PT  - JOURNAL ARTICLE
AU  - Holger Apitz
AU  - Iris Salecker
TI  - Spatio-temporal relays control layer specificity of motion-direction sensitive neurons in <em>Drosophila</em>
AID  - 10.1101/262451
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 262451
4099  - http://biorxiv.org/content/early/2018/02/10/262451.short
4100  - http://biorxiv.org/content/early/2018/02/10/262451.full
AB  - Visual motion detection in sighted animals is essential to guide behavioral actions ensuring their survival. In Drosophila, motion direction is first detected by T4/T5 neurons. Their axons innervate four lobula plate layers tuned to the four cardinal motion directions. How T4/T5 neurons with layer-specific representation of motion-direction preferences are specified during development is unknown. We show that diffusible Wingless (Wg) between adjacent neuroepithelia induces its own expression to form secondary signaling centers. These activate decapentaplegic (dpp) in apposing tertiary domains dedicated to producing layer 3/4-specific T4/T5 neurons. In the absence of Dpp signaling, T4/T5 neurons adopt the default layer 1/2 fate. Dpp signaling induces the expression of the T-box transcription factor Optomotor-blind (Omb), serving as a relay to postmitotic neurons. Omb-mediated repression of Dachshund transforms layer 1/2- into layer 3/4-specific neurons. Hence, spatio-temporal relay mechanisms, bridging the distances between neuroepithelial domains and their postmitotic progeny, implement T4/T5 neuron layer-specificity.