References of "Schurmans, Stéphane"
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See detailINPP5E Preserves Genomic Stability through Regulation of Mitosis
Sierra Potchanant, EA; Cerabona, D; Sater, ZA et al

in Molecular and Cellular Biology (2017), 37(6), 500-516

The partially understood phosphoinositide signaling cascade regulates multiple aspects of cellular metabolism. Previous studies revealed that INPP5E, the inositol polyphosphate-5-phosphatase that is ... [more ▼]

The partially understood phosphoinositide signaling cascade regulates multiple aspects of cellular metabolism. Previous studies revealed that INPP5E, the inositol polyphosphate-5-phosphatase that is mutated in the developmental disorders Joubert and MORM syndromes, is essential for the function of the primary cilium and maintenance of phosphoinositide balance in nondividing cells. Here, we report that INPP5E further contributes to cellular homeostasis by regulating cell division. We found that silencing or genetic knockout of INPP5E in human and murine cells impairs the spindle assembly checkpoint, centrosome and spindle function, and maintenance of chromosomal integrity. Consistent with a cell cycle regulatory role, we found that INPP5E expression is cell cycle dependent, peaking at mitotic entry. INPP5E localizes to centrosomes, chromosomes, and kinetochores in early mitosis and shuttles to the midzone spindle at mitotic exit. Our findings identify the previously unknown, essential role of INPP5E in mitosis and prevention of aneuploidy, providing a new perspective on the function of this phosphoinositide phosphatase in health and development. [less ▲]

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See detailEndothelial SHIP2 suppresses Nox2 NADPH oxidase-dependent vascular oxidative stress, endothelial dysfunction and systemic insulin resistance
Watt, NT; Gage, MC; Patel, PA et al

in Diabetes (2017)

Shc homology 2-containing inositol 5´ phosphatase-2 (SHIP2) is as lipid phosphatase which inhibits insulin signaling downstream of phosphoinositide-3-kinase (PI3K); its role in vascular function is poorly ... [more ▼]

Shc homology 2-containing inositol 5´ phosphatase-2 (SHIP2) is as lipid phosphatase which inhibits insulin signaling downstream of phosphoinositide-3-kinase (PI3K); its role in vascular function is poorly understood. To examine its role in endothelial cell (EC) biology, we generated mice with catalytic inactivation of one SHIP2 allele selectively in EC (ECSHIP2Δ/+). Hyperinsulinemic euglycemic clamping studies revealed ECSHIP2Δ/+ were resistant to insulin-stimulated glucose uptake in adipose tissue and skeletal muscle, compared with littermate controls. EC from ECSHIP2Δ/+ had increased basal expression and activation of PI3K downstream targets, including Akt and endothelial nitric oxide synthase (eNOS), although incremental activation by insulin and shear stress was impaired. Insulin-mediated vasodilation was blunted in ECSHIP2Δ/+, as was aortic nitric oxide bioavailability. Acetylcholine-induced vasodilation was also impaired in ECSHIP2Δ/+, which was exaggerated in the presence of a superoxide dismutase/catalase mimetic. Superoxide abundance was elevated in ECSHIP2Δ/+ EC, and was suppressed by PI3K and Nox2 NADPH oxidase inhibitors. These findings were phenocopied in healthy human EC after SHIP2 silencing. Our data suggest that endothelial SHIP2 is required to maintain normal systemic glucose homeostasis and prevent oxidative stress-induced endothelial dysfunction. [less ▲]

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See detailThe lipid 5-phoshatase SHIP2 controls renal brush border ultrastructure and function by regulating ERM proteins activation
Sayyed, Sufyan Ali ULiege; JOURET, François ULiege; Vermeersch, Marjorie et al

in Kidney International (2017)

The microvillus brush border on the renal proximal tubule epithelium allows the controlled reabsorption of solutes that are filtered through the glomerulus and thus participates in general body ... [more ▼]

The microvillus brush border on the renal proximal tubule epithelium allows the controlled reabsorption of solutes that are filtered through the glomerulus and thus participates in general body homeostasis. Here, using the lipid 5-phosphatase Ship2 global knock-out mice, proximal tubule-specific Ship2 knock-out mice and a proximal tubule cell model where SHIP2 is inactivated, we show that SHIP2 is a negative regulator of microvilli formation, thereby controlling solute reabsorption by the proximal tubule. We found increased PtdIns(4,5)P2 substrate and decreased PtdIns4P product when SHIP2 was inactivated, associated with hyperactivated Ezrin/Radixin/Moesin proteins and increased Rho-GTP. Thus, inactivation of SHIP2 leads to increased microvilli formation and solute reabsorption by the renal proximal tubule. This may represent an innovative therapeutic target for renal Fanconi syndromes characterized by decreased reabsorption of solutes by this nephron segment. [less ▲]

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See detailInositol-triphosphate-3-kinase C mediates inflammasome activation and treatment response in Kawasaki Disease
Alphonse, M. P.; Duong, T. T.; Shumitzu, C. et al

in Journal of Immunology (2016), 197

Kawasaki disease (KD) is a multisystem vasculitis that predominantly targets the coronary arteries in children. Phenotypic similarities between KD and recurrent fever syndromes point to the potential role ... [more ▼]

Kawasaki disease (KD) is a multisystem vasculitis that predominantly targets the coronary arteries in children. Phenotypic similarities between KD and recurrent fever syndromes point to the potential role of inflammasome activation in KD. Mutations in NLRP3 are associated with recurrent fever/auto-inflammatory syndromes. We show that the KD-associated genetic polymorphism in Inositol-triphosphate 3-kinase C (ITPKC) (rs28493229) has important functional consequences, governing ITPKC protein levels and thereby intracellular calcium, which in turn regulates NLRP3 expression and production of IL-1β and IL-18. Analysis of transcript abundance, protein levels, and cellular response profiles from matched, serial biospecimens from a cohort of genotyped KD subjects points to the critical role of ITPKC in mediating NLRP3 inflammasome activation. Treatment failure in those with the ‘high-risk’ ITPKC-genotype was associated with the highest basal and stimulated intracellular calcium levels and with increased cellular production of IL-1β and IL-18 and higher circulating levels of both cytokines. Mechanistic studies using Itpkc-deficient mice in a disease model support the genomic, cellular and clinical findings in affected children. Our findings provide the mechanism behind the observed efficacy of rescue therapy with IL-1 blockade in recalcitrant KD, and identify that regulation of calcium mobilization is fundamental to the underlying immunobiology in KD. [less ▲]

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See detailSpecific expression and function of inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) in wild type and knock-out mice
Scoumanne, Ariane; Molina Ortiz, Patricia ULiege; Monteyne, Daniel et al

in Advances in Biological Regulation (2016), 62

Inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) is the last identified member of the inositol 1,4,5-trisphosphate 3-kinases family which phosphorylates inositol 1,4,5-trisphosphate into inositol 1,3,4,5 ... [more ▼]

Inositol 1,4,5-trisphosphate 3-kinase C (ITPKC) is the last identified member of the inositol 1,4,5-trisphosphate 3-kinases family which phosphorylates inositol 1,4,5-trisphosphate into inositol 1,3,4,5-tetrakisphosphate. Although expression and function of the two other family members ITPKA and ITPKB are rather well characterized, similar information is lacking for ITPKC. Here, we first defined the expression of Itpkc mRNA and protein in mouse tissues and cells using in situ hybridization and new antibodies. Surprisingly, we found that cells positive for ITPKC in the studied tissues express either a multicilium (tracheal and bronchial epithelia, brain ependymal cells), microvilli forming a brush border (small and large intestine, and kidney proximal tubule cells) or a flagellum (spermatozoa), suggesting a role for ITPKC either in the development or the function of these specialized cellular structures. Given this surprising expression, we then analyzed ITPKC function in multiciliated tracheal epithelial cells and sperm cells using our Itpkc knock-out mouse model. Unfortunately, no significant difference was observed between control and mutant mice for any of the parameters tested, leaving the exact in vivo function of this third Ins(1,4,5)P3 3-kinase still open. [less ▲]

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See detailThe Ras/Rap GTPase activating protein RASA3 : from gene structure to in vivo functions
Schurmans, Stéphane ULiege; Polizzi, Séléna; Scoumanne, Ariane ULiege et al

in Advances in Biological Regulation (2015), 57

RASA3 (or GTPase Activating Protein III, R-Ras GTPase-activating protein, GAP1IP4BP) is a GTPase activating protein of the GAP1 subfamily which targets Ras and Rap1. RASA3 was originally purified from pig ... [more ▼]

RASA3 (or GTPase Activating Protein III, R-Ras GTPase-activating protein, GAP1IP4BP) is a GTPase activating protein of the GAP1 subfamily which targets Ras and Rap1. RASA3 was originally purified from pig platelet membranes through its intrinsic ability to bind inositol 1,3,4,5-tetrakisphosphate (I(1,3,4,5)P4) with high affinity, hence its first name GAP1IP4BP (for GAP1 subfamily member which binds I(1,3,4,5)P4). RASA3 was thus the first I(1,3,4,5)P4 receptor identified and cloned. The in vitro and in vivo functions of RASA3 remained somewhat elusive for a long time. However, recently, using genetically-modified mice and cells derived from these mice, the function of RASA3 during megakaryopoiesis, megakaryocyte adhesion and migration as well as integrin signaling has been reported. The goal of this review is thus to summarize and comment recent and less recent data in the literature on RASA3, in particular on the in vivo function of this specific GAP1 subfamily member. [less ▲]

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See detailPhosphoinositides Regulate Ciliary Protein Trafficking to Modulate Hedgehog Signaling.
Garcia-Gonzalo, F. R.; Phua, S. C.; Roberson, E. C. et al

in Developmental Cell (2015), 34

Primary cilia interpret vertebrate Hedgehog (Hh) signals. Why cilia are essential for signaling is unclear. One possibility is that some forms of signaling require a distinct membrane lipid composition ... [more ▼]

Primary cilia interpret vertebrate Hedgehog (Hh) signals. Why cilia are essential for signaling is unclear. One possibility is that some forms of signaling require a distinct membrane lipid composition, found at cilia. We found that the ciliary membrane contains a particular phosphoinositide, PI(4)P, whereas a different phosphoinositide, PI(4,5)P2, is restricted to the membrane of the ciliary base. This distribution is created by Inpp5e, a ciliary phosphoinositide 5-phosphatase. Without Inpp5e, ciliary PI(4,5)P2 levels are elevated and Hh signaling is disrupted. Inpp5e limits the ciliary level s of inhibitors of Hh signaling, including Gpr161 and the PI(4,5)2-binding protein Tulp3. Increasing ciliary PI(4,5)P2levels or conferring the ability to bind PI(4)P on Tulp3 increases the ciliary localization of Tulp3. Lowering Tulp3 in cells lacking Inpp5e [less ▲]

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See detailThe ciliogenic transcription factor Rfx3 is required for the formation of the thalamocortical tract by regulating patterning of prethalamus and ventral telencephalon.
Magnani, D; Morlé, L; Hasenpusch-Theil, K et al

in Human Molecular Genetics (2015), 24

Primary cilia are complex subcellular structures that play key roles during embryogenesis by controlling the cellular response to several signaling pathways. Defects in the function and/or structure of ... [more ▼]

Primary cilia are complex subcellular structures that play key roles during embryogenesis by controlling the cellular response to several signaling pathways. Defects in the function and/or structure of primary cilia underlie a large number of human syndromes collectively referred to as ciliopathies. Often, ciliopathies are associated with mental retardation (MR) and malformation of the corpus callosum. However, the possibility of defects in other forebrain axon tracts, which could contribute to the cognitive disorders of these patients, has not been explored. Here, we investigate the formation of the corticothalamic/thalamocortical tracts in mice mutant for Rfx3, which regulates the expression of many genes involved in ciliogenesis and cilia function. Using DiI axon tracing and immunohistochemistry experiments, we show that some Rfx3-/- corticothalamic axons abnormally migrate toward the pial surface of the ventral telencephalon (VT). Some thalamocortical axons (TCAs) also fail to leave the diencephalon or abnormally project toward the amygdala. Moreover, the Rfx3-/- VT displays heterotopias containing attractive guidance cues and expressing the guidance molecules Slit1 and Netrin1. Finally, the abnormal projection of TCAs toward the amygdala is also present in mice carrying a mutation in the Inpp5e gene, which is mutated in Joubert Syndrome and which controls cilia signaling and stability. The presence of identical thalamocortical malformations in two independent ciliary mutants indicates a novel role for primary cilia in the formation of the corticothalamic/thalamocortical tracts by establishing the correct cellular environment necessary for its development. [less ▲]

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See detailModulation of ciliary phosphoinositide content regulates trafficking and Sonic hedgehog signaling output
Chavez, M; Van Sande, J; de Kerchove d'Exaerde, A et al

in Developmental Cell (2015), 34

Ciliary transport is required for ciliogenesis, signal transduction, and trafficking of receptors to the primary cilium. Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) have been associated ... [more ▼]

Ciliary transport is required for ciliogenesis, signal transduction, and trafficking of receptors to the primary cilium. Mutations in inositol polyphosphate 5-phosphatase E (INPP5E) have been associated with ciliary dysfunction; however, its role in regulating ciliary phosphoinositides is unknown. Here we report that in neural stem cells, phosphatidylinositol 4-phosphate (PI4P) is found in high levels in cilia whereas phosphatidylinositol (4,5)-bisphosphate (PI(4,5)P2) is not detectable. Upon INPP5E inactivation, PI(4,5)P2 accumulates at the ciliary tip whereas PI4P is depleted. This is accompanied by recruitment of the PI(4,5)P2-interacting protein TULP3 to the ciliary membrane, along with Gpr161. This results in an increased production of cAMP and a repression of the Shh transcription gene Gli1. Our results reveal the link between ciliary regulation of phosphoinositides by INPP5E and Shh regulation via ciliary trafficking of TULP3/Gpr161 and also provide mechanistic insight into ciliary alterations found in Joubert and MORM syndromes resulting from INPP5E mutations. [less ▲]

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See detailRasa3 Controls Megakaryocyte Rap1 Activation, Integrin Signaling and Differentiation into Proplatelet
Molina Ortiz, Patricia ULiege; Polizzi, Séléna; Ramery, Eve ULiege 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 detailGeneration and validation of a mouse model for conditional inactivation of PLAGL1
Pirottin, Dimitri ULiege; Schurmans, Stéphane ULiege; Francois, Cédric ULiege et al

in Proceedings of the 4th edition : FARAH Day 2014 (2014)

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See detailSHIP2 signaling in normal and pathological situations: Its impact on cell proliferation.
Elong Edimo, W; Schurmans, Stéphane ULiege; 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 ULiege

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 ULiege; 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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