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Aggregation-prone GFAP mutation in Alexander disease validated using a zebrafish model. BMC Neurol 2017; 17:175. [PMID: 28882119 PMCID: PMC5590178 DOI: 10.1186/s12883-017-0938-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 08/03/2017] [Indexed: 11/26/2022] Open
Abstract
Background Alexander disease (AxD) is an astrogliopathy that predominantly affects the white matter of the central nervous system (CNS), and is caused by a mutation in the gene encoding the glial fibrillary acidic protein (GFAP), an intermediate filament primarily expressed in astrocytes and ependymal cells. The main pathologic feature of AxD is the presence of Rosenthal fibers (RFs), homogeneous eosinophilic inclusions found in astrocytes. Because of difficulties in procuring patient’ CNS tissues and the presence of RFs in other pathologic conditions, there is a need to develop an in vivo assay that can determine whether a mutation in the GFAP results in aggregation and is thus disease-causing. Methods We found a GFAP mutation (c.382G > A, p.Asp128Asn) in a 68-year-old man with slowly progressive gait disturbance with tendency to fall. The patient was tentatively diagnosed with AxD based on clinical and radiological findings. To develop a vertebrate model to assess the aggregation tendency of GFAP, we expressed several previously reported mutant GFAPs and p.Asp128Asn GFAP in zebrafish embryos. Results The most common GFAP mutations in AxD, p.Arg79Cys, p.Arg79His, p.Arg239Cys and p.Arg239His, and p.Asp128Asn induced a significantly higher number of GFAP aggregates in zebrafish embryos than wild-type GFAP. Conclusions The p.Asp128Asn GFAP mutation is likely to be a disease-causing mutation. Although it needs to be tested more extensively in larger case series, the zebrafish assay system presented here would help clinicians determine whether GFAP mutations identified in putative AxD patients are disease-causing.
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Lee SH, Nam TS, Li W, Kim JH, Yoon W, Choi YD, Kim KH, Cai H, Kim MJ, Kim C, Choy HE, Kim N, Chay KO, Kim MK, Choi SY. Functional validation of novel MKS3/TMEM67 mutations in COACH syndrome. Sci Rep 2017; 7:10222. [PMID: 28860541 PMCID: PMC5579020 DOI: 10.1038/s41598-017-10652-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 08/10/2017] [Indexed: 12/18/2022] Open
Abstract
COACH syndrome is an autosomal recessive developmental disorder, a subtype of Joubert syndrome and related disorders, characterized by cerebellar vermis hypoplasia, oligophrenia, ataxia, coloboma, and hepatic fibrosis. Although mutations in TMEM67 (transmembrane protein 67)/MKS3 (Meckel-Gruber syndrome, type 3) were reported to cause COACH syndrome, this causality has not verified by functional studies. In a 20-year-old Korean man, we found cerebellar ataxia, isolated elevation in serum γ-glutamyl transpeptidase (γ-GTP) activity, oligophrenia, the molar tooth sign (MTS) in the brain MR images and congenital hepatic fibrosis (CHF). Two novel compound heterozygous mutations were found in TMEM67 in the patient: i) missense mutation (c.395 G > C and p.Gly132Ala) in exon 3, and ii) deletion in exon 26 (c.2758delT and p.Tyr920ThrfsX40). Western blotting showed that the p.Tyr920ThrfsX40 mutation accelerates turnover of the TMEM67 protein. Although wild-type human TMEM67 RNA rescued phenotypes of zebrafish embryos injected with anti-sense oligonucleotide morpholinos against tmem67, the two human TMEM67 RNAs individually harboring the two mutations did not. Finally, Wnt signaling, but not Hedgehog signaling, was suppressed in tmem67 morphants. To the best of our knowledge, this is the first report verifying the causality between COACH syndrome and TMEM67, which will further our understanding of molecular pathogenesis of the syndrome.
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Affiliation(s)
- So-Hyun Lee
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, Republic of Korea.,Center for Creative Biomedical Scientists at Chonnam National University, Gwangju, Republic of Korea
| | - Tai-Seung Nam
- Department of Neurology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Wenting Li
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Jung Ha Kim
- Department of Pharmacology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Woong Yoon
- Department of Radiology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Yoo-Duk Choi
- Department of Pathology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Kun-Hee Kim
- Department of Microbiology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Hua Cai
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Min Jung Kim
- Department of Biological Sciences, Sookmyung Women's University, Seoul, Republic of Korea
| | - Changsoo Kim
- School of Biological Sciences and Technology, Chonnam National University, Gwangju, Republic of Korea
| | - Hyon E Choy
- Department of Microbiology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Nacksung Kim
- Department of Pharmacology, Chonnam National University Medical School, Gwangju, Republic of Korea
| | - Kee Oh Chay
- Department of Biochemistry, Chonnam National University Medical School, Gwangju, Republic of Korea.
| | - Myeong-Kyu Kim
- Department of Neurology, Chonnam National University Medical School, Gwangju, Republic of Korea.
| | - Seok-Yong Choi
- Department of Biomedical Sciences, Chonnam National University Medical School, Gwangju, Republic of Korea.
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