03-P055 Expression of ROBO1/SRGAP1 and CTIP2 suggests that the motor cortex initially forms at the anterior pole during development of the human foetal neocortex

mechanisms of wing vein formation have been well studied in Drosophila melanogaster, however little is known about if the mechanisms are conserved to develop diversified wing vein patterns among insects. In Drosophila, Dpp, BMP2/4 ortholog, is initially expressed at longitudinal veins and later at crossveins to specify both veins during pupal stages. Using a GFP tagged Dpp, we first addressed how the diffusible Dpp draws elaborate wing vein patterns in Drosophila and demonstrate that the combination of facilitated transport and active retention tightly regulates Dpp diffusion. Dpp diffuses from the longitudinal veins to the prospective posterior crossvein (PCV). BMP binding proteins Sog and Cv actively transport Dpp to PCV. Gbb, BMP5/6/7 ortholog, also diffuses to PCV and is required for Dpp transport suggesting that Dpp/Gbb heterodimer is a primary ligand moved by Sog/Cv complex. Intriguingly Dpp is highly immobilized in the longitudinal veins and its retention is mediated by type I receptor Tkv and unknown positive feedback mechanisms. To understand how complex wing vein patterns develop, we then analyzed the Hymenoptera Athalia rosae (sawfly). We found that BMP signal is detected at prepupal wing veins of sawfly and vein patterns become complex in a way that crossveins are formed later during prepupal stages as Drosophila PCV. Since Drosophila PCV is initially induced by facilitated transport of BMP ligands, we propose that active control of BMP diffusion provides an evolutionary conserved genetic tool kit for drawing diversified wing vein patterns.