Biology subjects

Vetter, I.

Publications and source records attributed to Vetter, I..

3 recordsLinked to original sources

bioRxiv2021

A kinase-dead Csf1r mutation associated with adult-onset leukoencephalopathy has a dominant-negative impact on CSF1R signaling.

Amino acid substitutions in the kinase domain of the human CSF1R gene are associated with autosomal dominant adult-onset leukoencephalopathy with axonal spheroids and pigmented glia (ALSP). To model the human disease, we created a disease-associated mutation (Glu631Lys; E631K) in the mouse Csf1r locus. Homozygous mutation (Csf1rE631K/E631K) phenocopied the Csf1r knockout; with prenatal mortality or severe postnatal growth retardation and hydrocephalus. Heterozygous mutation delayed the postnatal expansion of tissue macrophage populations in most organs. Bone marrow cells from Csf1rE631K/+ mice were resistant to CSF1 stimulation in vitro, and Csf1rE631K/+ mice were unresponsive to administration of a CSF1-Fc fusion protein which expands tissue macrophage populations in controls. In the brain, microglial cell numbers and dendritic arborization were reduced in the Csf1rE631K/+ mice as in ALSP patients. The microglial phenotype is the opposite of microgliosis observed in Csf1r+/- mice. However, we found no evidence of brain pathology or impacts on motor function in aged Csf1rE631K/+ mice. We conclude that disease-associated CSF1R mutations encode dominant negative repressors of CSF1R signaling. We speculate that leukoencephalopathy associated with human CSF1R mutations requires an environmental trigger and/or epistatic interaction with common neurodegenerative disease-associated alleles. Summary StatementThis study describes the effect of a human disease-associated mutation in the mouse CSF1R gene on postnatal development and growth factor responsiveness of cells of the macrophage lineage.

developmental biology↗

bioRxiv2021

The allosteric activation of α7 nAChR by α-conotoxin MrIC is modified by mutations at the vestibular site

-conotoxins are 13-19 amino acid toxin peptides that bind various nicotinic acetylcholine receptor (nAChR) subtypes. -conotoxin Mr1.7c (MrIC) is a 17 amino acid peptide that targets 7 nAChR. Although MrIC has no activating effect on 7 nAChR when applied by itself, it evokes a large response when co-applied with the type II positive allosteric modulator PNU-120596, which potentiates 7 nAChR response by recovering it from a desensitized state. Lack of standalone activity despite activation upon co-application with a positive allosteric modulator was previously observed for molecules that bind to an extracellular domain allosteric activation (AA) site at the vestibule of the receptor. We hypothesized that MrIC may activate 7 nAChR allosterically through this site. We ran voltage-clamp electrophysiology experiments and in silico peptide docking calculations to gather evidence in support of 7 nAChR activation by MrIC through the AA site. The experiments with the wild-type 7 nAChR supported an allosteric mode of action, which was confirmed by the increased MrIC + PNU-120596 responses of three 7 nAChR AA site mutants that were designed in silico to improve MrIC binding. Overall, our results shed light on allosteric activation of 7 nAChR by MrIC and suggest involvement of the AA site. Significance Statement-conotoxin MrIC (MrIC) is an allosteric agonist of the 7 nicotinic acetylcholine receptor (nAChR). This mode of action is unique among -conotoxins since these peptides typically act as orthosteric antagonists of nAChR. However, the mechanism of 7 nAChR activation by MrIC has been elusive so far. This work demonstrates that activation by MrIC is independent of the 7 nAChR orthosteric site and is related to a vestibular allosteric activation site at the extracellular domain of the receptor. Our experimental and computational studies identified the residues that play a role in allosteric activation and confirmed the utility of ensemble docking methods in understanding peptide - nAChR interactions, thus providing a basis for the design of peptides for allosteric modulation of nAChR.

biophysics↗

bioRxiv2019

NaV1.1 and NaV1.6 selective compounds reduce the behavior phenotype in a novel zebrafish model for Dravet Syndrome

Dravet syndrome is caused by dominant loss-of-function mutations in SCN1A which cause reduced activity of Nav1.1 leading to lack of neuronal inhibition. On the other hand, gain-of-function mutations in SCN8A can lead to a severe epileptic encephalopathy subtype by over activating NaV1.6 channels. These observations suggest that Nav1.1 and Nav1.6 represent two opposing sides of the neuronal balance between inhibition and activation. Here, we hypothesize that Dravet syndrome may be treated by either enhancing Nav1.1 or reducing Nav1.6 activity. To test this hypothesis we generated and characterized a novel DS zebrafish model and tested new compounds that selectively activate or inhibit the human NaV1.1 or NaV1.6 channel respectively. We used CRISPR/Cas9 to generate two separate Scn1Lab knockout lines as an alternative to previous knock-down models. Using an optimized locomotor assay, spontaneous burst movements were detected that were unique to Scn1Lab knockouts and disappear when introducing human SCN1A mRNA. Besides the behavioral phenotype, Scn1Lab knockouts show sudden, electrical discharges in the brain that indicate epileptic seizures in zebrafish. Scn1Lab knockouts showed increased sensitivity to the convulsant pentylenetetrazole and a reduction in whole organism GABA levels. Drug screenings further validated a Dravet syndrome phenotype. We tested the NaV1.1 activator AA43279 and our newly synthesized NaV1.6 inhibitors MV1369 and MV1312 in the Scn1Lab knockouts. Both type of compounds significantly reduced the number of burst movements. Our results show that selective inhibition of NaV1.6 could be just as efficient as selective activation of NaV1.1 and these approaches could prove to be novel potential treatment strategies for Dravet syndrome and other (genetic) epilepsies. Compounds tested in zebrafish however, should always be further validated in other model systems, preferably human derived.

genetics↗