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Xie C, Chen G, Li M, Huang P, Chen Z, Lei K, Li D, Wang Y, Cleetus A, Mohamed MA, Sonar P, Feng W, Ökten Z, Ou G. Neurons dispose of hyperactive kinesin into glial cells for clearance. EMBO J 2024; 43:2606-2635. [PMID: 38806659 PMCID: PMC11217292 DOI: 10.1038/s44318-024-00118-0] [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: 11/22/2023] [Revised: 04/06/2024] [Accepted: 04/25/2024] [Indexed: 05/30/2024] Open
Abstract
Microtubule-based kinesin motor proteins are crucial for intracellular transport, but their hyperactivation can be detrimental for cellular functions. This study investigated the impact of a constitutively active ciliary kinesin mutant, OSM-3CA, on sensory cilia in C. elegans. Surprisingly, we found that OSM-3CA was absent from cilia but underwent disposal through membrane abscission at the tips of aberrant neurites. Neighboring glial cells engulf and eliminate the released OSM-3CA, a process that depends on the engulfment receptor CED-1. Through genetic suppressor screens, we identified intragenic mutations in the OSM-3CA motor domain and mutations inhibiting the ciliary kinase DYF-5, both of which restored normal cilia in OSM-3CA-expressing animals. We showed that conformational changes in OSM-3CA prevent its entry into cilia, and OSM-3CA disposal requires its hyperactivity. Finally, we provide evidence that neurons also dispose of hyperactive kinesin-1 resulting from a clinic variant associated with amyotrophic lateral sclerosis, suggesting a widespread mechanism for regulating hyperactive kinesins.
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Affiliation(s)
- Chao Xie
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- State Key Laboratory for Membrane Biology, Beijing, China
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Guanghan Chen
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- State Key Laboratory for Membrane Biology, Beijing, China
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Ming Li
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- State Key Laboratory for Membrane Biology, Beijing, China
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Peng Huang
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- State Key Laboratory for Membrane Biology, Beijing, China
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Zhe Chen
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- State Key Laboratory for Membrane Biology, Beijing, China
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Kexin Lei
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- State Key Laboratory for Membrane Biology, Beijing, China
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Dong Li
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, 100101, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Yuhe Wang
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China
- State Key Laboratory for Membrane Biology, Beijing, China
- School of Life Sciences, Tsinghua University, Beijing, China
| | - Augustine Cleetus
- Physik Department E22, Technische Universitat Munchen, James-Franck-Strasse, Garching, 85748, Germany
| | - Mohamed Aa Mohamed
- Physik Department E22, Technische Universitat Munchen, James-Franck-Strasse, Garching, 85748, Germany
| | - Punam Sonar
- Physik Department E22, Technische Universitat Munchen, James-Franck-Strasse, Garching, 85748, Germany
| | - Wei Feng
- National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, 100101, Beijing, China
- College of Life Sciences, University of Chinese Academy of Sciences, 100049, Beijing, China
| | - Zeynep Ökten
- Physik Department E22, Technische Universitat Munchen, James-Franck-Strasse, Garching, 85748, Germany
| | - Guangshuo Ou
- Tsinghua-Peking Center for Life Sciences, Tsinghua University, Beijing, China.
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, China.
- McGovern Institute for Brain Research, Tsinghua University, Beijing, China.
- State Key Laboratory for Membrane Biology, Beijing, China.
- School of Life Sciences, Tsinghua University, Beijing, China.
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2
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Zhai Y, Ballios BG. Exploring the diverse clinical and variant spectrum of CEP78-associated syndrome: Novel pathogenic variants identified in a case series. Am J Med Genet A 2024:e63720. [PMID: 38780195 DOI: 10.1002/ajmg.a.63720] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 04/25/2024] [Accepted: 05/09/2024] [Indexed: 05/25/2024]
Abstract
Dual sensory impairment, commonly referred to as combined hearing and vision loss, can stem from a diverse spectrum of conditions, each presenting with its unique set of clinical characteristics. Our understanding of dual sensory impairment has expanded significantly in the past decade, broadening the scope of genetic differential diagnoses, including genes such as CEP250, ARSG, TUBB4B, CEP78, and ABHD12. A case series including three patients from two families with genetically diagnosed CEP78-associated cone-rod dystrophy was identified. We collected and reviewed their clinical records, imaging data, and genetic testing results. In addition, a comprehensive literature review was conducted on the phenotype and the genetic testing modality employed in all published CEP78 cases through a PubMed search using the keyword "CEP78." A retinal dystrophy panel detected a novel homozygous CEP78 pathogenic variant (c.1447C>T, p.Arg483*) in siblings-Cases 1 and 2-from Family 1. Both teenagers have a clinical diagnosis of cone-rod dystrophy with presumed normal hearing. Case 3 from Family 2, diagnosed with cone-rod dystrophy and early-onset hearing loss, was found to carry a CEP78 pathogenic variant (c.1206-2A>C) and a likely pathogenic variant (c.856_857del, p.Leu286Glyfs*12) also through panel-based genetic testing. Intriguingly, neither of these variants was reported in an affected sibling's clinical whole-exome sequencing (WES) report when performed in 2015. A review of CEP78-related literature unveiled that the initial report linking CEP78 to cone-rod dystrophy and hearing loss was published in September 2016. Any pathogenic variant found in CEP78 before 2016 would have been categorized as a "clearly disruptive variant in a gene of uncertain significance (GUS)" and might not have been reported in the WES report. It is important to acknowledge that our understanding of genotype-phenotype associations is undergoing rapid expansion. It is also crucial to recognize that repeat genetic testing may represent a fundamentally different approach, given the technological advancements not only in the coverage of the sequencing but also in the more comprehensive understanding of genotype-phenotype associations. This case series also enriches the existing CEP78 literature by providing phenotypic details of the youngest case of CEP78-associated retinopathy reported in the literature (Case 2), which expands our perspective on the natural history of disease in this disorder.
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Affiliation(s)
- Yi Zhai
- Division of Clinical and Metabolic Genetics, Department of Pediatrics, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
| | - Brian G Ballios
- Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ontario, Canada
- Department of Ophthalmology, University Health Network, Toronto, Ontario, Canada
- Kensington Vision and Research Centre, Toronto, Ontario, Canada
- Krembil Research Institute, University Health Network, Toronto, Ontario, Canada
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3
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Fernández-Suárez E, González-Del Pozo M, Méndez-Vidal C, Martín-Sánchez M, Mena M, de la Morena-Barrio B, Corral J, Borrego S, Antiñolo G. Long-read sequencing improves the genetic diagnosis of retinitis pigmentosa by identifying an Alu retrotransposon insertion in the EYS gene. Mob DNA 2024; 15:9. [PMID: 38704576 PMCID: PMC11069205 DOI: 10.1186/s13100-024-00320-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2024] [Accepted: 04/10/2024] [Indexed: 05/06/2024] Open
Abstract
BACKGROUND Biallelic variants in EYS are the major cause of autosomal recessive retinitis pigmentosa (arRP) in certain populations, a clinically and genetically heterogeneous disease that may lead to legal blindness. EYS is one of the largest genes (~ 2 Mb) expressed in the retina, in which structural variants (SVs) represent a common cause of disease. However, their identification using short-read sequencing (SRS) is not always feasible. Here, we conducted targeted long-read sequencing (T-LRS) using adaptive sampling of EYS on the MinION sequencing platform (Oxford Nanopore Technologies) to definitively diagnose an arRP family, whose affected individuals (n = 3) carried the heterozygous pathogenic deletion of exons 32-33 in the EYS gene. As this was a recurrent variant identified in three additional families in our cohort, we also aimed to characterize the known deletion at the nucleotide level to assess a possible founder effect. RESULTS T-LRS in family A unveiled a heterozygous AluYa5 insertion in the coding exon 43 of EYS (chr6(GRCh37):g.64430524_64430525ins352), which segregated with the disease in compound heterozygosity with the previously identified deletion. Visual inspection of previous SRS alignments using IGV revealed several reads containing soft-clipped bases, accompanied by a slight drop in coverage at the Alu insertion site. This prompted us to develop a simplified program using grep command to investigate the recurrence of this variant in our cohort from SRS data. Moreover, LRS also allowed the characterization of the CNV as a ~ 56.4kb deletion spanning exons 32-33 of EYS (chr6(GRCh37):g.64764235_64820592del). The results of further characterization by Sanger sequencing and linkage analysis in the four families were consistent with a founder variant. CONCLUSIONS To our knowledge, this is the first report of a mobile element insertion into the coding sequence of EYS, as a likely cause of arRP in a family. Our study highlights the value of LRS technology in characterizing and identifying hidden pathogenic SVs, such as retrotransposon insertions, whose contribution to the etiopathogenesis of rare diseases may be underestimated.
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Affiliation(s)
- Elena Fernández-Suárez
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - María González-Del Pozo
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Cristina Méndez-Vidal
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Marta Martín-Sánchez
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Marcela Mena
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain
| | - Belén de la Morena-Barrio
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER-ISCIII, Murcia, Spain
| | - Javier Corral
- Servicio de Hematología y Oncología Médica, Hospital Universitario Morales Meseguer, Centro Regional de Hemodonación, Universidad de Murcia, IMIB-Pascual Parrilla, CIBERER-ISCIII, Murcia, Spain
| | - Salud Borrego
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain.
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain.
| | - Guillermo Antiñolo
- Department of Maternofetal Medicine, Genetics and Reproduction, Institute of Biomedicine of Seville (IBiS), University Hospital Virgen del Rocío/CSIC, University of Seville, Seville, Spain.
- Center for Biomedical Network Research On Rare Diseases (CIBERER), Seville, Spain.
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4
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Zhang Z, Moye AR, He F, Chen M, Agosto MA, Wensel TG. Centriole and transition zone structures in photoreceptor cilia revealed by cryo-electron tomography. Life Sci Alliance 2024; 7:e202302409. [PMID: 38182160 PMCID: PMC10770417 DOI: 10.26508/lsa.202302409] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 12/12/2023] [Accepted: 12/12/2023] [Indexed: 01/07/2024] Open
Abstract
Primary cilia mediate sensory signaling in multiple organisms and cell types but have structures adapted for specific roles. Structural defects in them lead to devastating diseases known as ciliopathies in humans. Key to their functions are structures at their base: the basal body, the transition zone, the "Y-shaped links," and the "ciliary necklace." We have used cryo-electron tomography with subtomogram averaging and conventional transmission electron microscopy to elucidate the structures associated with the basal region of the "connecting cilia" of rod outer segments in mouse retina. The longitudinal variations in microtubule (MT) structures and the lumenal scaffold complexes connecting them have been determined, as well as membrane-associated transition zone structures: Y-shaped links connecting MT to the membrane, and ciliary beads connected to them that protrude from the cell surface and form a necklace-like structure. These results represent a clearer structural scaffold onto which molecules identified by genetics, proteomics, and superresolution fluorescence can be placed in our emerging model of photoreceptor sensory cilia.
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Affiliation(s)
- Zhixian Zhang
- https://ror.org/02pttbw34 Verna and Marrs McLean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Abigail R Moye
- https://ror.org/02pttbw34 Verna and Marrs McLean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
- Department of Ophthalmic Genetics, Institute of Molecular and Clinical Ophthalmology Basel, Basel, Switzerland
| | - Feng He
- https://ror.org/02pttbw34 Verna and Marrs McLean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
| | - Muyuan Chen
- https://ror.org/02pttbw34 Verna and Marrs McLean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
- Division of CryoEM and Bioimaging, SSRL, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA, USA
| | - Melina A Agosto
- Department of Physiology and Biophysics and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Canada
| | - Theodore G Wensel
- https://ror.org/02pttbw34 Verna and Marrs McLean Department of Biochemistry and Molecular Pharmacology, Baylor College of Medicine, Houston, TX, USA
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5
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Shimogawa MM, Jonnalagadda K, Hill KL. FAP20 is required for flagellum assembly in Trypanosoma brucei. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.19.576295. [PMID: 38293126 PMCID: PMC10827224 DOI: 10.1101/2024.01.19.576295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2024]
Abstract
Trypanosoma brucei is a human and animal pathogen that depends on flagellar motility for transmission and infection. The trypanosome flagellum is built around a canonical "9+2" axoneme, containing nine doublet microtubules (DMTs) surrounding two singlet microtubules. Each DMT contains a 13-protofilament A-tubule and a 10-protofilament B-tubule, connected to the A-tubule by a conserved, non-tubulin inner junction (IJ) filament made up of alternating PACRG and FAP20 subunits. Here we investigate FAP20 in procyclic form T. brucei. A FAP20-NeonGreen fusion protein localized to the axoneme as expected. Surprisingly, FAP20 knockdown led to a catastrophic failure in flagellum assembly and concomitant lethal cell division defect. This differs from other organisms, where FAP20 is required for normal flagellum motility, but generally dispensable for flagellum assembly and viability. Transmission electron microscopy demonstrates failed flagellum assembly in FAP20 mutants is associated with a range of DMT defects and defective assembly of the paraflagellar rod, a lineage-specific flagellum filament that attaches to DMT 4-7 in trypanosomes. Our studies reveal a lineage-specific requirement for FAP20 in trypanosomes, offering insight into adaptations for flagellum stability and motility in these parasites and highlighting pathogen versus host differences that might be considered for therapeutic intervention in trypanosome diseases.
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Affiliation(s)
- Michelle M. Shimogawa
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Keya Jonnalagadda
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
| | - Kent L. Hill
- Department of Microbiology, Immunology and Molecular Genetics, University of California Los Angeles, Los Angeles, CA, 90095, USA
- California NanoSystems Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, CA, 90095, USA
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6
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Bangera M, Dungdung A, Prabhu S, Sirajuddin M. Doublet microtubule inner junction protein FAP20 recruits tubulin to the microtubule lattice. Structure 2023; 31:1535-1544.e4. [PMID: 37816351 PMCID: PMC7615566 DOI: 10.1016/j.str.2023.09.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Revised: 07/12/2023] [Accepted: 09/13/2023] [Indexed: 10/12/2023]
Abstract
Doublet microtubules of eukaryotic cilia and flagella are made up of a complete A- and an incomplete B-tubule that are fused together. Of the two fusion points, the outer junction is made of tripartite tubulin connections, while the inner junction contains non-tubulin elements. The latter includes flagellar-associated protein 20 (FAP20) and Parkin co-regulated gene protein (PACRG) that together link the A- and B-tubule at the inner junction. While structures of doublet microtubules reveal molecular details, their assembly is poorly understood. In this study, we purified recombinant FAP20 and characterized its effects on microtubule dynamics. We use in vitro reconstitution and cryo-electron microscopy to show that FAP20 recruits free tubulin to the existing microtubule lattice. Our cryo-electron microscopy reconstruction of microtubule:FAP20:tubulin complex reveals the mode of tubulin recruitment by FAP20 onto microtubules, providing insights into assembly steps of B-tubule closure during doublet microtubule formation.
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Affiliation(s)
- Mamata Bangera
- Institute for Stem Cell Science and Regenerative Medicine, GKVK Campus, Bengaluru 560065, India
| | - Archita Dungdung
- Institute for Stem Cell Science and Regenerative Medicine, GKVK Campus, Bengaluru 560065, India
| | - Sujana Prabhu
- Institute for Stem Cell Science and Regenerative Medicine, GKVK Campus, Bengaluru 560065, India
| | - Minhajuddin Sirajuddin
- Institute for Stem Cell Science and Regenerative Medicine, GKVK Campus, Bengaluru 560065, India.
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7
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Black CS, Bui KH. Unveiling the intriguing role of FAP20 in tubulin recruitment at the doublet microtubule inner junctions. Structure 2023; 31:1518-1519. [PMID: 38065073 DOI: 10.1016/j.str.2023.11.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Revised: 11/10/2023] [Accepted: 11/10/2023] [Indexed: 12/18/2023]
Abstract
In this issue of Structure, Bangera et al. investigate the role of the inner junction protein FAP20 in doublet microtubule assembly. Using cryo-EM and microtubule dynamic assays, they demonstrate that FAP20 recruits free tubulins to existing microtubule lattices, shedding light on B-tubule closure during doublet microtubule formation.
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Affiliation(s)
- Corbin S Black
- Facility for Electron Microscopy Research, McGill University, Montreal, QC, Canada.
| | - Khanh Huy Bui
- Department of Anatomy and Cell Biology, McGill University, Montreal, QC, Canada.
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8
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Hodges ED, Chrystal PW, Footz T, Doucette LP, Noel NCL, Li Z, Walter MA, Allison WT. Disrupting the Repeat Domain of Premelanosome Protein (PMEL) Produces Dysamyloidosis and Dystrophic Ocular Pigment Reflective of Pigmentary Glaucoma. Int J Mol Sci 2023; 24:14423. [PMID: 37833870 PMCID: PMC10572516 DOI: 10.3390/ijms241914423] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 09/11/2023] [Accepted: 09/14/2023] [Indexed: 10/15/2023] Open
Abstract
Pigmentary glaucoma has recently been associated with missense mutations in PMEL that are dominantly inherited and enriched in the protein's fascinating repeat domain. PMEL pathobiology is intriguing because PMEL forms functional amyloid in healthy eyes, and this PMEL amyloid acts to scaffold melanin deposition. This is an informative contradistinction to prominent neurodegenerative diseases where amyloid formation is neurotoxic and mutations cause a toxic gain of function called "amyloidosis". Preclinical animal models have failed to model this PMEL "dysamyloidosis" pathomechanism and instead cause recessively inherited ocular pigment defects via PMEL loss of function; they have not addressed the consequences of disrupting PMEL's repetitive region. Here, we use CRISPR to engineer a small in-frame mutation in the zebrafish homolog of PMEL that is predicted to subtly disrupt the protein's repetitive region. Homozygous mutant larvae displayed pigmentation phenotypes and altered eye morphogenesis similar to presumptive null larvae. Heterozygous mutants had disrupted eye morphogenesis and disrupted pigment deposition in their retinal melanosomes. The deficits in the pigment deposition of these young adult fish were not accompanied by any detectable glaucomatous changes in intraocular pressure or retinal morphology. Overall, the data provide important in vivo validation that subtle PMEL mutations can cause a dominantly inherited pigment pathology that aligns with the inheritance of pigmentary glaucoma patient pedigrees. These in vivo observations help to resolve controversy regarding the necessity of PMEL's repeat domain in pigmentation. The data foster an ongoing interest in an antithetical dysamyloidosis mechanism that, akin to the amyloidosis of devastating dementias, manifests as a slow progressive neurodegenerative disease.
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Affiliation(s)
- Elizabeth D. Hodges
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Faculty of Science, University of Alberta, Edmonton, AB T6G 2E9, Canada
| | - Paul W. Chrystal
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Tim Footz
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
| | - Lance P. Doucette
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
| | - Nicole C. L. Noel
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
- Institute of Ophthalmology, University College London, London EC1V 9EL, UK
| | - Zixuan Li
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
| | - Michael A. Walter
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
| | - W. Ted Allison
- Department of Biological Sciences, University of Alberta, Edmonton, AB T6G 2E9, Canada; (E.D.H.); (P.W.C.)
- Department of Medical Genetics, University of Alberta, Edmonton, AB T6G 2R3, Canada (M.A.W.)
- Centre for Prions & Protein Folding Disease, University of Alberta, Edmonton, AB T6G 2M8, Canada
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