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Green TE, Fujita A, Ghaderi N, Heinzen EL, Matsumoto N, Klein KM, Berkovic SF, Hildebrand MS. Brain mosaicism of hedgehog signalling and other cilia genes in hypothalamic hamartoma. Neurobiol Dis 2023; 185:106261. [PMID: 37579995 DOI: 10.1016/j.nbd.2023.106261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2023] [Revised: 08/02/2023] [Accepted: 08/11/2023] [Indexed: 08/16/2023] Open
Abstract
Hypothalamic hamartoma (HH) is a rare benign developmental brain lesion commonly associated with a well characterized epilepsy phenotype. Most individuals with HH are non-syndromic without additional developmental anomalies nor a family history of disease. Nonetheless, HH is a feature of Pallister-Hall (PHS) and Oro-Facial-Digital Type VI (OFD VI) syndromes, both characterized by additional developmental anomalies. Initial genetic of analysis HH began with syndromic HH, where germline inherited or de novo variants in GLI3, encoding a central transcription factor in the sonic hedgehog (Shh) signalling pathway, were identified in most individuals with PHS. Following these discoveries in syndromic HH, the hypothesis that post-zygotic mosaicism in related genes may underly non-syndromic HH was tested. We discuss the identified mosaic variants within individuals with non-syndromic HH, review the analytical methodologies and diagnostic yields, and explore understanding of the functional role of the implicated genes with respect to Shh signalling, and cilia development and function. We also outline future challenges in studying non-syndromic HH and suggest potential novel strategies to interrogate brain mosaicism in HH.
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Affiliation(s)
- Timothy E Green
- Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Heidelberg, Victoria 3084, Australia
| | - Atsushi Fujita
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Navid Ghaderi
- Departments of Clinical Neurosciences, Medical Genetics and Community Health Sciences, Hotchkiss Brain Institute & Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Canada
| | - Erin L Heinzen
- Eshelman School of Pharmacy, Division of Pharmacotherapy and Experimental Therapeutics, Department of Genetics, University of North Carolina, Chapel Hill, NC, USA
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama 236-0004, Japan
| | - Karl Martin Klein
- Departments of Clinical Neurosciences, Medical Genetics and Community Health Sciences, Hotchkiss Brain Institute & Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Canada; Epilepsy Center Frankfurt Rhine-Main and Department of Neurology, Goethe University and University Hospital Frankfurt, Frankfurt am Main, Germany; LOEWE Center for Personalized Translational Epilepsy Research (CePTER), Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Samuel F Berkovic
- Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Heidelberg, Victoria 3084, Australia
| | - Michael S Hildebrand
- Epilepsy Research Centre, Department of Medicine, The University of Melbourne, Austin Health, Heidelberg, Victoria 3084, Australia; Murdoch Children's Research Institute, The Royal Children's Hospital, Parkville, Victoria, Australia.
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Jiwani T, Kim JJ, Rosenblum ND. Suppressor of fused controls cerebellum granule cell proliferation by suppressing Fgf8 and spatially regulating Gli proteins. Development 2020; 147:dev.170274. [PMID: 31932349 DOI: 10.1242/dev.170274] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 12/19/2019] [Indexed: 01/07/2023]
Abstract
Cerebellar granule cell (GC) development relies on precise regulation of sonic hedgehog (Shh)-Gli signalling activity, failure of which is associated with motor disorders and medulloblastoma. Mutations in the pathway regulator suppressor of fused (Sufu), which modulates Gli activators and repressors, are linked to cerebellar dysfunction and tumourigenesis. The mechanism by which Sufu calibrates Shh signalling in GCs is unknown. Math1-Cre-mediated deletion of Sufu in mouse GC progenitors (GCPs) demonstrated that Sufu restricts GCP proliferation and promotes cell cycle exit, by promoting expression of Gli3R and suppressing Gli2 levels. Sufu is also required to promote a high threshold of pathway activity in GCPs. Remarkably, central cerebellar lobules are more deleteriously impacted by Sufu deletion, but are less sensitive to downstream genetic manipulations to reduce Gli2 expression or overexpress a Gli3R mimic, compared with anterior lobules. Transcriptome sequencing uncovered new Sufu targets, especially Fgf8, which is upregulated in Sufu-mutant GCPs. We demonstrate that Fgf8 is necessary and sufficient to drive Sufu-mutant GCP proliferation. This study reveals new insights into the spatial and temporal regulation of cerebellar Shh-Gli signalling, while uncovering new targets, such as Fgf8.
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Affiliation(s)
- Tayyaba Jiwani
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada.,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Jinny J Kim
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada
| | - Norman D Rosenblum
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 0A4, Canada .,Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Department of Physiology, University of Toronto, Toronto, Ontario M5S 1A8, Canada.,Department of Paediatrics, University of Toronto, Toronto, Ontario M5G 1X8, Canada
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Cañizares MA, Albors AR, Singer G, Suttie N, Gorkic M, Felts P, Storey KG. Multiple steps characterise ventricular layer attrition to form the ependymal cell lining of the adult mouse spinal cord central canal. J Anat 2019; 236:334-350. [PMID: 31670387 PMCID: PMC6956438 DOI: 10.1111/joa.13094] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/03/2019] [Indexed: 12/22/2022] Open
Abstract
The ventricular layer of the spinal cord is remodelled during embryonic development and ultimately forms the ependymal cell lining of the adult central canal, which retains neural stem cell potential. This anatomical transformation involves the process of dorsal collapse; however, accompanying changes in tissue organisation and cell behaviour as well as the precise origin of cells contributing to the central canal are not well understood. Here, we describe sequential localised cell rearrangements which accompany the gradual attrition of the spinal cord ventricular layer during development. This includes local breakdown of the pseudostratified organisation of the dorsal ventricular layer prefiguring dorsal collapse and evidence for a new phenomenon, ventral dissociation, during which the ventral‐most floor plate cells separate from a subset that are retained around the central canal. Using cell proliferation markers and cell‐cycle reporter mice, we further show that following dorsal collapse, ventricular layer attrition involves an overall reduction in cell proliferation, characterised by an intriguing increase in the percentage of cells in G1/S. In contrast, programmed cell death does not contribute to ventricular layer remodelling. By analysing transcript and protein expression patterns associated with key signalling pathways, we provide evidence for a gradual decline in ventral sonic hedgehog activity and an accompanying ventral expansion of initial dorsal bone morphogenetic protein signalling, which comes to dominate the forming the central canal lining. This study identifies multiple steps that may contribute to spinal cord ventricular layer attrition and adds to increasing evidence for the heterogeneous origin of the spinal cord ependymal cell population, which includes cells from the floor plate and the roof plate as well as ventral progenitor domains.
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Affiliation(s)
- Marco A Cañizares
- Division of Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Aida Rodrigo Albors
- Division of Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Gail Singer
- Division of Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Nicolle Suttie
- Division of Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Metka Gorkic
- Division of Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
| | - Paul Felts
- Centre for Anatomy & Human Identification, University of Dundee, Dundee, UK
| | - Kate G Storey
- Division of Cell & Developmental Biology, School of Life Sciences, University of Dundee, Dundee, UK
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Mok GF, Lozano-Velasco E, Maniou E, Viaut C, Moxon S, Wheeler G, Münsterberg A. miR-133-mediated regulation of the Hedgehog pathway orchestrates embryo myogenesis. Development 2018; 145:dev.159657. [PMID: 29802149 PMCID: PMC6031409 DOI: 10.1242/dev.159657] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2017] [Accepted: 05/10/2018] [Indexed: 12/23/2022]
Abstract
Skeletal myogenesis serves as a paradigm to investigate the molecular mechanisms underlying exquisitely regulated cell fate decisions in developing embryos. The evolutionarily conserved miR-133 family of microRNAs is expressed in the myogenic lineage, but how it acts remains incompletely understood. Here, we performed genome-wide differential transcriptomics of miR-133 knockdown (KD) embryonic somites, the source of vertebrate skeletal muscle. These analyses, performed in chick embryos, revealed extensive downregulation of Sonic hedgehog (Shh) pathway components: patched receptors, Hedgehog interacting protein and the transcriptional activator Gli1. By contrast, Gli3, a transcriptional repressor, was de-repressed and confirmed as a direct miR-133 target. Phenotypically, miR-133 KD impaired myotome formation and growth by disrupting proliferation, extracellular matrix deposition and epithelialization. Together, these observations suggest that miR-133-mediated Gli3 silencing is crucial for embryonic myogenesis. Consistent with this idea, we found that activation of Shh signalling by either purmorphamine, or KD of Gli3 by antisense morpholino, rescued the miR-133 KD phenotype. Thus, we identify a novel Shh/myogenic regulatory factor/miR-133/Gli3 axis that connects epithelial morphogenesis with myogenic fate specification. Summary: Here, using chick embryos, we showed that post-transcriptional silencing of the Gli3 repressor by miR-133 is required to stably establish the myogenic programme in early somites.
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Affiliation(s)
- Gi Fay Mok
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Estefania Lozano-Velasco
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Eirini Maniou
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Camille Viaut
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Simon Moxon
- The Earlham Institute, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
| | - Grant Wheeler
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Andrea Münsterberg
- School of Biological Sciences, Cell and Developmental Biology, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
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