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Heinonen T, Flegel T, Müller H, Kehl A, Hundi S, Matiasek K, Fischer A, Donner J, Forman OP, Lohi H, Hytönen MK. A loss-of-function variant in canine GLRA1 associates with a neurological disorder resembling human hyperekplexia. Hum Genet 2023; 142:1221-1230. [PMID: 37222814 PMCID: PMC10449970 DOI: 10.1007/s00439-023-02571-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2022] [Accepted: 05/08/2023] [Indexed: 05/25/2023]
Abstract
Hereditary hyperekplexia is a rare neuronal disorder characterized by an exaggerated startle response to sudden tactile or acoustic stimuli. In this study, we present a Miniature Australian Shepherd family showing clinical signs, which have genetic and phenotypic similarities with human hereditary hyperekplexia: episodes of muscle stiffness that could occasionally be triggered by acoustic stimuli. Whole genome sequence data analysis of two affected dogs revealed a 36-bp deletion spanning the exon-intron boundary in the glycine receptor alpha 1 (GLRA1) gene. Further validation in pedigree samples and an additional cohort of 127 Miniature Australian Shepherds, 45 Miniature American Shepherds and 74 Australian Shepherds demonstrated complete segregation of the variant with the disease, according to an autosomal recessive inheritance pattern. The protein encoded by GLRA1 is a subunit of the glycine receptor, which mediates postsynaptic inhibition in the brain stem and spinal cord. The canine GLRA1 deletion is located in the signal peptide and is predicted to cause exon skipping and subsequent premature stop codon resulting in a significant defect in glycine signaling. Variants in GLRA1 are known to cause hereditary hyperekplexia in humans; however, this is the first study to associate a variant in canine GLRA1 with the disorder, establishing a spontaneous large animal disease model for the human condition.
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Affiliation(s)
- Tiina Heinonen
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
- Folkhälsan Research Center, Helsinki, Finland
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Thomas Flegel
- Department of Small Animals, Leipzig University, Leipzig, Germany
| | - Hanna Müller
- Tieraerztliches Fachzentrum Muehlhausen Dr. Ortmann & Dr. Stief, Muehlhausen/Thueringen, Germany
| | | | - Sruthi Hundi
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland
- Folkhälsan Research Center, Helsinki, Finland
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland
| | - Kaspar Matiasek
- Section of Clinical and Comparative Neuropathology, Institute of Veterinary Pathology, Centre for Clinical Veterinary Medicine, LMU Munich, Munich, Germany
| | - Andrea Fischer
- Clinic of Small Animal Medicine, Centre for Clinical Veterinary Medicine, LMU Munich, Munich, Germany
| | - Jonas Donner
- Wisdom Panel Research Team, Wisdom Panel, Kinship, Helsinki, Finland
| | - Oliver P Forman
- Wisdom Panel Research Team, Wisdom Panel, Kinship, Leicestershire, UK
| | - Hannes Lohi
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland.
- Folkhälsan Research Center, Helsinki, Finland.
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.
| | - Marjo K Hytönen
- Department of Medical and Clinical Genetics, University of Helsinki, Helsinki, Finland.
- Folkhälsan Research Center, Helsinki, Finland.
- Department of Veterinary Biosciences, University of Helsinki, Helsinki, Finland.
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2
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Valberg SJ. Movement Disorders and Cerebellar Abiotrophy. Vet Clin North Am Equine Pract 2022; 38:409-426. [PMID: 35811199 DOI: 10.1016/j.cveq.2022.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022] Open
Abstract
Movement disorders are defined as involuntary movements that are not due to a painful stimulus or associated with changes in consciousness or proprioception. Diagnosis involves ruling out any lameness and neurologic disease and characterizing the gait during walking backward and forward and trotting. Shivers causes abnormal hindlimb hypertonicity during walking backward and, when advanced, a few strides walking forward. Stringhalt causes consistent hyperflexion during walking forward and trotting and variable difficulty when walking backward. Classification and potential causes are discussed as well as other enigmatic movement disorders in horses are presented. Cerebellar abiotrophy is reviewed.
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Affiliation(s)
- Stephanie J Valberg
- Michigan State University, Large Animal Clinical Sciences, College of Veterinary Medicine, 736 Wilson Road, East Lansing, MI 48824, USA.
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3
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Abstract
Neurologic disease in horses can be particularly challenging to diagnose and treat. These diseases can result in economic losses, emotional distress to owners, and injury to the horse or handlers. To date, there are 5 neurologic diseases caused by known genetic mutations and several more are suspected to be heritable: lethal white foal syndrome, lavender foal syndrome, cerebellar abiotrophy, occipitoatlantoaxial malformation, and Friesian hydrocephalus. Genetic testing allows owners, breeders, and veterinarians to make informed decisions when selecting dams and sires for breeding or deciding the treatment or prognosis of a neurologic animal.
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Affiliation(s)
- Lisa Edwards
- Department of Veterinary Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Room 4206 Vet Med 3A One Shields Avenue, Davis, CA 95616, USA
| | - Carrie J Finno
- Department of Veterinary Population Health and Reproduction, School of Veterinary Medicine, University of California Davis, Room 4206 Vet Med 3A One Shields Avenue, Davis, CA 95616, USA.
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Murphy SC, Recio A, de la Fuente C, Guo LT, Shelton GD, Clark LA. A glycine transporter SLC6A5 frameshift mutation causes startle disease in Spanish greyhounds. Hum Genet 2019; 138:509-513. [PMID: 30847549 DOI: 10.1007/s00439-019-01986-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 02/19/2019] [Indexed: 11/29/2022]
Abstract
Startle disease, or hyperekplexia, is a glycinergic disorder characterized by hypertonia and apnea that is triggered by noise and/or touch. Mutations in five genes have been associated with startle disease in humans, dogs, cattle, and mice. We identified a novel recessive startle disease in a family of Spanish greyhounds. Whole genome resequencing of an affected dog revealed a homozygous two base pair deletion in the ninth exon of SLC6A5, encoding the presynaptic glycine transporter. The deletion is predicted to cause a frameshift, p.S460FfsX47, leading to a premature stop codon that truncates over a third of the protein. Family members were genotyped for the deletion, and findings were consistent with an autosomal recessive inheritance pattern. The pathogenic variant was absent from 34 unrelated greyhounds, 659 domestic dogs of pure and mixed breeds, and 54 wild canids, suggesting it occurred recently and may be private to the family. The findings of this study can be used to inform future breeding decisions and prevent dissemination of the deleterious allele in greyhounds.
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Affiliation(s)
- Sarah C Murphy
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, 29634, USA
| | - Alfredo Recio
- Fundació Hospital Clínic Veterinari, Universitat Autònoma de Barcelona, Bellaterra, Spain
- Clinica Veterinaria Levante, San Javier, Murcia, Spain
| | - Cristian de la Fuente
- Fundació Hospital Clínic Veterinari, Universitat Autònoma de Barcelona, Bellaterra, Spain
| | - Ling T Guo
- Department of Pathology, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA
| | - G Diane Shelton
- Department of Pathology, School of Medicine, University of California San Diego, La Jolla, CA, 92093, USA.
| | - Leigh Anne Clark
- Department of Genetics and Biochemistry, Clemson University, Clemson, SC, 29634, USA.
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5
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Abstract
The inhibitory glycine receptor is a ligand-gated chloride channel that exists in developmentally regulated isoforms. These oligomeric transmembrane proteins are composed of variants of the ligand binding α subunit and structural β polypeptides. The agonist and antagonist sites of the α subunits are formed by discontinuous sequence motifs. In the murine genome, the genes encoding the α1 ( Glra1), α3 ( Glra3), and β ( Glyrb) subunit are autosomally located, whereas the α2 ( Glra2) and α4 ( Glra4) genes reside on the X-chromosome. Mutations of glycine receptor genes have been found to underly hypertonic motor disorders in mice and humans. The mouse mutants spasmodic (spd) and oscillator ( spdot) carry recessive mutations of the Glra 1 gene. In the phenotypically similar mouse mutant spastic ( spa), the intronic insertion of a LINE-1 transposable element into the Gyrb gene results in the aberrant splicing and a consecutive loss of glycine receptors. The human neurological disorder hyperekplexia (startle disease, stiff baby syndrome) is caused by point mutations within the α1 subunit gene ( GLRA1) localized in the human chromosomal region 5q31.3. The Neuroscientist 1:130- 141,1995
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Affiliation(s)
- Cord-Michael Becker
- Neurologische Klinik and Zentrum für Molekulare Biologie
Universität Heidelberg Heidelberg, Germany
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Blignaut DJC, Holm DE, Leask R, Stander N, Steyl JCA. Congenital reflex myoclonus in two Merino cross lambs in South Africa. Vet Rec 2011; 169:684. [PMID: 21984564 DOI: 10.1136/vr.d5812] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- D J C Blignaut
- Department of Production Animal Studies, University of Pretoria, Private Bag X04, Onderstepoort, 0110, South Africa.
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Gill JL, James VM, Carta E, Harris D, Topf M, Scholes SFE, Hateley G, Harvey RJ. Identification of congenital muscular dystonia 2 associated with an inherited GlyT2 defect in Belgian Blue cattle from the United Kingdom. Anim Genet 2011; 43:267-70. [PMID: 22486497 DOI: 10.1111/j.1365-2052.2011.02255.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Two newborn Belgian Blue calves from a farm in the United Kingdom exhibited lateral recumbency, low head carriage and transient muscle spasms following tactile or auditory stimulation. DNA sequence analysis indicated that both calves were homozygous for the recessive congenital muscular dystonia type 2 (CMD2) mutation (c.809T>C, p.Leu270Pro) in SLC6A5, encoding the neuronal glycine transporter GlyT2. Further testing of animals from the index farm and a sample of Belgian Blue sires revealed an unexpectedly high frequency of CMD2 carriers. This implies that linked quantitative trait loci may be influencing the prevalence of CMD2 in the estimated 55,000 Belgian Blue cattle in the United Kingdom. We have therefore developed new inexpensive tests for the CMD2 allele that can be used to confirm diagnosis, identify carriers and guide future breeding strategy, thus avoiding animal distress/premature death and minimizing the future economic impact of this disorder.
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Affiliation(s)
- J L Gill
- Department of Pharmacology, The School of Pharmacy, London, UK.
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Startle disease in Irish wolfhounds associated with a microdeletion in the glycine transporter GlyT2 gene. Neurobiol Dis 2011; 43:184-9. [PMID: 21420493 PMCID: PMC4068303 DOI: 10.1016/j.nbd.2011.03.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2010] [Revised: 03/01/2011] [Accepted: 03/11/2011] [Indexed: 11/21/2022] Open
Abstract
Defects in glycinergic synaptic transmission in humans, cattle, and rodents result in an exaggerated startle reflex and hypertonia in response to either acoustic or tactile stimuli. Molecular genetic studies have determined that mutations in the genes encoding the postsynaptic glycine receptor (GlyR) α1 and β subunits (GLRA1 and GLRB) and the presynaptic glycine transporter GlyT2 (SLC6A5) are the major cause of these disorders. Here, we report the first genetically confirmed canine cases of startle disease. A litter of seven Irish wolfhounds was identified in which two puppies developed muscle stiffness and tremor in response to handling. Although sequencing of GLRA1 and GLRB did not reveal any pathogenic mutations, analysis of SLC6A5 revealed a homozygous 4.2 kb microdeletion encompassing exons 2 and 3 in both affected animals. This results in the loss of part of the large cytoplasmic N-terminus and all subsequent transmembrane domains due to a frameshift. This genetic lesion was confirmed by defining the deletion breakpoint, Southern blotting, and multiplex ligation-dependent probe amplification (MLPA). This analysis enabled the development of a rapid genotyping test that revealed heterozygosity for the deletion in the dam and sire and three other siblings, confirming recessive inheritance. Wider testing of related animals has identified a total of 13 carriers of the SLC6A5 deletion as well as non-carrier animals. These findings will inform future breeding strategies and enable a rational pharmacotherapy of this new canine disorder.
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Fanelli HH. Coat colour dilution lethal (‘lavender foal a’): syndrome tetany syndrome of Arabian foals. EQUINE VET EDUC 2010. [DOI: 10.1111/j.2042-3292.2005.tb00386.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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10
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The genetics of hyperekplexia: more than startle! Trends Genet 2008; 24:439-47. [DOI: 10.1016/j.tig.2008.06.005] [Citation(s) in RCA: 152] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2008] [Revised: 06/04/2008] [Accepted: 06/04/2008] [Indexed: 11/20/2022]
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Page P, Parker R, Harper C, Guthrie AI, Neser J. Clinical, Clinicopathologic, Postmortem Examination Findings and Familial History of 3 Arabians with Lavender Foal Syndrome. J Vet Intern Med 2006. [DOI: 10.1111/j.1939-1676.2006.tb00772.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Abstract
The glycine receptor chloride channel (GlyR) is a member of the nicotinic acetylcholine receptor family of ligand-gated ion channels. Functional receptors of this family comprise five subunits and are important targets for neuroactive drugs. The GlyR is best known for mediating inhibitory neurotransmission in the spinal cord and brain stem, although recent evidence suggests it may also have other physiological roles, including excitatory neurotransmission in embryonic neurons. To date, four alpha-subunits (alpha1 to alpha4) and one beta-subunit have been identified. The differential expression of subunits underlies a diversity in GlyR pharmacology. A developmental switch from alpha2 to alpha1beta is completed by around postnatal day 20 in the rat. The beta-subunit is responsible for anchoring GlyRs to the subsynaptic cytoskeleton via the cytoplasmic protein gephyrin. The last few years have seen a surge in interest in these receptors. Consequently, a wealth of information has recently emerged concerning GlyR molecular structure and function. Most of the information has been obtained from homomeric alpha1 GlyRs, with the roles of the other subunits receiving relatively little attention. Heritable mutations to human GlyR genes give rise to a rare neurological disorder, hyperekplexia (or startle disease). Similar syndromes also occur in other species. A rapidly growing list of compounds has been shown to exert potent modulatory effects on this receptor. Since GlyRs are involved in motor reflex circuits of the spinal cord and provide inhibitory synapses onto pain sensory neurons, these agents may provide lead compounds for the development of muscle relaxant and peripheral analgesic drugs.
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Affiliation(s)
- Joseph W Lynch
- School of Biomedical Sciences, Univ. of Queensland, Brisbane QLD 4072, Australia.
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Jentsch TJ, Stein V, Weinreich F, Zdebik AA. Molecular structure and physiological function of chloride channels. Physiol Rev 2002; 82:503-68. [PMID: 11917096 DOI: 10.1152/physrev.00029.2001] [Citation(s) in RCA: 934] [Impact Index Per Article: 42.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Cl- channels reside both in the plasma membrane and in intracellular organelles. Their functions range from ion homeostasis to cell volume regulation, transepithelial transport, and regulation of electrical excitability. Their physiological roles are impressively illustrated by various inherited diseases and knock-out mouse models. Thus the loss of distinct Cl- channels leads to an impairment of transepithelial transport in cystic fibrosis and Bartter's syndrome, to increased muscle excitability in myotonia congenita, to reduced endosomal acidification and impaired endocytosis in Dent's disease, and to impaired extracellular acidification by osteoclasts and osteopetrosis. The disruption of several Cl- channels in mice results in blindness. Several classes of Cl- channels have not yet been identified at the molecular level. Three molecularly distinct Cl- channel families (CLC, CFTR, and ligand-gated GABA and glycine receptors) are well established. Mutagenesis and functional studies have yielded considerable insights into their structure and function. Recently, the detailed structure of bacterial CLC proteins was determined by X-ray analysis of three-dimensional crystals. Nonetheless, they are less well understood than cation channels and show remarkably different biophysical and structural properties. Other gene families (CLIC or CLCA) were also reported to encode Cl- channels but are less well characterized. This review focuses on molecularly identified Cl- channels and their physiological roles.
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Affiliation(s)
- Thomas J Jentsch
- Zentrum für Molekulare Neurobiologie Hamburg, Universität Hamburg, Hamburg, Germany.
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14
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Vafa B, Schofield PR. Heritable mutations in the glycine, GABAA, and nicotinic acetylcholine receptors provide new insights into the ligand-gated ion channel receptor superfamily. INTERNATIONAL REVIEW OF NEUROBIOLOGY 1998; 42:285-332. [PMID: 9476176 DOI: 10.1016/s0074-7742(08)60613-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- B Vafa
- Garvan Institute of Medical Research, Darlinghurst, Sydney, Australia
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15
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Abstract
The inhibitory glycine receptor (GlyR) is a member of the ligand-gated ion channel receptor superfamily. The GlyR comprises a pentameric complex that forms a chloride-selective transmembrane channel, which is predominantly expressed in the spinal cord and brain stem. We review the pharmacological and physiological properties of the GlyR and relate this information to more recent insights that have been obtained through the cloning and recombinant expression of the GlyR subunits. We also discuss insights into our understanding of GlyR structure and function that have been obtained by the genetic characterisation of various heritable disorders of glycinergic neurotransmission.
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Affiliation(s)
- S Rajendra
- School of Physiology and Pharmacology, University of New South Wales, Sydney, Australia
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16
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Blednov YA, Bleck V, Harris RA. Measurement of glycine receptor function by radioactive chloride uptake. J Neurosci Methods 1996; 68:253-7. [PMID: 8912198 DOI: 10.1016/0165-0270(96)00088-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The glycine receptor is an important inhibitory receptor for both spinal and supraspinal functions, and mutations in receptor subunits are responsible for neurological disorders in several species, including humans. However, functional measurements of glycine receptors have generally been restricted to electrophysiological analysis of immature, cultured neurons. We developed a 36Cl- flux assay to measure glycine receptor function using membrane vesicles from spinal cord and brainstem of adult mice. The uptake of 36Cl- stimulated by glycine was characterized by a glycine EC50 of 22 microM for the major component and an EC50 of 0.5 microM for a minor component. Strychnine inhibited the glycine-stimulated uptake with an IC50 of 0.4 microM. The uptake was not affected by picrotoxin, bicuculline, or pentobarbital. Glycine-stimulated uptake reached a maximum by 10 s. This technique should prove useful for genetic and pharmacological analysis of the function of glycine receptors.
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Affiliation(s)
- Y A Blednov
- Denver VA Medical Center, University of Colorado School of Medicine 80262, USA
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Kingsmore SF, Giros B, Suh D, Bieniarz M, Caron MG, Seldin MF. Glycine receptor beta-subunit gene mutation in spastic mouse associated with LINE-1 element insertion. Nat Genet 1994; 7:136-41. [PMID: 7920630 DOI: 10.1038/ng0694-136] [Citation(s) in RCA: 152] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Congenital myoclonus is a widespread neurologic disorder characterized by hyperexcitability, muscular spasticity and myoclonus associated with marked reduction in neural glycine binding sites. The recessive mouse mutation spastic (spa) is a prototype of inherited myoclonus. Here we show that defects in the gene encoding the beta-subunit of the glycine receptor (Glrb) underlie spa: Glrb maps to the same region of mouse chromosome 3 as spa, and Glrb mRNA is markedly reduced throughout brains of spa mice, most likely as a result of an insertional mutation of a 7.1 kilobase LINE-1 element within intron 6 of Glrb. These results provide evidence that Glrb is necessary for postsynaptic expression of glycine receptor complexes, and suggest Glrb as a candidate gene for inherited myoclonus in other species.
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Affiliation(s)
- S F Kingsmore
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710
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