Worm Breeder's Gazette 14(3): 37 (June 1, 1996)

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.

A C. elegans synaptic vesicle amine transporter

Janet Duerr, Angie Duke, Jim Rand

Program in Molecular and Cell Biology Oklahoma Medical Research Foundation Oklahoma City, OK 73104

In mammals, monoamine neurotransmitters (including dopamine,
norepinephrine, epinephrine, and serotonin) are transported into
synaptic vesicles by one of 2 vesicular transporters, designated VMAT1
and VMAT2. These transporters contain 12 transmembrane domains and are
part of a family that also includes the synaptic vesicle acetylcholine
transporters (e.g., the C. elegans UNC-17 protein). The biological
significance of the differences between the two transporters is unclear.
The Genome Sequencing Project recently identified part of a C. elegans
VMAT homolog, and we have now cloned a 2.0 kb cDNA (from Bob Barstead's
LambdaZAP library) which appears to encode a full-length VMAT protein.
The C. elegans homolog has comparable similarity to both of the
mammalian sequences, suggesting that it is likely to be able to
transport dopamine, serotonin, and other putative neurotransmitters,
such as octopamine.
We have prepared antibodies against a peptide derived from a region near
the C-terminus of the VMAT homolog. Antibody staining indicates that the
C. elegans VMAT homolog is primarily localized to synaptic regions of a
subset of neurons. These neurons are (with one clear exception) distinct
from those that are immunopositive for UNC-17 (the acetylcholine
transporter). VMAT-positive cells include the dopamine containing ADE,
CEP, and PDE neurons, the serotonin containing NSM, HSN, and RIH
neurons, some of the cholinergic and FMRFaimde positive VC cells, as
well as a few, still unidentified cells in hermaphrodites, and numerous
cells in the male tail.
Based on map position, the cat-1 gene is the best candidate to be the C.
elgans VMAT homolog. In cat-1 mutants, dopamine (visualized by
formaldehyde-induced fluorescence) and serotonin (visualized by
immunohistochemistry) are no longer localized to neuronal processes, but
are only found in cell bodies. Using our anti-VMAT antibodies, we have
now shown that cat-1(e1111) mutants are completely deficient for
synaptic VMAT immunoreactivity. We now plan to attempt rescue of the
cat-1 mutant phenotype with cloned VMATs.
Supported by research grants from NIH and OCAST.