Molecular Genetics of Nematode Development and Behavior 
from the inductive signal that instructs the 2° 
cells to be 2° and not other types of cells. The 
lin-18 gene must be involved in the response to 
this signal. 
In another project, we have been analyzing the 
function of the nematode homologues of signal 
transduction molecules identified in mammals. 
-We have cloned a nematode gene similar to the 
raf-1 protein kinase as well as four nematode 
genes similar to mammalian G protein a-subunit 
genes. We have placed these on the C. elegans 
genomic map. To identify the cells expressing 
these genes, we have constructed chimeric genes 
consisting of their transcriptional control regions 
linked to a reporter gene. We then introduced the 
engineered genes back into the nematode by mi- 
croinjection of DNA to create transgenic nema- 
todes. All four G protein genes are expressed pri- 
marily in neurons, including neurons in the male 
tail. We plan to engineer poisonous forms of 
these genes to disrupt their function in intact 
animals. 
A G protein a-subunit gene expressed in a sensory neuron of a male spicule o/ Caenorhabditis 
elegans. The cell body is seen as a large round blue spot, and the dendrite as blue inside the yellow 
spicule. 
Research of Paul Sternberg; photograph by Jane Mendel. 
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