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Wang X, Zhang H, Huang H, Wang W, Wen Y, Dai Z, Huang S, Zhou J, Zhou Y. Functional and structural analysis of a novel splice site HMBS variant in a Chinese AIP patient. Front Genet 2023; 14:1333111. [PMID: 38192441 PMCID: PMC10773753 DOI: 10.3389/fgene.2023.1333111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2023] [Accepted: 12/07/2023] [Indexed: 01/10/2024] Open
Abstract
Background: Acute intermittent porphyria (AIP) is a rare metabolic disorder that results from mutations in the gene encoding hydroxymethylbilane synthase (HMBS), an enzyme involved in heme biosynthesis. AIP follows an autosomal dominant inheritance pattern, but most carriers are asymptomatic. The clinical manifestations of AIP include acute attacks of abdominal pain and neuropsychiatric disturbances. The pathogenicity of novel HMBS variants identified in Chinese patients has not been well established. Objective: The article aims to identify the pathogenic mutation in an AIP patient and prove its pathogenicity through in vitro experiments. Methods: A 22-year-old female diagnosed with AIP participated in the study. Variant screening of her HMBS gene was carried out through Sanger sequencing. To ascertain the consequences of the newly discovered variant, we conducted in vitro experimentation targeting HMBS gene expression and enzymatic function. Additionally, protein structure analysis was performed. Cycloheximide treatment and UPF1-specific siRNA knockdown were employed to assess the impact of the mutation on the mechanism of non-sense-mediated mRNA decay (NMD). Results: A novel splice site variant in the HMBS gene (c.648_651+1delCCAGG) was detected in the patient, which caused aberrant mRNA splicing. In vitro experiments demonstrated that this variant significantly decreased the expression of HMBS. Further investigation confirmed that this decrease was due to NMD. Additionally, structural analysis indicated that this variant would destabilize the HMBS protein and impair its catalytic activity. To gain a comprehensive understanding of HMBS mutations in the context of AIP, we conducted a literature search on PubMed using the keywords 'HMBS' and 'Acute intermittent porphyria' from 2013 to 2023. This search yielded 19 clinical case reports written in English, which collectively described 220 HMBS gene mutations worldwide. Conclusion: The study identified and proved the pathogenicity of a novel splice site HMBS variant for the first time. Our results elucidated the pathological mechanism by which this mutation causes AIP through reducing HMBS expression and activity. These findings provide theoretical guidance for the diagnosis, treatment and genetic counseling of AIP patients.
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Affiliation(s)
- Xiaoqing Wang
- Dongguan Hospital, Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
| | - Huifen Zhang
- Department of Endocrinology, Dongguan Hospital of Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
| | - Huanhuan Huang
- Dongguan Hospital, Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
| | - Wenli Wang
- Dongguan Hospital, Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
| | - Yuping Wen
- Dongguan Hospital, Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
| | - Zhuojin Dai
- The First Clinical Medical College, Guangdong Medical University, Zhanjiang, Guangdong Province, China
| | - Shuling Huang
- Department of Endocrinology, Dongguan Hospital of Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
| | - Jingyi Zhou
- Dongguan Hospital, Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
| | - Yuqing Zhou
- Department of Endocrinology, Dongguan Hospital of Guangzhou University of Chinese Medicine, Dongguan, Guangdong Province, China
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Ren Y, Li S, Lei JJ, Li R, Dong BX, Yang J. Clinical feature and genetic analysis of HMBS gene in Chinese patients with acute intermittent porphyria: a systematic review. Front Genet 2023; 14:1291719. [PMID: 38148975 PMCID: PMC10750365 DOI: 10.3389/fgene.2023.1291719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2023] [Accepted: 11/22/2023] [Indexed: 12/28/2023] Open
Abstract
Background: Early detection and diagnosis are important crucial to prevent life-threatening acute attacks in patients with acute intermittent porphyria (AIP). We aim to provide comprehensive data on the clinical and hydroxymethylbilane synthase (HMBS) gene variant characteristics and genotype-phenotype association of Chinese patients with AIP in order to improve clinicians' knowledge of AIP and reduce misdiagnosis and mistaken treatment. Methods: We searched the literature on Chinese patients with AIP in PubMed, Web of Science, Wiley Online Library, ScienceDirect and Chinese literature databases up to August 2023 in our analysis to explore the clinical and HMBS gene variant characteristics of Chinese patients with AIP. Results: A total of 41 original articles associated with Chinese AIP patients were included for analysis: 97 variants were detected in 160 unrelated families, including 35 missense, 29 frameshift, 24 splicing and 9 nonsense variants, with c.517C>T being the most common variant. Clinical data were reported in 77 of 160 patients: Most of them were female (67/77) and the age was 28.8 ± 9.9 years. The most common symptom was abdominal pain (73/77, 94.8%), followed by central nervous system symptoms (45/77, 58.4%). 13.0% (10/77) of patients experienced psychiatric symptoms. Hyponatremia was the most common electrolyte abnormality (42/77). 31 patients received carbohydrate loading therapy, and 30 of them were improved. 6 patients were treated with carbohydrate loading combined with hemin therapy and 5 eventually improved. All variants causing premature stop codons, frameshifts or enzyme activity center may experience more severe clinical phenotypes such as seizures, respiratory paralysis, intracranial hemorrhage disorder or respiratory failure. Conclusion: The most common presenting symptom in Chinese AIP patients was abdominal pain, followed by central nervous system symptoms. The HMBS gene analysis in Chinese AIP patients revealed that the heterogeneity is strong and the most common variant was missense mutation, with c.517C>T being the most common variant. The genotype-phenotype association helps guide clinical diagnosis and treatment. However, the treatment for AIP in China is limited and monolithic, and more attention needs to be paid to the treatment.
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Affiliation(s)
- Yi Ren
- Department of Endocrinology, The First Hospital of Shanxi Medical University, Taiyuan, China
| | - Shuang Li
- Department of First Clinical Medical School, Shanxi Medical University, Taiyuan, China
| | - Jia-Jia Lei
- Department of First Clinical Medical School, Shanxi Medical University, Taiyuan, China
| | - Ru Li
- Department of First Clinical Medical School, Shanxi Medical University, Taiyuan, China
| | - Bai-Xue Dong
- Department of First Clinical Medical School, Shanxi Medical University, Taiyuan, China
| | - Jing Yang
- Department of Endocrinology, The First Hospital of Shanxi Medical University, Taiyuan, China
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Christie MS, Laitaoja M, Aarsand AK, Kallio JP, Bustad HJ. Characterisation of a common hotspot variant in acute intermittent porphyria sheds light on the mechanism of hydroxymethylbilane synthase function. FEBS Open Bio 2022; 12:2136-2146. [PMID: 36115019 PMCID: PMC9714363 DOI: 10.1002/2211-5463.13490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Revised: 08/10/2022] [Accepted: 09/16/2022] [Indexed: 01/25/2023] Open
Abstract
Hydroxymethylbilane synthase (HMBS) is the third enzyme involved in haem biosynthesis, in which it catalyses the formation of tetrapyrrole 1-hydroxymethylbilane (HMB). In this process, HMBS binds four consecutive substrate molecules, creating the enzyme-intermediate complexes ES, ES2 , ES3 and ES4 . Pathogenic variants in the HMBS gene are associated with the dominantly inherited disorder acute intermittent porphyria. In this study, we have characterised the p.R26H variant to shed light on the role of Arg26 in the elongation mechanism of HMBS and to provide insights into its effect on the enzyme. With selected biophysical methods, we have been able to show that p.R26H forms a single enzyme-intermediate complex in the ES2 -state. We were also able to demonstrate that the p.R26H variant results in an inactive enzyme, which is unable to produce the HMB product.
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Affiliation(s)
- Marthe S. Christie
- Department of BiomedicineUniversity of BergenNorway,Norwegian Porphyria Centre (NAPOS), Department for Medical Biochemistry and PharmacologyHaukeland University HospitalBergenNorway
| | - Mikko Laitaoja
- Department of ChemistryUniversity of Eastern FinlandJoensuuFinland
| | - Aasne K. Aarsand
- Norwegian Porphyria Centre (NAPOS), Department for Medical Biochemistry and PharmacologyHaukeland University HospitalBergenNorway,Norwegian Organization for Quality Improvement of Laboratory ExaminationsHaraldsplass Deaconess HospitalBergenNorway
| | | | - Helene J. Bustad
- Norwegian Porphyria Centre (NAPOS), Department for Medical Biochemistry and PharmacologyHaukeland University HospitalBergenNorway
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Therapy Follows Diagnosis: Old and New Approaches for the Treatment of Acute Porphyrias, What We Know and What We Should Know. Diagnostics (Basel) 2022; 12:diagnostics12071618. [PMID: 35885523 PMCID: PMC9325038 DOI: 10.3390/diagnostics12071618] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Revised: 06/29/2022] [Accepted: 06/30/2022] [Indexed: 12/18/2022] Open
Abstract
Heme, iron protoporphyrin IX, is one of life’s most central molecules. Hence, availability of the enzymatic machinery necessary for its synthesis is crucial for every cell. Consequently, inborn errors of porphyrin metabolism that compromise normal synthesis, namely the family of porphyrias, undermine normal cellular metabolism given that heme has functions in catalytic centers, signal transduction and functional regulation and its synthesis is fully integrated into the center of intermediary metabolism. Very often, diagnosis of porphyrias is difficult and therefore delayed. Therapy can be as complicated. Over the last 50 years, several strategies have been developed: because of its integration with other parts of intermediary metabolism, the infusion of glucose (glucose effect) was one of the first attempts to counterbalance the dysregulation of porphyrin synthesis in porphyrias. Since heme synthesis is impaired, infusional replacement of heme was the next important therapeutic step. Recently, siRNA technology has been introduced in order to downregulate 5-ALA-synthase 1, which contributes to the patho-physiology of these diseases. Moreover, other novel therapies using enzyme protein replacement, mRNA techniques or proteostasis regulators are being developed.
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Lin CN, Shiao MS, Cheng ML, Chen CM, Kuo HC. Profiling of Serum Metabolites of Acute Intermittent Porphyria and Asymptomatic HMBS Mutation Carriers. Cells 2021; 10:cells10102579. [PMID: 34685558 PMCID: PMC8533736 DOI: 10.3390/cells10102579] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2021] [Revised: 09/25/2021] [Accepted: 09/25/2021] [Indexed: 11/16/2022] Open
Abstract
This study aims to present the serum metabolite profiles of patients with acute intermittent porphyria (AIP) and identify specific metabolites that could potentially discriminate between AIP, asymptomatic HMBS mutation carriers, and healthy individuals. The study cohort included 46 female participants: 21 AIP patients, 5 asymptomatic carriers, and 20 ‘normal’ participants (without HMBS gene mutation). Serum samples were analyzed for 157 selected metabolites or clinical variables using an assay combining liquid chromatography MS/MS and direct flow injection. AUC analysis was used to distinguish unique variables between the three groups. A total of 15 variables differed significantly between the AIP and normal control group (VIP score > 1.0 and p < 0.05 with FDR correction). In AIP patients, the levels tyrosine, valine, and eGFR were significantly lower, and the levels of sphingomyelin C16:0, C24:0, C24:1, phosphatidylcholine diacyl C32:1, C36:1, C36:3, ornithine, sarcosine, citrulline, blood urea nitrogen AST, and ALT were significantly higher. The AUC of these 15 variables in discriminating between normal and AIP patients ranged between 0.73 and 0.94 (p < 0.05). In conclusion, serum metabolic profiles differ between normal individuals and patients carrying the HMBS mutation. The unique metabolites associated with AIP identified in this study may be useful for monitoring the development of AIP symptoms.
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Affiliation(s)
- Chia-Ni Lin
- Department of Laboratory Medicine, Chang Gung Memorial Hospital, Taoyuan 333, Taiwan;
- Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
| | - Ming-Shi Shiao
- Metabolomics Core Laboratory, Healthy Aging Research Center, Chang Gung University, Taoyuan 333, Taiwan; (M.-S.S.); (M.-L.C.)
| | - Mei-Ling Cheng
- Metabolomics Core Laboratory, Healthy Aging Research Center, Chang Gung University, Taoyuan 333, Taiwan; (M.-S.S.); (M.-L.C.)
- Department of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan
- Clinical Metabolomics Core Laboratory, Chang Gung Memorial Hospital at Linkou, Taoyuan 333, Taiwan
| | - Chiung-Mei Chen
- Linkou Medical Center, Department of Neurology, Chang Gung Memorial Hospital, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan;
| | - Hung-Chou Kuo
- Linkou Medical Center, Department of Neurology, Chang Gung Memorial Hospital, College of Medicine, Chang Gung University, Taoyuan 333, Taiwan;
- Correspondence: ; Tel.: +886-3-3281200 (ext. 8340)
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Ma L, Tian Y, Peng C, Zhang Y, Zhang S. Recent advances in the epidemiology and genetics of acute intermittent porphyria. Intractable Rare Dis Res 2020; 9:196-204. [PMID: 33139978 PMCID: PMC7586877 DOI: 10.5582/irdr.2020.03082] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/07/2020] [Accepted: 08/11/2020] [Indexed: 02/07/2023] Open
Abstract
Acute intermittent porphyria (AIP) is a dominant inherited disorder with a low penetrance that is caused by mutations in the gene coding for hydroxymethylbilane synthase (HMBS). Information about the epidemiology and molecular genetic features of this rare disorder is crucial to clinical research, and particularly to the evaluation of new treatments. Variations in the prevalence and penetrance of AIP in various studies may due to the different inclusion criteria and methods of assessment. Here, the prevalence and penetrance of AIP are analyzed systematically, and the genetic traits of different populations and findings regarding the genotype-phenotype correlation are summarized. In addition, quite a few studies have indicated that AIP susceptibility was affected by other factors, such as modifying genes. Findings regarding possible modifying genes are documented here, helping to reveal the pathogenesis of and treatments for AIP. The status of research on AIP in China reveals the lack of epidemiological and genetic studies of the Chinese population, a situation that needs to be promptly remedied.
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Affiliation(s)
- Liyan Ma
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yu Tian
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Chenxing Peng
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
| | - Yiran Zhang
- School of First Clinical Medical College, Southern Medical University, Guangzhou, Guangdong, China
| | - Songyun Zhang
- Department of Endocrinology, The second Hospital of Hebei Medical University, Shijiazhuang, Hebei, China
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