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Kebschull JM, Casoni F, Consalez GG, Goldowitz D, Hawkes R, Ruigrok TJH, Schilling K, Wingate R, Wu J, Yeung J, Uusisaari MY. Cerebellum Lecture: the Cerebellar Nuclei-Core of the Cerebellum. CEREBELLUM (LONDON, ENGLAND) 2024; 23:620-677. [PMID: 36781689 PMCID: PMC10951048 DOI: 10.1007/s12311-022-01506-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/10/2022] [Indexed: 02/15/2023]
Abstract
The cerebellum is a key player in many brain functions and a major topic of neuroscience research. However, the cerebellar nuclei (CN), the main output structures of the cerebellum, are often overlooked. This neglect is because research on the cerebellum typically focuses on the cortex and tends to treat the CN as relatively simple output nuclei conveying an inverted signal from the cerebellar cortex to the rest of the brain. In this review, by adopting a nucleocentric perspective we aim to rectify this impression. First, we describe CN anatomy and modularity and comprehensively integrate CN architecture with its highly organized but complex afferent and efferent connectivity. This is followed by a novel classification of the specific neuronal classes the CN comprise and speculate on the implications of CN structure and physiology for our understanding of adult cerebellar function. Based on this thorough review of the adult literature we provide a comprehensive overview of CN embryonic development and, by comparing cerebellar structures in various chordate clades, propose an interpretation of CN evolution. Despite their critical importance in cerebellar function, from a clinical perspective intriguingly few, if any, neurological disorders appear to primarily affect the CN. To highlight this curious anomaly, and encourage future nucleocentric interpretations, we build on our review to provide a brief overview of the various syndromes in which the CN are currently implicated. Finally, we summarize the specific perspectives that a nucleocentric view of the cerebellum brings, move major outstanding issues in CN biology to the limelight, and provide a roadmap to the key questions that need to be answered in order to create a comprehensive integrated model of CN structure, function, development, and evolution.
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Affiliation(s)
- Justus M Kebschull
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, 21205, USA.
| | - Filippo Casoni
- Division of Neuroscience, San Raffaele Scientific Institute, and San Raffaele University, Milan, Italy
| | - G Giacomo Consalez
- Division of Neuroscience, San Raffaele Scientific Institute, and San Raffaele University, Milan, Italy
| | - Daniel Goldowitz
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Richard Hawkes
- Department of Cell Biology & Anatomy and Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, T2N 4N1, Canada
| | - Tom J H Ruigrok
- Department of Neuroscience, Erasmus MC, Rotterdam, the Netherlands
| | - Karl Schilling
- Department of Anatomy, Anatomy & Cell Biology, Rheinische Friedrich-Wilhelms-Universität, 53115, Bonn, Federal Republic of Germany
| | - Richard Wingate
- MRC Centre for Neurodevelopmental Disorders, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK
| | - Joshua Wu
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Joanna Yeung
- Department of Medical Genetics, Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada
| | - Marylka Yoe Uusisaari
- Neuronal Rhythms in Movement Unit, Okinawa Institute of Science and Technology, 1919-1 Tancha, Onna-Son, Kunigami-Gun, Okinawa, 904-0495, Japan.
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2
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Gafner M, Garel C, Leibovitz Z, Valence S, Krajden Haratz K, Oegema R, Mancini GMS, Heron D, Bueltmann E, Burglen L, Rodriguez D, Huisman TAGM, Lequin MH, Arad A, Kidron D, Muqary M, Gindes L, Lev D, Boltshauser E, Lerman-Sagie T. Medullary Tegmental Cap Dysplasia: Fetal and Postnatal Presentations of a Unique Brainstem Malformation. AJNR Am J Neuroradiol 2023; 44:334-340. [PMID: 36822823 PMCID: PMC10187821 DOI: 10.3174/ajnr.a7805] [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: 10/14/2022] [Accepted: 01/09/2023] [Indexed: 02/25/2023]
Abstract
BACKGROUND AND PURPOSE Medullary tegmental cap dysplasia is a rare brainstem malformation, first described and defined by James Barkovich in his book Pediatric Neuroimaging from 2005 as an anomalous mass protruding from the posterior medullary surface. We describe the neuroimaging, clinical, postmortem, and genetic findings defining this unique malformation. MATERIALS AND METHODS This is a multicenter, international, retrospective study. We assessed the patients' medical records, prenatal ultrasounds, MR images, genetic findings, and postmortem results. We reviewed the medical literature for all studies depicting medullary malformations and evaluated cases in which a dorsal medullary protuberance was described. RESULTS We collected 13 patients: 3 fetuses and 10 children. The medullary caps had multiple characteristics. Associated brain findings were a rotated position of the medulla, a small and flat pons, cerebellar anomalies, a molar tooth sign, and agenesis of the corpus callosum. Systemic findings included the following: polydactyly, hallux valgus, large ears, and coarse facies. Postmortem analysis in 3 patients revealed that the cap contained either neurons or white matter tracts. We found 8 publications describing a dorsal medullary protuberance in 27 patients. The syndromic diagnosis was Joubert-Boltshauser syndrome in 11 and fibrodysplasia ossificans progressiva in 14 patients. CONCLUSIONS This is the first study to describe a series of 13 patients with medullary tegmental cap dysplasia. The cap has different shapes: distinct in Joubert-Boltshauser syndrome and fibrodysplasia ossificans progressive. Due to the variations in the clinical, imaging, and postmortem findings, we conclude that there are multiple etiologies and pathophysiology. We suggest that in some patients, the pathophysiology might be abnormal axonal guidance.
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Affiliation(s)
- M Gafner
- From the Department of Pediatrics B (M.G.), Schneider Children's Medical Center of Israel, Petach Tikva, Israel
- Sackler Faculty ofMedicine (M.G., K.K.H., L.G., D.L., T.L.-S.), Tel Aviv University, Tel Aviv, Israel
| | - C Garel
- Department of Radiology (C.G.)
- Reference Center for Cerebellar Malformations and Congenital Diseases (C.G., S.V., D.H., L.B., D.R.), Hôpital d'Enfants Armand-Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - Z Leibovitz
- Obstetrics and Gynecology Ultrasound Unit (Z.L.), Bnai-Zion Medical Center, Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, Haifa, Israel
| | - S Valence
- Reference Center for Cerebellar Malformations and Congenital Diseases (C.G., S.V., D.H., L.B., D.R.), Hôpital d'Enfants Armand-Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
- Service de Neuropédiatrie (S.V., L.B., D.R.), Hôpital Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - K Krajden Haratz
- Sackler Faculty ofMedicine (M.G., K.K.H., L.G., D.L., T.L.-S.), Tel Aviv University, Tel Aviv, Israel
- Division of Ultrasound in ObGyn (K.K.H.), Lis Maternity Hospital, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel
| | | | - G M S Mancini
- Department of Clinical Genetics (G.M.S.M.), Erasmus MC University Medical Center, GD Rotterdam, the Netherlands
| | - D Heron
- Reference Center for Cerebellar Malformations and Congenital Diseases (C.G., S.V., D.H., L.B., D.R.), Hôpital d'Enfants Armand-Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
- Service de Génétique Clinique (D.H.), Hôpital de la Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - E Bueltmann
- Institute of Diagnostic und Interventional Neuroradiology (E. Bueltmann), Hannover Medical School, Hannover, Germany
| | - L Burglen
- Reference Center for Cerebellar Malformations and Congenital Diseases (C.G., S.V., D.H., L.B., D.R.), Hôpital d'Enfants Armand-Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
- Service de Neuropédiatrie (S.V., L.B., D.R.), Hôpital Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - D Rodriguez
- Reference Center for Cerebellar Malformations and Congenital Diseases (C.G., S.V., D.H., L.B., D.R.), Hôpital d'Enfants Armand-Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
- Service de Neuropédiatrie (S.V., L.B., D.R.), Hôpital Trousseau, Assistance Publique-Hôpitaux de Paris, Paris, France
| | - T A G M Huisman
- Edward B. Singleton Department of Radiology (T.A.G.M.H.), Texas Children's Hospital and Baylor College of Medicine, Houston, Texas
| | - M H Lequin
- Radiology (M.H.L.), University Medical Center Utrecht, Utrecht University, Utrecht, the Netherlands
| | - A Arad
- Department of Pathology (A.A.), Bnai-Zion Medical Center, Haifa, Israel
| | - D Kidron
- Department of Pathology (D.K.), Meir Medical Center, Kfar Saba, Israel
| | - M Muqary
- Department of Obstetrics and Gynecology (M.M.), Poriya Medical Center, Tiberias, Galilee, Israel
| | - L Gindes
- Sackler Faculty ofMedicine (M.G., K.K.H., L.G., D.L., T.L.-S.), Tel Aviv University, Tel Aviv, Israel
- Department of Obstetrics and Gynecology (L.G.)
| | - D Lev
- Sackler Faculty ofMedicine (M.G., K.K.H., L.G., D.L., T.L.-S.), Tel Aviv University, Tel Aviv, Israel
- The Rina Mor Institute of Medical Genetics (D.L.)
- Fetal Neurology Clinic (D.L., T.L.-S.)
| | - E Boltshauser
- Pediatric Neurology (Emeritus) (E. Boltshauser), Children's University Hospital, Zürich, Switzerland
| | - T Lerman-Sagie
- Sackler Faculty ofMedicine (M.G., K.K.H., L.G., D.L., T.L.-S.), Tel Aviv University, Tel Aviv, Israel
- Fetal Neurology Clinic (D.L., T.L.-S.)
- Magen Center for Rare Diseases (T.L.-S.)
- Pediatric Neurology Unit (T.L.-S.), Wolfson Medical Center, Holon, Israel
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Meoded A, Kukreja M, Orman G, Boltshauser E, Huisman TAGM. Another Piece of the Puzzle of Anomalous Connectivity in Joubert's Syndrome. Neuropediatrics 2022; 53:195-199. [PMID: 34674207 DOI: 10.1055/s-0041-1732310] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
We report on the conventional and diffusion tensor imaging (DTI) findings of a 2-year-old child with clinical presentation of Joubert's Syndrome (JS) and brainstem structural abnormalities as depicted by neuroimaging.Conventional magnetic resonance imaging (MRI) showed a "molar tooth" configuration of the brainstem. A band-like formation coursing in an apparent axial plane anterior to the interpeduncular fossa was noted and appeared to partially cover the interpeduncular fossa.DTI maps and three-dimensional (3D) tractography demonstrated a prominent red-encoded white matter bundle anterior to the midbrain. Probable aberrant course of the bilateral corticospinal tracts (CST) was also depicted. Absence of the decussation of the superior cerebellar peduncles and elongated thickened, horizontal superior cerebellar peduncle (SCP) reflecting the molar tooth sign were also shown.Our report and the review of the published cases suggest that DTI and tractography may be very helpful to differentiate between interpeduncular heterotopias and similarly located white matter bundles corroborating the underlying etiology of axonal guidance disorders in the complex group of ciliopathies including JS. Our case represents an important additional puzzle piece to explore the variability of these ciliopathies.
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Affiliation(s)
- Avner Meoded
- Edward B. Singleton Department of Radiology, Texas Children's Hospital, Houston, Texas, United States
| | - Marcia Kukreja
- Edward B. Singleton Department of Radiology, Texas Children's Hospital, Houston, Texas, United States
| | - Gunes Orman
- Edward B. Singleton Department of Radiology, Texas Children's Hospital, Houston, Texas, United States
| | - Eugen Boltshauser
- Department of Pediatric Neurology, University Children's Hospital, Zurich, Switzerland
| | - Thierry A G M Huisman
- Edward B. Singleton Department of Radiology, Texas Children's Hospital, Houston, Texas, United States
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Chang CH, Chen TY, Tang TK. Using in vivo cerebellar electroporation to study neuronal cell proliferation and differentiation in a Joubert syndrome mouse model. Methods Cell Biol 2022; 175:235-249. [PMID: 36967143 DOI: 10.1016/bs.mcb.2022.07.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Joubert syndrome (JS) is an autosomal recessive ciliopathy that mainly affects the morphogenesis of the cerebellum and brain stem. To date, mutations in at least 39 genes have been identified in JS; all these gene-encoding proteins are involved in the biogenesis of the primary cilium and centrioles. Recent studies using the mouse model carrying deleted or mutated JS-related genes exhibited cerebellar hypoplasia with a reduction in neurogenesis; however, investigating specific neuronal behaviors during their development in vivo remains challenging. Here, we describe an in vivo cerebellar electroporation technique that can be used to deliver plasmids carrying GFP and/or shRNAs into the major cerebellar cell type, granule neurons, from their progenitor state to their maturation in a spatiotemporal-specific manner. By combining this method with cerebellar immunostaining and EdU incorporation, these approaches enable the investigation of the cell-autonomous effect of JS-related genes in granule neuron progenitors, including the pathogenesis of ectopic neurons and the defects in neuronal differentiation. This approach provides information toward understanding the multifaceted roles of JS-related genes during cerebellar development in vivo.
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Affiliation(s)
| | - Ting-Yu Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Tang K Tang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan.
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5
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Chang CH, Chen TY, Lu IL, Li RB, Tsai JJ, Lin PY, Tang TK. CEP120-mediated KIAA0753 recruitment onto centrioles is required for timely neuronal differentiation and germinal zone exit in the developing cerebellum. Genes Dev 2021; 35:1445-1460. [PMID: 34711653 PMCID: PMC8559671 DOI: 10.1101/gad.348636.121] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2021] [Accepted: 09/28/2021] [Indexed: 11/25/2022]
Abstract
Here, Chang et al. report that CEP120, a JS-associated protein involved in centriole biogenesis and cilia assembly, regulates timely neuronal differentiation and the departure of granule neuron progenitors (GNPs) from their germinal zone during cerebellar development. Their findings reveal a close interplay between CEP120 and KIAA0753 for the germinal zone exit and timely neuronal differentiation of GNPs during cerebellar development, and mutations in CEP120 and KIAA0753 may participate in the heterotopia and cerebellar hypoplasia observed in JS patients. Joubert syndrome (JS) is a recessive ciliopathy in which all affected individuals have congenital cerebellar vermis hypoplasia. Here, we report that CEP120, a JS-associated protein involved in centriole biogenesis and cilia assembly, regulates timely neuronal differentiation and the departure of granule neuron progenitors (GNPs) from their germinal zone during cerebellar development. Our results show that depletion of Cep120 perturbs GNP cell cycle progression, resulting in a delay of cell cycle exit in vivo. To dissect the potential mechanism, we investigated the association between CEP120 interactome and the JS database and identified KIAA0753 (a JS-associated protein) as a CEP120-interacting protein. Surprisingly, we found that CEP120 recruits KIAA0753 to centrioles, and that loss of this interaction induces accumulation of GNPs in the germinal zone and impairs neuronal differentiation. Importantly, the replenishment of wild-type CEP120 rescues the above defects, whereas expression of JS-associated CEP120 mutants, which hinder KIAA0753 recruitment, does not. Together, our data reveal a close interplay between CEP120 and KIAA0753 for the germinal zone exit and timely neuronal differentiation of GNPs during cerebellar development, and mutations in CEP120 and KIAA0753 may participate in the heterotopia and cerebellar hypoplasia observed in JS patients.
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Affiliation(s)
- Chia-Hsiang Chang
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Ting-Yu Chen
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - I-Ling Lu
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Rong-Bin Li
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Jhih-Jie Tsai
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Pin-Yeh Lin
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
| | - Tang K Tang
- Institute of Biomedical Sciences, Academia Sinica, Taipei 11529, Taiwan
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6
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Suciu SK, Long AB, Caspary T. Smoothened and ARL13B are critical in mouse for superior cerebellar peduncle targeting. Genetics 2021; 218:6300527. [PMID: 34132778 PMCID: PMC8864748 DOI: 10.1093/genetics/iyab084] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 06/15/2021] [Indexed: 01/07/2023] Open
Abstract
Patients with the ciliopathy Joubert syndrome present with physical anomalies, intellectual disability, and a hindbrain malformation described as the "molar tooth sign" due to its appearance on an MRI. This radiological abnormality results from a combination of hypoplasia of the cerebellar vermis and inappropriate targeting of the white matter tracts of the superior cerebellar peduncles. ARL13B is a cilia-enriched regulatory GTPase established to regulate cell fate, cell proliferation, and axon guidance through vertebrate Hedgehog signaling. In patients, mutations in ARL13B cause Joubert syndrome. To understand the etiology of the molar tooth sign, we used mouse models to investigate the role of ARL13B during cerebellar development. We found that ARL13B regulates superior cerebellar peduncle targeting and these fiber tracts require Hedgehog signaling for proper guidance. However, in mouse, the Joubert-causing R79Q mutation in ARL13B does not disrupt Hedgehog signaling nor does it impact tract targeting. We found a small cerebellar vermis in mice lacking ARL13B function but no cerebellar vermis hypoplasia in mice expressing the Joubert-causing R79Q mutation. In addition, mice expressing a cilia-excluded variant of ARL13B that transduces Hedgehog normally showed normal tract targeting and vermis width. Taken together, our data indicate that ARL13B is critical for the control of cerebellar vermis width as well as superior cerebellar peduncle axon guidance, likely via Hedgehog signaling. Thus, our work highlights the complexity of ARL13B in molar tooth sign etiology.
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Affiliation(s)
- Sarah K Suciu
- Genetics and Molecular Biology Graduate Program, Emory University, Atlanta, GA 30322, USA,Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
| | - Alyssa B Long
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA
| | - Tamara Caspary
- Department of Human Genetics, Emory University, Atlanta, GA 30322, USA,Corresponding author: Department of Human Genetics, 615 Michael Street, Suite 301, Atlanta, GA 30322.
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7
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Filippopulos FM, Brem C, Seelos K, Köglsperger T, Sonnenfeld S, Kellert L, Vollmar C. Uncrossed corticospinal tract in health and genetic disorders: Review, case report, and clinical implications. Eur J Neurol 2021; 28:2804-2811. [PMID: 33949047 DOI: 10.1111/ene.14897] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 04/30/2021] [Indexed: 11/28/2022]
Abstract
BACKGROUND AND PURPOSE Crossing pathologies of the corticospinal tract (CST) are rare and often associated with genetic disorders. However, they can be present in healthy humans and lead to ipsilateral motor deficits when a lesion to motor areas occurs. Here, we review historical and current literature of CST crossing pathologies and present a rare case of asymmetric crossing of the CST. METHODS Description of the case and systematic review of the literature were based on the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed database was searched for peer-reviewed articles in English since 1950. All articles on ipsilateral stroke, uncrossed CST, and associated neurologic disorders were screened. Furthermore, a literature review between the years 1850 and 1980 including articles in other languages, books, opinions, and case studies was conducted. RESULTS Only a few descriptions of CST crossing pathologies exist in healthy humans, whereas they seem to be more common in genetic disorders such as horizontal gaze palsy with progressive scoliosis or congenital mirror movements. Our patient presented with aphasia and left-sided hemiparesis. Computed tomographic (CT) scan revealed a perfusion deficit in the left middle cerebral artery territory, which was confirmed by diffusion-weighted magnetic resonance imaging (MRI), so that thrombolysis was administered. Diffusion tensor imaging with fibre tracking revealed an asymmetric CST crossing. CONCLUSIONS The knowledge of CST crossing pathologies is essential if a motor deficit occurs ipsilateral to the lesion side. An ipsilateral deficit should not lead to exclusion or delay of therapeutic options in patients with suspected stroke. Here, a combined evaluation of CT perfusion imaging and MRI diffusion imaging may be of advantage.
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Affiliation(s)
| | - Christian Brem
- Institute of Neuroradiology, University Hospital of the LMU Munich, Munich, Germany
| | - Klaus Seelos
- Institute of Neuroradiology, University Hospital of the LMU Munich, Munich, Germany
| | - Thomas Köglsperger
- Department of Neurology, University Hospital of the LMU Munich, Munich, Germany
| | - Stefan Sonnenfeld
- Department of Neurology, University Hospital of the LMU Munich, Munich, Germany
| | - Lars Kellert
- Department of Neurology, University Hospital of the LMU Munich, Munich, Germany
| | - Christian Vollmar
- Department of Neurology, University Hospital of the LMU Munich, Munich, Germany.,Institute of Neuroradiology, University Hospital of the LMU Munich, Munich, Germany
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Visual Evoked Potentials in Joubert Syndrome: A Suggested Useful Method for Evaluating Future Approaches Targeted to Improve Visual Pathways' Function. Adv Ther 2021; 38:278-289. [PMID: 33098555 PMCID: PMC7854410 DOI: 10.1007/s12325-020-01534-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Accepted: 10/14/2020] [Indexed: 11/19/2022]
Abstract
Introduction Joubert syndrome (JS) is a recessive disorder characterized by a congenital malformation of the mid-hindbrain and a large spectrum of clinical features including optic nerve morphologic abnormalities. The function of the visual pathways, including the optic nerve, can be objectively evaluated by visual evoked potential (VEP) recordings. Our work aims to employ VEP to evaluate the neural conduction along the visual pathways in JS patients with or without optic nerve morphologic abnormalities (ONMA). Methods In this observational and prospective study, 18 children with genetic diagnosis of JS (mean age 8.78 ± 5.87 years) and 17 healthy age-similar control subjects (control group, 9.05 ± 6.02 years) were enrolled. Based on presence/absence of ONMA at fundus examination, JS patients were divided into two groups: the JS-A group (eight patients with ONMA) and JS-N group (ten patients without ONMA). Following the ISCEV standards, pattern VEPs were recorded in patients and controls in response to 60’ and 15’ checks to obtain a prevalent activation of large or small axons, respectively. Results Compared to controls, both the JS-A and JS-N groups showed significant abnormalities in 60’ and 15’ VEP implicit time and amplitude. Only in the JS-N group were values of 15’ VEP implicit significantly correlated with the corresponding values of visual acuity. Conclusions Our results suggest that a visual pathways dysfunction (of both large and small axons) detectable by VEP may occur in JS patients regardless of the presence of ONMA. Since clinical trials are envisaged in the near future to address JS-related ocular problems, our results might provide information about the potential usefulness of VEP recordings to assess the efficacy of treatments targeted to improve the visual pathways’ function.
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9
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Bhowmick SS, Lang AE. Movement Disorders and Renal Diseases. Mov Disord Clin Pract 2020; 7:763-779. [PMID: 33043074 DOI: 10.1002/mdc3.13005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 06/03/2020] [Accepted: 06/05/2020] [Indexed: 02/06/2023] Open
Abstract
Movement disorders often emerge from the interplay of complex pathophysiological processes involving the kidneys and the nervous system. Tremor, myoclonus, ataxia, chorea, and parkinsonism can occur in the context of renal dysfunction (azotemia and electrolyte abnormalities) or they can be part of complications of its management (dialysis and renal transplantation). On the other hand, myoglobinuria from rhabdomyolysis in status dystonicus and certain drugs used in the management of movement disorders can cause nephrotoxicity. Distinct from these well-recognized associations, it is important to appreciate that there are several inherited and acquired disorders in which movement abnormalities do not occur as a consequence of renal dysfunction or vice versa but are manifestations of common pathophysiological processes affecting the nervous system and the kidneys. These disorders are the emphasis of this review. Increasing awareness of these conditions among neurologists may help them to identify renal involvement earlier, take timely intervention by anticipating complications and focus on therapies targeting common mechanisms in addition to symptomatic management of movement disorders. Recognition of renal impairment in a patient with complex neurological presentation may narrow down the differentials and aid in reaching a definite diagnosis.
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Affiliation(s)
- Suvorit S Bhowmick
- Division of Neurology, Department of Medicine, Morton and Gloria Shulman Movement Disorders Clinic and the Edmond J. Safra Program in Parkinson's Disease, Toronto Western Hospital University Health Network Toronto Ontario Canada
| | - Anthony E Lang
- Division of Neurology, Department of Medicine, Morton and Gloria Shulman Movement Disorders Clinic and the Edmond J. Safra Program in Parkinson's Disease, Toronto Western Hospital University Health Network Toronto Ontario Canada
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10
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Song Q, Gleeson JG. Primary Cilia and Brain Wiring, Connecting the Dots. Dev Cell 2020; 51:661-663. [PMID: 31951539 DOI: 10.1016/j.devcel.2019.11.017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Primary cilia function as cellular signaling hubs, integrating multiple signaling pathways. Patients with the ciliopathy Joubert syndrome have been suggested to have axonal tract defects. In this issue of Developmental Cell, Guo et al. (2019) demonstrate a ciliary signaling requirement for axonal tract development and connectivity through dysregulated PI3K/AKT/ACIII signaling.
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Affiliation(s)
- Qiong Song
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joseph G Gleeson
- Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA; Rady Children's Institute for Genomic Medicine, Rady Children's Hospital, San Diego, CA 92123, USA.
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11
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Ferent J, Constable S, Gigante ED, Yam PT, Mariani LE, Legué E, Liem KF, Caspary T, Charron F. The Ciliary Protein Arl13b Functions Outside of the Primary Cilium in Shh-Mediated Axon Guidance. Cell Rep 2019; 29:3356-3366.e3. [PMID: 31825820 PMCID: PMC6927553 DOI: 10.1016/j.celrep.2019.11.015] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 09/19/2019] [Accepted: 11/04/2019] [Indexed: 12/19/2022] Open
Abstract
The small GTPase Arl13b is enriched in primary cilia and regulates Sonic hedgehog (Shh) signaling. During neural development, Shh controls patterning and proliferation through a canonical, transcription-dependent pathway that requires the primary cilium. Additionally, Shh controls axon guidance through a non-canonical, transcription-independent pathway whose connection to the primary cilium is unknown. Here we show that inactivation of Arl13b results in defective commissural axon guidance in vivo. In vitro, we demonstrate that Arl13b functions autonomously in neurons for their Shh-dependent guidance response. We detect Arl13b protein in axons and growth cones, far from its well-established ciliary enrichment. To test whether Arl13b plays a non-ciliary function, we used an engineered, cilia-localization-deficient Arl13b variant and found that it was sufficient to mediate Shh axon guidance in vitro and in vivo. Together, these results indicate that, in addition to its ciliary role in canonical Shh signaling, Arl13b plays a cilia-independent role in Shh-mediated axon guidance.
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Affiliation(s)
- Julien Ferent
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada; Department of Neuroscience, University of Montreal, Montreal, QC H3T 1J4, Canada
| | - Sandii Constable
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Eduardo D Gigante
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Patricia T Yam
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada
| | - Laura E Mariani
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA
| | - Emilie Legué
- Vertebrate Developmental Biology Program and Department of Pediatrics, Yale School of Medicine, 333 Cedar St., New Haven, CT 06520, USA
| | - Karel F Liem
- Vertebrate Developmental Biology Program and Department of Pediatrics, Yale School of Medicine, 333 Cedar St., New Haven, CT 06520, USA
| | - Tamara Caspary
- Department of Human Genetics, 615 Michael St., Suite 301, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | - Frédéric Charron
- Montreal Clinical Research Institute (IRCM), 110 Pine Avenue West, Montreal, QC H2W 1R7, Canada; Department of Neuroscience, University of Montreal, Montreal, QC H3T 1J4, Canada; Department of Anatomy and Cell Biology, Division of Experimental Medicine, McGill University, Montreal, QC H3A 0G4, Canada; Department of Medicine, University of Montreal, Montreal, QC H3T 1J4, Canada.
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12
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Meoded A, Huisman TAGM. Diffusion Tensor Imaging of Brain Malformations: Exploring the Internal Architecture. Neuroimaging Clin N Am 2019; 29:423-434. [PMID: 31256863 DOI: 10.1016/j.nic.2019.03.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Diffusion tensor imaging (DTI) is an advanced MR imaging technique that provides noninvasive qualitative and quantitative information about the white matter microarchitecture. By measuring the three-dimensional directional characteristics of water molecule diffusion/mobility, DTI generates unique tissue contrasts that are used to study the axonal organization of the central nervous system. Its applications include quantitative evaluation of the brain connectivity, development, and white matter diseases. This article reviews DTI and fiber tractography findings in several brain malformations and highlights the added value of DTI and fiber tractography compared with conventional MR imaging.
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Affiliation(s)
- Avner Meoded
- Johns Hopkins All Children's Hospital, 501 6th Avenue South, St Petersburg, FL 33701, USA.
| | - Thierry A G M Huisman
- Edward B. Singleton Department of Radiology, Texas Children's Hospital, 6701 Fannin Street, Suite 470, Houston, TX 77030, USA
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13
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Zhu L, Chen L, Yan L, Perkins BD, Li S, Li B, Xu HA, Li XJ. Mutant Ahi1 Affects Retinal Axon Projection in Zebrafish via Toxic Gain of Function. Front Cell Neurosci 2019; 13:81. [PMID: 30949029 PMCID: PMC6438259 DOI: 10.3389/fncel.2019.00081] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 02/18/2019] [Indexed: 12/23/2022] Open
Abstract
Joubert syndrome (JBTS) is an inherited autosomal recessive disorder associated with cerebellum and brainstem malformation and can be caused by mutations in the Abelson helper integration site-1 (AHI1) gene. Although AHI1 mutations in humans cause abnormal cerebellar development and impaired axonal decussation in JBTS, these phenotypes are not robust or are absent in various mouse models with Ahi1 mutations. AHI1 contains an N-terminal coiled-coil domain, multiple WD40 repeats, and a C-terminal Src homology 3 (SH3) domain, suggesting that AHI1 functions as a signaling or scaffolding protein. Since most AHI1 mutations in humans can result in truncated AHI1 proteins lacking WD40 repeats and the SH3 domain, it remains unclear whether mutant AHI1 elicits toxicity via a gain-of-function mechanism by the truncated AHI1. Because Ahi1 in zebrafish and humans share a similar N-terminal region with a coiled-coil domain that is absent in mouse Ahi1, we used zebrafish as a model to investigate whether Ahi1 mutations could affect axonal decussation. Using in situ hybridization, we found that ahi1 is highly expressed in zebrafish ocular tissues, especially in retina, allowing us to examine its effect on retinal ganglion cell (RGC) projection and eye morphology. We injected a morpholino to zebrafish embryos, which can generate mutant Ahi1 lacking the intact WD40 repeats, and found RGC axon misprojection and ocular dysplasia in 4 dpf (days post-fertilization) larvae after the injection. However, ahi1 null zebrafish showed normal RGC axon projection and ocular morphology. We then used CRISPR/Cas9 to generate truncated ahi1 and also found similar defects in the RGC axon projection as seen in those injected with ahi1 morpholino. Thus, the aberrant retinal axon projection in zebrafish is caused by the presence of mutant ahi1 rather than the loss of ahi1, suggesting that mutant Ahi1 may affect axonal decussation via toxic gain of function.
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Affiliation(s)
- Louyin Zhu
- School of Life Sciences and Institute of Life Science, Nanchang University, Nanchang, China.,Jiangxi Provincial Collaborative Innovation Center for Cardiovascular, Digestive and Neuropsychiatric Diseases, Nanchang, China.,Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, United States
| | - Laiqiang Chen
- School of Life Sciences and Institute of Life Science, Nanchang University, Nanchang, China.,Guangdong-Hongkong-Macau Institute of CNS Regeneration (GHMICR), Jinan University, Guangzhou, China
| | - Lingya Yan
- School of Life Sciences and Institute of Life Science, Nanchang University, Nanchang, China
| | - Brian D Perkins
- Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, United States
| | - Shihua Li
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, United States
| | - Baoming Li
- School of Life Sciences and Institute of Life Science, Nanchang University, Nanchang, China.,Jiangxi Provincial Collaborative Innovation Center for Cardiovascular, Digestive and Neuropsychiatric Diseases, Nanchang, China
| | - Hong A Xu
- School of Life Sciences and Institute of Life Science, Nanchang University, Nanchang, China.,Jiangxi Provincial Collaborative Innovation Center for Cardiovascular, Digestive and Neuropsychiatric Diseases, Nanchang, China
| | - Xiao-Jiang Li
- Department of Human Genetics, Emory University School of Medicine, Atlanta, GA, United States
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14
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Loss of the neurodevelopmental Joubert syndrome causing protein, Ahi1, causes motor and muscle development delays independent of central nervous system involvement. Dev Biol 2019; 448:36-47. [PMID: 30695685 DOI: 10.1016/j.ydbio.2019.01.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Revised: 01/25/2019] [Accepted: 01/25/2019] [Indexed: 12/15/2022]
Abstract
Joubert syndrome (JBTS) is a predominantly autosomal recessive neurodevelopmental disorder that presents with characteristic malformations of the cerebellar vermis, superior cerebellar peduncles and midbrain in humans. Accompanying these malformations are a heterogeneous set of clinical symptoms, which frequently include deficits in motor and muscle function, such as hypotonia (low muscle tone) and ataxia (clumsiness). These symptoms are attributed to improper development of the hindbrain, but no direct evidence has been reported linking these in JBTS. Here, we describe muscle developmental defects in a mouse with a targeted deletion of the Abelson helper integration site 1 gene, Ahi1, one of the genes known to cause JBTS in humans. While FVB/NJ Ahi1-/- mice display no gross malformations of the cerebellum, deficits are observed in several measures of motor function, strength, and body development. Specifically, Ahi1-/- mice show delayed physical development, delays in surface reflex righting as neonates, and reductions in grip strength and spontaneous locomotor activity as adults. Additionally, Ahi1-/- mice showed evidence of muscle-specific contributions to this phenotype, such as reductions in 1) myoblast differentiation potential in vitro, 2) muscle desmin expression, and 3) overall muscle mass, myonuclear domain, and muscle fiber cross-sectional area. Together, these data suggest that loss of Ahi1 may cause abnormalities in the differentiation of myoblasts to mature muscle cells. Moreover, Ahi1 loss impacts muscle development directly, outside of any indirect impact of cerebellar malformations, revealing a novel myogenic cause for hypotonia in JBTS.
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15
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Dell'Osso LF. Ocular Motor System Control Models and the Cerebellum: Hypothetical Mechanisms. CEREBELLUM (LONDON, ENGLAND) 2019; 18:605-614. [PMID: 30617628 DOI: 10.1007/s12311-018-1001-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
To review our studies and "top-down" models of saccadic intrusions and infantile nystagmus syndrome with the aim of hypothesizing areas of cerebellar connections controlling parts of the ocular motor subsystems involved in both types of function and dysfunction. The methods of eye-movement recording and modeling are described in detail in the cited references. Saccadic intrusions, such as square-wave jerks and square-wave oscillations, can be simulated by a single malfunction, whereas staircase saccadic intrusions required two independent malfunctions. The major infantile nystagmus syndrome waveforms are traceable to a failure to calibrate the damping ratio of the smooth pursuit system. The use of a behavioral ocular motor system model demonstrated how putative cerebellar dysfunctions could accurately simulate both the oscillations and the ocular motor responses seen in patients with both saccadic and pursuit disorders.
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Affiliation(s)
- Louis F Dell'Osso
- From the Daroff-Dell'Osso Ocular Motility Laboratory, Louis Stokes Cleveland Department of Veterans Affairs Medical Center and CASE Medical School; and the Department of Neurology, Case Western Reserve University and University Hospitals Case Medical Center, 10701 East Boulevard, Cleveland, OH, 44106, USA.
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16
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Review of Ocular Manifestations of Joubert Syndrome. Genes (Basel) 2018; 9:genes9120605. [PMID: 30518138 PMCID: PMC6315342 DOI: 10.3390/genes9120605] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Revised: 11/13/2018] [Accepted: 11/27/2018] [Indexed: 12/13/2022] Open
Abstract
Joubert syndrome is a group of rare disorders that stem from defects in a sensory organelle, the primary cilia. Affected patients often present with disorders involving multiple organ systems, including the brain, eyes, and kidneys. Common symptoms include breathing abnormalities, mental developmental delays, loss of voluntary muscle coordination, and abnormal eye movements, with a diagnostic “molar tooth” sign observed by magnetic resonance imaging (MRI) of the midbrain. We reviewed the ocular phenotypes that can be found in patients with Joubert syndrome. Ocular motor apraxia is the most frequent (80% of patients), followed by strabismus (74%) and nystagmus (72%). A minority of patients also present with ptosis (43%), chorioretinal coloboma (30%), and optic nerve atrophy (22%). Although mutations in 34 genes have been found to be associated with Joubert syndrome, retinal degeneration has been reported in only 38% of patients. Mutations in AHI1 and CEP290, genes critical to primary cilia function, have been linked to retinal degeneration. In conclusion, Joubert syndrome is a rare pleiotropic group of disorders with variable ocular presentations.
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17
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Abstract
PURPOSE OF REVIEW To review disorders that are associated with renal cystic disease during prenatal life and to highlight the strong association between renal cystic disease and ciliopathies. RECENT FINDINGS There are numerous causative genes for ciliopathies that can present with cystic kidney disease. In the group of single gene ciliopathies, autosomal dominant polycystic kidney disease is by far the most prevalent one. Other examples are autosomal recessive polycystic kidney disease, nephronophthisis, Bardet-Biedl syndrome, Meckel-Gruber syndrome, Joubert syndrome and related disorders as well as X-linked orofaciodigital syndrome type 1, respectively. The prevalence of these inherited disorders sums up to about in 1 : 2000 people. These disorders with their hepatorenal fibrocystic character should be classified as multisystem diseases. SUMMARY Understanding of the origin of renal cystic disease and associated disorders is important to make the appropriate prenatal diagnosis and for counseling affected parents. In the future, understanding of the pathophysiology may help to develop new treatment strategies.
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18
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Arrigoni F, Romaniello R, Peruzzo D, De Luca A, Parazzini C, Valente EM, Borgatti R, Triulzi F. Anterior Mesencephalic Cap Dysplasia: Novel Brain Stem Malformative Features Associated with Joubert Syndrome. AJNR Am J Neuroradiol 2017; 38:2385-2390. [PMID: 28838911 DOI: 10.3174/ajnr.a5360] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2017] [Accepted: 06/30/2017] [Indexed: 11/07/2022]
Abstract
In Joubert syndrome, the "molar tooth" sign can be associated with several additional supra- and infratentorial malformations. Here we report on 3 subjects (2 siblings, 8-14 years of age) with Joubert syndrome, showing an abnormal thick bulging of the anterior profile of the mesencephalon causing a complete obliteration of the interpeduncular fossa. DTI revealed that the abnormal tissue consisted of an ectopic white matter tract with a laterolateral transverse orientation. Tractographic reconstructions support the hypothesis of impaired axonal guidance mechanisms responsible for the malformation. The 2 siblings were compound heterozygous for 2 missense variants in the TMEM67 gene, while no mutations in a panel of 120 ciliary genes were detected in the third patient. The name "anterior mesencephalic cap dysplasia," referring to the peculiar aspect of the mesencephalon on sagittal MR imaging, is proposed for this new malformative feature.
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Affiliation(s)
- F Arrigoni
- From the Neuroimaging Lab (F.A., D.P., A.D.L.)
| | - R Romaniello
- Neuropsychiatry and Neurorehabilitation Unit (R.R., R.B.), Scientific Institute Istituto Di Ricovero e Cura a Carattere Scientific Eugenio Medea, Bosisio Parini, Italy
| | - D Peruzzo
- From the Neuroimaging Lab (F.A., D.P., A.D.L.)
| | - A De Luca
- From the Neuroimaging Lab (F.A., D.P., A.D.L.)
- Department of Information Engineering (A.D.L.), University of Padova, Padova, Italy
| | - C Parazzini
- Department of Pediatric Radiology and Neuroradiology (C.P.), "V. Buzzi" Children's Hospital, Milan, Italy
| | - E M Valente
- Department of Molecular Medicine (E.M.V.), University of Pavia, Pavia, Italy
- Neurogenetics Unit (E.M.V.), Istituto Di Ricovero e Cura a Carattere Scientific Santa Lucia Foundation, Rome, Italy
| | - R Borgatti
- Neuropsychiatry and Neurorehabilitation Unit (R.R., R.B.), Scientific Institute Istituto Di Ricovero e Cura a Carattere Scientific Eugenio Medea, Bosisio Parini, Italy
| | - F Triulzi
- Department of Neuroradiology (F.T.), Scientific Institute Istituto Di Ricovero e Cura a Carattere Scientific Cà Granda Foundation-Ospedale Maggiore Policlinico, Milan, Italy
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19
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Physiotherapy and Rehabilitation in a Child with Joubert Syndrome. Case Rep Pediatr 2017; 2017:8076494. [PMID: 29138705 PMCID: PMC5613706 DOI: 10.1155/2017/8076494] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 07/09/2017] [Accepted: 07/20/2017] [Indexed: 11/17/2022] Open
Abstract
Objective Joubert syndrome (JS) is a rare autosomal recessive genetic disorder characterized by brain malformation, hypotonia, breathing abnormalities, ataxia, oculomotor apraxia, and developmental delay. The purpose of this study was to report the efficiency of the physiotherapy and rehabilitation program in a child with JS. Materials and Methods Our case is a 19-month-old female child with mild clinical signs of JS. The pretreatment and posttreatment motor functioning level of the case was evaluated through the Gross Motor Function Measure (GMFM), whereas the independence level was evaluated through the Pediatric Functional Independence Measure (WeeFIM). The case was included in the rehabilitation program by the physiotherapist for one hour for five days a week throughout the period of 13 months in accordance with the neurodevelopmental treatment principles. Results The case was able to turn around from the supine position to the reverse direction by oneself, and she was able to rise on her forearms facedown and was able to sit, crawl, and walk independently. The GMFM score was 210, whereas WeeFIM score was 65. Discussion In the direction of those findings, in Joubert Syndrome, physiotherapy and rehabilitation can be effective in coping with the symptoms causing developmental delay.
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20
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Kim NS, Park SH. Joubert Syndrome Presenting With Normal Pyramidal Decussation: A Case Report. Ann Rehabil Med 2017; 41:701-704. [PMID: 28971056 PMCID: PMC5608679 DOI: 10.5535/arm.2017.41.4.701] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2016] [Accepted: 09/19/2016] [Indexed: 11/06/2022] Open
Abstract
Joubert syndrome (JS) is a rare genetic disorder characterized by a congenital malformation of the hindbrain, and accompanied by axonal decussation abnormalities affecting the corticospinal tract and the superior cerebellar peduncles. To the best of our knowledge, there are no reports of normal pyramidal decussation in JS. Here, we describe the case of an 18-year-old boy presenting midline-crossing corticospinal projections, which were considered normal corticospinal tract trajectories. Diffusion tensor imaging and motor evoked potential study analysis demonstrated the exclusive presence of decussating corticospinal projections in the patient. Based on these results, we suggest that JS might be associated with several, diverse corticospinal motor tract organization patterns.
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Affiliation(s)
- Nam-Sik Kim
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Medical School, Jeonju, Korea
| | - Sung-Hee Park
- Department of Physical Medicine and Rehabilitation, Chonbuk National University Medical School, Jeonju, Korea
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21
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Van De Weghe JC, Rusterholz TD, Latour B, Grout ME, Aldinger KA, Shaheen R, Dempsey JC, Maddirevula S, Cheng YHH, Phelps IG, Gesemann M, Goel H, Birk OS, Alanzi T, Rawashdeh R, Khan AO, Bamshad MJ, Nickerson DA, Neuhauss SC, Dobyns WB, Alkuraya FS, Roepman R, Bachmann-Gagescu R, Doherty D, Doherty D. Mutations in ARMC9, which Encodes a Basal Body Protein, Cause Joubert Syndrome in Humans and Ciliopathy Phenotypes in Zebrafish. Am J Hum Genet 2017. [PMID: 28625504 DOI: 10.1016/j.ajhg.2017.05.010] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Joubert syndrome (JS) is a recessive neurodevelopmental disorder characterized by hypotonia, ataxia, abnormal eye movements, and variable cognitive impairment. It is defined by a distinctive brain malformation known as the "molar tooth sign" on axial MRI. Subsets of affected individuals have malformations such as coloboma, polydactyly, and encephalocele, as well as progressive retinal dystrophy, fibrocystic kidney disease, and liver fibrosis. More than 35 genes have been associated with JS, but in a subset of families the genetic cause remains unknown. All of the gene products localize in and around the primary cilium, making JS a canonical ciliopathy. Ciliopathies are unified by their overlapping clinical features and underlying mechanisms involving ciliary dysfunction. In this work, we identify biallelic rare, predicted-deleterious ARMC9 variants (stop-gain, missense, splice-site, and single-exon deletion) in 11 individuals with JS from 8 families, accounting for approximately 1% of the disorder. The associated phenotypes range from isolated neurological involvement to JS with retinal dystrophy, additional brain abnormalities (e.g., heterotopia, Dandy-Walker malformation), pituitary insufficiency, and/or synpolydactyly. We show that ARMC9 localizes to the basal body of the cilium and is upregulated during ciliogenesis. Typical ciliopathy phenotypes (curved body shape, retinal dystrophy, coloboma, and decreased cilia) in a CRISPR/Cas9-engineered zebrafish mutant model provide additional support for ARMC9 as a ciliopathy-associated gene. Identifying ARMC9 mutations as a cause of JS takes us one step closer to a full genetic understanding of this important disorder and enables future functional work to define the central biological mechanisms underlying JS and other ciliopathies.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | - Dan Doherty
- Department of Pediatrics, University of Washington, Seattle, WA 98195, USA; Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA 98101, USA.
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22
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Brodsky MC. Marshall M. Parks Memorial Lecture: Ocular Motor Misbehavior in Children: Where Neuro-Ophthalmology Meets Strabismus. Ophthalmology 2017; 124:835-842. [PMID: 28385301 DOI: 10.1016/j.ophtha.2017.01.050] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2016] [Revised: 01/24/2017] [Accepted: 01/26/2017] [Indexed: 01/19/2023] Open
Abstract
Clinical diagnosis has been supplemented by neuroimaging advances, genetic discoveries, and molecular research to generate new neurobiological discoveries pertaining to early maldevelopment of ocular motor control systems. In this focused review, I examine recent paradigm shifts that have transformed our understanding of pediatric ocular motor disease at the prenuclear and infranuclear levels. The pathogenesis of complex ocular motor disorders, such as paradoxical pupillary constriction to darkness, benign tonic upgaze of infancy, congenital fibrosis syndrome, and the constellation of unique eye movements that accompany Joubert syndrome, are elucidated.
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Affiliation(s)
- Michael C Brodsky
- Departments of Ophthalmology and Neurology, Mayo Clinic, Rochester, Minnesota.
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23
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Dempsey JC, Phelps IG, Bachmann-Gagescu R, Glass IA, Tully HM, Doherty D. Mortality in Joubert syndrome. Am J Med Genet A 2017; 173:1237-1242. [PMID: 28371402 DOI: 10.1002/ajmg.a.38158] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 01/08/2017] [Indexed: 11/05/2022]
Abstract
Joubert syndrome (JS) is a rare, recessively inherited neurodevelopmental disorder characterized by a distinctive mid-hindbrain malformation. Little is known about mortality in affected individuals. Identifying the timing and causes of death will allow for development of healthcare guidelines for families and providers and, thus, help to prolong and improve the lives of patients with JS. We evaluated information on 40 deceased individuals with JS to characterize age and cause of death. We compared this population with 525 living individuals with JS to estimate associations between risk of death and extra-neurological features. Genetic causes were examined in both groups. Mean age of death in this cohort was 7.2 years, and the most prevalent causes of death were respiratory failure (35%), particularly in individuals younger than 6 years, and kidney failure (37.5%), which was more common in older individuals. We identified possible associations between risk of death and kidney disease, liver fibrosis, polydactyly, occipital encephalocele, and genetic cause. This work highlights factors (genetic cause, extra-neurological organ involvement, and other malformations) likely to be associated with higher risk of mortality in JS, which should prompt increased monitoring for respiratory issues, kidney disease, and liver fibrosis.
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Affiliation(s)
| | - Ian G Phelps
- Department of Pediatrics, University of Washington, Seattle, Washington
| | - Ruxandra Bachmann-Gagescu
- Institute for Molecular Life Sciences and Institute of Medical Genetics, University of Zurich, Zurich, Switzerland
| | - Ian A Glass
- Department of Pediatrics, University of Washington, Seattle, Washington.,Seattle Children's Research Institute, Seattle, Washington
| | - Hannah M Tully
- Seattle Children's Research Institute, Seattle, Washington.,Department of Neurology, University of Washington, Seattle, Washington
| | - Dan Doherty
- Department of Pediatrics, University of Washington, Seattle, Washington.,Seattle Children's Research Institute, Seattle, Washington
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24
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Rollins NK, Booth TN, Chahrour MH. Variability of Ponto-cerebellar Fibers by Diffusion Tensor Imaging in Diverse Brain Malformations. J Child Neurol 2017; 32:271-285. [PMID: 27920266 DOI: 10.1177/0883073816680734] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
To describe pontine axonal anomalies across diverse brain malformations. Institutional review board-approved review of magnetic resonance imaging (MRI) and genetic testing of 31 children with brain malformations and abnormal pons by diffusion tensor imaging. Anomalous dorsal pontocerebellar tracts were seen in mid-hindbrain anomalies and in diffuse malformations of cortical development including lissencephaly, gyral disorganization with dysplastic basal ganglia, presumed congenital fibrosis of extraocular muscles type 3, and in callosal agenesis without malformations of cortical development. Heterotopic and hypoplastic corticospinal tracts were seen in callosal agenesis and in focal malformations of cortical development. There were no patterns by chromosomal microarray analysis in the non-lissencephalic brains. In lissencephaly, there was no relationship between severity, deletion size, or appearance of the pontocerebellar tract. Pontine axonal anomalies may relate to defects in precerebellar neuronal migration, chemotactic signaling of the pontine neurons, and/or corticospinal tract pathfinding and collateral branching not detectable with routine genetic testing.
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Affiliation(s)
- Nancy K Rollins
- 1 Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.,2 Department of Radiology, Children's Health System of Texas, Dallas, TX, USA
| | - Timothy N Booth
- 1 Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.,2 Department of Radiology, Children's Health System of Texas, Dallas, TX, USA
| | - Maria H Chahrour
- 3 Departments of Neuroscience and Psychiatry, Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX, USA
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25
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Enokizono M, Aida N, Niwa T, Osaka H, Naruto T, Kurosawa K, Ohba C, Suzuki T, Saitsu H, Goto T, Matsumoto N. Neuroimaging findings in Joubert syndrome with C5orf42 gene mutations: A milder form of molar tooth sign and vermian hypoplasia. J Neurol Sci 2017; 376:7-12. [PMID: 28431631 DOI: 10.1016/j.jns.2017.02.065] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 02/27/2017] [Accepted: 02/28/2017] [Indexed: 12/12/2022]
Abstract
PURPOSE Little is known regarding neuroimaging-genotype correlations in Joubert syndrome (JBTS). To elucidate one of these correlations, we investigated the neuroimaging findings of JBTS patients with C5orf42 mutations. MATERIALS AND METHODS Neuroimaging findings in five JBTS patients with C5orf42 mutations were retrospectively assessed with regard to the infratentorial and supratentorial structures on T1-magnetization prepared rapid gradient echo (MPRAGE), T2-weighted images, and color-coded fractional anisotropy (FA) maps; the findings were compared to those in four JBTS patients with mutations in other genes (including three with AHI1 and one with TMEM67 mutations). RESULTS In C5orf42-mutant patients, the infratentorial magnetic resonance (MR) images showed normal or minimally thickened and minimally elongated superior cerebellar peduncles (SCP), normal or minimally deepened interpeduncular fossa (IF), and mild vermian hypoplasia (VH). However, in other patients, all had severe abnormalities in the SCP and IF, and moderate to marked VH. Supratentorial abnormalities were found in one individual in other JBTS. In JBTS with all mutations, color-coded FA maps showed the absence of decussation of the SCP (DSCP). CONCLUSION The morphological neuroimaging findings in C5orf42-mutant JBTS were distinctly mild and made diagnosis difficult. However, the absence of DSCP on color-coded FA maps may facilitate the diagnosis of JBTS.
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Affiliation(s)
- Mikako Enokizono
- Department of Radiology, Kanagawa Children's Medical Center, Yokohama, Japan.
| | - Noriko Aida
- Department of Radiology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Tetsu Niwa
- Department of Radiology, Kanagawa Children's Medical Center, Yokohama, Japan; Department of Radiology, Tokai University School of Medicine, Isehara, Japan
| | - Hitoshi Osaka
- Department of Pediatrics, Jichi Medical University, Tochigi, Japan
| | - Takuya Naruto
- Department of Genetics, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Kenji Kurosawa
- Department of Genetics, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Chihiro Ohba
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Clinical Neurology and Stroke Medicine, Yokohama City University, Yokohama, Japan
| | - Toshifumi Suzuki
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan; Department of Obstetrics and Gynecology, Juntendo University Faculty of Medicine, Tokyo, Japan
| | - Hirotomo Saitsu
- Department of Biochemistry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Tomohide Goto
- Department of Neurology, Kanagawa Children's Medical Center, Yokohama, Japan
| | - Naomichi Matsumoto
- Department of Human Genetics, Yokohama City University Graduate School of Medicine, Yokohama, Japan
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Singh D, Kaur L, Kaur M, Kaur M. Joubert Syndrome: Classic Sonographic Signs at 19 Weeks of Gestation. JOURNAL OF FETAL MEDICINE 2016. [DOI: 10.1007/s40556-016-0101-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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27
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Lee N, Nam SO, Kim YM, Lee YJ. A neonate with Joubert syndrome presenting with symptoms of Horner syndrome. KOREAN JOURNAL OF PEDIATRICS 2016; 59:S32-S36. [PMID: 28018441 PMCID: PMC5177707 DOI: 10.3345/kjp.2016.59.11.s32] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Revised: 04/08/2015] [Accepted: 05/21/2015] [Indexed: 11/27/2022]
Abstract
Joubert syndrome (JS) is characterized by the “molar tooth sign” (MTS) with cerebellar vermis agenesis, episodic hyperpnea, abnormal eye movements, and hypotonia. Ocular and oculomotor abnormalities have been observed; however, Horner syndrome (HS) has not been documented in children with JS. We present the case of a 2-month-old boy having ocular abnormalities with bilateral nystagmus, left-dominant bilateral ptosis, and unilateral miosis and enophthalmos of the left eye, which were compatible with HS. Brain magnetic resonance imaging (MRI) revealed the presence of the MTS. Neck MRI showed no definite lesion or mass around the cervical sympathetic chain. His global development was delayed. He underwent ophthalmologic surgery, and showed some improvement in his ptosis. To the best of our knowledge, the association of HS with JS has not yet been described. We suggest that early neuroimaging should be considered for neonates or young infants with diverse eye abnormalities to evaluate the underlying etiology.
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Affiliation(s)
- Narae Lee
- Department of Pediatrics, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea
| | - Sang-Ook Nam
- Department of Pediatrics, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea
| | - Young Mi Kim
- Department of Pediatrics, Pusan National University Hospital, Busan, Korea
| | - Yun-Jin Lee
- Department of Pediatrics, Pusan National University Yangsan Hospital, Pusan National University School of Medicine, Yangsan, Korea
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28
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Buke B, Canverenler E, İpek G, Canverenler S, Akkaya H. Diagnosis of Joubert syndrome via ultrasonography. J Med Ultrason (2001) 2016; 44:197-202. [DOI: 10.1007/s10396-016-0751-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2016] [Accepted: 09/26/2016] [Indexed: 01/25/2023]
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Welniarz Q, Dusart I, Roze E. The corticospinal tract: Evolution, development, and human disorders. Dev Neurobiol 2016; 77:810-829. [PMID: 27706924 DOI: 10.1002/dneu.22455] [Citation(s) in RCA: 135] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 09/18/2016] [Accepted: 09/19/2016] [Indexed: 01/22/2023]
Abstract
The corticospinal tract (CST) plays a major role in cortical control of spinal cord activity. In particular, it is the principal motor pathway for voluntary movements. Here, we discuss: (i) the anatomic evolution and development of the CST across mammalian species, focusing on its role in motor functions; (ii) the molecular mechanisms regulating corticospinal tract formation and guidance during mouse development; and (iii) human disorders associated with abnormal CST development. A comparison of CST anatomy and development across mammalian species first highlights important similarities. In particular, most CST axons cross the anatomical midline at the junction between the brainstem and spinal cord, forming the pyramidal decussation. Reorganization of the pattern of CST projections to the spinal cord during evolution led to improved motor skills. Studies of the molecular mechanisms involved in CST formation and guidance in mice have identified several factors that act synergistically to ensure proper formation of the CST at each step of development. Human CST developmental disorders can result in a reduction of the CST, or in guidance defects associated with abnormal CST anatomy. These latter disorders result in altered midline crossing at the pyramidal decussation or in the spinal cord, but spare the rest of the CST. Careful appraisal of clinical manifestations associated with CST malformations highlights the critical role of the CST in the lateralization of motor control. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 810-829, 2017.
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Affiliation(s)
- Quentin Welniarz
- Institut du Cerveau et de la Moelle épinière, Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, F-75013, Paris, France.,Institut de Biologie Paris Seine, Neuroscience Paris Seine, Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, F-75005, Paris, France
| | - Isabelle Dusart
- Institut de Biologie Paris Seine, Neuroscience Paris Seine, Sorbonne Universités, UPMC Univ Paris 06, INSERM, CNRS, F-75005, Paris, France
| | - Emmanuel Roze
- Institut du Cerveau et de la Moelle épinière, Sorbonne Universités, UPMC Univ Paris 06, INSERM U 1127, CNRS UMR 7225, F-75013, Paris, France.,Département des Maladies du Système Nerveux, AP-HP, Hôpital de la Salpêtrière, Paris, France
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30
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Mariani LE, Bijlsma MF, Ivanova AA, Suciu SK, Kahn RA, Caspary T. Arl13b regulates Shh signaling from both inside and outside the cilium. Mol Biol Cell 2016; 27:mbc.E16-03-0189. [PMID: 27682584 PMCID: PMC5170560 DOI: 10.1091/mbc.e16-03-0189] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Revised: 08/16/2016] [Accepted: 09/20/2016] [Indexed: 12/21/2022] Open
Abstract
The regulatory GTPase Arl13b localizes to primary cilia, where it regulates Sonic hedgehog (Shh) signaling. Missense mutations in ARL13B can cause the ciliopathy Joubert syndrome, while the mouse null allele is embryonic lethal. We used mouse embryonic fibroblasts as a system to determine the effects of Arl13b mutations on Shh signaling. We tested a total of seven different mutants, three JS-causing variants, two point mutants predicted to alter guanine nucleotide handling, one that disrupts cilia localization, and one that prevents palmitoylation and thus membrane binding, in assays of transcriptional and non-transcriptional Shh signaling. We found that mutations disrupting Arl13b's palmitoylation site, cilia localization signal, or GTPase handling altered the Shh response in distinct assays of transcriptional or non-transcriptional signaling. In contrast, JS-causing mutations in Arl13b did not affect Shh signaling in these same assays, suggesting these mutations result in more subtle defects, likely affecting only a subset of signaling outputs. Finally, we show that restricting Arl13b from cilia interferes with its ability to regulate Shh-stimulated chemotaxis, despite previous evidence that cilia themselves are not required for this non-transcriptional Shh response. This points to a more complex relationship between the ciliary and non-ciliary roles of this regulatory GTPase than previously envisioned.
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Affiliation(s)
- Laura E Mariani
- *Department of Human Genetics, Emory University, Atlanta, GA, USA Neuroscience Graduate Program, Emory University, Atlanta, GA, USA
| | - Maarten F Bijlsma
- Laboratory for Experimental Oncology and Radiobiology, Center for Experimental and Molecular Medicine, Academic Medical Center and Cancer Center Amsterdam, Amsterdam, The Netherlands
| | - Anna A Ivanova
- Department of Biochemistry, Emory University, Atlanta, GA, USA
| | - Sarah K Suciu
- *Department of Human Genetics, Emory University, Atlanta, GA, USA Genetics and Molecular Biology Graduate Program, Emory University, Atlanta, GA, USA
| | - Richard A Kahn
- Department of Biochemistry, Emory University, Atlanta, GA, USA
| | - Tamara Caspary
- *Department of Human Genetics, Emory University, Atlanta, GA, USA
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Abstract
AbstractInfantile-onset saccade initiation delay (ISID), commonly known as congenital ocular motor apraxia, is characterized by difficulty in triggering horizontal volitional saccades. It typically presents with head thrusts in infancy and is often associated with developmental delay. Patients with ISID are reported to have abnormalities in various brain regions including the corpus callosum, brainstem, and cerebellum. We propose that ISID is caused by the disruption or disconnection of axons linking analogous brain regions involved in processing saccades across the two sides of the brain or bilateral damage to these regions.
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32
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Mitter C, Jakab A, Brugger PC, Ricken G, Gruber GM, Bettelheim D, Scharrer A, Langs G, Hainfellner JA, Prayer D, Kasprian G. Validation of In utero Tractography of Human Fetal Commissural and Internal Capsule Fibers with Histological Structure Tensor Analysis. Front Neuroanat 2015; 9:164. [PMID: 26732460 PMCID: PMC4689804 DOI: 10.3389/fnana.2015.00164] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2015] [Accepted: 12/07/2015] [Indexed: 12/20/2022] Open
Abstract
Diffusion tensor imaging (DTI) and tractography offer the unique possibility to visualize the developing white matter macroanatomy of the human fetal brain in vivo and in utero and are currently under investigation for their potential use in the diagnosis of developmental pathologies of the human central nervous system. However, in order to establish in utero DTI as a clinical imaging tool, an independent comparison between macroscopic imaging and microscopic histology data in the same subject is needed. The present study aimed to cross-validate normal as well as abnormal in utero tractography results of commissural and internal capsule fibers in human fetal brains using postmortem histological structure tensor (ST) analysis. In utero tractography findings from two structurally unremarkable and five abnormal fetal brains were compared to the results of postmortem ST analysis applied to digitalized whole hemisphere sections of the same subjects. An approach to perform ST-based deterministic tractography in histological sections was implemented to overcome limitations in correlating in utero tractography to postmortem histology data. ST analysis and histology-based tractography of fetal brain sections enabled the direct assessment of the anisotropic organization and main fiber orientation of fetal telencephalic layers on a micro- and macroscopic scale, and validated in utero tractography results of corpus callosum and internal capsule fiber tracts. Cross-validation of abnormal in utero tractography results could be achieved in four subjects with agenesis of the corpus callosum (ACC) and in two cases with malformations of internal capsule fibers. In addition, potential limitations of current DTI-based in utero tractography could be demonstrated in several brain regions. Combining the three-dimensional nature of DTI-based in utero tractography with the microscopic resolution provided by histological ST analysis may ultimately facilitate a more complete morphologic characterization of axon guidance disorders at prenatal stages of human brain development.
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Affiliation(s)
- Christian Mitter
- Division of Neuroradiology and Musculoskeletal Radiology, Department of Biomedical Imaging and Image-guided Therapy, Medical University of ViennaVienna, Austria; Institute of Neurology, Medical University of ViennaVienna, Austria
| | - András Jakab
- Computational Imaging Research Lab, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna Vienna, Austria
| | - Peter C Brugger
- Department of Systematic Anatomy, Center for Anatomy and Cell Biology, Medical University of Vienna Vienna, Austria
| | - Gerda Ricken
- Institute of Neurology, Medical University of Vienna Vienna, Austria
| | - Gerlinde M Gruber
- Department of Systematic Anatomy, Center for Anatomy and Cell Biology, Medical University of Vienna Vienna, Austria
| | - Dieter Bettelheim
- Division of Obstetrics and Feto-maternal Medicine, Department of Obstetrics and Gynecology, Medical University of Vienna Vienna, Austria
| | - Anke Scharrer
- Clinical Institute for Pathology, Medical University of Vienna Vienna, Austria
| | - Georg Langs
- Computational Imaging Research Lab, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna Vienna, Austria
| | | | - Daniela Prayer
- Division of Neuroradiology and Musculoskeletal Radiology, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna Vienna, Austria
| | - Gregor Kasprian
- Division of Neuroradiology and Musculoskeletal Radiology, Department of Biomedical Imaging and Image-guided Therapy, Medical University of Vienna Vienna, Austria
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33
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Chen JA, Peñagarikano O, Belgard TG, Swarup V, Geschwind DH. The emerging picture of autism spectrum disorder: genetics and pathology. ANNUAL REVIEW OF PATHOLOGY-MECHANISMS OF DISEASE 2015; 10:111-44. [PMID: 25621659 DOI: 10.1146/annurev-pathol-012414-040405] [Citation(s) in RCA: 180] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Autism spectrum disorder (ASD) is defined by impaired social interaction and communication accompanied by stereotyped behaviors and restricted interests. Although ASD is common, its genetic and clinical features are highly heterogeneous. A number of recent breakthroughs have dramatically advanced our understanding of ASD from the standpoint of human genetics and neuropathology. These studies highlight the period of fetal development and the processes of chromatin structure, synaptic function, and neuron-glial signaling. The initial efforts to systematically integrate findings of multiple levels of genomic data and studies of mouse models have yielded new clues regarding ASD pathophysiology. This early work points to an emerging convergence of disease mechanisms in this complex and etiologically heterogeneous disorder.
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34
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Kim C, Yeom KW, Iv M. Congenital brain malformations in the neonatal and early infancy period. Semin Ultrasound CT MR 2015; 36:97-119. [PMID: 26001941 DOI: 10.1053/j.sult.2015.01.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Congenital brain malformations are a major cause of morbidity and mortality in pediatric patients who are younger than 2 years. Optimization of patient care requires accurate diagnosis, which can be challenging as congenital brain malformations include an extensive variety of anomalies. Radiologic imaging helps to identify the malformations and to guide management. Understanding radiologic findings necessitates knowledge of central nervous system embryogenesis. This review discusses the imaging of congenital brain malformations encountered in patients who are younger than 2 years in the context of brain development.
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Affiliation(s)
- Christine Kim
- Department of Radiology, Lucile Packard Children׳s Hospital, Stanford University, Stanford, CA.
| | - Kristen W Yeom
- Department of Radiology, Lucile Packard Children׳s Hospital, Stanford University, Stanford, CA
| | - Michael Iv
- Department of Radiology, Stanford University and Stanford University Medical Center, Stanford, CA
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35
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Huisman TA, Bosemani T, Poretti A. Diffusion Tensor Imaging for Brain Malformations. Neuroimaging Clin N Am 2014; 24:619-37. [DOI: 10.1016/j.nic.2014.07.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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36
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Guemez-Gamboa A, Coufal NG, Gleeson JG. Primary cilia in the developing and mature brain. Neuron 2014; 82:511-21. [PMID: 24811376 DOI: 10.1016/j.neuron.2014.04.024] [Citation(s) in RCA: 195] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Primary cilia were the largely neglected nonmotile counterparts of their better-known cousin, the motile cilia. For years these nonmotile cilia were considered evolutionary remnants of little consequence to cellular function. Fast forward 10 years and we now recognize primary cilia as key integrators of extracellular ligand-based signaling and cellular polarity, which regulate neuronal cell fate, migration, differentiation, as well as a host of adult behaviors. Important future questions will focus on structure-function relationships, their roles in signaling and disease and as areas of target for treatments.
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Affiliation(s)
- Alicia Guemez-Gamboa
- Howard Hughes Medical Institute, Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nicole G Coufal
- Howard Hughes Medical Institute, Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA
| | - Joseph G Gleeson
- Howard Hughes Medical Institute, Department of Neurosciences, University of California, San Diego, La Jolla, CA 92093, USA.
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37
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Miyata H, Miyata M, Ohama E. Pyramidal tract abnormalities in the human fetus and infant with trisomy 18 syndrome. Neuropathology 2013; 34:219-26. [DOI: 10.1111/neup.12081] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2013] [Accepted: 10/28/2013] [Indexed: 11/29/2022]
Affiliation(s)
- Hajime Miyata
- Department of Neuropathology; Research Institute for Brain and Blood Vessels - Akita; Akita Japan
- Department of Neuropathology; Institute of Neurological Sciences; Faculty of Medicine; Tottori University; Yonago Japan
| | - Mio Miyata
- Department of Neurology; Igarashi Memorial Hospital; Akita Japan
- Department of Neuropathology; Institute of Neurological Sciences; Faculty of Medicine; Tottori University; Yonago Japan
| | - Eisaku Ohama
- Kurashiki Heisei Hospital; Kurashiki Japan
- Department of Neuropathology; Institute of Neurological Sciences; Faculty of Medicine; Tottori University; Yonago Japan
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38
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Théoret H, Gleeson J, Pascual-Leone A. Neurophysiologic characterization of motor and sensory projections in Joubert syndrome. Clin Neurophysiol 2013; 124:2283-4. [PMID: 23906682 DOI: 10.1016/j.clinph.2013.06.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2013] [Revised: 05/23/2013] [Accepted: 06/06/2013] [Indexed: 11/27/2022]
Affiliation(s)
- Hugo Théoret
- University of Montreal and CHU Sainte-Justine, Montreal, Canada
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39
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Abstract
Joubert syndrome is a congenital cerebellar ataxia with autosomal recessive or X-linked inheritance, the diagnostic hallmark of which is a unique cerebellar and brainstem malformation recognisable on brain imaging-the so-called molar tooth sign. Neurological signs are present from the neonatal period and include hypotonia progressing to ataxia, global developmental delay, ocular motor apraxia, and breathing dysregulation. These signs are variably associated with multiorgan involvement, mainly of the retina, kidneys, skeleton, and liver. 21 causative genes have been identified so far, all of which encode for proteins of the primary cilium or its apparatus. The primary cilium is a subcellular organelle that has key roles in development and in many cellular functions, making Joubert syndrome part of the expanding family of ciliopathies. Notable clinical and genetic overlap exists between distinct ciliopathies, which can co-occur even within families. Such variability is probably explained by an oligogenic model of inheritance, in which the interplay of mutations, rare variants, and polymorphisms at distinct loci modulate the expressivity of the ciliary phenotype.
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40
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Poretti A, Meoded A, Rossi A, Raybaud C, Huisman TAGM. Diffusion tensor imaging and fiber tractography in brain malformations. Pediatr Radiol 2013; 43:28-54. [PMID: 23288476 DOI: 10.1007/s00247-012-2428-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2012] [Accepted: 04/09/2012] [Indexed: 01/19/2023]
Abstract
Diffusion tensor imaging (DTI) is an advanced MR technique that provides qualitative and quantitative information about the micro-architecture of white matter. DTI and its post-processing tool fiber tractography (FT) have been increasingly used in the last decade to investigate the microstructural neuroarchitecture of brain malformations. This article aims to review the use of DTI and FT in the evaluation of a variety of common, well-described brain malformations, in particular by pointing out the additional information that DTI and FT renders compared with conventional MR sequences. In addition, the relevant existing literature is summarized.
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Affiliation(s)
- Andrea Poretti
- Division of Pediatric Radiology, The Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, 600 N. Wolfe St., Nelson Basement, B-173, Baltimore, MD 21287-0842, USA
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41
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Valente EM, Dallapiccola B, Bertini E. Joubert syndrome and related disorders. HANDBOOK OF CLINICAL NEUROLOGY 2013; 113:1879-1888. [PMID: 23622411 DOI: 10.1016/b978-0-444-59565-2.00058-7] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Joubert syndrome (JS) is a rare autosomal recessive condition characterized by a peculiar midbrain-hindbrain malformation, known as the molar tooth sign (MTS). The neurological presentation of JS includes hypotonia that evolves into ataxia, developmental delay, abnormal eye movements, and neonatal breathing abnormalities. This picture is often associated with variable multiorgan involvement, mainly of the retina, kidneys, and liver, defining a group of conditions termed Joubert syndrome and related disorders (JSRDs), that share the MTS. To date, 16 causative genes have been identified, all encoding for proteins expressed in the primary cilium or its apparatus. Indeed, JSRD present clinical and genetic overlap with a growing field of disorders due to mutations in ciliary proteins, that are collectively known as "ciliopathies." These include isolated nephronophthisis, Senior-Løken syndrome, Bardet-Biedl syndrome and, in particular, Meckel syndrome, which is allelic at JSRD at seven distinct loci. Significant genotype-phenotype correlates are emerging between specific clinical presentations and mutations in JSRD genes, with relevant implications in terms of molecular diagnosis, clinical follow-up, and management of mutated patients. Moreover, the identification of mutations allows early prenatal diagnosis in couples at risk, while fetal neuroimaging may remain uninformative until the late second trimester of pregnancy.
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Affiliation(s)
- Enza Maria Valente
- IRCCS CSS-Mendel Institute, Rome and Department of Medicine and Surgery, University of Salerno, Salerno, Italy.
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42
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Zaki MS, Saleem SN, Dobyns WB, Barkovich AJ, Bartsch H, Dale AM, Ashtari M, Akizu N, Gleeson JG, Grijalvo-Perez AM. Diencephalic-mesencephalic junction dysplasia: a novel recessive brain malformation. Brain 2012; 135:2416-27. [PMID: 22822038 DOI: 10.1093/brain/aws162] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
We describe six cases from three unrelated consanguineous Egyptian families with a novel characteristic brain malformation at the level of the diencephalic-mesencephalic junction. Brain magnetic resonance imaging demonstrated a dysplasia of the diencephalic-mesencephalic junction with a characteristic 'butterfly'-like contour of the midbrain on axial sections. Additional imaging features included variable degrees of supratentorial ventricular dilatation and hypoplasia to complete agenesis of the corpus callosum. Diffusion tensor imaging showed diffuse hypomyelination and lack of an identifiable corticospinal tract. All patients displayed severe cognitive impairment, post-natal progressive microcephaly, axial hypotonia, spastic quadriparesis and seizures. Autistic features were noted in older cases. Talipes equinovarus, non-obstructive cardiomyopathy and persistent hyperplastic primary vitreous were additional findings in two families. One of the patients required shunting for hydrocephalus; however, this yielded no change in ventricular size suggestive of dysplasia rather than obstruction. We propose the term 'diencephalic-mesencephalic junction dysplasia' to characterize this autosomal recessive malformation.
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Affiliation(s)
- Maha S Zaki
- Department of Clinical Genetics, Division of Human Genetics and Genome Research, National Research Centre, El-Tahrir Street, Dokki, Cairo 12311, Egypt.
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43
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Joubert syndrome: brain and spinal cord malformations in genotyped cases and implications for neurodevelopmental functions of primary cilia. Acta Neuropathol 2012; 123:695-709. [PMID: 22331178 DOI: 10.1007/s00401-012-0951-2] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2012] [Revised: 01/25/2012] [Accepted: 01/27/2012] [Indexed: 12/12/2022]
Abstract
Joubert syndrome (JS) is an autosomal recessive ciliopathy characterized by hypotonia, ataxia, abnormal eye movements, and intellectual disability. The brain is malformed, with severe vermian hypoplasia, fourth ventriculomegaly, and "molar tooth" appearance of the cerebral and superior cerebellar peduncles visible as consistent features on neuroimaging. Neuropathological studies, though few, suggest that several other brain and spinal cord structures, such as the dorsal cervicomedullary junction, may also be affected in at least some patients. Genetically, JS is heterogeneous, with mutations in 13 genes accounting for approximately 50% of patients. Here, we compare neuropathologic findings in five subjects with JS, including four with defined mutations in OFD1 (2 siblings), RPGRIP1L, or TCTN2. Characteristic findings in all JS genotypes included vermian hypoplasia, fragmented dentate and spinal trigeminal nuclei, hypoplastic pontine and inferior olivary nuclei, and nondecussation of corticospinal tracts. Other common findings, seen in multiple genotypes but not all subjects, were dorsal cervicomedullary heterotopia, nondecussation of superior cerebellar peduncles, enlarged arcuate nuclei, hypoplastic reticular formation, hypoplastic medial lemnisci, and dorsal spinal cord disorganization. Thus, while JS exhibits significant neuropathologic as well as genetic heterogeneity, no genotype-phenotype correlations are apparent as yet. Our findings suggest that primary cilia are important for neural patterning, progenitor proliferation, cell migration, and axon guidance in the developing human brain and spinal cord.
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Simms RJ, Hynes AM, Eley L, Inglis D, Chaudhry B, Dawe HR, Sayer JA. Modelling a ciliopathy: Ahi1 knockdown in model systems reveals an essential role in brain, retinal, and renal development. Cell Mol Life Sci 2012; 69:993-1009. [PMID: 21959375 PMCID: PMC11115044 DOI: 10.1007/s00018-011-0826-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Revised: 09/09/2011] [Accepted: 09/12/2011] [Indexed: 02/03/2023]
Abstract
Joubert syndrome and related diseases (JSRD) are cerebello-oculo-renal syndromes with phenotypes including cerebellar hypoplasia, retinal dystrophy, and nephronophthisis (a cystic kidney disease). Mutations in AHI1 are the most common genetic cause of JSRD, with developmental hindbrain anomalies and retinal degeneration being prominent features. We demonstrate that Ahi1, a WD40 domain-containing protein, is highly conserved throughout evolution and its expression associates with ciliated organisms. In zebrafish ahi1 morphants, the phenotypic spectrum of JSRD is modeled, with embryos showing brain, eye, and ear abnormalities, together with renal cysts and cloacal dilatation. Following ahi1 knockdown in zebrafish, we demonstrate loss of cilia at Kupffer's vesicle and subsequently defects in cardiac left-right asymmetry. Finally, using siRNA in renal epithelial cells we demonstrate a role for Ahi1 in both ciliogenesis and cell-cell junction formation. These data support a role for Ahi1 in epithelial cell organization and ciliary formation and explain the ciliopathy phenotype of AHI1 mutations in man.
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Affiliation(s)
- Roslyn J. Simms
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - Ann Marie Hynes
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - Lorraine Eley
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - David Inglis
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE UK
| | - Bill Chaudhry
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
| | - Helen R. Dawe
- Biosciences: College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter, EX4 4QD UK
| | - John A. Sayer
- Institute of Genetic Medicine, Newcastle University, Central Parkway, Newcastle upon Tyne, NE1 3BZ UK
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Brumback RA. Neurobiology of disease in children: a decade of successful symposia and a robust partnership with the Journal of Child Neurology. J Child Neurol 2011; 26:1475-9. [PMID: 22114242 DOI: 10.1177/0883073811426934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Kamdar BB, Nandkumar P, Krishnan V, Gamaldo CE, Collop NA. Self-reported sleep and breathing disturbances in Joubert syndrome. Pediatr Neurol 2011; 45:395-9. [PMID: 22115003 DOI: 10.1016/j.pediatrneurol.2011.09.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/2011] [Accepted: 09/12/2011] [Indexed: 10/15/2022]
Abstract
Joubert syndrome is a rare autosomal recessive disease characterized by malformations of the cerebellar vermis, hypotonia, developmental delay, and respiratory variability. Because little is known about sleep and ventilatory dysregulation in this patient population, a questionnaire was distributed at the Joubert Syndrome and Related Disorders Foundation Conference. This questionnaire addressed respiratory and sleep abnormalities, and included the Pediatric Sleep Questionnaire. Parents or proxies completed questionnaires for patients unable to do so themselves because of young age or neurologic problems. Twenty surveys were collected. The median age was 8.3 years, and 45% were female. Seven patients (35%) reported existing episodic tachypnea, four (20%) reported apnea, and three (15%) reported both. Snoring was reported by 10 patients (50%), of whom four snored nightly and five had coexisting daytime tachypnea. Six of 14 (43%) Pediatric Sleep Questionnaire responders had scores suggestive of sleep-related breathing disorder. These results suggest that episodic tachypnea, apnea, snoring, and Pediatric Sleep Questionnaire scores suggestive of sleep-related breathing disorder are common in Joubert syndrome. Early detection and improved understanding of sleep and breathing abnormalities may contribute to improved outcomes for patients with Joubert syndrome.
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Affiliation(s)
- Biren B Kamdar
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland, USA
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Pugash D, Oh T, Godwin K, Robinson AJ, Byrne A, Van Allen MI, Osiovich H. Sonographic 'molar tooth' sign in the diagnosis of Joubert syndrome. ULTRASOUND IN OBSTETRICS & GYNECOLOGY : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF ULTRASOUND IN OBSTETRICS AND GYNECOLOGY 2011; 38:598-602. [PMID: 21370303 DOI: 10.1002/uog.8979] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The characteristic imaging finding common to Joubert syndrome and related disorders is the 'molar tooth' sign. The prenatal diagnosis of Joubert syndrome using both ultrasound and fetal magnetic resonance imaging (MRI) in families with an affected child has been reported previously. We report two cases in which the molar tooth sign was identified by sonography at 26 + 4 weeks and at 20 + 6 weeks, respectively, prior to fetal MRI or genetic testing. In both cases the finding was subsequently confirmed on fetal MRI. As definitive prenatal genetic testing may not be conclusive in Joubert syndrome, the ability to identify the molar tooth sign sonographically before 24 weeks provides a valuable adjunct to prenatal diagnosis.
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Affiliation(s)
- D Pugash
- Department of Radiology, Division of Maternal-Fetal Medicine, British Columbia Women's Hospital and University of British Columbia, Vancouver, BC, Canada.
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Abstract
Dysplasia of the cerebellar dentate nucleus is a state of apparent maturational arrest that involves the cerebellar dentate nucleus. Origins include Joubert syndrome, other disorders of axon guidance and dentato-olivary dysplasia. An overview is given, linking the diverse etiologies.
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Affiliation(s)
- Peter G Barth
- Emma Children's Hospital/AMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
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Harting I, Kotzaeridou U, Poretti A, Seitz A, Pietz J, Bendszus M, Boltshauser E. Interpeduncular heterotopia in Joubert syndrome: a previously undescribed MR finding. AJNR Am J Neuroradiol 2011; 32:1286-9. [PMID: 21636654 DOI: 10.3174/ajnr.a2488] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The so-called molar tooth sign is the radiologic hallmark of JSRD. Joubert syndrome is a rare, most often autosomal-recessive disorder with a characteristic malformation of the midhindbrain. We describe 3 patients with JSRD and the additional MR finding of tissue resembling heterotopia in the interpeduncular fossa, which in one patient was combined with a more extensive intramesencephalic heterotopia. Interpeduncular heterotopia has not been reported previously, either in the context of JSRD or as a separate entity. This new imaging feature enlarges the spectrum of brain stem abnormalities in JSRD. In view of the underlying ciliopathy, it seems likely that the interpeduncular heterotopia results from misdirected migration.
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Affiliation(s)
- I Harting
- Department of Neuroradiology, University of Heidelberg Medical School, Heidelberg, Germany.
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Defective Wnt-dependent cerebellar midline fusion in a mouse model of Joubert syndrome. Nat Med 2011; 17:726-31. [PMID: 21623382 PMCID: PMC3110639 DOI: 10.1038/nm.2380] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 04/19/2011] [Indexed: 01/15/2023]
Abstract
The ciliopathy Joubert syndrome is marked by cerebellar vermis hypoplasia, a phenotype for which the pathogenic mechanism is unclear1–3. In order to investigate Joubert syndrome pathogenesis, we have examined mice with mutated Ahi1, the first identified Joubert syndrome gene4,5. These mice exhibit cerebellar hypoplasia with a vermis/midline fusion defect early in development. This defect is concomitant with expansion of the roof plate and is also evident in a mouse mutant for another Joubert syndrome gene, Cep2906,7. Further, fetal magnetic resonance imaging (MRI) from human subjects with Joubert syndrome reveals a similar midline cleft suggesting parallel pathogenic mechanisms. Previous evidence has suggested a role for Jouberin (Jbn), the protein encoded by Ahi1, in canonical Wnt signaling8. Consistent with this, we found decreased Wnt reporter activity at the site of hemisphere fusion in the developing cerebellum of Ahi1 mutant mice. This decrease was accompanied by reduced proliferation at the site of fusion. Finally, treatment with lithium, a Wnt pathway agonist9, partially rescued this phenotype. Our findings implicate a defect in Wnt signaling in the cerebellar midline phenotype seen in Joubert syndrome, which can be overcome with Wnt stimulation.
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