Worm Breeder's Gazette 10(1): 45

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Genes influencing Acetylcholine Levels

R. Hosono and T. Sassa

Mutation in the unc-17 region of the cha-1 
or choline levels, but causes abnormal 
accumulation of acetylcholine (ACh)(1).  To further clarify the 
related genes, we isolated spontaneous mutants resistant to 
trichlorfon using mutator strains.  Of twenty resistants, five 
mutations were assigned to the unc-13(cn490), 355), 
347), 146) and unc-10(cn257) 
genes.  Another mutation, cn252 was 2.5% distant to the right from dpy-
11(V) but complements near by the gene unc-42 allele e270.  The 
mutation was therefore tentatively denoted as tcf-1.  In addition to 
resistance to acetylcholinesterase inhibitors, all mutants exhibited 
abnormal movement.  These mutations are classified into two groups 
based on ACh levels: those with normal ACh levels (unc-10 and unc-13 
mutations) and those with abnormally high ACh levels (unc-13, 
d unc-18 mutations).  Mutations in the latter 
gene groups also exhibited growth retardation and small body size in 
adulthood.  We are especially interested in the latter group for 
elucidating mechanism of synaptic transmission of ACh.
Three mutations, unc-13(cn490), tcf-1(cn252) and unc-18(cn347) 
frequently reverted to wild-type phenotype, indicating mutations were 
induced by insertion of Tc1.  Of the isolates, the unc-18(cn347) 
mutation showed the most severely paralyzed phenotype and the highest 
ACh levels.  No double mutants were detected between unc-17(e245) and 
unc-18(cn347), suggesting the important contribution to the survival.  
Southern blotting of the BglII restriction digestion revealed one 
extra band 6.8 kb, unique to the unc-18(cn347) mutant DNA.  Cloning of 
this fragment is currently in progress.
We thank Drs. P.  Anderson, B.  Waterston, D.  Moerman and Miss I.  
Mori for giving us mutator strains and valuable advice.  We want to 
thank Drs. A.  Levitt and S.  Emmons for giving us Tc1.  We are also 
grateful to Dr. J.  Rand for information on other trichlorfon 
resistant genes that were already mapped as Unc mutants.