Fig. 3

Central and peripheral motor neuron axon guidance defects in mutant olf413^SG1.1, olf413^MI02014 and trans-heterozygotes olf413^SG1.1/olf413^MI02014 embryos. A and B The bright field images of lethal embryos of olf413^SG1.1 and olf413^MI02014 homozygotes respectively showing the mouth hook (MH) and trachea (TR) completely formed (green arrows). C–S Embryos at stage 16–17 stained with Anti-Fasciclin II antibody (mAB-1D4) to label the axonal tracts of both ventral nerve cord and peripheral nerves. C and D are the Oregon-K embryos of stage 16–17, showing the wild type VNC and the peripheral motor nerves (PMN) respectively. The inter-segmental nerve (ISN) and segmental nerve (SN) are marked with white arrows. E–I Represent the VNC and the PMN of olf413^SG1.1 homozygotes. E Most severe VNC and PNS deformities. F and G Moderate phenotype with axonal growth defect in VNC, disrupted and misrouted PMN. H Midline crossing of longitudinal tracts. E’–H’ Enlarged view of marked region in (E–H). I Lateral view of peripheral projection nerves showing different growth and pathfinding defects. J–N Represent the VNC and PMN of olf413^MI02014 homozygotes. J–M Most severe VNC and PNS deformities. J’–M’ Enlarged view of marked region in (J–M). N Lateral view of peripheral projection nerves showing severe growth and pathfinding defects. O–S Represent the VNC and PMN of olf413^SG1.1/olf413^MI02014 transheterozygotes. O Most severe VNC and PNS deformities. P and Q moderate growth and pathfinding defects. R Mid line crossing of longitudinal tracts. O’–R’ Enlarged view of marked region in (O–R). S Lateral view of peripheral projection nerves showing different growth and pathfinding defects. In all figures, arrows indicate breaks in VNC (red), axonal thinning and growth defect (purple), disordered or misrouted axons evading segmental boundaries (blue), and midline crossing of the longitudinal tracts (yellow). The peripheral motor projection defects are indicated by arrowheads- premature termination of growth, asterisks- fusion or fasciculation of ISN and SN into one nerve, rhomboid- excessive or abnormal branching of axons, star- misrouting of axons extending across the segmental boundaries, where the ISN of one segment fasciculate with the nearby ISN segment, and white arrow- de-fasciculation or branching at the ends of ISN. In the images showing VNC, the embryos are positioned with anterior to the top, whereas for the embryos showing PMN, they are positioned with anterior to the left. Scale bar represents 50 μm