Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027947 (neutropenia)
 17,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Glycogen storage disease type Ib has all the clinical manifestations of glycogen storage disease type Ia such as hepatomegaly, growth retardation, bleeding tendency, hypoglycemia, hyperlactacidemia, hyperuricemia, hyperlipidemia, impaired platelet function plus neutropenia. The overall glucose-6-phosphatase activity in disrupted microsomes from liver is normal whereas glucose-6-phosphate translocase, the first enzyme in the glucose-6-phosphate transport system is absent. There is no glucose-6-phosphatase activity in vivo. Recent results show that in granulocytes the glucose-6-phosphate-dependent hexosemonophosphate-shunt is impaired.
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PMID:Glycogen storage disease type Ib. 631 72

A male child presented at 5 months of age with vomiting, diarrhoea, hypoglycaemia and hepatomegaly. Histology on a frozen liver biopsy suggested glycogen storage disease (GSD), while biochemical analyses confirmed an elevated glycogen content and normal activities of the GSD enzymes with the proviso that a variant of GSD 1 should be considered. The patient presented at 9 months of age with severe lactic acidosis and hypoglycaemia. A glucagon tolerance test and galactose load test on the patient produced no glycaemic response. A second biopsy was obtained and appropriately handled for the investigation of variants of the glucose-6-phosphatase enzyme (G6Pase) complex. Results showed that the patient had a deficiency of two transport proteins of the G6Pase complex, namely glucose-6-phosphate translocase and pyrophosphate translocase, i.e. GSD 1b/1c beta. These results were confirmed by additional kinetic analyses which provided confirmation of the double translocase deficiency. Evidence for inhibitors to these translocases was not found. The patient's treatment has resulted in the hypoglycaemia now being well controlled; however, at 3 years of age, height and weight are markedly lagging and he is moderately developmentally delayed. Neutropenia has not been found and neutrophil function is normal. Double enzyme deficiencies are very rare and possible explanations which might lead to this phenotype are considered. This, to the authors' knowledge, is the first report of a double translocase deficiency causing GSD type 1.
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PMID:Multiple transport protein defects in a patient with glycogen storage disease type 1: GSD 1b/1c beta. 859 36

Glycogen-storage diseases type I (GSD type I) are due to a deficiency in glucose-6-phosphatase, an enzymatic system present in the endoplasmic reticulum that plays a crucial role in blood glucose homeostasis. Unlike GSD type Ia, types Ib and Ic are not due to mutations in the phosphohydrolase gene and are clinically characterized by the presence of associated neutropenia and neutrophil dysfunction. Biochemical evidence indicates the presence of a defect in glucose-6-phosphate (GSD type Ib) or inorganic phosphate (Pi) (GSD type Ic) transport in the microsomes. We have recently cloned a cDNA encoding a putative glucose-6-phosphate translocase. We have now localized the corresponding gene on chromosome 11q23, the region where GSD types Ib and Ic have been mapped. Using SSCP analysis and sequencing, we have screened this gene, for mutations in genomic DNA, from patients from 22 different families who have GSD types Ib and Ic. Of 20 mutations found, 11 result in truncated proteins that are probably nonfunctional. Most other mutations result in substitutions of conserved or semiconserved residues. The two most common mutations (Gly339Cys and 1211-1212 delCT) together constitute approximately 40% of the disease alleles. The fact that the same mutations are found in GSD types Ib and Ic could indicate either that Pi and glucose-6-phosphate are transported in microsomes by the same transporter or that the biochemical assays used to differentiate Pi and glucose-6-phosphate transport defects are not reliable.
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PMID:A gene on chromosome 11q23 coding for a putative glucose- 6-phosphate translocase is mutated in glycogen-storage disease types Ib and Ic. 975 26

The purpose of this work was to test the hypothesis that mutations in the putative glucose 6-phosphate translocase gene would account for most of the cases of GSD I that are not explained by mutations in the phosphohydrolase gene, ie that are not type Ia. Twenty-three additional families diagnosed as having GSD I non-a (GSDIb, Ic or Id) have now been analysed. The 9exons of the gene were amplified by PCR and mutations searched both by SSCP and heteroduplex analysis. Except for one family in which only one mutation was found, all patients had two allelic mutations in the gene encoding the putative glucose 6-phosphate translocase. Sixteen of the mutations are new and they are all predicted to lead to non-functional proteins. All investigated patients had some degree of neutropenia or neutrophil dysfunction and the clinical phenotype of the four new patients who had been diagnosed as GSD Ic and the one diagnosed as GSD Id was no different from the GSD Ib patients. Since these patients, and the four type Ic patients from two families previously studied, shared several mutations with GSD Ib patients, we conclude that their basic defect is in the putative glucose 6-phosphate translocase and that they should be reclassified as GSD Ib. Isolated defects in microsomal Pi transporter or in microsomal glucose transporter must be very rare or have phenotypes that are not recognised as GSD I, so that in practice there are only two subtypes of GSD I (GSD Ia and GSD Ib).
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PMID:The putative glucose 6-phosphate translocase gene is mutated in essentially all cases of glycogen storage disease type I non-a. 1048 62

Glycogen storage diseases type 1 (GSD 1) are a group of autosomal recessive disorders characterized by impairment of terminal steps of glycogenolysis and gluconeogenesis. Mutations of the glucose-6-phosphatase gene are responsible for the most frequent form of GSD 1, the subtype 1a, while mutations of the glucose-6-phosphate transporter gene (G6PT) have recently been shown to cause the non 1a forms of GSD, namely the 1b and 1c subtypes. Here, we report on the analysis by single-stranded conformation polymorphism (SSCP) and/or DNA sequencing of the exons of the G6PT in 14 patients diagnosed either as affected by the GSD 1b or 1c subtypes. Mutations in the G6PT gene were found in all patients. Four of the detected mutations were novel mutations, while the others were previously described. Our results confirm that the GSD 1b and 1c forms are due to mutations in the same gene, i.e. the G6PT gene. We also show that the same kind of mutation can be associated or not with evident clinical complications such as neutrophil impairment. Since no correlation between the type and position of the mutation and the severity of the disease was found, other unknown factors may cause the expression of symptoms, such as neutropenia, which dramatically influence the severity of the disease.
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PMID:Mutations in the glucose-6-phosphate transporter (G6PT) gene in patients with glycogen storage diseases type 1b and 1c. 1051 30

We report 2 patients with atypical glycogen storage disease type Ib without neutropenia or infectious complications. Neither patient was deficient in hepatic glucose-6-phosphatase activities in microsome-disrupted homogenates; both had mutations in the glucose-6-phosphate transporter gene, suggesting an allelic variant of glycogen storage disease type Ib.
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PMID:Glycogen storage disease type Ib without neutropenia. 1093 21

We investigated the quantitative expression of the human glucose-6-phosphate translocase gene (G6PT1) and its splicing variants in human tissues. The G6PT1 gene was strongly expressed in liver, kidney and haematopoietic progenitor cells, which might explain major clinical symptoms such as hepatomegaly, nephromegaly and neutropenia in glycogen storage diseases type Ib. Reverse transcriptase-mediated PCR amplification of G6PT1 cDNA revealed several splicing variants in tissue-specific manners. The brain-specific isoform, which has an additional 22 amino acids between exons 6 and 8, was also identified in heart and skeletal muscle. A new splicing variant, although less prominent in quantity and lacking polypeptide loops corresponding to exons 2 and 3, may have a distinct substrate affinity or specificity in leukocytes and haematopoietic progenitors. In conclusion, the G6PT1 gene was expressed in various tissues, and alternative splicing variants exist in tissue-specific manners.
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PMID:Quantitative analysis of glucose-6-phosphate translocase gene expression in various human tissues and haematopoietic progenitor cells. 1103 33

Glycogen storage disease type 1 (GSD-1), also known as von Gierke disease, is a group of autosomal recessive metabolic disorders caused by deficiencies in the activity of the glucose-6-phosphatase (G6Pase) system that consists of at least two membrane proteins, glucose-6-phosphate transporter (G6PT) and G6Pase. G6PT translocates glucose-6-phosphate (G6P) from cytoplasm to the lumen of the endoplasmic reticulum (ER) and G6Pase catalyzes the hydrolysis of G6P to produce glucose and phosphate. Therefore, G6PT and G6Pase work in concert to maintain glucose homeostasis. Deficiencies in G6Pase and G6PT cause GSD-1a and GSD-1b, respectively. Both manifest functional G6Pase deficiency characterized by growth retardation, hypoglycemia, hepatomegaly, kidney enlargement, hyperlipidemia, hyperuricemia, and lactic acidemia. GSD-1b patients also suffer from chronic neutropenia and functional deficiencies of neutrophils and monocytes, resulting in recurrent bacterial infections as well as ulceration of the oral and intestinal mucosa. The G6Pase gene maps to chromosome 17q21 and encodes a 36-kDa glycoprotein that is anchored to the ER by 9 transmembrane helices with its active site facing the lumen. Animal models of GSD-1a have been developed and are being exploited to delineate the disease more precisely and to develop new therapies. The G6PT gene maps to chromosome 11q23 and encodes a 37-kDa protein that is anchored to the ER by 10 transmembrane helices. A functional assay for the recombinant G6PT protein has been established, which showed that G6PT functions as a G6P transporter in the absence of G6Pase. However, microsomal G6P uptake activity was markedly enhanced in the simultaneous presence of G6PT and G6Pase. The cloning of the G6PT gene now permits animal models of GSD-1b to be generated. These recent developments are increasing our understanding of the GSD-l disorders and the G6Pase system, knowledge that will facilitate the development of novel therapeutic approaches for these disorders.
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PMID:The molecular basis of type 1 glycogen storage diseases. 1189 41

Glycogen storage disease type I (GSD-I) is a group of autosomal recessive disorders with an incidence of 1 in 100,000. The two major subtypes are GSD-Ia (MIM232200), caused by a deficiency of glucose-6-phosphatase (G6Pase), and GSD-Ib (MIM232220), caused by a deficiency in the glucose-6-phosphate transporter (G6PT). Both G6Pase and G6PT are associated with the endoplasmic reticulum (ER) membrane. G6PT translocates glucose-6-phosphate (G6P) from the cytoplasm into the lumen of the ER, where G6Pase hydrolyses the G6P into glucose and phosphate. Together G6Pase and G6PT maintain glucose homeostasis. G6Pase is expressed in gluconeogenic tissues, the liver, kidney, and intestine. However G6PT, which transports G6P efficiently only in the presence of G6Pase, is expressed ubiquitously. This suggests that G6PT may play other roles in tissues lacking G6Pase. Both GSD-Ia and GSD-Ib patients manifest phenotypic G6Pase deficiency, characterized by growth retardation, hypoglycemia, hepatomegaly, nephromegaly, hyperlipidemia, hyperuricemia, and lactic academia and the current treatment is a dietary therapy. GSD-Ib patients also suffer from chronic neutropenia and functional deficiencies of neutrophils and monocytes, which is treated with granulocyte colony stimulating factor to restore myeloid function. The GSD-Ia and GSD-Ib genes have been cloned. To date, 76 G6Pase and 69 G6PT mutations have been identified in GSD-I patients. A database of the residual enzymatic activity retained by the G6Pase missense mutants is facilitating the correlation of the disease phenotype with the patients' genotype. While the molecular basis for the GSD-I disorders are now known and symptomatic therapies are available, many aspects of the diseases are still poorly understood, and there are no cures. Recently developed animal models of the disorders are now being exploited to delineate the disease more precisely and develop new, more causative therapies.
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PMID:Type I glycogen storage diseases: disorders of the glucose-6-phosphatase complex. 1194 31

Glycogen storage disease (GSD) is a rare autosomal-recessive disorder characterized by hypoglycemia, hepatosplenomegaly, seizures, and failure to thrive in infants. Neutropenia and/or neutrophil dysfunction develops in GSD1b, but not in other types. GSD1b results from a deficiency of the glucose-6-phosphate translocase enzyme and the genetic defect maps to chromosome 11q23. Patients with GSD1b are susceptible to recurrent bacterial infections, commonly involving the perirectal area, ears, skin, and urinary tract, although life-threatening infections, such as septicemia, pneumonia, and meningitis occur less frequently. Although the exact mechanism of neutropenia in patients with GSD1b is not known, treatment with recombinant human granulocyte colony-stimulating factor (G-CSF) has reduced the incidence of infections and has improved the quality of life of these patients. Defects in neutrophil chemotaxis and intracellular bacterial killing have been described and appear to be corrected by the use of G-CSF. To date, no cases of myelodysplasia or acute myeloid leukemia have been observed in patients with GSD1b treated with G-CSF. A significant complication of cytokine therapy is the development of hypersplenism, requiring either a reduction in the dosage of G-CSF or splenectomy.
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PMID:Glycogen storage disease. 1195 92


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