Worm Breeder's Gazette 15(2): 20 (February 1, 1998)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Expression patterns of candidate serotonin receptors

Timothy Niacaris, Leon Avery

UT Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75235-9148

Serotonin increases the rate of pharyngeal pumping and egg laying,
decreases foraging behavior and is required for proper male mating
behavior.  Serotonin can influence pharyngeal pumping rate by
stimulating MC, a motor neuron which stimulates pharyngeal muscle
contraction, or by acting directly on pharyngeal muscle.  To determine
the receptor or receptors that mediate this response, we have searched
the genomic sequence for candidate genes having sequence identity to
known vertebrate and invertebrate serotonin receptors.  We found seven
candidate genes using this method: C02D4.2, C09B7.1, C52B11.3, F01E11.5,
F14D12.6, F59C12.2 and M03F4.3.  Two of these genes (F59C12.2 and
M03F4.3) were previously identified as possible serotonin receptor
candidates (Ribeiro and Hamdan IWM97, p278.)  We were not able to
distinguish octopamine receptors from metabotropic serotonin receptors
based on sequence.  In addition, there are no sequences in the C.
elegans database with significant similarity to the ionotropic serotonin
receptor subclass, 5-HT3.
We have created GFP fusion constructs of four of the candidate genes
(C02D4.2, F01E11.5, F14D12.6 and F59C12.2) using overlap extension PCR. 
We directly injected these PCR products into worms to determine GFP
expression patterns.  F01E11.5 and F14D12.6 show limited expression
outside the pharynx.  The F01E11.5 construct expresses in a few
unidentified neurons of the head, while F14D12.6 expression is most
pronounced in the spermatheca of the adult. Two of the genes, C02D4.2
and F59C12.2, show pharyngeal expression of the fusion construct.
F59C12.2 shows nearly ubiquitous pharyngeal and extrapharyngeal
staining. C02D4.2 pharyngeal muscle expression is specific for the
metastomal flap muscles, pm1, and the anterior terminal bulb muscles,
pm6. The C02D4.2 construct also expresses in muscles of the head, the
pharyngeal serotonergic neuron NSM, the ventral nerve cord and
unidentified neurons in the nerve ring, head and tail regions. In males,
C02D4.2 expresses in dorsal and ventral body muscles of the tail region.
The construct also expresses in the male-specific diagonal muscles and
serotonergic CP neurons.  The expression pattern of C02D4.2 appears to
be consistent with several known effects of serotonin. We are currently
working to knock out both C02D4.2 and F59C12.2 using PCR detection of
EMS-induced deletions of these genes.