1
|
Shields MC, Bowers MR, Fulcer MM, Bollig MK, Rock PJ, Sutton BR, Vrailas-Mortimer AD, Lochmüller H, Whittaker RG, Horvath R, Reist NE. Drosophila studies support a role for a presynaptic synaptotagmin mutation in a human congenital myasthenic syndrome. PLoS One 2017; 12:e0184817. [PMID: 28953919 PMCID: PMC5617158 DOI: 10.1371/journal.pone.0184817] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 08/31/2017] [Indexed: 12/04/2022] Open
Abstract
During chemical transmission, the function of synaptic proteins must be coordinated to efficiently release neurotransmitter. Synaptotagmin 2, the Ca2+ sensor for fast, synchronized neurotransmitter release at the human neuromuscular junction, has recently been implicated in a dominantly inherited congenital myasthenic syndrome associated with a non-progressive motor neuropathy. In one family, a proline residue within the C2B Ca2+-binding pocket of synaptotagmin is replaced by a leucine. The functional significance of this residue has not been investigated previously. Here we show that in silico modeling predicts disruption of the C2B Ca2+-binding pocket, and we examine the in vivo effects of the homologous mutation in Drosophila. When expressed in the absence of native synaptotagmin, this mutation is lethal, demonstrating for the first time that this residue plays a critical role in synaptotagmin function. To achieve expression similar to human patients, the mutation is expressed in flies carrying one copy of the wild type synaptotagmin gene. We now show that Drosophila carrying this mutation developed neurological and behavioral manifestations similar to those of human patients and provide insight into the mechanisms underlying these deficits. Our Drosophila studies support a role for this synaptotagmin point mutation in disease etiology.
Collapse
Affiliation(s)
- Mallory C. Shields
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
- Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, United States of America
| | - Matthew R. Bowers
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
- Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, United States of America
| | - McKenzie M. Fulcer
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Madelyn K. Bollig
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
| | - Patrick J. Rock
- School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Bryan R. Sutton
- Department of Cell Physiology and Molecular Biophysics, Center for Membrane Protein Research, Texas Tech University Health Sciences Center, Lubbock, Texas, United States of America
| | - Alysia D. Vrailas-Mortimer
- Department of Biological Sciences, University of Denver, Denver, CO, United States of America
- School of Biological Sciences, Illinois State University, Normal, IL, United States of America
| | - Hanns Lochmüller
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, United Kingdom
| | - Roger G. Whittaker
- Institute of Neuroscience, Newcastle University, Newcastle upon Tyne, NE2 4HH, United Kingdom
| | - Rita Horvath
- John Walton Muscular Dystrophy Research Centre, Institute of Genetic Medicine, Newcastle University, Newcastle upon Tyne, NE1 3BZ, United Kingdom
| | - Noreen E. Reist
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, United States of America
- Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, United States of America
- * E-mail:
| |
Collapse
|
3
|
Coover GD, Sutton BR, Heybach JP. Conditioning decreases in plasma corticosterone level in rats by paring stimuli with daily feedings. J Comp Physiol Psychol 1977; 91:716-26. [PMID: 893743 DOI: 10.1037/h0077363] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
This study examined the nature of a stimulus-induced decrease in the plasma corticosterone levels of rats. Rats maintained on a 23-hr food and water deprivation regimen were fed each morning immediately upon entrance of the experimenter into the otherwise isolated animal quarters. After only 14 feeding trials, the rats showed a marked decrease in corticosterone levels within 10 min of the experimenter's entrance whether fed and watered or not. The acquisition of this decrease was then examined over training trials and by comparing the conditioned animals (Group CD) with a group designed to control for pseudoconditioning, sensitization, and habituation (Group PC) during the use of the more distinctive conditioning stimulus of placing the rat's cage in a sound-attenuating chamber. During training. Group CD was fed .5-6 min after placement in the chamber, and Group PC was fed 1.5-2.5 hr before or after placement. After one training trial, the CD and PC groups showed an increase in corticosterone levels in response to chamber placement when not fed or watered. However, after 14 training trials the CD group exhibited a significant decline, whereas the PC group exhibited a rise in corticosterone levels. The results indicate that external stimuli can cause a decrease in corticosterone level by virtue of prior association with feeding and drinking. This strongly suggests an acquired inhibition of the pituitary-adrenal system.
Collapse
|