Growth arrest-specific 1 (GAS1) acts as a co-receptor to patched 1, promoting sonic hedgehog (SHH) signaling in the developing nervous system. GAS1 mutations in humans and animal models result in forebrain and craniofacial malformations, defects ascribed to a function for GAS1 in SHH signaling during early neurulation. Here, we confirm loss of SHH activity in the forebrain neuroepithelium in GAS1-deficient mice and in induced pluripotent stem cell-derived cell models of human neuroepithelial differentiation. However, our studies document that this defect can be attributed, at least in part, to a novel role for GAS1 in facilitating NOTCH signaling, which is essential to sustain a persistent SHH activity domain in the forebrain neuroepithelium. GAS1 directly binds NOTCH1, enhancing ligand-induced processing of the NOTCH1 intracellular domain, which drives NOTCH pathway activity in the developing forebrain. Our findings identify a unique role for GAS1 in integrating NOTCH and SHH signal reception in neuroepithelial cells, and they suggest that loss of GAS1-dependent NOTCH1 activation contributes to forebrain malformations in individuals carrying GAS1 mutations.

Acute lymphoblastic leukemia (ALL) is the most common malignancy in pediatric patients. About 10-15% of pediatric ALL belong to T-cell ALL (T-ALL), which is characterized by aggressive expansion of immature T-lymphoblasts and is categorized as high-risk leukemia. Leukemia initiating cells represent a reservoir that is responsible for the initiation and propagation of leukemia. Its perinatal origin has been suggested in some childhood acute B-lymphoblastic and myeloblastic leukemias. Therefore, we hypothesized that child T-ALL initiating cells also exist during the perinatal period. In this study, T-ALL potential of the hematopoietic precursors was found in the para-aortic splanchnopleura (P-Sp) region, but not in the extraembryonic yolk sac (YS) of the mouse embryo at embryonic day 9.5. We overexpressed the Notch intracellular domain (NICD) in the P-Sp and YS cells and transplanted them into lethally irradiated mice. NICD-overexpressing P-Sp cells rapidly developed T-ALL while YS cells failed to display leukemia propagation despite successful NICD induction. These results suggest a possible role of fetal-derived T-cell precursors as leukemia-initiating cells.

Notch intracellular domain (NICD), also known as the activated form of Notch1 is closely associated with cell differentiation and tumor invasion. However, the role of NICD in glioblastoma (GBM) proliferation and the underlying regulatory mechanism remains unclear. The present study aimed to investigate the expression of NICD and Notch1 downstream gene HES5 in human GBM and normal brain samples and to further detect the effect of NICD on human GBM cell proliferation. For this purpose, western blotting and immunohistochemical staining were performed to analyze the expression of NICD in human GBM tissues, while western blotting and reverse-transcription quantitative PCR experiments were used to analyze the expression of Hes5 in human GBM tissues. A Flag-NICD vector was used to overexpress NICD in U87 cells and compound E and small interfering (si) Notch1 were used to downregulate NICD. Cellular proliferation curves were generated and BrdU assays performed to evaluate the proliferation of U87 cells. The results demonstrated that compared with normal brain tissues, the level of NICD protein in human GBM tissues was upregulated and the protein and mRNA levels of Hes5 were also upregulated in GBM tissues indicating that the Notch1 signaling pathway is activated in GBM. Overexpression of NICD promoted the proliferation of U87 cells in vitro while downregulation of NICD by treatment with compound E or siNotch1 suppressed the proliferation of U87 cells in vitro. In conclusion, NICD was upregulated in human GBM and NICD promoted GBM proliferation via the Notch1 signaling pathway. NICD may be a potential diagnostic marker and therapeutic target for GBM treatment.

Quiescent neural stem cells (NSCs) are occasionally activated to undergo proliferation and subsequent neuronal differentiation. It was previously shown that the transcriptional repressor Hes1 is involved in both active and quiescent states of NSCs: when Hes1 expression oscillates, it periodically represses the proneural gene Ascl1, thereby driving Ascl1 oscillations, which regulate the active state, while sustained Hes1 expression continuously suppresses Ascl1, promoting quiescence. However, it remains to be analyzed how the transition from quiescent to active states of NSCs is controlled. Here, we found that overexpression of the active form of Notch1 significantly activates NSCs in both in-vitro and in-vivo conditions and that its levels are proportional to NSC activation. The active form of Notch1 induces a burst of Hes1 oscillations in quiescent NSCs, and the frequency of Hes1 oscillations, rather than the Hes1 peak levels, correlates with the efficiency of NSC activation. These results raised the possibility that bursting Hes1 oscillations could increase the chance of Ascl1 oscillations in quiescent NSCs, suggesting that Notch1-induced Hes1 oscillation is a cue for a transition from quiescent to active states of NSCs.

OBJECTIVE: To investigate whether the Notch-Hif-1α signaling pathway is involved in liver regeneration.
METHODS: Rats were divided into two groups and treated with daily intraperitoneal injections of saline (control) or the gamma-secretase inhibitor, Fli-06, for 2 days. Two-thirds of the rat livers were resected and rats were later euthanized at specific time points post-resection to analyze the remnant livers. Each group\'s liver/body weight ratio was calculated, and immunostaining and western blotting were used to determine the cell proliferation marker, PCNA and Ki-67 expression. Real-time PCR and western blotting were used to compare the mRNA expression of Notch homolog-1 (Notch1), hairy and enhancer of split-1 (Hes1), and vascular endothelial growth factor (Vegf), and the protein expression of NICD and HIF-1α, respectively.
RESULTS: The liver/body weight ratios and number of Ki-67- and PCNA-positive cells were significantly lower in the experimental group than the control group, indicating lower levels of liver regeneration following the disruption of Notch signaling by Fli-06. The Hes1 and Vegf mRNA levels and NICD and HIF-1α protein expression levels were all down-regulated by Fli-06 treatment.
CONCLUSIONS: Notch-Hif-α signaling pathway activation plays an important role in liver regeneration, where it may contribute toward liver cell proliferation.

The release and nuclear translocation of the intracellular domain of Notch receptor (NICD) is the prerequisite for Notch signaling-mediated transcriptional activation. NICD is subjected to various posttranslational modifications including ubiquitination. Here, we surprisingly found that NUMB proteins stabilize the intracellular domain of NOTCH1 receptor (N1ICD) by regulating the ubiquitin-proteasome machinery, which is independent of NUMB\'s role in modulating endocytosis. BAP1, a deubiquitinating enzyme (DUB), was further identified as a positive N1ICD regulator, and NUMB facilitates the association between N1ICD and BAP1 to stabilize N1ICD. Intriguingly, BAP1 stabilizes N1ICD independent of its DUB activity but relying on the BRCA1-inhibiting function. BAP1 strengthens Notch signaling and maintains stem-like properties of cortical neural progenitor cells. Thus, NUMB enhances Notch signaling by regulating the ubiquitinating activity of the BAP1-BRCA1 complex.

Objective: To investigate the effect of overexpression of Notch intracellular domain (NICD) on proliferation and osteogenic differentiation of human periodontal ligament stem cells (hPDLSC). Methods: The third generation hPDLSC with stable overexpressing of NICD were assigned as experimental group, normal hPDLSC were as negative control group and hPDLSC transfected with empty vector were as blank control group. The effect of overexpressing NICD on proliferation ability of hPDLSC was detected by using cell counting kit-8 (CCK-8). Alizarin Red staining and real-time quantitative PCR (qPCR) were used to detect the effects of NICD on cementum attachment proteins (CAP), osteocalcin (OCN), Runt-related transcription factor 2 (RUNX2) and Notch signal pathway receptor Notch1. The effect of overexpressing NICD on hPDLSC osteogenic protein RUNX2 and flag marker protein (used to label NICD) were detected by using Western blotting. Results: CCK-8 results showed that there were no significant differences in A values amongst the three groups for 1-2 days (P>0.05). The number of cells in the experimental group was significantly increase than that of the two control groups from the third to seventh days (A values were 0.203±0.016, 0.364±0.014, 0.449±0.020, 0.549±0.020 and 0.570±0.020, respectively) (P<0.05). Alizarin red staining showed that compared with the blank control group and negative control group, the mineralized nodules in the experimental group had smaller formation range and lighter color, and the differences were statistically significant (P<0.05). The expressions of CAP gene (0.751±0.058, 0.887±0.025), osteocalcin gene (0.592±0.051, 0.670±0.045) and RUNX2 gene (0.319±0.038, 0.684±0.055) at 14 and 21 days in the experimental group were significantly lower than those in the negative control group respectively (P<0.05). However, the expression levels of Notch1 gene at 14 and 21 days (2.507±0.047, 4.041±0.219) were significantly higher than those of negative and blank control groups (P<0.05). The results of Western blotting showed that the expressions of flag marker protein (0.167±0.007, 0.204±0.010) at 14 and 21 days in the experimental group were significantly higher than those in the negative and blank control groups (P<0.05). However, the expressions of RUNX2 protein (0.075±0.006, 0.074±0.013) at 14 and 21 days were significantly lower than that in the negative control group (0.092±0.003, 0.118±0.008) and blank control group (0.174±0.006, 0.212±0.008) (P<0.05). Conclusions: Overexpression of NICD can promote the proliferation capacity of hPDLSC and inhibit its osteogenic differentiation.
目的： 探讨超表达Notch胞内结构域（Notch intracellular domain，NICD）对人牙周膜干细胞（human periodontal ligament stem cells，hPDLSC）增殖和成骨分化的影响，为牙周病骨缺损的治疗提供依据。 方法： 以第3代稳定超表达NICD的hPDLSC为实验组，以正常hPDLSC为阴性对照组，转染空载体的hPDLSC为空白对照组，通过细胞计数试剂盒（cell counting kit-8，CCK-8）检测超表达NICD对hPDLSC增殖能力的影响；通过茜素红染色和实时荧光定量PCR（real-time quantitative PCR，qPCR）检测超表达NICD对hPDLSC成骨相关基因：牙骨质附着蛋白（cementum attachment proteins，CAP）、骨钙蛋白、Runt相关转录因子2（Runt-related transcription factor 2，RUNX2），Notch信号通路受体Notch1的影响；通过蛋白质免疫印迹法检测超表达NICD对hPDLSC成骨蛋白RUNX2和flag标记蛋白（用以标记NICD）的影响。 结果： CCK-8结果显示，3组1~2 d的A值相比差异均无统计学意义（P>0.05）；实验组3~7 d的细胞数量（A值分别为0.203±0.016、0.364±0.014、0.449±0.020、0.549±0.020及0.570±0.020）与其他两组相比显著增加（P<0.05）。茜素红染色结果示，与空白对照组及阴性对照组相比，实验组染色的矿化结节形成范围小颜色浅；qPCR结果显示，实验组14及21 d CAP基因表达量（0.751±0.058、0.887±0.025）、骨钙蛋白基因表达量（0.592±0.051、0.670±0.045）及RUNX2基因表达量（0.319±0.038、0.684±0.055），均较阴性对照组及空白对照组显著降低（P<0.05），但14及21 d的Notch1表达水平（2.507±0.047、4.041±0.219）显著高于阴性对照组及空白对照组（P<0.05）。蛋白质印迹法结果显示，实验组14及21 d flag标记蛋白表达量（0.167±0.007、0.204±0.010）均显著高于阴性对照组及空白对照组（P<0.05），但RUNX2的蛋白表达量（0.075±0.006、0.074±0.013）均显著低于阴性对照组（0.092±0.003、0.118±0.008）及空白对照组（0.174±0.006、0.212±0.008）（P<0.05）。 结论： 超表达NICD可以促进hPDLSC的增殖能力，同时抑制其成骨分化。.

BACKGROUND: The Notch signaling pathway plays an important role in regulating human immune function, but the relationship between allergic rhinitis (AR) and Notch signaling remains unclear.
OBJECTIVE: To investigate the role of Notch signaling in the pathogenesis of AR and its regulation on Foxp3-Treg cells.
METHODS: The sera of 100 patients with AR and 50 controls were collected to assess the differences in Notch1, Jagged1, and DLL1 (Delta-like 1) expression. Experimental mice were divided into normal control, AR, Notch inhibitor, and dexamethasone groups. Allergic symptoms, total IgE levels, and the proportion of Treg cells in the peripheral blood were detected. Notch1, Jagged1, NICD (Notch intracellular domain, also known as ICN), and Foxp3 expression and Th1/Th2/Th17-related cytokines in the spleen were detected and compared between each group of mice.
RESULTS: Compared with the control group, the expression of Notch1 and Jagged1 in patients with AR was significantly elevated (p < 0.05). The expression of Notch1 and Jagged1 in patients with severe AR was higher than that observed in the mild to moderate AR patients and positively correlated with the levels of allergen sIgE (p < 0.05). The animal experiments revealed that compared with the normal control group, the expression of Notch1, Jagged1, and NICD in the AR group was increased, Foxp3 expression was decreased, and the proportion of Treg cells was decreased (p < 0.05). Compared with the AR group, allergic symptoms and total serum IgE levels and the expression of Notch1, Jagged1, and NICD were significantly decreased in the Notch inhibited group, whereas the expression of Foxp3 and the proportion of Treg cells were increased significantly (p < 0.05). The Th2-type immune responses were also enhanced and Th1-type immune responses decreased in the AR group, but the Th1/Th2 imbalance was reversed in the Notch inhibited group.
CONCLUSIONS: Notch signaling downregulates Foxp3 expression and inhibits the differentiation of Treg cells to promote the development of AR. Blocking Notch signaling may be a potential treatment for AR.

The mutant form of the protein ataxin-1 (ATXN1) causes the neurodegenerative disease spinocerebellar ataxia type-1. Recently, ATXN1 was reported to enhance E-cadherin expression in the breast cancer cell line MCF-7, suggesting a potential association between ATXN1 and cancer development. In the present study, we discovered a novel mechanism through which ATXN1 regulates the epithelial-mesenchymal transition (EMT) of cancer cells. Hypoxia-induced upregulation of the Notch intracellular domain expression decreased ATXN1 expression via MDM2-associated ubiquitination and degradation. In cervical cancer cells, ATXN1 knockdown induced EMT by directly regulating Snail expression, leading to matrix metalloproteinase activation and the promotion of cell migration and invasion. These findings provide insights into a novel mechanism of tumorigenesis and will facilitate the development of new and more effective therapies for cancer.

The multiple-layer structure of the cerebral cortex is important for its functions. Such a structure is generated based on the proliferation and differentiation of neural stem/progenitor cells. Notch functions as a molecular switch for neural stem/progenitor cell fate during cortex development but the mechanism remains unclear. Biochemical and cellular studies showed that Notch receptor activation induces several proteases to release the Notch intracellular domain (NICD). A Disintegrin and Metalloprotease 10 (ADAM10) might be a physiological rate-limiting S2 enzyme for Notch activation. Nestin-driven conditional ADAM10 knockout in mouse cortex showed that ADAM10 is critical for maintenance of the neural stem cell population during early embryonic cortex development. However, the expression pattern and function of ADAM10 during later cerebral cortex development remains poorly understood. We performed in situ hybridization for ADAM10 mRNA and immunofluorescent analysis to determine the expression of ADAM10 and NICD in mouse cortex from embryonic day 9 (E14.5) to postnatal day 1 (P1). ADAM10 and NICD were highly co-localized in the cortex of E16.5 to P1 mice. Comparisons of expression patterns of ADAM10 with Nestin (neural stem cell marker), Tuj1 (mature neuron marker), and S100β (glia marker) showed that ADAM10 expression highly matched that of S100β and partially matched that of Tuj1 at later embryonic to early postnatal cortex developmental stages. Such expression patterns indicated that ADAM10-Notch signaling might have a critical function in neuronal maturation and gliogenesis during cortex development.