Genetic screens for Caenorhabditis elegans mutants defective in left/right asymmetric neuronal fate specification.
We describe here the results of genetic screens for Caenorhabditis elegans mutants in which a single neuronal fate decision is inappropriately executed. In wild-type animals, the two morphologically bilaterally symmetric gustatory neurons ASE left (ASEL) and ASE right (ASER) undergo a left/right asymmetric diversification in cell fate, manifested by the differential expression of a class of putative chemoreceptors and neuropeptides. Using single cell-specific gfp reporters and screening through a total of almost 120,000 haploid genomes, we isolated 161 mutants that define at least six different classes of mutant phenotypes in which ASEL/R fate is disrupted. Each mutant phenotypic class encompasses one to nine different complementation groups. Besides many alleles of 10 previously described genes, we have identified at least 16 novel "lsy" genes ("laterally symmetric"). Among mutations in known genes, we retrieved four alleles of the miRNA lsy-6 and a gain-of-function mutation in the 3'-UTR of a target of lsy-6, the cog-1 homeobox gene. Using newly found temperature-sensitive alleles of cog-1, we determined that a bistable feedback loop controlling ASEL vs. ASER fate, of which cog-1 is a component, is only transiently required to initiate but not to maintain ASEL and ASER fate. Taken together, our mutant screens identified a broad catalog of genes whose molecular characterization is expected to provide more insight into the complex genetic architecture of a left/right asymmetric neuronal cell fate decision.
Sarin
Sumeet
S
Howard Hughes Medical Institute, Department of Biochemistry and Molecular Biophysics, Columbia University Medical Center, 701 W. 168th Street, New York, NY 10032, USA.
O'Meara
M Maggie
MM
Flowers
Eileen B
EB
Antonio
Celia
C
Poole
Richard J
RJ
Didiano
Dominic
D
Johnston
Robert J
RJ
Chang
Sarah
S
Narula
Surinder
S
Hobert
Oliver
O
D000483:Alleles; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics; D017173:Caenorhabditis elegans / Q000166:cytology / Q000235:genetics* / Q000254:growth & development*; D016923:Cell Death / Q000235:genetics; D002874:Chromosome Mapping; D017931:DNA Primers / Q000235:genetics; D018509:DNA, Helminth / Q000235:genetics; D017238:Genes, Helminth; D005801:Genes, Homeobox; D017930:Genes, Reporter; D007473:Ion Channels / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D009474:Neurons / Q000166:cytology; D010641:Phenotype; D012689:Sequence Homology, Nucleic Acid
D017931:DNA Primers; D018509:DNA, Helminth; D007473:Ion Channels
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