Figure 5
Axonal projection pattern of dI2 neurons. (A, B) Chick embryos were electroporated at stage 16 with three plasmids: dI1/2::Cre, dI2/V1::Gal4 and UAS::LoxP-STOP-LoxP-GFP. The schematic (B) illustrates the axonal projection pattern of the dI2 neuronal population. At the sacral and lumbar levels on the contra-lateral side, dI2caud axons turn caudally (A, A1, magenta arrows). At the caudal thoracic level of the contra-lateral side a crisscross pattern of axons turning either rostrally or caudally is apparent (A, A2, A3, white and magenta crossed arrows). At the rostral thoracic level, and the cervical level, dI2rost axons turn rostrally (A, A4, white arrows). Along the entire longitudinal axis, dI2 axons initially form a fascicle at the contra-lateral ventral funiculus (VF; arrowheads in A, A1, A2) and subsequently axons are deflected to the lateral funiculus (LF; A, A4). At the ipsi-lateral side only few axons project longitudinally (A5, yellow arrow). Most of the axons grow toward the floor plate (A, A6). c, cervical level; b, brachial level; FP, floor plate; l, lumbar level, s, sacral level; t, thoracic level. Asterisks represent the level of the limbs. Scale bar: 150 μm (A); 75 μm (A1, A2, A4, A6); 35 μm (A3, A5).