1) should respond faster and at lower Notch concentration than other targets, we showed that Hes5-GFP was extinguished fast and recovered slowly, whereas Hes1-GFP was inhibited late and recovered quickly after a pulse of DAPT in metanephroi cultures.

Animals↗

Analysis of coding-polymorphisms in NOTCH-related genes reveals NUMBL poly-glutamine repeat to be associated with schizophrenia in Brazilian and Danish subjects.

Abnormality in neurodevelopment is one of the most robust hypotheses on the etiology of schizophrenia and has found substantial support from brain imaging and genetic studies. Neurodevelopmental processes involve several signaling pathways, including the Notch, but little is known at present regarding their possible involvement in schizophrenia. In the present study we investigated the link of non-synonymous variants of five genes of the Notch pathway (NOTCH2, NOTCH3, JAGGED2, ASCL1 and NUMBL) to schizophrenia in a group of 200 Brazilian patients and 200-paired controls. Also, we replicated the association of the NUMBL variant, our most promising finding, in an unrelated set of 684 Danish patients and controls. When the Brazilian and Danish cohorts were merged, a total of 1084 subjects, we found the allele 18 CAG of NUMBL (p=0.003, x2=8.88, OR=1.30, 95% CI 1.09-1.56) as well as the 18/18 CAG genotype (p=0.002, x2=9.46, OR=1.46, 95% CI 1.15-1.87) to be associated with schizophrenia. The consistency of this finding in two independent and unrelated populations reinforces the veracity of this association.

Adult↗

Developmental regulation of Notch signaling genes in the embryonic pituitary: Prop1 deficiency affects Notch2 expression.

Normal development of the pituitary gland requires coordination between the maintenance of a progenitor cell pool and the selection of progenitor cells for differentiation. As Notch signaling controls progenitor cell differentiation in many embryonic tissues, we investigated the involvement of this important developmental pathway in the embryonic pituitary. We report that expression of Notch signaling genes is spatially and temporally regulated in pituitary embryogenesis and implicate Notch2 in the differentiation of several cell lineages. Notch2, Notch3, and Dll1 are initially expressed by most cells within the pituitary primordium and become restricted to a subset of the progenitor cell pool as differentiated pituitary cells begin to appear. Mutations in the transcription factor Prop1 interfere with pituitary growth and cell specification, although the mechanism is unknown. Notch2 expression is nearly absent in the developing pituitaries of Prop1 mutant mice, but unaltered in some other panhypopituitary mutants, revealing that Prop1 is directly or indirectly required for normal Notch2 expression. Transgenic overexpression of Prop1 is not sufficient for enhancement of endogenous Notch2 expression, indicating that there are multiple inputs into this pathway. Dll3 is expressed only in the presumptive corticotrope and melanotrope cells. Analysis of Dll3 null mutants indicates that Dll3 is not required for specification of these two cell types, although there may be functional overlap with Dll1. The spatial and temporal expression patterns of Notch signaling genes in the pituitary suggest overlapping roles in pituitary growth and cell specification.

Animals↗

Transit-amplifying ductular (oval) cells and their hepatocytic progeny are characterized by a novel and distinctive expression of delta-like protein/preadipocyte factor 1/fetal antigen 1.

Hepatic regeneration from toxic or surgical injury to the adult mammalian liver, endorses different cellular responses within the hepatic lineage. The molecular mechanisms determining commitment of a cell population at a specific lineage level to participate in liver repair as well as the fate of its progeny in the hostile environment created by the injury are not well defined. Based on the role of the Notch/Delta/Jagged system in cell fate specification and recent reports linking Notch signaling with normal bile duct formation in mouse and human liver, we examined the expression of Notch1, Notch2, Notch3, Delta1, Delta3, Jagged1, and Jagged2, and delta-like protein/preadipocyte factor 1/fetal antigen 1 (dlk) in four well-defined experimental rat models of liver injury and regeneration. Although Delta3 and Jagged2 were undetectable by reverse transcriptase-polymerase chain reaction and Northern blot, we observed the most significant up-regulation of all other transcripts in the 2-acetylaminofluorene-70% hepatectomy (AAF/PHx) model, in which liver mass is restored by proliferation and differentiation of transit-amplifying ductular (oval) cells. The most profound change was observed for dlk. Accordingly, immunohistochemical analyses in the AAF/PHx model showed a specific expression of dlk in atypical ductular structures composed of oval cells. Delta-like protein was not observed in proliferating hepatocytes or bile duct cells after partial hepatectomy or ligation of the common bile duct whereas clusters of dlk immunoreactive oval cells were found in both the retrorsine and the AAF/PHx models. Finally, we used dlk to isolate alpha-fetoprotein-positive cells from fetal and adult regenerating rat liver by a novel antibody panning technique.

Animals↗