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Huang K, Duan HQ, Li QX, Luo YB, Bi FF, Yang H. Expanding the clinicopathological-genetic spectrum of glycogen storage disease type IXd by a Chinese neuromuscular center. Front Neurol 2022; 13:945280. [PMID: 36034300 PMCID: PMC9406516 DOI: 10.3389/fneur.2022.945280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 07/19/2022] [Indexed: 11/29/2022] Open
Abstract
Background Glycogen storage disease (GSDs) is characterized by abnormally inherited glycogen metabolism. GSD IXd, which is caused by mutations in the PHKA1 gene, is an X-linked rare disease with mild myopathic symptoms. To date, only 13 patients with GSD IXd have been reported. In this study, we aimed to expand the clinicopathological-genetic spectrum of GSD IXd at a neuromuscular center in China. Methods Data on patients diagnosed with GSD IXd at our neuromuscular center were collected retrospectively. Clinical features, electrophysiology, muscle pathology, and genetic information were analyzed. Results Between 2015 and 2021, three patients were diagnosed with GSD IXd based on clinical manifestations, pathological findings, and genetic testing. One patient presented with mitochondrial myopathy. All patients exhibited muscle weakness and elevated levels of creatine kinase. Electromyography-detected myopathic changes were found in two patients, whereas one patient refused to undergo this examination. Pathological examinations in all patients revealed subsarcolemmal accumulation of glycogen under PAS staining. All patients had mutations in the PHKA1 gene and the patient with mitochondrial myopathy also had a mutation in the MT-TL1 gene. Conclusion Our study expands the clinicogenotype and phenotype of GSD IXd in a Chinese population. Our study also expands the known mutation spectrum for GSD IXd, contributing to a better characterization and understanding of this ultrarare neuromuscular disorder.
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Affiliation(s)
- Kun Huang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
| | - Hui-Qian Duan
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
| | - Qiu-Xiang Li
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
| | - Yue-Bei Luo
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
| | - Fang-Fang Bi
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
| | - Huan Yang
- Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
- National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, Hunan Province, China
- *Correspondence: Huan Yang
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Gibson RA, Lim JA, Choi SJ, Flores L, Clinton L, Bali D, Young S, Asokan A, Sun B, Kishnani PS. Characterization of liver GSD IX γ2 pathophysiology in a novel Phkg2 -/- mouse model. Mol Genet Metab 2021; 133:269-276. [PMID: 34083142 PMCID: PMC9792075 DOI: 10.1016/j.ymgme.2021.05.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Revised: 05/15/2021] [Accepted: 05/22/2021] [Indexed: 10/21/2022]
Abstract
INTRODUCTION Liver Glycogen Storage Disease IX is a rare metabolic disorder of glycogen metabolism caused by deficiency of the phosphorylase kinase enzyme (PhK). Variants in the PHKG2 gene, encoding the liver-specific catalytic γ2 subunit of PhK, are associated with a liver GSD IX subtype known as PHKG2 GSD IX or GSD IX γ2. There is emerging evidence that patients with GSD IX γ2 can develop severe and progressive liver disease, yet research regarding the disease has been minimal to date. Here we characterize the first mouse model of liver GSD IX γ2. METHODS A Phkg2-/- mouse model was generated via targeted removal of the Phkg2 gene. Knockout (Phkg2-/-, KO) and wild type (Phkg2+/+, WT) mice up to 3 months of age were compared for morphology, Phkg2 transcription, PhK enzyme activity, glycogen content, histology, serum liver markers, and urinary glucose tetrasaccharide Glcα1-6Glcα1-4Glcα1-4Glc (Glc4). RESULTS When compared to WT controls, KO mice demonstrated significantly decreased liver PhK enzyme activity, increased liver: body weight ratio, and increased glycogen in the liver, with no glycogen accumulation observed in the brain, quadricep, kidney, and heart. KO mice demonstrated elevated liver blood markers as well as elevated urine Glc4, a commonly used biomarker for glycogen storage disease. KO mice demonstrated features of liver structural damage. Hematoxylin & Eosin and Masson's Trichrome stained KO mice liver histology slides revealed characteristic GSD hepatocyte architectural changes and early liver fibrosis, as have been reported in liver GSD patients. DISCUSSION This study provides the first evidence of a mouse model that recapitulates the liver-specific pathology of patients with GSD IX γ2. The model will provide the first platform for further study of disease progression in GSD IX γ2 as well as for the evaluation of novel therapeutics.
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Affiliation(s)
- Rebecca A Gibson
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA; Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Jeong-A Lim
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Su Jin Choi
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Leticia Flores
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Lani Clinton
- Department of Pathology, Duke University Medical Center, Durham, NC, USA
| | - Deeksha Bali
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Sarah Young
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Aravind Asokan
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA; Department of Surgery, Duke University Medical Center, Durham, NC, USA
| | - Baodong Sun
- Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA
| | - Priya S Kishnani
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC, USA; Division of Medical Genetics, Department of Pediatrics, Duke University Medical Center, Durham, NC, USA.
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