Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease
Mutations in GlyR α1 or β subunit genes in humans and rodents lead to severe startle disease characterized by rigidity, massive stiffness and excessive startle responses upon unexpected tactile or acoustic stimuli. The recently characterized startle disease mouse mutant shaky carries a missense muta...
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doaj-f5d80e63d5444f989867a5cb27d9b8fc2020-11-25T00:19:53ZengFrontiers Media S.A.Frontiers in Molecular Neuroscience1662-50992018-05-011110.3389/fnmol.2018.00167368616Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle DiseaseNatascha Schaefer0Fang Zheng1Johannes van Brederode2Alexandra Berger3Sophie Leacock4Hiromi Hirata5Christopher J. Paige6Robert J. Harvey7Robert J. Harvey8Christian Alzheimer9Carmen Villmann10Institute for Clinical Neurobiology, Julius-Maximilians-University of Würzburg, Würzburg, GermanyInstitute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, GermanyInstitute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, GermanyPrincess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, CanadaResearch Department of Pharmacology, UCL School of Pharmacy, London, United KingdomDepartment of Chemistry and Biological Science, College of Science and Engineering, Aoyama Gakuin University, Sagamihara, JapanPrincess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, CanadaSchool of Health and Sport Sciences, University of the Sunshine Coast, Sippy Downs, QLD, AustraliaSunshine Coast Health Institute, Birtinya, QLD, AustraliaInstitute of Physiology and Pathophysiology, Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen, GermanyInstitute for Clinical Neurobiology, Julius-Maximilians-University of Würzburg, Würzburg, GermanyMutations in GlyR α1 or β subunit genes in humans and rodents lead to severe startle disease characterized by rigidity, massive stiffness and excessive startle responses upon unexpected tactile or acoustic stimuli. The recently characterized startle disease mouse mutant shaky carries a missense mutation (Q177K) in the β8-β9 loop within the large extracellular N-terminal domain of the GlyR α1 subunit. This results in a disrupted hydrogen bond network around K177 and faster GlyR decay times. Symptoms in mice start at postnatal day 14 and increase until premature death of homozygous shaky mice around 4–6 weeks after birth. Here we investigate the in vivo functional effects of the Q177K mutation using behavioral analysis coupled to protein biochemistry and functional assays. Western blot analysis revealed GlyR α1 subunit expression in wild-type and shaky animals around postnatal day 7, a week before symptoms in mutant mice become obvious. Before 2 weeks of age, homozygous shaky mice appeared healthy and showed no changes in body weight. However, analysis of gait and hind-limb clasping revealed that motor coordination was already impaired. Motor coordination and the activity pattern at P28 improved significantly upon diazepam treatment, a pharmacotherapy used in human startle disease. To investigate whether functional deficits in glycinergic neurotransmission are present prior to phenotypic onset, we performed whole-cell recordings from hypoglossal motoneurons (HMs) in brain stem slices from wild-type and shaky mice at different postnatal stages. Shaky homozygotes showed a decline in mIPSC amplitude and frequency at P9-P13, progressing to significant reductions in mIPSC amplitude and decay time at P18-24 compared to wild-type littermates. Extrasynaptic GlyRs recorded by bath-application of glycine also revealed reduced current amplitudes in shaky mice compared to wild-type neurons, suggesting that presynaptic GlyR function is also impaired. Thus, a distinct, but behaviorally ineffective impairment of glycinergic synapses precedes the symptoms onset in shaky mice. These findings extend our current knowledge on startle disease in the shaky mouse model in that they demonstrate how the progression of GlyR dysfunction causes, with a delay of about 1 week, the appearance of disease symptoms.https://www.frontiersin.org/article/10.3389/fnmol.2018.00167/fullglycine receptorstartle diseaseβ8-β9 loopmouse modelfast decayshaky |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Natascha Schaefer Fang Zheng Johannes van Brederode Alexandra Berger Sophie Leacock Hiromi Hirata Christopher J. Paige Robert J. Harvey Robert J. Harvey Christian Alzheimer Carmen Villmann |
spellingShingle |
Natascha Schaefer Fang Zheng Johannes van Brederode Alexandra Berger Sophie Leacock Hiromi Hirata Christopher J. Paige Robert J. Harvey Robert J. Harvey Christian Alzheimer Carmen Villmann Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease Frontiers in Molecular Neuroscience glycine receptor startle disease β8-β9 loop mouse model fast decay shaky |
author_facet |
Natascha Schaefer Fang Zheng Johannes van Brederode Alexandra Berger Sophie Leacock Hiromi Hirata Christopher J. Paige Robert J. Harvey Robert J. Harvey Christian Alzheimer Carmen Villmann |
author_sort |
Natascha Schaefer |
title |
Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease |
title_short |
Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease |
title_full |
Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease |
title_fullStr |
Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease |
title_full_unstemmed |
Functional Consequences of the Postnatal Switch From Neonatal to Mutant Adult Glycine Receptor α1 Subunits in the Shaky Mouse Model of Startle Disease |
title_sort |
functional consequences of the postnatal switch from neonatal to mutant adult glycine receptor α1 subunits in the shaky mouse model of startle disease |
publisher |
Frontiers Media S.A. |
series |
Frontiers in Molecular Neuroscience |
issn |
1662-5099 |
publishDate |
2018-05-01 |
description |
Mutations in GlyR α1 or β subunit genes in humans and rodents lead to severe startle disease characterized by rigidity, massive stiffness and excessive startle responses upon unexpected tactile or acoustic stimuli. The recently characterized startle disease mouse mutant shaky carries a missense mutation (Q177K) in the β8-β9 loop within the large extracellular N-terminal domain of the GlyR α1 subunit. This results in a disrupted hydrogen bond network around K177 and faster GlyR decay times. Symptoms in mice start at postnatal day 14 and increase until premature death of homozygous shaky mice around 4–6 weeks after birth. Here we investigate the in vivo functional effects of the Q177K mutation using behavioral analysis coupled to protein biochemistry and functional assays. Western blot analysis revealed GlyR α1 subunit expression in wild-type and shaky animals around postnatal day 7, a week before symptoms in mutant mice become obvious. Before 2 weeks of age, homozygous shaky mice appeared healthy and showed no changes in body weight. However, analysis of gait and hind-limb clasping revealed that motor coordination was already impaired. Motor coordination and the activity pattern at P28 improved significantly upon diazepam treatment, a pharmacotherapy used in human startle disease. To investigate whether functional deficits in glycinergic neurotransmission are present prior to phenotypic onset, we performed whole-cell recordings from hypoglossal motoneurons (HMs) in brain stem slices from wild-type and shaky mice at different postnatal stages. Shaky homozygotes showed a decline in mIPSC amplitude and frequency at P9-P13, progressing to significant reductions in mIPSC amplitude and decay time at P18-24 compared to wild-type littermates. Extrasynaptic GlyRs recorded by bath-application of glycine also revealed reduced current amplitudes in shaky mice compared to wild-type neurons, suggesting that presynaptic GlyR function is also impaired. Thus, a distinct, but behaviorally ineffective impairment of glycinergic synapses precedes the symptoms onset in shaky mice. These findings extend our current knowledge on startle disease in the shaky mouse model in that they demonstrate how the progression of GlyR dysfunction causes, with a delay of about 1 week, the appearance of disease symptoms. |
topic |
glycine receptor startle disease β8-β9 loop mouse model fast decay shaky |
url |
https://www.frontiersin.org/article/10.3389/fnmol.2018.00167/full |
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