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Aberrations of Notch signaling in humans cause both congenital and acquired defects and cancers. Genetically engineered mice provide the most efficient and cost-effective models to study Notch signaling in a mammalian system. Here, we review the various types of genetic models, tools, and strategies to study Notch signaling in mice, and provide examples of their use. We also provide advice on breeding strategies for conditional mutant mice, and a protocol for tamoxifen administration to mouse strains expressing inducible Cre recombinase-estrogen receptor fusion proteins.

Conclusion: Jagged1-mediated Notch signaling regulates hair cell (HC) production in a distinct way rather than lateral inhibition mediated by Hes1 and Hes5. Jagged1 may interact with Notch3, probably via candidate downstream mediators Hesr1 and Hesr2, regulating the prosensory formation in the early stage. Objectives: To explore the function of the Jagged1-mediated Notch signaling pathway in mammalian inner ear development and its possible mechanism. Methods: Using conditional gene targeting, a novel Jagged1 conditional knockout (Jag1-cko), Pax8cre/+; Jag1flox/flox, was established. The auditory brainstem response and swim ability test were utilized to identify functional disability. The expression of Jagged1, Notch3, Hes1, Hesr1, and Hesr2 was detected by immunofluorescence and immunohistochemistry. Results: Our Jag1-cko model was established and survived well. It presented hearing impairment and balance disturbance with 'waltzing' behavior. Cochleae and vestibular apparatus were all found in our Jag1-cko model. Patch deficiency of outer hair cells (OHCs) was found on the apical and middle turns of the auditory epithelium. OHCs were totally missing on the basal turn. The stereociliary bundles were disorientated on the cristae. Unlike Hes1, no expression of Notch3, Hesr1, and Hesr2 was found on embryonic day 13.5 of the Jag1-cko model. [ABSTRACT FROM AUTHOR]

Presents research which showed that mice homozygous for a targeted mutation of the lunatic fringe (Lfng) gene have defects in somite formation and anterior-posterior patterning of the somites. Development of segmentation in vertebrates; Role of the Notch signaling pathway; Fringe gene in Drosophila; Irregularities of somites; Results of marker analysis; Importance of Lfng encoding.

[Display omitted] • Notch signaling is essential to maintain radial glial cells (RGCs). • The functional relationship between Notch1 and Notch2 in RGCs is elusive. • Notch1 knockout affected RGC maintenance in early to mid-neurogenesis. • Notch1 and Notch2 function together for RGC maintenance in late neurogenesis. During mammalian corticogenesis, Notch signaling is essential to maintain neural stem cells called radial glial cells (RGCs) and the cortical architecture. Because the conventional knockout of either Notch1 or Notch2 causes a neuroepithelial loss prior to neurogenesis, their functional relationship in RGCs remain elusive. Here, we investigated the impacts of single knockout of Notch1 and Notch2 genes, and their conditional double knockout (DKO) on mouse corticogenesis. We demonstrated that Notch1 single knockout affected RGC maintenance in early to mid-neurogenesis whereas Notch2 knockout caused no apparent defect. In contrast, Notch2 plays a role in the RGC maintenance as Notch1 does at the late stage. Notch1 and Notch2 DKO resulted in the complete loss of RGCs, suggesting their cooperative function. We found that Notch activity in RGCs depends on the Notch gene dosage irrespective of Notch1 or Notch2 at late neurogenic stage, and that Notch1 and Notch2 have a similar activity, most likely due to a drastic increase in Notch 2 transcription. Our results revealed that Notch1 has an essential role in establishing the RGC pool during the early stage, whereas Notch1 and Notch2 subsequently exhibit a comparable function for RGC maintenance and neurogenesis in the late neurogenic period in the mouse telencephalon. [ABSTRACT FROM AUTHOR]

Graft-versus-host disease (GVHD) is the main complication of allogeneic bone marrow transplantation. Current strategies to control GVHD rely on global immunosuppression. These strategies are incompletely effective and decrease the anticancer activity of the allogeneic graft. We previously identified Notch signaling in T cells as a new therapeutic target for preventing GVHD. Notch-deprived T cells showed markedly decreased production of inflammatory cytokines, but normal in vivo proliferation, increased accumulation of regulatory T cells, and preserved anticancer effects. Here, we report that γ-secretase inhibitors can block all Notch signals in alloreactive T cells, but lead to severe on-target intestinal toxicity. Using newly developed humanized antibodies and conditional genetic models, we demonstrate that Notch1/Notch2 receptors and the Notch ligands Delta-like1/4 mediate all the effects of Notch signaling in T cells during GVHD, with dominant roles for Notch1 and Delta-like4. Notch1 inhibition controlled GVHD, but led to treatment-limiting toxicity. In contrast, Delta-like1/4 inhibition blocked GVHD without limiting adverse effects while preserving substantial anticancer activity. Transient blockade in the peritransplant period provided durable protection. These findings open new perspectives for selective and safe targeting of individual Notch pathway components in GVHD and other T cell-mediated human disorders. [ABSTRACT FROM AUTHOR]

Formation of a fully functional artery proceeds through a multistep process. Here we show that Notch3 is required to generate functional arteries in mice by regulating arterial differentiation and maturation of vascular smooth muscle cells (vSMC). In adult Notch3-/- mice distal arteries exhibit structural defects and arterial myogenic responses are defective. The postnatal maturation stage of vSMC is deficient in Notch3-/- mice. We further show that Notch3 is required for arterial specification of vSMC but not of endothelial cells. Our data reveal Notch3 to be the first cell-autonomous regulator of arterial differentiation and maturation of vSMC. [ABSTRACT FROM AUTHOR]