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Nishad R, Betancourt-Solis M, Dey H, Heidelberger R, McNew JA. Regulation of Syntaxin3B-Mediated Membrane Fusion by T14, Munc18, and Complexin. Biomolecules 2023; 13:1463. [PMID: 37892145 PMCID: PMC10604575 DOI: 10.3390/biom13101463] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2023] [Revised: 09/22/2023] [Accepted: 09/26/2023] [Indexed: 10/29/2023] Open
Abstract
Retinal neurons that form ribbon-style synapses operate over a wide dynamic range, continuously relaying visual information to their downstream targets. The remarkable signaling abilities of these neurons are supported by specialized presynaptic machinery, one component of which is syntaxin3B. Syntaxin3B is an essential t-SNARE protein of photoreceptors and bipolar cells that is required for neurotransmitter release. It has a light-regulated phosphorylation site in its N-terminal domain at T14 that has been proposed to modulate membrane fusion. However, a direct test of the latter has been lacking. Using a well-controlled in vitro fusion assay, we found that a phosphomimetic T14 syntaxin3B mutation leads to a small but significant enhancement of SNARE-mediated membrane fusion following the formation of the t-SNARE complex. While the addition of Munc18a had only a minimal effect on membrane fusion mediated by SNARE complexes containing wild-type syntaxin3B, a more significant enhancement was observed in the presence of Munc18a when the SNARE complexes contained a syntaxin3B T14 phosphomimetic mutant. Finally, we showed that the retinal-specific complexins (Cpx III and Cpx IV) inhibited membrane fusion mediated by syntaxin3B-containing SNARE complexes in a dose-dependent manner. Collectively, our results establish that membrane fusion mediated by syntaxin3B-containing SNARE complexes is regulated by the T14 residue of syntaxin3B, Munc18a, and Cpxs III and IV.
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Affiliation(s)
- Rajkishor Nishad
- Department of BioSciences, Rice University, 6500 Main Street, MS 601, Houston, TX 77005, USA;
| | - Miguel Betancourt-Solis
- Department of BioSciences, Rice University, 6500 Main Street, MS 601, Houston, TX 77005, USA;
- Lonza Biologics, 14905 Kirby Dr, Houston, TX 77047, USA
| | - Himani Dey
- Department of Neurobiology and Anatomy, McGovern Medical School, The University of Texas Health Science Center, Houston (UTHealth Houston), 6431 Fannin Street, Houston, TX 77030, USA;
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, McGovern Medical School, The University of Texas Health Science Center, Houston (UTHealth Houston), 6431 Fannin Street, Houston, TX 77030, USA;
| | - James A. McNew
- Department of BioSciences, Rice University, 6500 Main Street, MS 601, Houston, TX 77005, USA;
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2
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Deesker LJ, Oosterveld MJS, van Mill MJ, Roelofs JJTH, van Heerde M. Weight loss and metabolic acidosis in a neonate: Answers. Pediatr Nephrol 2023; 38:2581-2584. [PMID: 36598597 DOI: 10.1007/s00467-022-05847-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2022] [Revised: 12/02/2022] [Accepted: 12/05/2022] [Indexed: 01/05/2023]
Affiliation(s)
- Lisa J Deesker
- Pediatric Nephrology, Emma Children's Hospital Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands.
| | - Michiel J S Oosterveld
- Pediatric Nephrology, Emma Children's Hospital Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
| | - Marije J van Mill
- Department of Pediatric Gastroenterology, Wilhelmina Children's Hospital, Utrecht Medical Center, University of Utrecht, Utrecht, The Netherlands
| | - Joris J T H Roelofs
- Department of Pathology, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Marc van Heerde
- Pediatric Intensive Care, Emma Children's Hospital Amsterdam UMC, University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands
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3
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Perez-Hurtado M, Dao C, Saenz AE, Heidelberger R. Syntaxin 3 is haplosufficient for long-term photoreceptor survival in the mouse retina. FRONTIERS IN OPHTHALMOLOGY 2023; 3:1208805. [PMID: 37609371 PMCID: PMC10443939 DOI: 10.3389/fopht.2023.1208805] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/24/2023]
Abstract
Biallelic loss-of-function mutations in the syntaxin 3 gene have been linked to a severe retinal dystrophy in humans that presents in early childhood. In mouse models, biallelic inactivation of the syntaxin 3 gene in photoreceptors rapidly leads to their death. What is not known is whether a monoallelic syntaxin 3 loss-of-function mutation might cause photoreceptor loss with advancing age. To address this question, we compared the outer nuclear layer of older adult mice (≈ 20 months of age) that were heterozygous for syntaxin 3 with those of similarly-aged control mice. We found that the photoreceptor layer maintains its thickness in mice that are heterozygous for syntaxin 3 relative to controls and that photoreceptor somatic counts are comparable. In addition, dendritic sprouting of the rod bipolar cell dendrites into the outer nuclear layer, which occurs following the loss of functional rod targets, was similar between genotypes. Thus, syntaxin 3 appears to be haplosufficient for photoreceptor survival, even with advancing age.
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Affiliation(s)
- Mariajose Perez-Hurtado
- Department of Neurobiology and Anatomy, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth Houston), Houston, TX
| | - Calvin Dao
- Department of Neurobiology and Anatomy, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth Houston), Houston, TX
| | - Amanda E. Saenz
- Department of Neurobiology and Anatomy, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth Houston), Houston, TX
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, McGovern Medical School at The University of Texas Health Science Center at Houston (UTHealth Houston), Houston, TX
- The University of Texas MDAnderson Cancer Center UTHealth Houston Graduate School of Biomedical Sciences, Houston TX
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4
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Leng C, Sun Y, van IJzendoorn SCD. Risk and Clinical Significance of Idiopathic Preterm Birth in Microvillus Inclusion Disease. J Clin Med 2021; 10:jcm10173935. [PMID: 34501384 PMCID: PMC8432107 DOI: 10.3390/jcm10173935] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/19/2021] [Accepted: 08/30/2021] [Indexed: 12/15/2022] Open
Abstract
Microvillus inclusion disease (MVID) is a rare enteropathy caused by mutations in the MYO5B or STX3 gene. MVID is a disease that is difficult to manage with clinical heterogeneity. Therefore, knowledge about factors influencing MVID morbidity and mortality is urgently needed. Triggered by a recent study that reported a high percentage of preterm births in twelve cases of MVID, we have conducted a comprehensive retrospective study involving 88 cases of MVID with reported gestational ages. We found that moderate to late preterm birth occurred in more than half of all cases, and this was particularly prominent in MYO5B-associated MVID. Preterm birth in MVID counterintuitively correlated with higher birth weight percentiles, and correlated with higher stool outputs and a significantly shorter average survival time. Data from this study thus demonstrate an increased risk of preterm birth in MYO5B-associated MVID, with a clinical impact on morbidity and mortality. Adverse effects associated with preterm birth should be taken into account in the care of children diagnosed with MVID. Documentation of gestational age may contribute to a better prognostic risk assessment in MVID.
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Affiliation(s)
- Changsen Leng
- Department of Biomedical Sciences of Cells and Systems, Centre for Liver, Digestive and Metabolic Disease, University of Groningen, University Medical Centre Groningen, 9713 AV Groningen, The Netherlands; (C.L.); (Y.S.)
- Department of Thoracic Surgery, Guangdong Esophageal Cancer Institute, State Key Laboratory of Oncology in South China, Collaborative Innovation Centre for Cancer Medicine, Sun Yat-sen University Cancer Centre, Guangzhou 510060, China
| | - Yue Sun
- Department of Biomedical Sciences of Cells and Systems, Centre for Liver, Digestive and Metabolic Disease, University of Groningen, University Medical Centre Groningen, 9713 AV Groningen, The Netherlands; (C.L.); (Y.S.)
| | - Sven C. D. van IJzendoorn
- Department of Biomedical Sciences of Cells and Systems, Centre for Liver, Digestive and Metabolic Disease, University of Groningen, University Medical Centre Groningen, 9713 AV Groningen, The Netherlands; (C.L.); (Y.S.)
- Correspondence:
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5
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Janecke AR, Liu X, Adam R, Punuru S, Viestenz A, Strauß V, Laass M, Sanchez E, Adachi R, Schatz MP, Saboo US, Mittal N, Rohrschneider K, Escher J, Ganesh A, Al Zuhaibi S, Al Murshedi F, AlSaleem B, Alfadhel M, Al Sinani S, Alkuraya FS, Huber LA, Müller T, Heidelberger R, Janz R. Pathogenic STX3 variants affecting the retinal and intestinal transcripts cause an early-onset severe retinal dystrophy in microvillus inclusion disease subjects. Hum Genet 2021; 140:1143-1156. [PMID: 33974130 PMCID: PMC8263458 DOI: 10.1007/s00439-021-02284-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 04/15/2021] [Indexed: 01/12/2023]
Abstract
Biallelic STX3 variants were previously reported in five individuals with the severe congenital enteropathy, microvillus inclusion disease (MVID). Here, we provide a significant extension of the phenotypic spectrum caused by STX3 variants. We report ten individuals of diverse geographic origin with biallelic STX3 loss-of-function variants, identified through exome sequencing, single-nucleotide polymorphism array-based homozygosity mapping, and international collaboration. The evaluated individuals all presented with MVID. Eight individuals also displayed early-onset severe retinal dystrophy, i.e., syndromic-intestinal and retinal-disease. These individuals harbored STX3 variants that affected both the retinal and intestinal STX3 transcripts, whereas STX3 variants affected only the intestinal transcript in individuals with solitary MVID. That STX3 is essential for retinal photoreceptor survival was confirmed by the creation of a rod photoreceptor-specific STX3 knockout mouse model which revealed a time-dependent reduction in the number of rod photoreceptors, thinning of the outer nuclear layer, and the eventual loss of both rod and cone photoreceptors. Together, our results provide a link between STX3 loss-of-function variants and a human retinal dystrophy. Depending on the genomic site of a human loss-of-function STX3 variant, it can cause MVID, the novel intestinal-retinal syndrome reported here or, hypothetically, an isolated retinal dystrophy.
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Affiliation(s)
- Andreas R Janecke
- Department of Pediatrics I, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
- Division of Human Genetics, Medical University of Innsbruck, Innsbruck, Austria.
| | - Xiaoqin Liu
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
| | - Rüdiger Adam
- University Children's Hospital, Medical Faculty Mannheim, Heidelberg University, 68167 Mannheim, Germany
| | - Sumanth Punuru
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
| | - Arne Viestenz
- Department of Ophthalmology, University Medical Center Halle, Martin-Luther-University Halle-Wittenberg, Halle, Germany
| | - Valeria Strauß
- Klinik für Kinder- und Jugendmedizin, Universitätsklinikum Halle, Halle, Germany
| | - Martin Laass
- Klinik und Poliklinik f. Kinder- u. Jugendmedizin, University of Dresden, Dresden, Germany
| | - Elizabeth Sanchez
- Department of Pulmonary Medicine, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Roberto Adachi
- Department of Pulmonary Medicine, Division of Internal Medicine, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Martha P Schatz
- Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Ujwala S Saboo
- Department of Ophthalmology, University of Texas Health Science Center, San Antonio, TX, USA
| | - Naveen Mittal
- Department of Department of Pediatrics, Division of Pediatric Gastroenterology, University of Texas Health Science Center, San Antonio, TX, USA
| | | | - Johanna Escher
- Erasmus MC-Sophia Children's Hospital, Rotterdam, The Netherlands
| | - Anuradha Ganesh
- Department of Ophthalmology, Sultan Qaboos University Hospital, Muscat, Oman
| | - Sana Al Zuhaibi
- Department of Ophthalmology, Sultan Qaboos University Hospital, Muscat, Oman
| | - Fathiya Al Murshedi
- Genetic and Developmental Medicine Clinic, Sultan Qaboos University Hospital, Muscat, Oman
| | - Badr AlSaleem
- King Fahad Medical City, Children's Specialized Hospital, Riyadh, Saudi Arabia
| | - Majid Alfadhel
- Genetics Division and Medical Genomic Research Lab, King Saud Bin Abdulaziz University for Health Sciences (KSAU-HS), Riyadh, Saudi Arabia
| | - Siham Al Sinani
- Department of Child Health, Sultan Qaboos University Hospital, Muscat, Oman
| | - Fowzan S Alkuraya
- Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia
| | - Lukas A Huber
- Division of Cell Biology, Medical University of Innsbruck, Innsbruck, Austria
| | - Thomas Müller
- Department of Pediatrics I, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA.
| | - Roger Janz
- Department of Neurobiology and Anatomy, MSB 7.046, McGovern Medical School at the University of Texas HSC (UTHealth), 6431 Fannin Street, Houston, TX, 77030, USA
- Center for Scientific Review, National Institutes of Health, Bethesda, MD, USA
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6
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Li Y, Jiang L, Wang L, Wang C, Liu C, Guo A, Liu M, Zhang L, Ma C, Zhang X, Gao S, Liu JY. p.His16Arg of STXBP1 (MUNC18-1) Associated With Syntaxin 3B Causes Autosomal Dominant Congenital Nystagmus. Front Cell Dev Biol 2020; 8:591781. [PMID: 33251218 PMCID: PMC7672047 DOI: 10.3389/fcell.2020.591781] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2020] [Accepted: 10/15/2020] [Indexed: 02/04/2023] Open
Abstract
Congenital nystagmus (CN) is an ocular movement disorder manifested as involuntary conjugated binocular oscillation and usually occurs in early infancy. The pathological mechanism underlying CN is still poorly understood. We mapped a novel genetic locus 9q33.1-q34.2 in a larger Chinese family with autosomal dominant CN and identified a variant (c.47A>G/p.His16Arg) of STXBP1 by exome sequencing, which fully co-segregated with the nystagmus phenotype in this family and was absent in 571 healthy unrelated individuals. The STXBP1 encodes syntaxin binding protein 1 (also known as MUNC18-1), which plays a pivotal role in neurotransmitter release. In unc-18 (nematode homolog of MUNC18-1) null Caenorhabditis elegans, we found that the p.His16Arg exhibits a compromised ability to rescue the locomotion defect and aldicarb sensitivity, indicating a functional defect in neurotransmitter release. In addition, we also found an enhanced binding of the p.His16Arg mutant to syntaxin 3B, which is a homolog of syntaxin 1A and specifically located in retinal ribbon synapses. We hypothesize that the variant p.His16Arg of STXBP1 is likely to affect neurotransmitter release in the retina, which may be the underlying etiology of CN in this family. Our results provide a new perspective on understanding the molecular mechanism of CN.
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Affiliation(s)
- Yulei Li
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China.,School of Basic Medical Sciences, Hubei University of Medicine, Shiyan, China
| | - Lei Jiang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Lejin Wang
- Department of Ophthalmology, Peking University People's Hospital, Beijing, China
| | - Cheng Wang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Chunjie Liu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Anyuan Guo
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Mugen Liu
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Luoying Zhang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Cong Ma
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Xianqin Zhang
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Shangbang Gao
- Key Laboratory of Molecular Biophysics of the Ministry of Education, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, China
| | - Jing Yu Liu
- Institute of Neuroscience, State Key Laboratory of Neuroscience, CAS Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai, China
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7
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Campbell JR, Li H, Wang Y, Kozhemyakin M, Hunt AJ, Liu X, Janz R, Heidelberger R. Phosphorylation of the Retinal Ribbon Synapse Specific t-SNARE Protein Syntaxin3B Is Regulated by Light via a Ca 2 +-Dependent Pathway. Front Cell Neurosci 2020; 14:587072. [PMID: 33192329 PMCID: PMC7606922 DOI: 10.3389/fncel.2020.587072] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Accepted: 09/11/2020] [Indexed: 12/27/2022] Open
Abstract
Neurotransmitter release at retinal ribbon-style synapses utilizes a specialized t-SNARE protein called syntaxin3B (STX3B). In contrast to other syntaxins, STX3 proteins can be phosphorylated in vitro at T14 by Ca2+/calmodulin-dependent protein kinase II (CaMKII). This modification has the potential to modulate SNARE complex formation required for neurotransmitter release in an activity-dependent manner. To determine the extent to which T14 phosphorylation occurs in vivo in the mammalian retina and characterize the pathway responsible for the in vivo phosphorylation of T14, we utilized quantitative immunofluorescence to measure the levels of STX3 and STX3 phosphorylated at T14 (pSTX3) in the synaptic terminals of mouse retinal photoreceptors and rod bipolar cells (RBCs). Results demonstrate that STX3B phosphorylation at T14 is light-regulated and dependent upon the elevation of intraterminal Ca2+. In rod photoreceptor terminals, the ratio of pSTX3 to STX3 was significantly higher in dark-adapted mice, when rods are active, than in light-exposed mice. By contrast, in RBC terminals, the ratio of pSTX3 to STX3 was higher in light-exposed mice, when these terminals are active, than in dark-adapted mice. These results were recapitulated in the isolated eyecup preparation, but only when Ca2+ was included in the external medium. In the absence of external Ca2+, pSTX3 levels remained low regardless of light/dark exposure. Using the isolated RBC preparation, we next showed that elevation of intraterminal Ca2+ alone was sufficient to increase STX3 phosphorylation at T14. Furthermore, both the non-specific kinase inhibitor staurosporine and the selective CaMKII inhibitor AIP inhibited the Ca2+-dependent increase in the pSTX3/STX3 ratio in isolated RBC terminals, while in parallel experiments, AIP suppressed RBC depolarization-evoked exocytosis, measured using membrane capacitance measurements. Our data support a novel, illumination-regulated modulation of retinal ribbon-style synapse function in which activity-dependent Ca2+ entry drives the phosphorylation of STX3B at T14 by CaMKII, which in turn, modulates the ability to form SNARE complexes required for exocytosis.
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Affiliation(s)
- Joseph R Campbell
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Hongyan Li
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Yanzhao Wang
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Maxim Kozhemyakin
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Albert J Hunt
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Xiaoqin Liu
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States
| | - Roger Janz
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
| | - Ruth Heidelberger
- Department of Neurobiology and Anatomy, University of Texas Health Science Center at Houston, Houston, TX, United States.,MD Anderson Cancer Center UTHealth Graduate School of Biomedical Sciences, Houston, TX, United States
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8
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Tang BL. SNAREs and developmental disorders. J Cell Physiol 2020; 236:2482-2504. [PMID: 32959907 DOI: 10.1002/jcp.30067] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 08/20/2020] [Accepted: 09/09/2020] [Indexed: 12/12/2022]
Abstract
Members of the soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) family mediate membrane fusion processes associated with vesicular trafficking and autophagy. SNAREs mediate core membrane fusion processes essential for all cells, but some SNAREs serve cell/tissue type-specific exocytic/endocytic functions, and are therefore critical for various aspects of embryonic development. Mutations or variants of their encoding genes could give rise to developmental disorders, such as those affecting the nervous system and immune system in humans. Mutations to components in the canonical synaptic vesicle fusion SNARE complex (VAMP2, STX1A/B, and SNAP25) and a key regulator of SNARE complex formation MUNC18-1, produce variant phenotypes of autism, intellectual disability, movement disorders, and epilepsy. STX11 and MUNC18-2 mutations underlie 2 subtypes of familial hemophagocytic lymphohistiocytosis. STX3 mutations contribute to variant microvillus inclusion disease. Chromosomal microdeletions involving STX16 play a role in pseudohypoparathyroidism type IB associated with abnormal imprinting of the GNAS complex locus. In this short review, I discuss these and other SNARE gene mutations and variants that are known to be associated with a variety developmental disorders, with a focus on their underlying cellular and molecular pathological basis deciphered through disease modeling. Possible pathogenic potentials of other SNAREs whose variants could be disease predisposing are also speculated upon.
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Affiliation(s)
- Bor L Tang
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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9
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Pournami F, MK AK, Panackal AV, Nandakumar A, Prabhakar J, Jain N. Microvillus Inclusion Disease: A Rare Mutation of STX3 in Exon 9 Causing Fatal Congenital Diarrheal Disease. J Pediatr Genet 2020; 11:154-157. [DOI: 10.1055/s-0040-1716401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Accepted: 07/26/2020] [Indexed: 10/23/2022]
Abstract
AbstractInherited diarrheal disorders cause serious morbidity resulting in dependence on intensive care and parenteral nutrition. Microvillus inclusion disease (MVID) has been classically described and results from mutations in the gene coding myosin Vb, which is responsible for enterocyte polarization. Newer reports of mutations resulting in truncated syntaxin 3 (STX3) and Munc18-2 (STXBP2) proteins have been elucidated as causative. To date, five cases of STX3 abnormalities resulting in MVID have been described. We report an infant who presented with congenital diarrhea and was determined to have a rare mutation of STX3. This new finding would be beneficial in future functional genotype–phenotype correlation studies.
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Affiliation(s)
- Femitha Pournami
- Department of Neonatology, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India
| | - Alok Kumar MK
- Department of Neonatology, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India
| | - Anila V. Panackal
- Department of Neonatology, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India
| | - Anand Nandakumar
- Department of Neonatology, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India
| | - Jyothi Prabhakar
- Department of Neonatology, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India
| | - Naveen Jain
- Department of Neonatology, Kerala Institute of Medical Sciences, Trivandrum, Kerala, India
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10
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Abstract
Congenital diarrheal disorders are heterogeneous conditions characterized by diarrhea with onset in the first years of life. They range from simple temporary conditions, such as cow's milk protein intolerance to irreversible complications, such as microvillous inclusion disease with significant morbidity and mortality. Advances in genomic medicine have improved our understanding of these disorders, leading to an ever-increasing list of identified causative genes. The diagnostic approach to these conditions consists of establishing the presence of diarrhea by detailed review of the history, followed by characterizing the composition of the diarrhea, the response to fasting, and with further specialized testing.
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Affiliation(s)
- Abdul Aziz Elkadri
- Medical College of Wisconsin, 8701 Watertown Plank Road, Milwaukee, WI, USA.
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