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. Author manuscript; available in PMC: 2008 Feb 13.
Published in final edited form as: Neuron Glia Biol. 2004 May 1;1(2):101–112. doi: 10.1017/s1740925x04000225

Fig. 6.

Fig. 6

Ectopic expression of robo2 does not displace the MP2 axons along lateral longitudinal tracts in the absence of glia. FasII axons are visualised in red at stage 16. The MP2 axons are visualised with anti-GFP (green) by the expression of 15J2/UASGAPGFP in multiple genotypes (A-D). Colocalisation of GFP and FasII is seen in yellow. Ectopic expression of robo2 with 15J2/UASrobo2-myc, visualised with anti-Myc (green) antibodies in embryos of different genotypes (E-H). Colocalisation of Myc and FasII is seen in yellow. (A) Wild-type. The MP2 axons run parallel to the midline along the medial FasII fascicle at this stage (arrowheads, 15J2/UASGAPGFP). (E) When expression of robo2 is driven ectopically in the MP2 axons, their trajectories are displaced to the central fascicle (arrowheads, 15J2/UASRobo2myc). (B) In gcm-mutant embryos, the MP2 axons still run along the medial fascicle (arrowheads, gcmΔP1/gcmΔP1; 15J2/UASGAPGFP). (F) When robo2 is expressed ectopically in the MP2 neurons in gcm mutants (gcmΔP1/gcmΔP1; 15J2/UASrobo2myc), the MP2 axons stay within the fused, single fascicle (arrowheads). This gcm-mutant embryo is phenotypically more severe than in B, where the fasicles are defasciculated but not fused. (C) In robo1 mutants, the MP2 axons run on the medial fascicle, collapsed along the midline (arrowheads, robo1/robo1; 15J2/UASGAPGFP). (G) Expression of robo2 in the MP2 axons in robo1 mutants (robo1/robo1; 15J2/UASrobo2myc) displaces the MP2 axons laterally onto the central fascicle (arrowheads). (D) gcm-robo1 double mutant with midline collapse of the longitudinal fascicles, in which the MP2 axons run along the midline (arrowheads, gcmΔP1 robo/gcmΔP1 robo; 15J2/UASGAPGFP). (H) gcm-robo1 double mutant embryo with midline collapse of the longitudinal fascicles, expressing robo2 in the MP2 axons (gcmΔP1 robo1/gcmΔP1 robo1; 15J2/UASrobo2myc): the MP2 axons leave the CNS and extend towards the periphery (empty arrowheads) or they do not grow at all (white arrowheads). There are no MP2 axons projecting longitudinally in these embryos. Anterior is up.