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Comments on Crowell T et al. (1997) International C. elegans Meeting "ANALYSIS OF C. elegans SYNAPTOTAGMIN (snt-1) MUTANTS REVEALS A SITE REQUIRED FOR PROPER TARGETING" (0)
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Crowell T, Duerr JS, McManus JR, Gaskin J, Duke A, & Rand JB (1997). ANALYSIS OF C. elegans SYNAPTOTAGMIN (snt-1) MUTANTS REVEALS A SITE REQUIRED FOR PROPER TARGETING presented in International C. elegans Meeting. Unpublished information; cite only with author permission.
Synaptotagmin is a major synaptic vesicle protein; it contains 2 apparent calcium-binding (PKC-C2) domains and may be involved in both exocytosis and endocytosis. A large number of mammalian synaptic proteins appear to have specific, high-affinity interactions with different domains of synaptotagmin. The cloningof snt-1 and the isolation of mutants were reported by Nonet et al. (1993). Because C. elegans snt-1 mutants are viable and resistant to cholinesterase inhibitors, it has been relatively easy to identify a large number of alleles. We have now analyzed the molecular, behavioral, and immunocytochemical properties of 17 independent snt-1 mutations. Some of the alleles provide guaranteed molecular null alleles; null mutants are quite uncoordinated, but viable. Analysis of all snt-1 mutants included quantitative behavioral studies (pharyngeal pumping, body thrashing in liquid, and expulsion failure) and immunostaining. Partial gene function was retained by some point mutants, and also by several deletions. Of particular interest was snt-1(md220), an (in-frame) 9-bp deletion which disrupts part of the second C2 domain. Immunocytochemical and Western analyses indicate that the mutant protein is present at approximately the wild-type level, but virtually all of the immunostaining is in the cell bodies, rather than at synapses. Since other synaptic vesicle markers (e.g., UNC-17) are properly localized in snt-1(md220) animals, it appears that this mutation disrupts a site on the synaptotagmin molecule necessary for proper targeting of the protein to synaptic vesicles. This mutant is of interest behaviorally because it has the null phenotype for pharyngeal pumping and body thrashing, but its expulsion failure rate is almost that of wild-type. Expulsion is different from the other behaviors because: a) it is 100-fold less frequent; b) it is mediated by excitatory GABAergic synapses; c) which seem to be located in the cell body of the DVB neuron. (Supported by grants from NINDS and MDA.)
Affiliation:
- Oklahoma Medical Research Foundation, Oklahoma City, OK