Epileptic-like convulsions associated with LIS-1 in the cytoskeletal control of neurotransmitter signaling in Caenorhabditis elegans.
Cortical malformations are a collection of disorders affecting brain development. Mutations in the LIS1 gene lead to a disorganized and smooth cerebral cortex caused by failure in neuronal migration. Among the clinical consequences of lissencephaly are mental retardation and intractable epilepsy. It remains unclear whether the seizures result from aberrant neuronal placement, disruption of intrinsic properties of neurons, or both. The nematode Caenorhabditis elegans offers an opportunity to study such convulsions in a simple animal with a defined nervous system. Here we show that convulsions mimicking epilepsy can be induced by a mutation in a C. elegans lis-1 allele (pnm-1), in combination with a chemical antagonist of gamma-aminobutyric acid (GABA) neurotransmitter signaling. Identical convulsions were obtained using C. elegans mutants defective in GABA transmission, whereas none of these mutants or the antagonist alone caused convulsions, indicating a threshold was exceeded in response to this combination. Crosses between pnm-1 and fluorescent marker strains designed to exclusively illuminate either the processes of GABAergic neurons or synaptic vesicles surprisingly showed no deviations in neuronal architecture. Instead, presynaptic defects in GABAergic vesicle distribution were clearly evident and could be phenocopied by RNAi directed against cytoplasmic dynein, a known LIS1 interactor. Furthermore, mutations in UNC-104, a neuronal-specific kinesin, and SNB-1, a synaptic vesicle-associated protein termed synaptobrevin, exhibit similar convulsion phenotypes following chemical induction. Taken together, these studies establish C. elegans as a system to investigate subtle cytoskeletal mechanisms regulating intrinsic neuronal activity and suggest that it may be possible to dissociate the epileptic consequences of lissencephaly from the more phenotypically overt cortical defects associated with neuronal migration.
Williams
Shelli N
SN
Department of Biological Sciences, The University of Alabama, Tuscaloosa, AL 35487-0344, USA.
Locke
Cody J
CJ
Braden
Andrea L
AL
Caldwell
Kim A
KA
Caldwell
Guy A
GA
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects / Q000235:genetics*; D029742:Caenorhabditis elegans Proteins; D018389:Codon, Nonsense / Q000235:genetics; D003599:Cytoskeleton / Q000502:physiology*; D004195:Disease Models, Animal; D004827:Epilepsy / Q000209:etiology* / Q000235:genetics; D018756:GABA Antagonists / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D009474:Neurons / Q000166:cytology; D010433:Pentylenetetrazole / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D012640:Seizures / Q000209:etiology / Q000235:genetics; D016415:Sequence Alignment; D013572:Synaptic Vesicles / Q000378:metabolism; D005680:gamma-Aminobutyric Acid / Q000502:physiology*
D029742:Caenorhabditis elegans Proteins; D018389:Codon, Nonsense; D018756:GABA Antagonists; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; C513193:lis-1 protein, C elegans; D005680:gamma-Aminobutyric Acid; D010433:Pentylenetetrazole