Differentially expressed Drl and Drl-2 play opposing roles in Wnt5 signaling during Drosophila olfactory system development.
In Drosophila, odor information received by olfactory receptor neurons (ORNs) is processed by glomeruli, which are organized in a stereotypic manner in the antennal lobe (AL). This glomerular organization is regulated by Wnt5 signaling. In the embryonic CNS, Wnt5 signaling is transduced by the Drl receptor, a member of the Ryk family. During development of the olfactory system, however, it is antagonized by Drl. Here, we identify Drl-2 as a receptor mediating Wnt5 signaling. Drl is found in the neurites of brain cells in the AL and specific glia, whereas Drl-2 is predominantly found in subsets of growing ORN axons. A drl-2 mutation produces only mild deficits in glomerular patterning, but when it is combined with a drl mutation, the phenotype is exacerbated and more closely resembles the Wnt5 phenotype. Wnt5 overexpression in ORNs induces aberrant glomeruli positioning. This phenotype is ameliorated in the drl-2 mutant background, indicating that Drl-2 mediates Wnt5 signaling. In contrast, forced expression of Drl-2 in the glia of drl mutants rescues the glomerular phenotype caused by the loss of antagonistic Drl function. Therefore, Drl-2 can also antagonize Wnt5 signaling. Additionally, our genetic data suggest that Drl localized to developing glomeruli mediates Wnt5 signaling. Thus, these two members of the Ryk family are capable of carrying out a similar molecular function, but they can play opposing roles in Wnt5 signaling, depending on the type of cells in which they are expressed. These molecules work cooperatively to establish the olfactory circuitry in Drosophila.
Laboratory for Neural Network Development, RIKEN Center for Developmental Biology, Hyogo 650-0047, Japan.
Masao
M
Sakurai
Tomoko
T
Aoki
Shingo
S
Yoshikawa
Linda A
LA
Santschi
Hiroko
H
Saito
Keita
K
Endo
Kyoko
K
Ishikawa
Ken-ichi
K
Kimura
Kei
K
Ito
John B
JB
Thomas
Chihiro
C
Hama
D000818:Animals; D030801:Animals, Genetically Modified; D004330:Drosophila; D029721:Drosophila Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology*; D009154:Mutation; D009457:Neuroglia / Q000378:metabolism / Q000502:physiology; D009833:Olfactory Pathways / Q000254:growth & development*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D012903:Smell / Q000502:physiology*; D051153:Wnt Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
D029721:Drosophila Proteins; D011518:Proto-Oncogene Proteins; D051153:Wnt Proteins; C491438:Wnt5 protein, Drosophila; C094492:DRL protein, Drosophila; D020794:Receptor Protein-Tyrosine Kinases