Worm Breeder's Gazette 13(5): 87 (February 1, 1995)

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.

The dpy-20 Gene Suppresses Expression of tba-1 (alpha-1) Tubulin Gene In a Set of Ventral Cord Excitatory Motor Neurons in C. elegans.

T. Fukushige1,2, S. S. Siddiqui1

1 Lab. of Molecular Biology, Toyohashi University of Technology, Toyohashi 441, Japan.
2 Present address: Dept of Medical Biochemistry. University of Calgary Medical School, Calgary, Alberta, Canada

DNA transformation is a widely used technique in C. elegans,
but little is known about the effect of cotransformation
markers on the pattern of gene expression in transgenic
animals. We have examined the effect of cotransformation
markers dpy-20 and rol-6 on the expression of tba-l::lacZ
alpha-1 tubulin fusion gene in germline transformants.
Cellular specificity of the fusion gene expression was
found to be very different, depending on the cotransformation
marker used. In case of the rol-6, the tubulin fusion gene
expressed in neurons in the head and tail ganglia and a set
of 38-39 excitatory motor neurons in the ventral cord along
the body length of the animal, which we have identified
as the set of DA, DB, VA, and VB neurons. In contrast, for
the dpy-20 marker system, not only fewer neurons were stained
in the head and tail ganglia, but the staining of motor neurons
in the ventral cord was dramatically reduced both in their
number and intensity. This down regulation of the fusion
gene expression in motor neurons was observed, irrespective
of the orientation of the dpy-20 chromosomal arrays whether
in cis or trans. The dpy-20 arrays in trans configuration
to the rol-6 and and tba-l::lacZ tubulin fusion gene arrays
in the dpy-20(e2017) background was obtained as follows.
Males from a dpy-20(e2017) transgenic culture, carrying
the dpy-20 marker in extra-chromosomal arrays (phenotypically
Wild Type), were mated with hermaphrodites carrying the
tba-l::lacZ/rol-6 arrays (phenotypically Rollers).
In the crossed progeny, many roller lines were selected
and individually cloned to produce progeny. Among these,
transgenic lines were identified that segregated rollers
and dumpy animals (in a non-Mendelian ratio), suggesting
that these lines carried the d*Y-20 and the rol-6 extrachromosomal
arrays in the dpy-20(e2017) mutant background. Since
these lines segregated roller and dumpy progeny independent
of each other, clearly the two arrays (dpy-20 and rol-6)
were not integrated in one extrachromosomal array in these
animals. Histochemical staining of these animals revealed
that dpy-20 marker suppressed the alpha tubulin fusion
gene expresion in both the cis and trans orientations.
In controls, where no cotransformation marker was used,
the fusion gene expression closely resembled that of the
rol-6 marker system. Similar suppression results were
observed when the tba-2::lacZ alpha-2 tubulin fusion
gene was used in the two systems. Whether the observed suppression
is caused by an overexpression of the dpy-20 gene product,
or due to the presence of a DNA sequence (e.g. in the promoter
region of the dpy-20 gene) that inhibits the alpha tubulin
expression in motor neurons (such as by titrating a specific
transcription factor), remains to be seen. We thank D.
Suleman, D. Baillie, J. Kramer. H. Yasuda, and A. Fire for
gene markers and suggestions.