In this issue of WBG our colleagues have reported that the
dpy-20 gene expresses in the ventral cord neurons and hypodermal cells during larval development (M.Y. Ali, Z. K. Siddiqui, D. Janke, D. Baillie, and S. S. Siddiqui). It has been suggested that the
dpy-20 encoded gene may function as a novel transcription regulator in motor neurons (See Fukushige and Siddiqui, 1995, and the abstracts by Ali et al., in this issue of WBG) To study the function of
dpy-20 gene (Hosono et al.,1982; Clark et al.,1995),
dpy-20::lacZ in different mutants background were constructed including those mutants that harbor defects in the ventral cord development. For example, we have constructed
dpy-20::lacZ in
unc-5(
e53) background. The mutant
unc-5(
e53) animals are severe coilers during larval and adult stages (Brenner, 1973, 1974). In
unc-5 mutants the hypodermal cells are defective, and animals lack the dorsal nerve cord, as seen at the ultrastructural level. The neuronal commissures(axonal processes) fail to reach target from ventrally located neuronal cell bodies to their synaptic targets in the dorsal region, such as the dorsal cord(Siddiqui, 1990; Hedgecock et al., 1990; Leung-Hagesteijn et al,1992, Hamelin et al.,1993). The
unc-5::lacZ fusion gene is expressed in the motor neuron cell bodies in the ventral cord, their axonal processes along the ventral cord, dorsally directed commissures, and their synaptic targets in the dorsal cord. The
unc-5::lacZ fusion gene is also expressed in the lateral cords, that run from anterior to the posterior along the entire body length. The fusion gene expression is seen during all larval and adult stages animals(Hamelin et al.,1993). The expresion of
dpy-20::lacZ reporter gene staining pattern does not change when the
dpy-20::lacZ is expressed in the
unc-5 mutant backgound, but when the
unc-5::lacZ reporter gene is expressed in the
dpy-20(
e2017) mutant background; staining in the motor neurons,lateral cords, dorsal cord and the dorsally directed commissures is reduced. In the
dpy-20 mutant background most of the animals do not show the staining in the commissures in the L3,L4 and young adult stages animals. But in the adult animals reduced staining is seen in the commissures that run from ventral cord to dorsal cord. These results suggest that the
dpy-20 gene may regulate the expression of
unc-5, whereas the
unc-5 gene may not affect the expression of the
dpy-20 gene. To test this, we have constructed a double mutant between
unc-5(
e53) and
dpy-20(
e2017, which is severely paralyzed and has very low brood size, suggesting strong genetic interaction between the
dpy-20 and
unc-5 genes. Whether this intercation is at the level of hypodermal cells or motor neurons, or the germ line is not known. We have also expressed the
dpy-20:: lacZ gene in the background of
unc-25(
e156) (Thomas 1990;McIntire et al., 1993; Reiner and Thomas 1995 and
unc-30(
e191(McIntire et al., 1993; Jin et al 1994)). Both of these genes affect locomotion as they are expressed in the motor neurons. Interestingly, we find that the
dpy-20::lacZ reporter gene in the
unc-25 and
unc-30 mutant background ectopically expresses in a few hypodermal cells in adult stage animals (in wild type background this expression is never observed). The pattern of
dpy-20 gene expression is unaffected during larval development in mutant background. A double mutant between
dpy-20(
e2017) and
unc-25(
e156) is severely paralyzed and has a very low brood size, producing sick animals of which 95% are sterile.
unc-25 gene expresses in all GABAergic neurons, including the VD 1-6, and DD 1-13, class of motor neurons.
unc-30 gene encodes a 318 aa transcription factor like protein that contains homeodomain motif and show similarity to the
unc-4 homeodomain protein(Jin et al.,1994). Anti beta tubulin antibodies and
unc-30 antibodies stain VD and DD classes of motor neurons(Jin et al., 1994, Siddiqui,1990). Both the
unc-25(
e156) and
unc-30(
e191) mutants are small in size, shrink, contract both dorsally and ventrally when touched, move slowly, normal forward locomotion but have difficulty in backing up. We also tested the
dpy-20::lacZ reporter gene in the
unc-4(
e120) (White et al 1992; Miller et al 1992),
unc-13(
e51) (Brenner 1974; Ahmed et al 1992; Nguyen et al. 1995),
unc-86(
e1416) (Chalfie et al. 1981; Finney et al.1988; Baumeister et al. 1996), and
unc-104(
rh1016*10)(Otsuka et al., 1991) mutant backgrounds and found no significant effect on the
dpy-20 expression pattern. Double mutants
dpy-20(
e2017);
unc-13(
e47);
dpy20(e2017);
unc-86(
e1416); and
dpy20(e2017);
unc-104(
rh1016*10) are severely paralyzed and have very low brood size. Most of the animals are sterile and some animals end up as a bag of worms. Since the
dpy-20 gene also expresses in hypodermal cells, we are examining the
dpy-20 gene expression in various mutants affected in hypodrmal development, including those encoding molecules that are known to play a role in signal transduction pathway. We thank T. Stiernagle, M. Chalfie, M. Hamelin, J. Culotti, A. Otsuka, Y.Kohara, for help in this project