The Experts below are selected from a list of 237 Experts worldwide ranked by ideXlab platform
Shinya Wakusawa - One of the best experts on this subject based on the ideXlab platform.
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Mutational analysis of the MRP2 gene and long-term follow-up of Dubin-Johnson Syndrome in Japan
Journal of Gastroenterology, 2005Co-Authors: Ikuo Machida, Hisao Hayashi, Shinya Wakusawa, Motoyoshi Yano, Fujiko Sanae, Atsushi Kusakabe, Hiroshi Ninomiya, Kentaro YoshiokaAbstract:Background Recent studies have indicated that dysfunction or loss of the multidrug resistance protein 2 (MRP2) is the molecular basis of Dubin-Johnson Syndrome (DJS). To clarify the genetic basis of the disease and the long-term stability of serum bilirubin levels, we conducted a mutational analysis of the MRP2 gene and followed up serum bilirubin levels in Japanese DJS patients 30 years after they were originally diagnosed, based on traditional criteria. Methods Patients were interviewed by telephone, and blood tests, including a genetic analysis of MRP2 , were performed on the patients and family members who gave informed consent. Results Over the 30 years, hyperbilirubinemia remained unchanged in four of the five patients studied, while it worsened in 1 patient whose DJS was complicated by chronic hepatitis C. From an MRP2 gene mutational analysis, six mutations, including the novel mutation 1177C>T, were found. Three patients of a consanguineous family were homozygotes for three mutations (298C>T, 1967+2T>C, and 2439+2T>C). Two patients were compound heterozygotes (1177C>T/2302C>T and 1967+2T>C/2026G>C). A familial study showed no difference in serum bilirubin levels between mutant/wild heterozygotes and wild/wild homozygotes. Conclusions The hyperbilirubinemia of four Japanese patients with DJS, one of whom had a novel mutation, 1177C>T, of the MRP2 gene, had not worsened with aging.
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Mutation analysis of the multidrug resistance protein 2 (MRP2) gene in a Japanese patient with Dubin-Johnson Syndrome.
Hepatology Research, 2004Co-Authors: Ikuo Machida, Hisao Hayashi, Satoshi Suzuki, Yasutaka Inagaki, Shinya WakusawaAbstract:Abstract Dubin–Johnson Syndrome (DJS) is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in a Japanese female with DJS. In this patient, we found a homozygous 2125T > C mutation in exon 17. This mutation affects the conversion of tryptophan 709 to arginine 709 (W709R) in the first ATP-binding cassette in the MRP2 protein. It was concluded that this homozygous mutation of the MRP2 gene contributed to the induction of hyperbilirubinemia in this case.
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Improvement of serum bilirubin levels after venesection in a patient with Dubin-Johnson Syndrome and HCV-positive chronic liver disease.
Journal of Gastroenterology, 2004Co-Authors: Ikuo Machida, Hisao Hayashi, Shinya Wakusawa, Satoshi Suzuki, Motoyoshi YanoAbstract:Direct-type hyperbilirubinemia in Dubin-Johnson Syndrome is due to the genetic dysfunction of multidrug resistance protein 2. However, serum bilirubin levels may fluctuate as a result of acquired conditions. Iron-reduction therapy by venesection, an alternative to interferon, was performed in a 55-year-old male patient with Dubin-Johnson Syndrome complicated by hepatitis C virus-positive chronic liver disease and hepatic iron overload. His pretreatment serum total bilirubin was 10.2 mg/dl, with a dominant direct fraction. The treatment induced a significant reduction in serum total bilirubin, although it remained as high as 7.9 mg/dl. A negative correlation between serum total bilirubin and cumulative bled volume suggested that venesection could suppress bilirubin production from aged erythrocytes. The hepatic iron overload was distributed in hepatocyte lysosomes with Dubin-Johnson granules; thus, it seems that iron removal from the lysosomal granules may also help to reduce serum bilirubin. In conclusion, deep jaundice in a patient with Dubin-Johnson Syndrome complicated by hepatitis C virus-positive chronic liver disease and iron overload was partially improved by iron-reduction therapy.
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Identification of a novel 2026G→C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly^676 to Arg^676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
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Identification of a novel 2026G-->C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome.
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly676 to Arg676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
Ikuo Machida - One of the best experts on this subject based on the ideXlab platform.
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Mutational analysis of the MRP2 gene and long-term follow-up of Dubin-Johnson Syndrome in Japan
Journal of Gastroenterology, 2005Co-Authors: Ikuo Machida, Hisao Hayashi, Shinya Wakusawa, Motoyoshi Yano, Fujiko Sanae, Atsushi Kusakabe, Hiroshi Ninomiya, Kentaro YoshiokaAbstract:Background Recent studies have indicated that dysfunction or loss of the multidrug resistance protein 2 (MRP2) is the molecular basis of Dubin-Johnson Syndrome (DJS). To clarify the genetic basis of the disease and the long-term stability of serum bilirubin levels, we conducted a mutational analysis of the MRP2 gene and followed up serum bilirubin levels in Japanese DJS patients 30 years after they were originally diagnosed, based on traditional criteria. Methods Patients were interviewed by telephone, and blood tests, including a genetic analysis of MRP2 , were performed on the patients and family members who gave informed consent. Results Over the 30 years, hyperbilirubinemia remained unchanged in four of the five patients studied, while it worsened in 1 patient whose DJS was complicated by chronic hepatitis C. From an MRP2 gene mutational analysis, six mutations, including the novel mutation 1177C>T, were found. Three patients of a consanguineous family were homozygotes for three mutations (298C>T, 1967+2T>C, and 2439+2T>C). Two patients were compound heterozygotes (1177C>T/2302C>T and 1967+2T>C/2026G>C). A familial study showed no difference in serum bilirubin levels between mutant/wild heterozygotes and wild/wild homozygotes. Conclusions The hyperbilirubinemia of four Japanese patients with DJS, one of whom had a novel mutation, 1177C>T, of the MRP2 gene, had not worsened with aging.
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Mutation analysis of the multidrug resistance protein 2 (MRP2) gene in a Japanese patient with Dubin-Johnson Syndrome.
Hepatology Research, 2004Co-Authors: Ikuo Machida, Hisao Hayashi, Satoshi Suzuki, Yasutaka Inagaki, Shinya WakusawaAbstract:Abstract Dubin–Johnson Syndrome (DJS) is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in a Japanese female with DJS. In this patient, we found a homozygous 2125T > C mutation in exon 17. This mutation affects the conversion of tryptophan 709 to arginine 709 (W709R) in the first ATP-binding cassette in the MRP2 protein. It was concluded that this homozygous mutation of the MRP2 gene contributed to the induction of hyperbilirubinemia in this case.
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Improvement of serum bilirubin levels after venesection in a patient with Dubin-Johnson Syndrome and HCV-positive chronic liver disease.
Journal of Gastroenterology, 2004Co-Authors: Ikuo Machida, Hisao Hayashi, Shinya Wakusawa, Satoshi Suzuki, Motoyoshi YanoAbstract:Direct-type hyperbilirubinemia in Dubin-Johnson Syndrome is due to the genetic dysfunction of multidrug resistance protein 2. However, serum bilirubin levels may fluctuate as a result of acquired conditions. Iron-reduction therapy by venesection, an alternative to interferon, was performed in a 55-year-old male patient with Dubin-Johnson Syndrome complicated by hepatitis C virus-positive chronic liver disease and hepatic iron overload. His pretreatment serum total bilirubin was 10.2 mg/dl, with a dominant direct fraction. The treatment induced a significant reduction in serum total bilirubin, although it remained as high as 7.9 mg/dl. A negative correlation between serum total bilirubin and cumulative bled volume suggested that venesection could suppress bilirubin production from aged erythrocytes. The hepatic iron overload was distributed in hepatocyte lysosomes with Dubin-Johnson granules; thus, it seems that iron removal from the lysosomal granules may also help to reduce serum bilirubin. In conclusion, deep jaundice in a patient with Dubin-Johnson Syndrome complicated by hepatitis C virus-positive chronic liver disease and iron overload was partially improved by iron-reduction therapy.
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Identification of a novel 2026G→C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly^676 to Arg^676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
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Identification of a novel 2026G-->C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome.
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly676 to Arg676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
Kentaro Yoshioka - One of the best experts on this subject based on the ideXlab platform.
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Mutational analysis of the MRP2 gene and long-term follow-up of Dubin-Johnson Syndrome in Japan
Journal of Gastroenterology, 2005Co-Authors: Ikuo Machida, Hisao Hayashi, Shinya Wakusawa, Motoyoshi Yano, Fujiko Sanae, Atsushi Kusakabe, Hiroshi Ninomiya, Kentaro YoshiokaAbstract:Background Recent studies have indicated that dysfunction or loss of the multidrug resistance protein 2 (MRP2) is the molecular basis of Dubin-Johnson Syndrome (DJS). To clarify the genetic basis of the disease and the long-term stability of serum bilirubin levels, we conducted a mutational analysis of the MRP2 gene and followed up serum bilirubin levels in Japanese DJS patients 30 years after they were originally diagnosed, based on traditional criteria. Methods Patients were interviewed by telephone, and blood tests, including a genetic analysis of MRP2 , were performed on the patients and family members who gave informed consent. Results Over the 30 years, hyperbilirubinemia remained unchanged in four of the five patients studied, while it worsened in 1 patient whose DJS was complicated by chronic hepatitis C. From an MRP2 gene mutational analysis, six mutations, including the novel mutation 1177C>T, were found. Three patients of a consanguineous family were homozygotes for three mutations (298C>T, 1967+2T>C, and 2439+2T>C). Two patients were compound heterozygotes (1177C>T/2302C>T and 1967+2T>C/2026G>C). A familial study showed no difference in serum bilirubin levels between mutant/wild heterozygotes and wild/wild homozygotes. Conclusions The hyperbilirubinemia of four Japanese patients with DJS, one of whom had a novel mutation, 1177C>T, of the MRP2 gene, had not worsened with aging.
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Identification of a novel 2026G→C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly^676 to Arg^676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
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Identification of a novel 2026G-->C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome.
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly676 to Arg676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
Hisao Hayashi - One of the best experts on this subject based on the ideXlab platform.
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Mutational analysis of the MRP2 gene and long-term follow-up of Dubin-Johnson Syndrome in Japan
Journal of Gastroenterology, 2005Co-Authors: Ikuo Machida, Hisao Hayashi, Shinya Wakusawa, Motoyoshi Yano, Fujiko Sanae, Atsushi Kusakabe, Hiroshi Ninomiya, Kentaro YoshiokaAbstract:Background Recent studies have indicated that dysfunction or loss of the multidrug resistance protein 2 (MRP2) is the molecular basis of Dubin-Johnson Syndrome (DJS). To clarify the genetic basis of the disease and the long-term stability of serum bilirubin levels, we conducted a mutational analysis of the MRP2 gene and followed up serum bilirubin levels in Japanese DJS patients 30 years after they were originally diagnosed, based on traditional criteria. Methods Patients were interviewed by telephone, and blood tests, including a genetic analysis of MRP2 , were performed on the patients and family members who gave informed consent. Results Over the 30 years, hyperbilirubinemia remained unchanged in four of the five patients studied, while it worsened in 1 patient whose DJS was complicated by chronic hepatitis C. From an MRP2 gene mutational analysis, six mutations, including the novel mutation 1177C>T, were found. Three patients of a consanguineous family were homozygotes for three mutations (298C>T, 1967+2T>C, and 2439+2T>C). Two patients were compound heterozygotes (1177C>T/2302C>T and 1967+2T>C/2026G>C). A familial study showed no difference in serum bilirubin levels between mutant/wild heterozygotes and wild/wild homozygotes. Conclusions The hyperbilirubinemia of four Japanese patients with DJS, one of whom had a novel mutation, 1177C>T, of the MRP2 gene, had not worsened with aging.
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Mutation analysis of the multidrug resistance protein 2 (MRP2) gene in a Japanese patient with Dubin-Johnson Syndrome.
Hepatology Research, 2004Co-Authors: Ikuo Machida, Hisao Hayashi, Satoshi Suzuki, Yasutaka Inagaki, Shinya WakusawaAbstract:Abstract Dubin–Johnson Syndrome (DJS) is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in a Japanese female with DJS. In this patient, we found a homozygous 2125T > C mutation in exon 17. This mutation affects the conversion of tryptophan 709 to arginine 709 (W709R) in the first ATP-binding cassette in the MRP2 protein. It was concluded that this homozygous mutation of the MRP2 gene contributed to the induction of hyperbilirubinemia in this case.
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Improvement of serum bilirubin levels after venesection in a patient with Dubin-Johnson Syndrome and HCV-positive chronic liver disease.
Journal of Gastroenterology, 2004Co-Authors: Ikuo Machida, Hisao Hayashi, Shinya Wakusawa, Satoshi Suzuki, Motoyoshi YanoAbstract:Direct-type hyperbilirubinemia in Dubin-Johnson Syndrome is due to the genetic dysfunction of multidrug resistance protein 2. However, serum bilirubin levels may fluctuate as a result of acquired conditions. Iron-reduction therapy by venesection, an alternative to interferon, was performed in a 55-year-old male patient with Dubin-Johnson Syndrome complicated by hepatitis C virus-positive chronic liver disease and hepatic iron overload. His pretreatment serum total bilirubin was 10.2 mg/dl, with a dominant direct fraction. The treatment induced a significant reduction in serum total bilirubin, although it remained as high as 7.9 mg/dl. A negative correlation between serum total bilirubin and cumulative bled volume suggested that venesection could suppress bilirubin production from aged erythrocytes. The hepatic iron overload was distributed in hepatocyte lysosomes with Dubin-Johnson granules; thus, it seems that iron removal from the lysosomal granules may also help to reduce serum bilirubin. In conclusion, deep jaundice in a patient with Dubin-Johnson Syndrome complicated by hepatitis C virus-positive chronic liver disease and iron overload was partially improved by iron-reduction therapy.
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Identification of a novel 2026G→C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly^676 to Arg^676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
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Identification of a novel 2026G-->C mutation of the MRP2 gene in a Japanese patient with Dubin-Johnson Syndrome.
Journal of Human Genetics, 2003Co-Authors: Shinya Wakusawa, Hisao Hayashi, Ikuo Machida, Satoshi Suzuki, Motoyoshi Yano, Kentaro YoshiokaAbstract:Dubin-Johnson Syndrome is a recessive inherited disorder with conjugated hyperbilirubinemia caused by a dysfunction of multidrug resistance protein 2 (MRP2) on the canalicular membrane of hepatocytes. A mutational analysis of the MRP2 gene was carried out in three Japanese patients and their family members. In two patients, the homozygous mutations c.1901del67 and c,2272del168 were found. In the third patient, a −24C→T polymorphism and the two mutations c.1901del67 and 2026G→C were detected. The 2026G→C mutation was a novel mutation in exon 16 affecting the conversion of Gly676 to Arg676 (G676R) in the MRP2 protein, and was not detected in fifty healthy volunteers. The G676R mutation was located in the Walker A motif of the first nucleotide binding domain in the MRP2 protein, and it was suggested that the mutation induced the dysfunction of the MRP2 protein. It was concluded that the compound heterozygosity of the two mutations of the MRP2 gene in the third patient contributed to the induction of hyperbilirubinemia in this case.
Dietrich Keppler - One of the best experts on this subject based on the ideXlab platform.
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A common Dubin-Johnson Syndrome mutation impairs protein maturation and transport activity of MRP2 (ABCC2)
American Journal of Physiology-gastrointestinal and Liver Physiology, 2002Co-Authors: Verena Keitel, Anne T. Nies, Manuela Brom, Johanna Hummel-eisenbeiss, Herbert Spring, Dietrich KepplerAbstract:Absence of a functional multidrug resistance protein 2 (MRP2; symbol ABCC2) from the hepatocyte canalicular membrane is the molecular basis of Dubin- Johnson Syndrome, an inherited disorder associa...
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Impaired protein maturation of the conjugate export pump multidrug resistance protein 2 as a consequence of a deletion mutation in Dubin-Johnson Syndrome.
Hepatology, 2000Co-Authors: Verena Keitel, Anne T. Nies, Manuela Brom, Herbert Spring, Jürgen Kartenbeck, Dietrich KepplerAbstract:The Dubin-Johnson Syndrome is an inherited disorder characterized by conjugated hyperbilirubinemia. The deficient hepatobiliary transport of anionic conjugates is caused by the absence of a functional multidrug-resistance protein 2 (MRP2, symbol ABCC2) from the apical (canalicular) membrane of hepatocytes. Mechanisms underlying this deficiency may include rapid degradation of mutated MRP2 messenger RNA (mRNA) or impaired MRP2 protein maturation and trafficking. We investigated the consequences of the mutation MRP2Δ(R,M), which leads to the loss of 2 amino acids from the second ATP-binding domain of MRP2. The MRP2Δ(R,M) mutation is associated with the absence of the MRP2 glycoprotein from the apical membrane of hepatocytes. Transfection of mutated MRP2 complementary DNA (cDNA) led to an MRP2Δ(R,M) protein that was only core glycosylated, sensitive to endoglycosidase H digestion, and located in the endoplasmic reticulum (ER) of transfected HEK293 and HepG2 cells. This indicated that deletion of Arg1392 and Met1393 leads to impaired maturation and trafficking of the protein from the ER to the Golgi complex. Inhibition of proteasome function resulted in a paranuclear accumulation of the MRP2Δ(R,M) protein, suggesting that proteasomes are involved in the degradation of the mutant protein. This is the first mutation in Dubin-Johnson Syndrome shown to cause deficient MRP2 maturation and impaired sorting of this glycoprotein to the apical membrane. (Hepatology2000;32:1317-1328.)
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Exon-intron organization of the human multidrug-resistance protein 2 (MRP2) gene mutated in Dubin–Johnson Syndrome
Gastroenterology, 1999Co-Authors: Hiroyuki Tsujii, Jörg König, Daniel Rost, Birgit Stöckel, Ulrich Leuschner, Dietrich KepplerAbstract:Abstract Background & Aims: The Dubin–Johnson Syndrome is characterized by conjugated hyperbilirubinemia and by impaired secretion of anionic conjugates from hepatocytes into bile. Absence of the multidrug-resistance protein 2 (MRP2; symbol ABCC2), an adenosine triphosphate–dependent conjugate export pump, from the hepatocyte canalicular membrane is the molecular basis of this Syndrome. The aim of this study was the elucidation of all exon-intron boundaries of the MRP2 gene as a prerequisite for the analysis of mutations in patients with Dubin–Johnson Syndrome. Methods: Exon-intron boundaries of MRP2 were determined, and the amplified exons were screened for mutations. Immunofluorescence microscopy served to localize the MRP2 protein in human liver. Results: The human MRP2 gene is ~45 kilobases long; it contains 32 exons and a high proportion of class 0 introns. In 2 patients with Dubin–Johnson Syndrome, we detected a nonsense mutation at codon 1066 and a 6-nucleotide deletion mutation affecting codons 1392–1394. The MRP2 protein was absent from the canalicular membrane of both patients. Conclusions: The mutations detected so far show that various mutations in the MRP2 gene can lead to the Dubin–Johnson Syndrome. The exon-intron boundaries established in this article will facilitate the analysis of additional mutations in the MRP2 gene. GASTROENTEROLOGY 1999;117:653-660
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Absence of the canalicular isoform of the MRP gene–encoded conjugate export pump from the hepatocytes in Dubin‐Johnson Syndrome
Hepatology, 1996Co-Authors: Jürgen Kartenbeck, U Leuschner, R Mayer, Dietrich KepplerAbstract:Abstract The Dubin-Johnson Syndrome is characterized by an inherited defect in the secretion of amphiphilic anionic conjugates from hepatocytes into the bile. We have recently identified the membrane protein mediating the adenosine triphosphate (ATP)-dependent transport of glutathione and glucuronate conjugates as a multidrug-resistance protein (MRP) and localized it to the canalicular as well as to the lateral hepatocyte plasma membrane. In the present study we show the selective absence of the canalicular isoform of MRP (cMRP) from the hepatocytes in a patient with Dubin-Johnson Syndrome by double-label immunofluorescence and confocal laser scanning microscopy using antibodies directed against MRP and dipeptidyl-peptidase IV (DPPIV). Another isoform of MRP was detected, however, in the lateral hepatocyte membrane of the patient. Moreover, MRP was present on immunoblots of erythrocyte membranes from Dubin-Johnson Syndrome and normal humans. These findings are analogous to our recent observations on the localization of the rat homolog of MRP and its canalicular isoform, cMRP, in normal and transport- deficient GY/TR- Wistar rat liver. The elucidation of the selective absence of an isoform of MRP and from the canalicular membrane domain in conjunction with the defined substrate specificity of the MRP and cMRP gene-encoded conjugate export pumps contributes to the molecular definition of the transport defect in Dubin-Johnson Syndrome. (Hepatology 1996 May;23(5):1061-6)
