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Phenotypic and functional characterization of a mouse model of targeted Pig-a deletion in hematopoietic cells.

ABSTRACT: Somatic mutation in the X-linked phosphatidylinositol glycan class A gene (PIG-A) causes glycosyl phosphatidylinositol anchor deficiency in human patients with paroxysmal nocturnal hemoglobinuria.We produced an animal model of paroxysmal nocturnal hemoglobinuria by conditional Pig-a gene inactivation (Pig-a(-/-)) in hematopoietic cells; mice carrying two lox sites flanking exon 6 of the Pig-a gene were bred with mice carrying the transgene Cre-recombinase under the human c-fes promoter. We characterized the phenotypic and functional properties of glycosyl phosphatidylinositol-deficient and glycosyl phosphatidylinositol-normal hematopoietic cells from these Pig-a(-/-) mice using gene expression microarray, flow cytometry, bone marrow transplantation, spectratyping, and immunoblotting.In comparison to glycosyl phosphatidylinositol-normal bone marrow cells, glycosyl phosphatidylinositol-deficient bone marrow cells from the same Pig-a(-/-) animals showed up-regulation of the expression of immune function genes and contained a significantly higher proportion of CD8 T cells. Both characteristics were maintained when glycosyl phosphatidylinositol-deficient cells were transplanted into lethally-irradiated recipients. Glycosyl phosphatidylinositol-deficient T cells were inactive, showed pronounced Vbeta5.1/5.2 skewing, had fewer gamma-interferon-producing cells after lectin stimulation, and contained fewer CD4(+)CD25(+)FoxP3(+) regulatory T cells. However, the levels of T-cell receptor signaling proteins from glycosyl phosphatidylinositol-deficient cells were normal relative to glycosyl phosphatidylinositol-normal cells from wild type animals, and cells were capable of inducing target cell apoptosis in vitro.Deletion of the Pig-a gene in hematopoietic cells does not cause frank marrow failure but leads to the appearance of clonally-restricted, inactive yet functionally competent CD8 T cells.

SUBMITTER: Visconte V

PROVIDER: S-EPMC2817023 | biostudies-literature | 2010 Feb

REPOSITORIES: biostudies-literature

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Phenotypic and functional characterization of a mouse model of targeted Pig-a deletion in hematopoietic cells.

Visconte Valeria V Raghavachari Nalini N Liu Delong D Keyvanfar Keyvan K Desierto Marie J MJ Chen Jichun J Young Neal S NS

Haematologica 20090813 2

<h4>Background</h4>Somatic mutation in the X-linked phosphatidylinositol glycan class A gene (PIG-A) causes glycosyl phosphatidylinositol anchor deficiency in human patients with paroxysmal nocturnal hemoglobinuria.<h4>Design and methods</h4>We produced an animal model of paroxysmal nocturnal hemoglobinuria by conditional Pig-a gene inactivation (Pig-a(-/-)) in hematopoietic cells; mice carrying two lox sites flanking exon 6 of the Pig-a gene were bred with mice carrying the transgene Cre-recomb ...[more]

PMID: 19679885

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Project description:Somatic mutation in the X-linked phosphatidylinositol glycan class A (PIG-A) gene causes glycosylphosphatidylinositol (GPI) anchor deficiency in humans with Paroxysmal Nocturnal Hemoglobinuria (PNH). Clinically, patients with PNH have intravascular hemolysis, venous thrombosis and bone marrow failure. We produced a conditional Pig-a knock-out mouse model specifically inactivating the Pig-a gene in hematopoietic cells to study the role of PIG-A deficiency in PNH pathophysiology. We used Affymetrix Mouse Genome 430 2.0 chips to investigate the gene expression pattern in the mouse model of targeted Pig-a deletion. Experiment Overall Design: We performed microarray analysis on 3 pools of sorted GPI-deficient (GPI-) and GPI normal (GPI+) bone marrow cells derived from the same Pig-a knock-out animals, and identified 1275/669 genes of the 45,101 transcripts potentially available for screening using 2-fold change, <10% false discovery rate (FDR) and percentage of present calls as selection criteria. The major representative genes belong to the category of immune response. We tested whether the molecular differences between GPI- and GPI+ bone marrow cells could be preserved when GPI- cells were transplanted in lethally-irradiated wild type mice (C57BL/6). Microarray analysis was performed using sorted bone marrow cells from 4 animals transplanted with GPI-deficient bone marrow cells (T-GPI-) from Pig-a knock-out donors, 3 animals transplanted with GPI-normal bone marrow cells from C57BL/6 donors (T-GPI+), and GPI-normal bone marrow cells from 4 wild-type C57BL/6 mice (WT-GPI+). We found 296 probesets with 2-fold change cutoff, of which T-GPI- cells had 145 up-regulated genes in comparison to WT-GPI+ cells, and had 123 genes differentially expressed when compared to T-GPI+ cells. The gene expression of the GPI-deficient cells was very similar between the two sets of microarray experiments affirming the maintenance of the phenotype before and after bone marrow cell transplantation.

Project description:More than 90% of the cases of Parkinson's disease have unknown etiology. Gradual loss of dopaminergic neurons of substantia nigra is the main cause of morbidity in this disease. External factors such as environmental toxins are believed to play a role in the cell loss, although the cause of the selective vulnerability of dopaminergic neurons remains unknown. We have previously shown that aquaglyceroporin AQP9 is expressed in dopaminergic neurons and astrocytes of rodent brain. AQP9 is permeable to a broad spectrum of substrates including purines, pyrimidines, and lactate, in addition to water and glycerol. Here we test our hypothesis that AQP9 serves as an influx route for exogenous toxins and, hence, may contribute to the selective vulnerability of nigral dopaminergic (tyrosine hydroxylase-positive) neurons. Using Xenopus oocytes injected with Aqp9 cRNA, we show that AQP9 is permeable to the parkinsonogenic toxin 1-methyl-4-phenylpyridinium (MPP+). Stable expression of AQP9 in HEK cells increases their vulnerability to MPP+ and to arsenite-another parkinsonogenic toxin. Conversely, targeted deletion of Aqp9 in mice protects nigral dopaminergic neurons against MPP+ toxicity. A protective effect of Aqp9 deletion was demonstrated in organotypic slice cultures of mouse midbrain exposed to MPP+ in vitro and in mice subjected to intrastriatal injections of MPP+ in vivo. Seven days after intrastriatal MPP+ injections, the population of tyrosine hydroxylase-positive cells in substantia nigra is reduced by 48% in Aqp9 knockout mice compared with 67% in WT littermates. Our results show that AQP9 -selectively expressed in catecholaminergic neurons-is permeable to MPP+ and suggest that this aquaglyceroporin contributes to the selective vulnerability of nigral dopaminergic neurons by providing an entry route for parkinsonogenic toxins. To our knowledge this is the first evidence implicating a toxin permeable membrane channel in the pathophysiology of Parkinson's disease.

Dataset Information

Phenotypic and functional characterization of a mouse model of targeted Pig-a deletion in hematopoietic cells.

Publications

Phenotypic and functional characterization of a mouse model of targeted Pig-a deletion in hematopoietic cells.

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