Interactions Between Wingless and Frizzled Molecules in Drosophila 7
suggested that the Dsh protein uses different domains to act in the W g or
Fz pathway, with the DEP domain implicated in PP and the PDZ domain
being required for W g signaling (Axelrod et a1. 1998; Boutros et a1.
1998). This would suggest that part of the specificity of Fz vs Wg
signaling in the cell is controlled by Dsh, which may interact differentially with two different receptors. More recent data showing that Fz
itself can also act as a Wg receptor (see below) indicate that the situation
is more complicated.
There are various other genes with PP phenotypes that either act in
parallel to the Fz pathway, or are thought to be involved in signal
transduction downstream of Fz (Fig. 3). In addition to dsh, the small
GTPase RhoA as well as JNK have been implicated in signal transduction. strabismus (stbm)IVan Gogh may act in parallel, as well as prickle
(Pk), dachsous (ds), and inturned (in).
1. 7 Interactions Between W g,
other W g Signaling Components, and Dfz2 in Development
We obtained evidence that Dfz2 can act as a receptor for W g during
development by a dominant-negative approach, i.e., by expressing the
extracellular domain of the Dfz2 protein as a GPI-linked cell surface
protein. The wings of the resulting flies have marked defects in the
margin, which is known to be specified by W g, and in other structures
such as the eyes and the legs. All the phenotypes observed are similar to
loss of W g function, which suggests that the extracellular domain binds
W g and inhibits its function.
Recently, several papers have taken genetic approaches to examine
the loss-of-function phenotype of Dfz2 (Bhat 1998; Kennerdell and
Carthew 1998; Muller et a1. 1999). It was found that Dfz2 by itself is not
required in the Drosophila embryo, but that double mutants betweenfz
and Dfz2 have the same phenotype as wg, showing that these two genes
are genetically redundant.
suggested that the Dsh protein uses different domains to act in the W g or
Fz pathway, with the DEP domain implicated in PP and the PDZ domain
being required for W g signaling (Axelrod et a1. 1998; Boutros et a1.
1998). This would suggest that part of the specificity of Fz vs Wg
signaling in the cell is controlled by Dsh, which may interact differentially with two different receptors. More recent data showing that Fz
itself can also act as a Wg receptor (see below) indicate that the situation
is more complicated.
There are various other genes with PP phenotypes that either act in
parallel to the Fz pathway, or are thought to be involved in signal
transduction downstream of Fz (Fig. 3). In addition to dsh, the small
GTPase RhoA as well as JNK have been implicated in signal transduction. strabismus (stbm)IVan Gogh may act in parallel, as well as prickle
(Pk), dachsous (ds), and inturned (in).
1. 7 Interactions Between W g,
other W g Signaling Components, and Dfz2 in Development
We obtained evidence that Dfz2 can act as a receptor for W g during
development by a dominant-negative approach, i.e., by expressing the
extracellular domain of the Dfz2 protein as a GPI-linked cell surface
protein. The wings of the resulting flies have marked defects in the
margin, which is known to be specified by W g, and in other structures
such as the eyes and the legs. All the phenotypes observed are similar to
loss of W g function, which suggests that the extracellular domain binds
W g and inhibits its function.
Recently, several papers have taken genetic approaches to examine
the loss-of-function phenotype of Dfz2 (Bhat 1998; Kennerdell and
Carthew 1998; Muller et a1. 1999). It was found that Dfz2 by itself is not
required in the Drosophila embryo, but that double mutants betweenfz
and Dfz2 have the same phenotype as wg, showing that these two genes
are genetically redundant.