Molecular Genetics of Nematode Development and Behavior 
least one of the two spicule sensory neurons are 
necessary for spicule insertion. 
The establishment of cellular asymmetry is a fun- 
damental yet relatively unexplored aspect of cell reg- 
ulation. We have begun to study this problem in the 
context of the male B lineage, M^hich generates the 
spicules as described above, and in a cell called 
the 2° vulval precursor cell. The lin- 18 gene (cell 
lineage gene 18) is necessary for the asymmetry of 
the 2° vulval precursor cell and is the starting point 
for molecular genetic studies of this problem. We 
have found that the 2° cells will orient posteriorly in 
the animal, unless they receive a signal from the 
developing gonad to orient anteriorly. This signal is 
distinct from the well-characterized signal that in- 
structs these cells to be 2° cells, and not other types 
of cells. 
In a project initiated this year, we are analyzing 
the function of the nematode homologues of sig- 
nal transduction molecules identified in mam- 
mals. We have cloned the nematode gene similar 
to the raf- 1 protein kinase and placed it on the C. 
elegans genomic map. To identify the cells ex- 
pressing G protein genes, we have constructed 
chimeric genes consisting of the transcriptional 
control regions of two G protein a-subunit genes 
linked to a "reporter" gene. We then create trans- 
genic nematodes by introducing the engineered 
genes back into the nematode through microin- 
jection of DNA. Both genes are expressed primar- 
ily in neurons, including neurons in the male tail. 
We plan to use these chimeric genes as markers 
for neuronal types to examine the molecular anat- 
omy of the Cod mutants. 
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