Academic literature on the topic 'Notch genes. Mice Notch genes Mice'

1064 Background: The Notch pathway is activated during mammary gland development and has been implicated as a key driver in breast cancer. There is an urgent need to identify new therapeutic strategies for triple-negative breast cancer (TNBC), a sub-type associated with poor prognosis and no available targeted therapies. Notch gain of function (GOF) genetic alterations are potential tumor drivers found in ~10% of TNBC. This motivated the development of Notch inhibitors, including AL101 a pan-Notch, gamma secretase inhibitor (J Clin Oncol 36, 2018 abstract 2515). AL101 is currently being evaluated in Adenoid Cystic Carcinoma patients with activating Notch mutations (NCT03691207, ACCURACY trial). Here, we aim to test the activity of AL101 in TNBC patient derived xenograft (PDX) models with Notch activating genetic alterations. Methods: Gene expression cluster analysis was performed for 38 TNBC PDX tumors using a list of 21 Notch target genes. Seven tumors, bearing a “Notch-on” signature, were enriched with mutated/fusion (M/F) Notch genes and clustered separately from all other tumors. Of 9 models selected for study, 4 had a Notch-on signature and were expected to respond to AL101. Tumors were implanted into female athymic nude mice. Once tumors reached an average size of 150-300 mm3, mice (n = 5/group) were randomized to Vehicle or AL101 treatment arms (3 mg/kg, PO, 4on/3off) until tumors reached 1500 mm3 or day 60. Results: As measured by tumor growth inhibition (TGI), AL101 was more potent in tumors with a putative Notch-on signature. Within these 4 models, M/F genes were present in Notch1-NRR GOF (103% TGI p = 0.0004); Notch2-fusion (62%TGI p = 0.036); Notch3-fusion (75% TGI p = 0.032); or Notch4-fusion (147% TGI p < 0.00001). Tumors lacking the Notch signature did not respond significantly to AL101: WT Notch (43% TGI p = 0.0104; 64% TGI p = 0.13); Notch1 with a predicted loss of function mutation (12% TGI p = 0.53), Notch1 Variant of Unknown Significance (VUS) (30% TGI p = 0.44), Notch2 VUS (41% TGI p = 0.44). Conclusions: We demonstrate that in TNBC PDX models, the presence of a Notch-on signature and Notch GOF mutations/fusions correlates with potent response to AL101. These data support the clinical development of AL101 as a targeted therapy for TNBC with Notch GOF alterations.

Ischemic acute kidney injury (AKI) is associated with high morbidity and frequent complications. Repeated episodes of AKI may lead to end-stage renal failure. The pathobiology of regeneration in AKI is not well understood and there is no effective clinical therapy that improves regeneration. The Notch signaling pathway plays an essential role in kidney development and has been implicated in tissue repair in the adult kidney. Here, we found that kidneys after experimental AKI in mice showed increased expression of Notch receptors, specifically Notch1-3, of the Notch ligands Jagged-1 (Jag1), Jag2 and Delta-like-4 (Dll4) and of the Notch target genes Hes1, Hey2, HeyL, Sox9 and platelet-derived growth factor receptor β (Pdgfrb). Treatment of ischemic mice with the γ-secretase inhibitor DBZ blocked Notch signaling and specifically downregulated the expression of Notch3 and the Notch target genes Hes1, Hey2, HeyL and Pdgfrb. After DBZ treatment, the mice developed less interstitial edema and displayed altered interstitial inflammation patterns. Furthermore, serum urea and creatinine levels were significantly decreased from 6 h onwards when compared to control mice treated with DMSO only. Our data are consistent with an amelioration of the severity of kidney injury by blocking Notch activation following AKI, and suggest an involvement of Notch-regulated Pdgfrb in AKI pathogenesis.

Abstract Notch1 and Notch2 receptor-mediated signaling appear to have important and unique roles in lymphoid lineage commitment. Notch1 is required for T cell development, while Notch2 is essential for marginal zone B cell development. This specificity is not completely explained by differential expression patterns of Notch1 and 2 or Notch ligands, suggesting that there are other genes that contribute to specifying Notch receptor functions. We have previously shown that the MAML family of transcriptional co-activators is essential for Notch-induced transcriptional events, and functions by forming ternary complexes with Notch and the transcription factor CSL in the nucleus. This MAML family currently consists of three members, MAML1-3, all of which can function as co-activators for Notch receptors in vitro . In this study, we investigated the possibility that MAML1 co-activator contributes to determining Notch receptor function by generating mice deficient in the Maml1 gene. Maml1 -deficient mice fail to thrive and die within 10 days of birth. The morphology of marrow, nodes, and spleen was grossly intact. The ability of Maml1-deficient stem cells to generate different T and B lineages of lymphoid cells was determined by transplanting fetal liver cells isolated from E14.5 embryos into lethally irradiated wild-type recipient mice and analyzing donor-derived lymphoid cells 12 weeks post-transplantation. We found that the deletion of Maml1 results in complete loss of marginal zone B cell lineage (MZB, defined by B220+CD21hiCD23lo). Moreover, the number of MZB cells was reduced to about 50% in Maml1 -heterozygous fetal liver chimeras as compared to wild type controls. However, T cell development was largely unaffected, with only a modest but significant increase in the number of γδ T cells (about 2 fold) in both the thymus and the spleen. Therefore, these results suggest the unexpected finding that targeted deletion of Maml1 in hematopoietic cells is similar to the targeted deletion of either Notch2 or the Notch ligand, Delta-like 1 (Dll1) resulting in the loss of marginal zone B cells and minimal effects on T cell development. Moreover, the number of marginal zone B cells is correlated with Maml1 gene dosage, indicating haploinsufficiency. These data suggest that the Notch ligand Dll1 activates Notch2 signaling resulting in a Notch2/MAML1/CSL complex that is essential for marginal zone B cell development. Further studies with respect to relative expression levels of various MAML genes and interactions of MAML co-activators and Notch receptors may shed additional light into understanding how different Notch receptors regulate cell fate decisions in hematopoiesis.

Signaling through Notch receptors has been implicated in the control of cellular differentiation in animals ranging from nematodes to humans. Starting from a human expressed sequence tag-containing sequence resembling that of Serrate, the gene for a ligand of Drosophila melanogaster Notch, we assembled a full-length cDNA, now called human Jagged2, from overlapping cDNA clones. The full-length cDNA encodes a polypeptide having extensive sequence homology to Serrate (40.6% identity and 58.7% similarity) and even greater homology to several putative mammalian Notch ligands that have subsequently been described. When in situ hybridization was performed, expression of the murine Jagged2 homolog was found to be highest in fetal thymus, epidermis, foregut, dorsal root ganglia, and inner ear. In Northern blot analysis of RNA from tissues of 2-week-old mice, the 5.0-kb Jagged2 transcript was most abundant in heart, lung, thymus, skeletal muscle, brain, and testis. Immunohistochemistry revealed coexpression of Jagged2 and Notch1 within thymus and other fetal murine tissues, consistent with interaction of the two proteins in vivo. Coculture of fibroblasts expressing human Jagged2 with murine C2C12 myoblasts inhibited myogenic differentiation, accompanied by increased Notch1 and the appearance of a novel 115-kDa Notch1 fragment. Exposure of C2C12 cells to Jagged2 led to increased amounts of Notch mRNA as well as mRNAs for a second Notch receptor, Notch3, and a second Notch ligand, Jagged1. Constitutively active forms of Notchl in C2C12 cells also induced increased levels of the same set of mRNAs, suggesting positive feedback control of these genes initiated by binding of Jagged2 to Notch1. This feedback control may function in vivo to coordinate differentiation across certain groups of progenitor cells adopting identical cell fates.

Abstract When stem cells first enter the thymus and become early T-cell precursor (ETP) cells, they are exposed to high levels of Notch1 ligand. Notch1 signal strength must be tightly regulated because on one hand, excessive Notch1 signals drive premature T-cell commitment, resulting in loss of ETP cells and alternative cell fates. On the other hand, complete loss of Notch1 signals impairs ETP proliferation, also resulting in loss of ETP cells. Thus, keeping Notch signals finely balanced in ETP cells preserves "stemness". However, after ETP cells commit to the T-cell lineage by the DN3 cell stage, Notch1 signals ramp up dramatically to drive proliferation. It is unclear how Notch1 signals are initially restrained and then amplified. We previously showed that the PIAS-like coregulator Zmiz1 is a direct, context-dependent cofactor of Notch1 in T-cell leukemia. In contrast to drosophila Zmiz1, mammalian Zmiz1 evolved a tetratricopeptide repeat (TPR) domain that binds directly to Notch1 and selectively induces oncogenic target genes such as Myc through its transactivation domain (TAD). To understand the role of Zmiz1 in T-cell development, we bred conditional Zmiz1 and Notch1 knockout mice to Cre strains that delete floxed genes in hematopoietic cells (VavCre/MxCre), in early T cells (LckCre), and in late T-cells (CD4Cre). Like deletion of Notch1, deletion of Zmiz1 caused an early defect at the ETP stage and a late defect at the DN3 stage. The defect with Zmiz1 deletion was less severe than with Notch1 deletion (~4-fold reduction for Zmiz1 deletion versus ~8-fold reduction for Notch1 deletion). Unexpectedly, the ETP defect in Zmiz1-deficient mice partially phenocopied excessive Notch1 activation with increased differentiation to DN2 cells and loss of ETP cells and alternative cell fates (myeloid and NK). To confirm this effect, we plated Zmiz1-deficient hematopoietic stem and progenitor cells (HSPCs) directly on OP9-DL stromal cells. Accordingly, these cultures recapitulated the in vivo phenotype, including suppression of myeloid cells. Reducing Notch signals slightly with modest doses of Notch inhibitors restored myeloid differentiation. In contrast to the ETP defect, the DN3 defect resembled Notch1 loss-of function. Accordingly, overexpression of activated Notch1 or a fusion protein containing only the Notch-interacting domain (TPR) and the TAD was sufficient to rescue the DN3 block. To determine mechanism, we performed RNA-Seq in sorted ETP and DN3 cells from Zmiz1-deficient mice and mice treated with the anti-NRR Notch1 antibody. Zmiz1 coregulated ~16% of Notch1 target genes in ETP cells and ~24% in DN3 cells. In ETP cells, Zmiz1 primarily acted as a repressor of Notch1 target genes. Enrichment analyses showed that Notch1 promoted changes associated with T-lineage commitment, such as induction of Dtx1, Notch3, and Ptcra. In contrast, Zmiz1 reversed these changes. Although generally antagonistic with each other, Zmiz1 and Notch1 concordantly activated a minority of target genes important for proliferation, such as Myc. Upon differentiation to the DN3 cell stage, Zmiz1 switched from primarily a repressor of Notch1 target genes to primarily an activator, inducing Myc and Wnt pathway genes. Accordingly, overexpression of Myc in Zmiz1-deficient DN3 cells was sufficient to rescue the DN3 block in OP9-DL culture. To determine whether Zmiz1 needed to bind Notch1 in order activate or repress Notch1 target genes, we used HSQC NMR to identify amino acids in the TPR that were required for Notch1 binding. Two amino acids, R14 and E34, were confirmed by reporter and co-IP assays to be critical for the Zmiz1-Notch1 interaction. The Zmiz1(R14A+E34A) mutant, which was incapable of binding Notch1, failed to induce Myc. In contrast, this mutant retained full ability to repress Notch target genes associated with T-cell commitment. These data suggest that in ETP cells, Zmiz1 preferentially restrains Notch1 T-cell commitment genes. However, after T-lineage commitment, Zmiz1 switches primarily into a Notch1-interaction mode that preferentially promotes Notch1 signals. It has been puzzling how Notch1 can drive seemingly conflicting biological processes of self-renewal and commitment. Zmiz1 appears to be one solution that evolved to differentially regulate Notch1 signals at a given Notch dosage strength in order to preserve ETP "stemness" while at the same time expanding committed T cells. Disclosures No relevant conflicts of interest to declare.

Abstract Signaling mediated by various Notch receptors and their ligands regulates diverse biological processes, including lymphoid cell fate decisions. Notch1 is required during T-cell development, while Notch2 and the Notch ligand Delta-like1 control marginal zone B (MZB) cell development. We previously determined that Mastermind-like (MAML) transcriptional coactivators are required for Notchinduced transcription by forming ternary nuclear complexes with Notch and the transcription factor CSL. The 3 MAML family members (MAML1-MAML3) are collectively essential for Notch activity in vivo, but whether individual MAMLs contribute to the specificity of Notch functions is unknown. Here, we addressed this question by studying lymphopoiesis in the absence of the Maml1 gene. Since Maml1−/− mice suffered perinatal lethality, hematopoietic chimeras were generated with Maml1−/−, Maml1+/−, or wild-type fetal liver progenitors. Maml1 deficiency minimally affected T-cell development, but was required for the development of MZB cells, similar to the phenotype of Notch2 deficiency. Moreover, the number of MZB cells correlated with Maml1 gene dosage. Since all 3 Maml genes were expressed in MZB cells and their precursors, these results suggest that Maml1 is specifically required for Notch2 signaling in MZB cells.

Notch family genes encode transmembrane proteins involved in cell-fate determination. Using gene targeting procedures, we disrupted the mouse Notch2 gene by replacing all but one of the ankyrin repeat sequences in the cytoplasmic domain with the E. coli (beta)-galactosidase gene. The mutant Notch2 gene encodes a 380 kDa Notch2-(beta)-gal fusion protein with (beta)-galactosidase activity. Notch2 homozygous mutant mice die prior to embryonic day 11.5, whereas heterozygotes show no apparent abnormalities and are fully viable. Analysis of Notch2 expression patterns, revealed by X-gal staining, demonstrated that the Notch2 gene is expressed in a wide variety of tissues including neuroepithelia, somites, optic vesicles, otic vesicles, and branchial arches, but not heart. Histological studies, including in situ nick end labeling procedures, showed earlier onset and higher incidence of apoptosis in homozygous mutant mice than in heterozygotes or wild type mice. Dying cells were particularly evident in neural tissues, where they were seen as early as embryonic day 9.5 in Notch2-deficient mice. Cells from Notch2 mutant mice attach and grow normally in culture, demonstrating that Notch2 deficiency does not interfere with cell proliferation and that expression of the Notch2-(beta)-gal fusion protein is not toxic per se. In contrast to Notch1-deficient mice, Notch2 mutant mice did not show disorganized somitogenesis, nor did they fail to properly regulate the expression of neurogenic genes such as Hes-5 or Mash1. In situ hybridization studies show no indication of altered Notch1 expression patterns in Notch2 mutant mice. The results indicate that Notch2 plays an essential role in postimplantation development in mice, probably in some aspect of cell specification and/or differentiation, and that the ankyrin repeats are indispensable for its function.

Abstract Abstract 1191 Objective: Hematopoietic stem cells (HSCs) can either self-renew or differentiate into various types of cells of the blood lineage. Little is known about the signaling pathways that regulate this choice of self-renewal versus differentiation. We studied the effect of altered Notch signaling on HSC differentiation in mouse models of Fanconi anemia (FA), a genetic disorder associated with bone marrow failure and progression to leukemia and other cancers. Methods: The study used a Notch reporter mouse, in which Notch-driven GFP expression acts as a sensor for HSC differentiation. Long-term hematopoietic stem cell (LT-HSC) and multipotential progenitor (MPP) cell compartments, as well as GFP expression in different cell populations were detected by Flow Cytometry analysis using primary bone marrow cells from Notch-eGFP-WT, Notch-eGFP-Fanca−/− or Notch-eGFP-Fancc−/− mice. Cell Cycle analysis was performed to distinguish the difference of quiescent state in GFP-gated LSK cells from these Notch-eGFP reporter mice. Colony forming units (CFU) assay and bone marrow transplantation (BMT) were utilized to determine HSC self-renew capacity. Gene arrays for pathways involved in DNA repair, cell cycle control, anti-oxidant defense, inflammatory response and apoptotic signaling were employed to define the gene expression signatures of the MPP population. Results and conclusions: In mice expressing a transgenic Notch reporter, deletion of the Fanca or Fancc gene enhanced Notch signaling in MPPs, which was correlated with decreased phenotypic long-term HSCs and increased formation of MPP1 progenitors. Furthermore, we found a functional correlation between Notch signaling and self-renewal capacity in FA hematopoietic stem and progenitor cells (HSPCs). Significantly, we show that FA deficiency in MPPs deregulates a complex network of genes in the Notch and canonical NF-kB pathways. Specifically, enhanced Notch signaling in FA MPPs was associated with the unregulation of genes involved in inflammatory and stress responses (including Rela, Tnfrsf1b, Gadd45b, Sod2, Stat1, Irf1 and Xiap), cell-cycle regulation (including Ccnd1, Cdc16, Cdkn1a, Gsk3b, Notch2 and Nr4a2), and transcription regulation (including Rela, Stat1, Hes1, Hey1, Hoxb4, Notch1 and Notch2). Consequently, TNF-a stimulation enhanced Notch signaling of FA LSK cells, leading to decreased HSC quiescence and compromised HSC self-renewal. Finally, genetic ablation of NF-kB reduced Notch signaling in FA MPPs to nearly wide-type level, and blocking either NF-kB or Notch signaling partially restored FA HSC quiescence and self-renewal capacity. Translational Applicability: The study identifies a functional interaction between the FA pathway and Notch signaling in HSC differentiation and establishes a role of FA proteins in the control of balance between renewal and lineage commitment, hence contributing to hematopoiesis. These findings indicate that the Notch signaling pathway may represent a novel and therapeutically accessible pathway in FA. Disclosures: No relevant conflicts of interest to declare.

Skeletal development and remodeling of adult bone are critically controlled by activated NOTCH signaling in genetically modified mice. It is yet unclear whether NOTCH signaling is activated by mechanical strain sensed by bone cells. We found that expression of specific NOTCH target genes is induced after in vivo tibial mechanical loading in wild-type mice. We further applied mechanical strain through cyclic stretching in human bone marrow-derived mesenchymal stromal cells (BMSCs) in vitro by using a bioreactor system and detected upregulation of NOTCH target gene expression. Inhibition of the NOTCH pathway in primary BMSCs as well as telomerase-immortalized human BMSCs (hMSC-TERT) through the gamma-secretase inhibitor GSI XII blocked mechanotransduction and modulated actin cytoskeleton organization. Short-hairpin RNA gene silencing identified NOTCH2 as the key receptor mediating NOTCH effects on hMSC-TERT cells. Our data indicate a functional link between NOTCH activation and mechanotransduction in human BMSCs. We suggest that NOTCH signaling is an important contributor to molecular mechanisms that mediate the bone formation response to mechanical strain.

Abstract Ovarian follicles form through a process in which somatic pregranulosa cells encapsulate individual germ cells from germ cell syncytia. Complementary expression of the Notch ligand, Jagged1, in germ cells and the Notch receptor, Notch2, in pregranulosa cells suggests a role for Notch signaling in mediating cellular interactions during follicle assembly. Using a Notch reporter mouse, we demonstrate that Notch signaling is active within somatic cells of the embryonic ovary, and these cells undergo dramatic reorganization during follicle histogenesis. This coincides with a significant increase in the expression of the ligands, Jagged1 and Jagged2; the receptor, Notch2; and the target genes, Hes1 and Hey2. Histological examination of ovaries from mice with conditional deletion of Jagged1 within germ cells (J1 knockout [J1KO]) or Notch2 within granulosa cells (N2 knockout [N2KO]) reveals changes in follicle dynamics, including perturbations in the primordial follicle pool and antral follicle development. J1KO and N2KO ovaries also contain multi-oocytic follicles, which represent a failure to resolve germ cell syncytia, and follicles with enlarged oocytes but lacking somatic cell growth, signifying a potential role of Notch signaling in follicle activation and the coordination of follicle development. We also observed decreased cell proliferation and increased apoptosis in the somatic cells of both conditional knockout lines. As a consequence of these defects, J1KO female mice are subfertile; however, N2KO female mice remain fertile. This study demonstrates important functions for Jagged1 and Notch2 in the resolution of germ cell syncytia and the coordination of somatic and germ cell growth within follicles of the mouse ovary.