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Sood V, Squires JE, Mazariegos GV, Vockley J, McKiernan PJ. Living Related Liver Transplantation for Metabolic Liver Diseases in Children. J Pediatr Gastroenterol Nutr 2021; 72:11-17. [PMID: 32969959 PMCID: PMC10657650 DOI: 10.1097/mpg.0000000000002952] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
ABSTRACT Metabolic liver diseases (MLDs) are a heterogeneous group of inherited conditions for which liver transplantation can provide definitive treatment. The limited availability of deceased donor organs means some who could benefit from transplant do not have this option. Living related liver transplant (LrLT) using relatives as donors has emerged as one solution to this problem. This technique is established worldwide, especially in Asian countries, with shorter waiting times and patient and graft survival rates equivalent to deceased donor liver transplantation. However, living donors are underutilized for MLDs in many western countries, possibly due to the fear of limited efficacy using heterozygous donors. We have reviewed the published literature and shown that the use of heterozygous donors for liver transplantation is safe for the majority of MLDs with excellent metabolic correction. The use of LrLT should be encouraged to complement deceased donor liver transplantation (DDLT) for treatment of MLDs.
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Affiliation(s)
- Vikrant Sood
- Department of Pediatric Hepatology, Institute of Liver and Biliary Sciences, New Delhi, India
| | | | - George V. Mazariegos
- Division of Pediatric Transplantation, Hillman Center for Pediatric Transplantation
| | - Jerry Vockley
- Center for Rare Disease Therapy, UPMC Children’s Hospital of Pittsburgh, Pittsburgh, PA
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2
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Liu M, Sun LY. Liver Transplantation for Glycogen Storage Disease Type IV. Front Pediatr 2021; 9:633822. [PMID: 33681109 PMCID: PMC7933444 DOI: 10.3389/fped.2021.633822] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/26/2020] [Accepted: 02/02/2021] [Indexed: 11/24/2022] Open
Abstract
Glycogen storage disease type IV (GSD IV) is a rare autosomal recessive disorder caused by glycogen-branching enzyme (GBE) deficiency, leading to accumulation of amylopectin-like glycogen that may damage affected tissues. The clinical manifestations of GSD IV are heterogeneous; one of which is the classic manifestation of progressive hepatic fibrosis. There is no specific treatment available for GSD IV. Currently, liver transplantation is an option. It is crucial to evaluate long-term outcomes of liver transplantation. We reviewed the published literature for GSD IV patients undergoing liver transplantation. To date, some successful liver transplantations have increased the quantity and quality of life in patients. Although the extrahepatic manifestations of GSD IV may still progress after transplantation, especially cardiomyopathy. Patients with cardiac involvement are candidates for cardiac transplantation. Liver transplantation remains the only effective therapeutic option for treatment of GSD IV. However, liver transplantation may not alter the extrahepatic progression of GSD IV. Patients should be carefully assessed before liver transplantation.
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Affiliation(s)
- Min Liu
- Department of Liver Transplantation Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China.,National Clinical Research Centre for Digestive Diseases, Beijing Friendship Hospital, Capital Medical University, Beijing, China
| | - Li-Ying Sun
- Department of Liver Transplantation Center, Beijing Friendship Hospital, Capital Medical University, Beijing, China.,National Clinical Research Centre for Digestive Diseases, Beijing Friendship Hospital, Capital Medical University, Beijing, China.,Department of Intensive Care Unit, Beijing Friendship Hospital, Capital Medical University, Beijing, China
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3
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Choi SY, Kang B, Choe JY, Lee Y, Jang HJ, Park HD, Lee SK, Choe YH. A Case of Glycogen Storage Disease IV with Rare Homozygous Mutations in the Glycogen Branching Enzyme Gene. Pediatr Gastroenterol Hepatol Nutr 2018; 21:365-368. [PMID: 30345254 PMCID: PMC6182483 DOI: 10.5223/pghn.2018.21.4.365] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/13/2018] [Accepted: 03/17/2018] [Indexed: 11/14/2022] Open
Abstract
Glycogen storage disease (GSD) IV is a rare autosomal recessive inherited disorder caused by mutations in the gene coding for glycogen branching enzyme leading to progressive liver disease. GSD IV is associated with mutations in GBE1, which encodes the glycogen branching enzyme. We report a case of GSD IV with rare homozygous mutations in the GBE1 gene (c.791G>A (p.Gly264Glu), which was successfully treated by liver transplantation.
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Affiliation(s)
- So Yoon Choi
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.,Department of Pediatrics, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea
| | - Ben Kang
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.,Department of Pediatrics, School of Medicine, Kyungpook National University, Daegu, Korea
| | - Jae Young Choe
- Department of Pediatrics, School of Medicine, Kyungpook National University, Daegu, Korea
| | - Yoon Lee
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.,Department of Pediatrics, Korea University College of Medicine, Seoul, Korea
| | - Hyo Jeong Jang
- Department of Pediatrics, Keimyung University School of Medicine, Daegu, Korea
| | - Hyung-Doo Park
- Department of Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Suk-Koo Lee
- Department of Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Yon Ho Choe
- Department of Pediatrics, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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4
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Szymańska E, Szymańska S, Truszkowska G, Ciara E, Pronicki M, Shin YS, Podskarbi T, Kępka A, Śpiewak M, Płoski R, Bilińska ZT, Rokicki D. Variable clinical presentation of glycogen storage disease type IV: from severe hepatosplenomegaly to cardiac insufficiency. Some discrepancies in genetic and biochemical abnormalities. Arch Med Sci 2018; 14:237-247. [PMID: 29379554 PMCID: PMC5778435 DOI: 10.5114/aoms.2018.72246] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Accepted: 06/26/2017] [Indexed: 12/20/2022] Open
Affiliation(s)
- Edyta Szymańska
- Department of Pediatrics, Nutrition and Metabolic Disorders, the Children’s Memorial Health Institute, Warsaw, Poland
| | - Sylwia Szymańska
- Department of Pathology, the Children’s Memorial Health Institute, Warsaw, Poland
| | - Grażyna Truszkowska
- Department of Medical Biology, Molecular Biology Laboratory, Institute of Cardiology, Warsaw, Poland
| | - Elżbieta Ciara
- Department of Medical Genetics, the Children’s Memorial Health Institute, Warsaw, Poland
| | - Maciej Pronicki
- Department of Pathology, the Children’s Memorial Health Institute, Warsaw, Poland
| | - Yoon S. Shin
- University Children’s Hospital and Molecular Genetics and Metabolism Laboratory, Munich, Germany
| | | | - Alina Kępka
- Department of Biochemistry, Radioimmunology and Experimental Medicine, the Children’s Memorial Health Institute, Warsaw, Poland
| | - Mateusz Śpiewak
- Cardiac Magnetic Resonance Unit, Institute of Cardiology, Warsaw, Poland
| | - Rafał Płoski
- Department of Medical Genetics, Centre of Biostructure, Medical University of Warsaw, Warsaw, Poland
| | - Zofia T. Bilińska
- Unit for Screening Studies in Inherited Cardiovascular Diseases, Institute of Cardiology, Warsaw, Poland
| | - Dariusz Rokicki
- Department of Pediatrics, Nutrition and Metabolic Disorders, the Children’s Memorial Health Institute, Warsaw, Poland
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5
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Yi H, Zhang Q, Brooks ED, Yang C, Thurberg BL, Kishnani PS, Sun B. Systemic Correction of Murine Glycogen Storage Disease Type IV by an AAV-Mediated Gene Therapy. Hum Gene Ther 2016; 28:286-294. [PMID: 27832700 DOI: 10.1089/hum.2016.099] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Deficiency of glycogen branching enzyme (GBE) causes glycogen storage disease type IV (GSD IV), which is characterized by the accumulation of a less branched, poorly soluble form of glycogen called polyglucosan (PG) in multiple tissues. This study evaluates the efficacy of gene therapy with an adeno-associated viral (AAV) vector in a mouse model of adult form of GSD IV (Gbe1ys/ys). An AAV serotype 9 (AAV9) vector containing a human GBE expression cassette (AAV-GBE) was intravenously injected into 14-day-old Gbe1ys/ys mice at a dose of 5 × 1011 vector genomes per mouse. Mice were euthanized at 3 and 9 months of age. In the AAV-treated mice at 3 months of age, GBE enzyme activity was highly elevated in heart, which is consistent with the high copy number of the viral vector genome detected. GBE activity also increased significantly in skeletal muscles and the brain, but not in the liver. The glycogen content was reduced to wild-type levels in muscles and significantly reduced in the liver and brain. At 9 months of age, though GBE activity was only significantly elevated in the heart, glycogen levels were significantly reduced in the liver, brain, and skeletal muscles of the AAV-treated mice. In addition, the AAV treatment resulted in an overall decrease in plasma activities of alanine transaminase, aspartate transaminase, and creatine kinase, and a significant increase in fasting plasma glucose concentration at 9 months of age. This suggests an alleviation of damage and improvement of function in the liver and muscles by the AAV treatment. This study demonstrated a long-term benefit of a systemic injection of an AAV-GBE vector in Gbe1ys/ys mice.
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Affiliation(s)
- Haiqing Yi
- 1 Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center , Durham, North Carolina
| | - Quan Zhang
- 1 Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center , Durham, North Carolina
| | - Elizabeth D Brooks
- 1 Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center , Durham, North Carolina
| | - Chunyu Yang
- 1 Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center , Durham, North Carolina
| | - Beth L Thurberg
- 2 Department of Pathology, Sanofi Genzyme , Framingham, Massachusetts
| | - Priya S Kishnani
- 1 Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center , Durham, North Carolina
| | - Baodong Sun
- 1 Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center , Durham, North Carolina
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Alglucosidase alfa treatment alleviates liver disease in a mouse model of glycogen storage disease type IV. Mol Genet Metab Rep 2016; 9:31-33. [PMID: 27747161 PMCID: PMC5053031 DOI: 10.1016/j.ymgmr.2016.09.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2016] [Revised: 09/20/2016] [Accepted: 09/20/2016] [Indexed: 01/21/2023] Open
Abstract
Patients with progressive hepatic form of GSD IV often die of liver failure in early childhood. We tested the feasibility of using recombinant human acid-α glucosidase (rhGAA) for treating GSD IV. Weekly intravenously injection of rhGAA at 40 mg/kg for 4 weeks significantly reduced hepatic glycogen accumulation, lowered liver/body weight ratio, and reduced plasma ALP and ALT activities in GSD IV mice. Our data suggests that rhGAA is a potential therapy for GSD IV. An FDA approved therapy is proposed as a new therapeutic approach for GSD IV. A short-term rhGAA treatment significantly reduced liver glycogen content in GSD IV mice. rhGAA treatment alleviated liver disease progression in GSD IV mice. Our data suggests that rhGAA is a potential therapy for hepatic form of GSD IV.
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Orhan Akman H, Emmanuele V, Kurt YG, Kurt B, Sheiko T, DiMauro S, Craigen WJ. A novel mouse model that recapitulates adult-onset glycogenosis type 4. Hum Mol Genet 2015; 24:6801-10. [PMID: 26385640 DOI: 10.1093/hmg/ddv385] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Accepted: 09/14/2015] [Indexed: 01/11/2023] Open
Abstract
Glycogen storage disease type IV (GSD IV) is a rare autosomal recessive disorder caused by deficiency of the glycogen-branching enzyme (GBE). The diagnostic hallmark of the disease is the accumulation of a poorly branched form of glycogen known as polyglucosan (PG). The disease is clinically heterogeneous, with variable tissue involvement and age at onset. Complete loss of enzyme activity is lethal in utero or in infancy and affects primarily the muscle and the liver. However, residual enzyme activity as low as 5-20% leads to juvenile or adult onset of a disorder that primarily affects the central and peripheral nervous system and muscles and in the latter is termed adult polyglucosan body disease (APBD). Here, we describe a mouse model of GSD IV that reflects this spectrum of disease. Homologous recombination was used to knock in the most common GBE1 mutation p.Y329S c.986A > C found in APBD patients of Ashkenazi Jewish decent. Mice homozygous for this allele (Gbe1(ys/ys)) exhibit a phenotype similar to APBD, with widespread accumulation of PG. Adult mice exhibit progressive neuromuscular dysfunction and die prematurely. While the onset of symptoms is limited to adult mice, PG accumulates in tissues of newborn mice but is initially absent from the cerebral cortex and heart muscle. Thus, PG is well tolerated in most tissues, but the eventual accumulation in neurons and their axons causes neuropathy that leads to hind limb spasticity and premature death. This mouse model mimics the pathology and pathophysiologic features of human adult-onset branching enzyme deficiency.
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Affiliation(s)
- H Orhan Akman
- Department of Neurology, Columbia University Medical Center, New York, NY, USA,
| | - Valentina Emmanuele
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | | | - Bülent Kurt
- Department of Pathology, Gülhane Medical Military Academy, Ankara, Turkey
| | | | - Salvatore DiMauro
- Department of Neurology, Columbia University Medical Center, New York, NY, USA
| | - William J Craigen
- Department of Molecular and Human Genetics and Department of Pediatrics, Baylor College of Medicine, Houston, TX, USA
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Froese DS, Michaeli A, McCorvie TJ, Krojer T, Sasi M, Melaev E, Goldblum A, Zatsepin M, Lossos A, Álvarez R, Escribá PV, Minassian BA, von Delft F, Kakhlon O, Yue WW. Structural basis of glycogen branching enzyme deficiency and pharmacologic rescue by rational peptide design. Hum Mol Genet 2015. [PMID: 26199317 PMCID: PMC4581599 DOI: 10.1093/hmg/ddv280] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Glycogen branching enzyme 1 (GBE1) plays an essential role in glycogen biosynthesis by generating α-1,6-glucosidic branches from α-1,4-linked glucose chains, to increase solubility of the glycogen polymer. Mutations in the GBE1 gene lead to the heterogeneous early-onset glycogen storage disorder type IV (GSDIV) or the late-onset adult polyglucosan body disease (APBD). To better understand this essential enzyme, we crystallized human GBE1 in the apo form, and in complex with a tetra- or hepta-saccharide. The GBE1 structure reveals a conserved amylase core that houses the active centre for the branching reaction and harbours almost all GSDIV and APBD mutations. A non-catalytic binding cleft, proximal to the site of the common APBD mutation p.Y329S, was found to bind the tetra- and hepta-saccharides and may represent a higher-affinity site employed to anchor the complex glycogen substrate for the branching reaction. Expression of recombinant GBE1-p.Y329S resulted in drastically reduced protein yield and solubility compared with wild type, suggesting this disease allele causes protein misfolding and may be amenable to small molecule stabilization. To explore this, we generated a structural model of GBE1-p.Y329S and designed peptides ab initio to stabilize the mutation. As proof-of-principle, we evaluated treatment of one tetra-peptide, Leu-Thr-Lys-Glu, in APBD patient cells. We demonstrate intracellular transport of this peptide, its binding and stabilization of GBE1-p.Y329S, and 2-fold increased mutant enzymatic activity compared with untreated patient cells. Together, our data provide the rationale and starting point for the screening of small molecule chaperones, which could become novel therapies for this disease.
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Affiliation(s)
- D Sean Froese
- Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, OX3 7DQ, UK
| | | | - Thomas J McCorvie
- Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, OX3 7DQ, UK
| | - Tobias Krojer
- Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, OX3 7DQ, UK
| | - Meitav Sasi
- Department of Neurology, Hadassah-Hebrew University Medical Center, Ein Kerem, Jerusalem, Israel
| | - Esther Melaev
- Department of Neurology, Hadassah-Hebrew University Medical Center, Ein Kerem, Jerusalem, Israel
| | - Amiram Goldblum
- Pepticom LTD, Jerusalem, Israel, Institute for Drug Research, The Hebrew University of Jerusalem, Jerusalem, Israel
| | | | - Alexander Lossos
- Department of Neurology, Hadassah-Hebrew University Medical Center, Ein Kerem, Jerusalem, Israel
| | - Rafael Álvarez
- Department of Biology, University of the Balearic Islands, Palma de Mallorca E-07122, Spain and
| | - Pablo V Escribá
- Department of Biology, University of the Balearic Islands, Palma de Mallorca E-07122, Spain and
| | - Berge A Minassian
- Program in Genetics and Genomic Medicine, The Hospital for Sick Children, University of Toronto, Toronto, Canada
| | - Frank von Delft
- Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, OX3 7DQ, UK
| | - Or Kakhlon
- Department of Neurology, Hadassah-Hebrew University Medical Center, Ein Kerem, Jerusalem, Israel,
| | - Wyatt W Yue
- Structural Genomics Consortium, Nuffield Department of Clinical Medicine, University of Oxford, OX3 7DQ, UK,
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Kim JA, Kim JH, Lee BH, Kim GH, Shin YS, Yoo HW, Kim KM. Clinical, Biochemical, and Genetic Characterization of Glycogen Storage Type IX in a Child with Asymptomatic Hepatomegaly. Pediatr Gastroenterol Hepatol Nutr 2015; 18:138-43. [PMID: 26157701 PMCID: PMC4493248 DOI: 10.5223/pghn.2015.18.2.138] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2014] [Revised: 11/03/2014] [Accepted: 12/05/2014] [Indexed: 11/14/2022] Open
Abstract
Glycogen storage disease type IX (GSD IX) is caused by a defect in phosphorylase b kinase (PhK) that results from mutations in the PHKA2, PHKB, and PHKG2 genes. Patients usually manifest recurrent ketotic hypoglycemia with growth delay, but some may present simple hepatomegaly. Although GSD IX is one of the most common causes of GSDs, its biochemical and genetic diagnosis has been problematic due to its rarity, phenotypic overlap with other types of GSDs, and genetic heterogeneities. In our report, a 22-month-old boy with GSD IX is described. No other manifestations were evident except for hepatomegaly. His growth and development also have been proceeding normally. Diagnosed was made by histologic examination, an enzyme assay, and genetic testing with known c.3210_3212del (p.Arg1070del) mutation in PHKA2 gene.
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Affiliation(s)
- Jung Ah Kim
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Ja Hye Kim
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Beom Hee Lee
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Gu-Hwan Kim
- Medical Genetics Center, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Yoon S Shin
- University Children's Hospital and Molecular Genetics and Metabolism Laboratory, Munich, Germany
| | - Han-Wook Yoo
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Kyung Mo Kim
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
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Squires RH, Ng V, Romero R, Ekong U, Hardikar W, Emre S, Mazariegos GV. Evaluation of the pediatric patient for liver transplantation: 2014 practice guideline by the American Association for the Study of Liver Diseases, American Society of Transplantation and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition. Hepatology 2014; 60:362-98. [PMID: 24782219 DOI: 10.1002/hep.27191] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 04/22/2014] [Indexed: 12/16/2022]
Affiliation(s)
- Robert H Squires
- Department of Pediatrics, University of Pittsburgh School of Medicine; Division of Pediatric Gastroenterology, Hepatology and Nutrition, Children's Hospital of Pittsburgh of UPMC, Pittsburgh, PA
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Akman HO, Sheiko T, Tay SKH, Finegold MJ, Dimauro S, Craigen WJ. Generation of a novel mouse model that recapitulates early and adult onset glycogenosis type IV. Hum Mol Genet 2011; 20:4430-9. [PMID: 21856731 DOI: 10.1093/hmg/ddr371] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Glycogen storage disease type IV (GSD IV) is a rare autosomal recessive disorder caused by deficiency of the glycogen branching enzyme (GBE). The diagnostic feature of the disease is the accumulation of a poorly branched form of glycogen known as polyglucosan (PG). The disease is clinically heterogeneous, with variable tissue involvement and age of disease onset. Absence of enzyme activity is lethal in utero or in infancy affecting primarily muscle and liver. However, residual enzyme activity (5-20%) leads to juvenile or adult onset of a disorder that primarily affects muscle as well as central and peripheral nervous system. Here, we describe two mouse models of GSD IV that reflect this spectrum of disease. Homologous recombination was used to insert flippase recognition target recombination sites around exon 7 of the Gbe1 gene and a phosphoglycerate kinase-Neomycin cassette within intron 7, leading to a reduced synthesis of GBE. Mice bearing this mutation (Gbe1(neo/neo)) exhibit a phenotype similar to juvenile onset GSD IV, with wide spread accumulation of PG. Meanwhile, FLPe-mediated homozygous deletion of exon 7 completely eliminated GBE activity (Gbe1(-/-)), leading to a phenotype of lethal early onset GSD IV, with significant in utero accumulation of PG. Adult mice with residual GBE exhibit progressive neuromuscular dysfunction and die prematurely. Differently from muscle, PG in liver is a degradable source of glucose and readily depleted by fasting, emphasizing that there are structural and regulatory differences in glycogen metabolism among tissues. Both mouse models recapitulate typical histological and physiological features of two human variants of branching enzyme deficiency.
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Affiliation(s)
- H Orhan Akman
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.
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