References of "Schurmans, Stéphane"
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See detailRasa3 Controls Megakaryocyte Rap1 Activation, Integrin Signaling and Differentiation into Proplatelet
Molina Ortiz, Patricia ULg; Polizzi, Séléna; Ramery, Eve ULg et al

in PLoS Genetics (2014), 10(6), 1004420

Rasa3 is a GTPase activating protein of the GAP1 family which targets Ras and Rap1. Ubiquitous Rasa3 catalytic inactivation in mouse results in early embryonic lethality. Here, we show that Rasa3 ... [more ▼]

Rasa3 is a GTPase activating protein of the GAP1 family which targets Ras and Rap1. Ubiquitous Rasa3 catalytic inactivation in mouse results in early embryonic lethality. Here, we show that Rasa3 catalytic inactivation in mouse hematopoietic cells results in a lethal syndrome characterized by severe defects during megakaryopoiesis, thrombocytopenia and a predisposition to develop preleukemia. The main objective of this study was to define the cellular and the molecular mechanisms of terminal megakaryopoiesis alterations. We found that Rasa3 catalytic inactivation altered megakaryocyte development, adherence, migration, actin cytoskeleton organization and differentiation into proplatelet forming megakaryocytes. These megakaryocyte alterations were associated with an increased active Rap1 level and a constitutive integrin activation. Thus, these mice presented a severe thrombocytopenia, bleeding and anemia associated with an increased percentage of megakaryocytes in the bone marrow, bone marrow fibrosis, extramedular hematopoiesis, splenomegaly and premature death. Altogether, our results indicate that Rasa3 catalytic activity controls Rap1 activation and integrin signaling during megakaryocyte differentiation in mouse. [less ▲]

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See detailSHIP2 signaling in normal and pathological situations: Its impact on cell proliferation.
Elong Edimo, W; Schurmans, Stéphane ULg; Roger, PP et al

in Advances in Biological Regulation (2014), 54

Phosphoinositide 5-phosphatases are critical enzymes in modulating the concentrations of PI(3,4,5)P3, PI(4,5)P2 and PI(3,5)P2. The SH2 domain containing inositol 5-phosphatases SHIP1 and SHIP2 belong to ... [more ▼]

Phosphoinositide 5-phosphatases are critical enzymes in modulating the concentrations of PI(3,4,5)P3, PI(4,5)P2 and PI(3,5)P2. The SH2 domain containing inositol 5-phosphatases SHIP1 and SHIP2 belong to this family of enzymes that dephosphorylate the 5 position of PI(3,4,5)P3 to produce PI(3,4)P2. Data obtained in zebrafish and in mice have shown that SHIP2 is critical in development and growth. Exome sequencing identifies mutations in the coding region of SHIP2 as a cause of opsismodysplasia, a severe but rare chondrodysplasia in human. SHIP2 has been reported to have both protumorigenic and tumor suppressor function in human cancer very much depending on the cell model. This could be linked to the relative importance of PI(3,4)P2 (a product of SHIP2 phosphatase activity) which is also controlled by the PI 4-phosphatase and tumor suppressor INPP4B. In the glioblastoma cell line 1321 N1, that do not express PTEN, lowering SHIP2 expression has an impact on the levels of PI(3,4,5)P3, cell morphology and cell proliferation. It positively stimulates cell proliferation by decreasing the expression of key regulatory proteins of the cell cycle such as p27. Together the data point out to a role of SHIP2 in development in normal cells and at least in cell proliferation in some cancer derived cells. [less ▲]

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See detailInositol trisphosphate 3-kinase B is increased in human Alzheimer brain and exacerbates mouse Alzheimer pathology
Stygelbout, V.; Leroy, K.; Pouillon, V. et al

in Brain : A Journal of Neurology (2014), 137

S. Schurmans and J.-P. Brion contributed equally to this work Corresponding author: S. Schurmans, Laboratoire de Génétique Fonctionnelle, GIGA-Research Centre, Building 34, Université de Liège, rue de ... [more ▼]

S. Schurmans and J.-P. Brion contributed equally to this work Corresponding author: S. Schurmans, Laboratoire de Génétique Fonctionnelle, GIGA-Research Centre, Building 34, Université de Liège, rue de l’Hôpital 1, 4000-Liège, Belgium. Abstract: Inositol (1,4,5) trisphosphate 3-kinase B phosphorylates inositol 1,4,5-trisphosphate into inositol 1,3,4,5-tetrakisphosphate and controls signal transduction in various hematopoietic cells. Surprisingly, it has been reported that Inositol (1,4,5) trisphosphate 3-kinase B mRNA level is significantly increased in the cerebral cortex of Alzheimer patients, compared to control subjects. Since Extracellular signal-regulated kinases 1/2 activation is increased in Alzheimer brain and since Inositol (1,4,5) trisphosphate 3-kinase B is a regulator of Extracellular signal-regulated kinases 1/2 activation in some hematopoietic cells, we tested whether this increased activation in Alzheimer’s disease might be related to an increased activity of Inositol (1,4,5) trisphosphate 3-kinase B. We show here that Inositol (1,4,5) trisphosphate 3-kinase B protein level was 3 fold increased in the cerebral cortex of most Alzheimer patients, compared to control subjects, and accumulated in dystrophic neurites associated to amyloid plaques. In mouse Neuro-2a neuroblastoma cells, Inositol (1,4,5) trisphosphate 3-kinase B overexpression was associated with increased cell apoptosis and increased β-secretase 1 activity leading to amyloid-β peptides overproduction. In this cellular model, an inhibitor of Mitogen-activated kinase kinases 1/2 completely prevented amyloid-β peptides overproduction. Transgenic overexpression of Inositol (1,4,5) trisphosphate 3-kinase B in mouse forebrain neurons was not sufficient to induce amyloid plaques formation or TAU hyperphosphorylation. However, in the 5X Familial Alzheimer’s Disease mouse model, neuronal Inositol (1,4,5) trisphosphate 3-kinase B overexpression significantly increased Extracellular signal-regulated kinases 1/2 activation and β-secretase 1 activity, resulting in exacerbated Alzheimer pathology as shown by increased astrogliosis, amyloid-β40 peptide production and TAU hyperphosphorylation. No impact on pathology was observed in the 5X Familial Alzheimer’s Disease mouse model when a catalytically inactive Inositol (1,4,5) trisphosphate 3-kinase B protein was overexpressed. Together, our results point to the Inositol (1,4,5) trisphosphate 3-kinase B /Inositol 1,3,4,5-tetrakisphosphate/Extracellular signal-regulated kinases 1/2 signaling pathway as an important regulator of neuronal cell apoptosis, Amyloid precursor protein processing and TAU phosphorylation in Alzheimer’s disease, and suggest that Inositol (1,4,5) trisphosphate 3-kinase B could represent a new target for reducing pathology in human AD patients with increased cortical Inositol (1,4,5) trisphosphate 3-kinase B expression. [less ▲]

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See detailThyroid-specific inactivation of Kif3a alters TSH signaling pathway and leads to hypothyroidism.
D'Amico, Eva; Gayral, Stéphanie; Massart, Claude et al

in Journal of Molecular Endocrinology (2013), 50

Kinesins, including the kinesin 2/KIF3 molecular motor, play an important role in intracellular traffic and can deliver vesicles to distal axon terminal, to cilia, to non-polarized cell surface or to ... [more ▼]

Kinesins, including the kinesin 2/KIF3 molecular motor, play an important role in intracellular traffic and can deliver vesicles to distal axon terminal, to cilia, to non-polarized cell surface or to epithelial cell basolateral membrane, thus taking part to the establishment of cellular polarity. We report here the consequences of the kinesin 2 motor inactivation in the thyroid of 3 week-old Kif3a∆/flox Pax8Cre/+ mutant mice. Our results indicate first that 3 week-old Pax8Cre/+ mice used in these experiments present minor thyroid functional defects resulting in a slight increase in circulating bioactive TSH and intracellular cAMP levels, sufficient to maintain blood T4 levels in the normal range. Second, Kif3a inactivation in thyrocytes markedly amplified the phenotype observed in Pax8Cre/+ mice, resulting in an altered TSH signaling upstream of the second messenger cAMP and mild hypothyroidism. Finally, our results in mouse embryonic fibroblasts indicate that Kif3a inactivation in the absence of any Pax8 gene alteration leads to altered GPCR plasma membrane expression, as shown for the β2 adrenergic receptor, and we suggest that a similar mechanism may explain the altered TSH signaling and mild hypothyroidism detected in Kif3a∆/flox Pax8Cre/+ mutant mice. [less ▲]

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See detailInositol 1,4,5-trisphosphate 3-kinase B (Itpkb) controls survival, proliferation and cytokine production in mouse peripheral T cells
Pouillon, Valérie; Maréchal, Yoann; Frippiat, Christophe et al

in Advances in Biological Regulation (2013), 53(1), 39-50

Mice genetically-deficient for the B isoform of the inositol 1,4,5-trisphosphate 3-kinase (or Itpkb) have a severe defect in thymocytes differentiation and thus lack peripheral T cells. In order to study ... [more ▼]

Mice genetically-deficient for the B isoform of the inositol 1,4,5-trisphosphate 3-kinase (or Itpkb) have a severe defect in thymocytes differentiation and thus lack peripheral T cells. In order to study the functional role of Itpkb in peripheral T cells, we constructed a new mouse where a transgene encoding mouse Itpkb is specifically and transiently expressed in thymocytes of Itpkb-/- mice. This allows a partial rescue of mature thymocyte/T cell differentiation and thus the functional characterization of peripheral T cells lacking Itpkb. We show here that Itpkb-/- CD4+ and CD8+ peripheral T cells present important functional alterations. Indeed, an increased activated/memory phenotype as well as a decreased proliferative capacity and survival were detected in these T cells. These Itpkb-deficient peripheral T cells have also an increased capacity to secrete cytokines upon stimulation. Together, our present results define the important role of Itpkb in peripheral mature T cell fate and function in mouse, suggesting a potential role for Itpkb in autoimmunity. [less ▲]

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See detailDevelopmental defects and rescue from glucose intolerance of a catalytically-inactive novel Ship2 mutant mouse
Dubois, E; Jacoby, M; Blockmans, M et al

in Cellular Signalling (2012), 24

The function of the phosphoinositide 5-phosphatase Ship2 was investigated in a new mouse model expressing a germline catalytically-inactive Ship2∆/∆ mutant protein. Ship2∆/∆ mice were viable with defects ... [more ▼]

The function of the phosphoinositide 5-phosphatase Ship2 was investigated in a new mouse model expressing a germline catalytically-inactive Ship2∆/∆ mutant protein. Ship2∆/∆ mice were viable with defects in somatic growth and in development of muscle, adipose tissue and female genital tract. Lipid metabolism and insulin secretion were also affected in these mice, but glucose tolerance, insulin sensitivity and insulin-induced PKB phosphorylation were not. We expected that the expression of the catalytically inactive Ship2 protein in PI 3’-kinase-defective p110αD933A/+ mice would counterbalance the phenotypes of parental mice by restoring normal PKB signaling but, for most of the parameters tested, this was not the case. Indeed, often, the Ship2∆/∆ phenotype had a dominant effect over the p110αD933A/+ phenotype and, sometimes, there was a surprising additive effect of both mutations. p110αD933A/+Ship2∆/∆ mice still displayed a reduced PKB phosphorylation in response to insulin, compared to wild type mice yet had a normal glucose tolerance and insulin sensitivity, like the Ship2∆/∆ mice. Together, our results suggest that the Ship2∆/∆ phenotype is not dependent on an overstimulated class I PI 3-kinase-PKB signaling pathway and thus, indirectly, that it may be more dependent on the lack of Ship2-produced phosphatidylinositol 3,4-bisphosphate and derived phosphoinositides. [less ▲]

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See detailThe Spinner-IBMM mouse is a new spontaneous mutant in the Tmie gene
D'Amico, E.; Stygelbout, V.; Schurmans, Stéphane ULg

in Genes & Genomics (2012), 34

A recessively inherited, spontaneous mutation named Spinner-IBMM (SI) was identified in a transgenic mouse colony in our institute. SI mutant mice displayed hyperactivity, including a severe circling ... [more ▼]

A recessively inherited, spontaneous mutation named Spinner-IBMM (SI) was identified in a transgenic mouse colony in our institute. SI mutant mice displayed hyperactivity, including a severe circling behavior, ataxia and inability to swim. Gene mapping revealed that the causative gene was located on a 35 Mb DNA fragment on chromosome 9. Candidate genes sequencing in this DNA fragment identified a new mutant allele in the Tmie gene. The identified mutant is characterized by a nucleotide deletion in exon 5, leading to a frameshift and a premature STOP codon. It has been reported that inactivating mutations in the mouse Tmie gene result in an identical phenotype, probably resulting from defects in the inner ear. However, the exact function of the Tmie protein in the ear and other organs is still unknown. The analysis of this new mouse mutant could contribute to a better understanding of Tmie functions in vivo in the ear and other organs. [less ▲]

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See detailThe inositol Inpp5k 5-phosphatase affects osmoregulation through the vasopressin-aquaporin 2 pathway in the collecting system.
Pernot, E.; Terryn, S.; Cheong, S. C. et al

in Pflügers Archiv : European Journal of Physiology (2011), 462

Inositol Inpp5k (or Pps, SKIP) is a member of the inositol polyphosphate 5-phosphatases family with a poorly characterized function in vivo. In this study, we explored the function of this inositol 5 ... [more ▼]

Inositol Inpp5k (or Pps, SKIP) is a member of the inositol polyphosphate 5-phosphatases family with a poorly characterized function in vivo. In this study, we explored the function of this inositol 5-phosphatase in mice and cells overexpressing the 42-kDa mouse Inpp5k protein. Inpp5k transgenic mice present defects in water metabolism characterized by a reduced plasma osmolality at baseline, a delayed urinary water excretion following a water load, and an increased acute response to vasopressin. These defects are associated with the expression of the Inpp5k transgene in renal collecting ducts and with alterations in the arginine vasopressin/aquaporin-2 signalling pathway in this tubular segment. Analysis in a mouse collecting duct mCCD cell line revealed that Inpp5k overexpression leads to increased expression of the arginine vasopressin receptor type 2 and increased cAMP response to arginine vasopressin, providing a basis for increased aquaporin-2 expression and plasma membrane localization with increased osmotically induced water transport. Altogether, our results indicate that Inpp5k 5-phosphatase is important for the control of the arginine vasopressin/aquaporin-2 signalling pathway and water transport in kidney collecting ducts. [less ▲]

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See detailHeterozygous inactivation of the Na/Ca exchanger increases glucose-induced insulin release, β-cell proliferation, and mass.
Nguidjoe, E.; Sokolow, S.; Bigabwa, S. et al

in Diabetes (2011), 60

We have previously shown that overexpression of the Na-Ca exchanger (NCX1), a protein responsible for Ca(2+) extrusion from cells, increases β-cell programmed cell death (apoptosis) and reduces β-cell ... [more ▼]

We have previously shown that overexpression of the Na-Ca exchanger (NCX1), a protein responsible for Ca(2+) extrusion from cells, increases β-cell programmed cell death (apoptosis) and reduces β-cell proliferation. To further characterize the role of NCX1 in β-cells under in vivo conditions, we developed and characterized mice deficient for NCX1. RESEARCH DESIGN AND METHODS: Biologic and morphologic methods (Ca(2+) imaging, Ca(2+) uptake, glucose metabolism, insulin release, and point counting morphometry) were used to assess β-cell function in vitro. Blood glucose and insulin levels were measured to assess glucose metabolism and insulin sensitivity in vivo. Islets were transplanted under the kidney capsule to assess their performance to revert diabetes in alloxan-diabetic mice. RESULTS: Heterozygous inactivation of Ncx1 in mice induced an increase in glucose-induced insulin release, with a major enhancement of its first and second phase. This was paralleled by an increase in β-cell proliferation and mass. The mutation also increased β-cell insulin content, proinsulin immunostaining, glucose-induced Ca(2+) uptake, and β-cell resistance to hypoxia. In addition, Ncx1(+/-) islets showed a two- to four-times higher rate of diabetes cure than Ncx1(+/+) islets when transplanted into diabetic animals. CONCLUSIONS: Downregulation of the Na/Ca exchanger leads to an increase in β-cell function, proliferation, mass, and resistance to physiologic stress, namely to various changes in β-cell function that are opposite to the major abnormalities seen in type 2 diabetes. This provides a unique model for the prevention and treatment of β-cell dysfunction in type 2 diabetes and after islet transplantation. [less ▲]

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See detailRegulation of B cell survival, development and function by inositol 1,4,5-trisphosphate 3-kinase B (Itpkb)
Schurmans, Stéphane ULg; Pouillon, V.; Marechal, Y.

in Advances in Enzyme Regulation (2011), 51

In mammals, Ins(1,4,5)P3, the well known calcium mobilization messenger, is phosphorylated in the cytosol at the 3-position of the inositol ring to yield Ins(1,3,4,5)P4 by Ins(1,4,5)P3 3-kinases A, B and ... [more ▼]

In mammals, Ins(1,4,5)P3, the well known calcium mobilization messenger, is phosphorylated in the cytosol at the 3-position of the inositol ring to yield Ins(1,3,4,5)P4 by Ins(1,4,5)P3 3-kinases A, B and C isoforms as well as by inositol polyphosphate multikinase (Ipmk). Studies in gene-deficient mice have revealed that these enzymes and Ins(1,3,4,5)P4, their reaction product, play essential role in multiple physiological processes, ranging from synaptic plasticity, hematopoietic cell survival, development and function, to mRNA export, transcriptional regulation and chromatin remodelling. Rather than to provide an unique and “universal” mechanism of Ins(1,3,4,5)P4 action, these studies in genetically-modified mice point for a role of this inositide in the control of calcium mobilization, of the subcellular localisation of PH domain-containing target proteins, and of higher inositol phosphate production. Mice deficient for the B isoform of inositol 1,4,5-trisphosphate 3-kinase (Itpkb) develop profound alterations in T and B cells as well as in neutrophils and mast cells. Our recent studies indicate that the 3-kinase Itpkb and Ins(1,3,4,5)P4 are important for the survival of naïve mature B cells and the control of proapoptotic Bim protein expression, rather than for the control of B cell transition from one developmental stage to another. They also suggest that Itpkb is an important component in the control of B cell anergy. [less ▲]

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See detailInositol 1,4,5-trisphosphate 3-kinase B controls survival and prevents anergy in B cells
Marechal, Y.; Queant, S.; Polizzi, S. et al

in Immunobiology (2011), 216

Inositol 1,4,5-trisphosphate 3-kinase B (or Itpkb) and inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), its reaction product, play an important role in the control of B lymphocyte fate and function in ... [more ▼]

Inositol 1,4,5-trisphosphate 3-kinase B (or Itpkb) and inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), its reaction product, play an important role in the control of B lymphocyte fate and function in vivo. In order to investigate the fine mechanisms of Itpkb and Ins(1,3,4,5)P4 action in B cells, we crossed Itpkb(-/-) mice with transgenic mice expressing a 3-83mudelta B cell receptor (BCR) specific for membrane-bound MHC-I H2-K(b) and H2-K(k) molecules. On a non-deleting H2-K(d) genetic background, we show that Itpkb is important for the control of Bim protein expression and B cell survival rather than for the control of B cell development from one stage to another. Analyses of cell surface markers expression, proapoptotic Bim protein expression, in vitro survival and in vivo turnover demonstrated that BCR transgenic Itpkb(-/-) B cells exhibit an anergic phenotype with the notable exception of their enhanced antigen-induced calcium signalling. On a deleting H2-K(b) genetic background, we show that Itpkb is not essential for BCR editing or negative selection. These data establish Itpkb as an important regulator of B cell survival and anergy in vivo. [less ▲]

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See detailVariegation and silencing in a lentiviral-based murine transgenic model.
Baup, Delphine; Fraga, Laurent; Pernot, Eileen et al

in Transgenic Research (2010), 19

Lentiviral based constructs represent a recent development in the generation of transgenic animals. The ease of use, and the fact that the same backbone vectors can be used to down-modulate endogenous ... [more ▼]

Lentiviral based constructs represent a recent development in the generation of transgenic animals. The ease of use, and the fact that the same backbone vectors can be used to down-modulate endogenous gene expression and to produce transgenic animals overexpressing a gene of interest, have fuelled growing interest in this technology. In this study, we have used a lentiviral delivery system to generate transgenic mice expressing altered levels (up or downregulated) of a gene of interest. Although this lentiviral-based approach led to high levels of transgenesis and germ line transmission, a wide variation in transgene expression was observed in most first and second generation mouse lines. In particular, despite the segregation of integrants into single-copy expressing mouse lines, transgene expression appeared to be the target of epigenetic regulatory mechanism, often causing the coexistence of high and low transgene expressing cells within a given tissue such as blood peripheral lymphocytes. The establishment and analysis of large number of mouse lines may therefore be required to select a stable transgenic line with pancellular expression of a gene of interest using this lentiviral-based approach. [less ▲]

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See detailINPP5E mutations cause primary cilium signaling defects, ciliary instability and ciliopathies in human and mouse
Jacoby, Monique; Cox, James J.; Gayral, Stéphanie et al

in Nature Genetics (2009), 41

The primary cilium is an antenna-like structure that protrudes from the cell surface of quiescent/differentiated cells and participates in extracellular signal processing1–3. Here, we report that mice ... [more ▼]

The primary cilium is an antenna-like structure that protrudes from the cell surface of quiescent/differentiated cells and participates in extracellular signal processing1–3. Here, we report that mice deficient for the lipid 5-phosphatase Inpp5e develop a multiorgan disorder associated with structural defects of the primary cilium. In ciliated mouse embryonic fibroblasts, Inpp5e is concentrated in the axoneme of the primary cilium. Inpp5e inactivation did not impair ciliary assembly but altered the stability of pre-established cilia after serum addition. Blocking phosphoinositide 3-kinase (PI3K) activity or ciliary platelet-derived growth factor receptor a (PDGFRa) restored ciliary stability. In human INPP5E, we identified a mutation affecting INPP5E ciliary localization and cilium stability in a family with MORM syndrome, a condition related to Bardet-Biedl syndrome. Together, our results show that INPP5E plays an essential role in the primary cilium by controlling ciliary growth factor and PI3K signaling and stability, and highlight the consequences of INPP5E dysfunction. [less ▲]

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See detailNeuronal injury in NCX3 knockout mice following permanent focal cerebral ischemia and in NCX3 knockout cortical neuronal cultures following oxygen-glucose deprivation and glutamate exposure
Cross, J. L.; Meloni, B. P.; Bakker, A. J. et al

in Journal of Experimental Stroke & Translational Medicine (2009), 2(1), 3-9

In this study we subjected NCX3 knockout and wildtype mice to permanent focal cerebral ischemia by intraluminal middle cerebral artery occlusion. Analysis of brain sections by 2,3,5-Triphenyl-2H ... [more ▼]

In this study we subjected NCX3 knockout and wildtype mice to permanent focal cerebral ischemia by intraluminal middle cerebral artery occlusion. Analysis of brain sections by 2,3,5-Triphenyl-2H-tetrazolium chloride staining, 12 hours after middle cerebral artery occlusion revealed no difference in infarct volume between NCX3 knockout and wildtype mice. In addition, we evaluated the effect of NCX3 protein knockdowri on neuronal viability in primary cortical neuronal cultures following in vitro ischemia (oxygen-glucose deprivation) and L-glutamate (glutamate) exposure. In vitro experiments revealed that neuronal viability was higher in NCX3 knockout neuronal cultures than in the wildtype cultures following ischemic and glutamate insults. The reduced sensitivity of neurons from NCX3 knockout mice to in vitro ischemia and excitotoxicity indicates that NCX3 calcium entry mode activity contributes to calcium overload and neuronal death. However our in vivo finding of e lack of differential sensitivity on infarct volume in NCX3 knockout and wildtype mice suggests that any benefit of reduced NCX3 activity is overridden following permanent focal cerebral ischemia. Taken together, these f]ndings suggest that reduced NXC3 activity limits calcium neurotoxicity during severe transient, but not during severe sustained ischemic insults. These results have important implications for the development of the NCX3 protein as a therapeutic target to reduce ischemic brain injury [less ▲]

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See detailMutations in the inositol polyphosphate-5-phosphatase E gene link phosphatidyl inositol signaling to the ciliopathies
Bielas, S. L.; Silhavy, J. L.; Brancati, F. et al

in Nature Genetics (2009), 41

Phosphotidylinositol (PtdIns) signaling is tightly regulated both spatially and temporally by subcellularly localized PtdIns kinases and phosphatases that dynamically alter downstream signaling events1 ... [more ▼]

Phosphotidylinositol (PtdIns) signaling is tightly regulated both spatially and temporally by subcellularly localized PtdIns kinases and phosphatases that dynamically alter downstream signaling events1. Joubert syndrome is characterized by a specific midbrain-hindbrain malformation (‘molar tooth sign’), variably associated retinal dystrophy, nephronophthisis, liver fibrosis and polydactyly2 and is included in the newly emerging group of ‘ciliopathies’. In individuals with Joubert disease genetically linked to JBTS1, we identified mutations in the INPP5E gene, encoding inositol polyphosphate-5-phosphatase E, which hydrolyzes the 5-phosphate of PtdIns(3,4,5)P3 and PtdIns(4,5)P2. Mutations clustered in the phosphatase domain and impaired 5-phosphatase activity, resulting in altered cellular PtdIns ratios. INPP5E localized to cilia in major organs affected by Joubert syndrome, and mutations promoted premature destabilization of cilia in response to stimulation. These data link PtdIns signaling to the primary cilium, a cellular structure that is becoming increasingly recognized for its role in mediating cell signals and neuronal function [less ▲]

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See detailDevelopmental regulation of the composite CAG promoter activity in the murine T lymphocyte cell lineage.
Baup, D.; Moser, M.; Schurmans, Stéphane ULg et al

in Genesis (New York, N.Y. : 2000) (2009), 47

Promoter selection is of utmost importance for the study of in vivo gene function using transgenic models. In the present study, we have analyzed the expression of the GFP marker under the control of the ... [more ▼]

Promoter selection is of utmost importance for the study of in vivo gene function using transgenic models. In the present study, we have analyzed the expression of the GFP marker under the control of the composite CAG promoter in the lymphoid compartment of several transgenic mouse strains. Despite the ability of the CAG promoter to drive gene expression in almost all tissues examined to date, its activity appears to be developmentally regulated within the T lymphocyte cell lineage. In particular, CD4 and CD8-expressing, thymic immature T cells displayed lower levels of the GFP marker when compared with both bone marrow precursors and mature circulating T cells, suggesting a transient downregulation of CAG activity during T cell development. Alternative promoters may therefore be preferred for the study of T cell development in vivo using a transgenic approach. [less ▲]

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See detailTargeted disruption of Na+/Ca2+ exchanger 3 (NCX3) gene leads to a worsening of ischemic brain damage
Molinaro, P.; Cuomo, O.; Pignataro, G. et al

in Journal of Neuroscience (2008), 28

Na+/Ca+ exchanger 3 (NCX3), one of the three isoforms of the NCX family, is highly expressed in the brain and is involved in the maintenance of intracellular Na+ and Ca2+ homeostasis. Interestingly ... [more ▼]

Na+/Ca+ exchanger 3 (NCX3), one of the three isoforms of the NCX family, is highly expressed in the brain and is involved in the maintenance of intracellular Na+ and Ca2+ homeostasis. Interestingly, whereas the function of NCX3 under physiological conditions has been determined, its role under anoxia is still unknown. To assess NCX3 role in cerebral ischemia, we exposed ncx3-/- mice to transient middle cerebral artery occlusion followed by reperfusion. In addition, to evaluate the effect of ncx3 ablation on neuronal survival, organotypic hippocampal cultures and primary cortical neurons from ncx3-/- mice were subjected to oxygen glucose deprivation (OGD) plus reoxygenation. Here we report that ncx3 gene suppression leads to a worsening of brain damage after focal ischemia and to a massive neuronal death in all the hippocampal fields of organotypic cultures as well as in cortical neurons from ncx3-/- mice exposed to OGD plus reoxygenation. In addition, in ncx3-/- cortical neurons exposed to hypoxia, NCX currents, recorded in the reverse mode of operation, were significantly lower than those detected in ncx3+/+. From these results, NCX3 protein emerges as a new molecular target that may have a potential therapeutic value in modulating cerebral ischemia [less ▲]

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See detailInositol trisphosphate 3-kinase B (InsP3KB) as a physiological modulator of myelopoiesis
Jia, Y.; Loison, F.; Erneux, C. et al

in Proceedings of the National Academy of Sciences of the United States of America (2008), 105

Inositol trisphosphate 3-kinase B (InsP3KB) belongs to a family of kinases that convert inositol 1,4,5-trisphosphate (Ins(1,4,5)P3 or IP3) to inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4). Previous ... [more ▼]

Inositol trisphosphate 3-kinase B (InsP3KB) belongs to a family of kinases that convert inositol 1,4,5-trisphosphate (Ins(1,4,5)P3 or IP3) to inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4). Previous studies have shown that disruption of InsP3KB leads to impaired T cell and B cell development as well as hyperactivation of neutrophils. Here, we demonstrate that InsP3KB is also a physiological modulator of myelopoiesis. The InsP3KB gene is expressed in all hematopoietic stem/progenitor cell populations. In InsP3KB null mice, the bone marrow granulocyte monocyte progenitor (GMP) population was expanded, and GMP cells proliferated significantly faster. Consequently, neutrophil production in the bone marrow was enhanced, and the peripheral blood neutrophil count was also substantially elevated in these mice. These effects might be due to enhancement of PtdIns(3,4,5)P3/Akt signaling in the InsP3KB null cells. Phosphorylation of cell cycle-inhibitory protein p21(cip1), one of the downstream targets of Akt, was augmented, which can lead to the suppression of the cell cycle-inhibitory effect of p21 [less ▲]

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See detailNCX3 knockout mice exhibit increased hippocampal CA1 and CA2 neuronal damage compared to wild-type mice following global cerebral ischemia
Jeffs, G. J.; Meloni, B.; Sokolow, S. et al

in Experimental Neurology (2008), 210

There is uncertainty as to whether the plasma membrane Na(+)/Ca(2+)exchanger (NCX) has a neuroprotective or neurodamaging role following cerebral ischemia. To address this issue we compared hippocampal ... [more ▼]

There is uncertainty as to whether the plasma membrane Na(+)/Ca(2+)exchanger (NCX) has a neuroprotective or neurodamaging role following cerebral ischemia. To address this issue we compared hippocampal neuronal injury in NCX3 knockout mice (Ncx3(-/-)) and wild-type mice (Ncx3(+/+)) following global cerebral ischemia. Using a bilateral common carotid artery occlusion (BCCAO) model of global ischemia we subjected NCX3 knockout and wild-type mice to 17 and 15 minutes of ischemia. Following the 17 minute period of ischemia, wild-type mice exhibited approximately 80% CA1 neuronal loss and approximately 40% CA2 neuronal loss. In contrast, NCX3 knockout mice displayed >95% CA1 neuronal loss and approximately 95% CA2 neuronal loss. Following the 15 minute period of ischemia, wild-type mice did not exhibit any significant hippocampal neuronal loss. In contrast, NCX3 knockout mice displayed approximately 45% CA1 neuronal loss and approximately 25% CA2 neuronal loss. The results clearly demonstrate that mice deficient in the NCX3 protein are more susceptible to global cerebral ischemia than wild-type mice. Our findings suggest NCX3 has a positive role in maintaining neuronal intracellular calcium homeostasis following ischemia, and that when exchanger function is compromised neurons are more susceptible to calcium deregulation and cell death [less ▲]

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See detailRegulation of innate immunity by inositol 1,3,4,5-tetrakisphosphate
Jia, Y.; Schurmans, Stéphane ULg; Luo, H. R.

in Cell Cycle (Georgetown, Tex.) (2008), 7

Many neutrophil functions are mediated by PtdIns(3,4,5)P3 that exerts its role by mediating protein translocation via binding to their PH-domains. Inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5) P4 ... [more ▼]

Many neutrophil functions are mediated by PtdIns(3,4,5)P3 that exerts its role by mediating protein translocation via binding to their PH-domains. Inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5) P4) binds the same PH domain, competes for its binding to PtdIns(3,4,5)P3, and thus negatively regulates PtdIns(3,4,5)P3 signaling. In neutrophils, chemoattractant stimulation triggers rapid elevation in Ins(1,3,4,5)P4 level. Depletion of Ins(1,3,4,5) P4 by deleting InsP3KB, the major enzyme producing Ins(1,3,4,5) P4 in neutrophils, augments PtdIns(3,4,5)P3 downstream signals, leading to enhanced sensitivity to chemoattractant stimulation, elevated superoxide production, and enhanced neutrophil recruitment to inflamed peritoneal cavity. nsP3KB gene is also expressed in hematopoietic stem/progenitor cells. In InsP3KB null mice, the bone marrow granulocyte monocyte progenitor (GMP) population is expanded and the proliferation of GMP cells is accelerated. As results, neutrophil production in the bone marrow is enhanced and peripheral blood neutrophil count is elevated. Ins(1,3,4,5)P4 also plays a role in maintaining neutrophil survival. Depletion of Ins(1,3,4,5)P4 leads to accelerated neutrophil spontaneous death. Finally, InsP3KB and Ins(1,3,4,5)P4 are essential components in bacterial killing by neutrophils. Despite of the augmented neutrophil recruitment, the clearance of bacteria in the InsP3KB knockout mice is significantly impaired. Collectively, these findings establish InsP3KB and its product Ins(1,3,4,5)P4 as essential modulators of neutrophil function and innate immunity [less ▲]

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