Figure 1.
Reduction in peripheral aborization of the ophthalmic projection from trigeminal ganglia in the Slit2;Slit3 or the Robo1;Robo2 double mutant.
A
,
B
, The ophthalmic projections of the trigeminal ganglion from E12.5 embryos were visualized by neurofilament immunostaining, which revealed the two ophthalmic branches surrounding the eye (*). When compared with its littermate control from the Slit2;Slit3 cross (
B
vs
A
), the top branched structure (arrows) is greatly reduced in the double mutant, whereas the bottom one (arrowheads) remains the same. Because of the variation in the overall growth of the two branched structures even in the same litter, a Slit2
+/−
;Slit3
+/+ is shown here as a littermate control to match the bottom arbor in the double mutant. Scale bars, 50 μm.
C
, The extent of branching in the wild-type or the Slit2;Slit3 mutant animals is quantified by measuring the area occupied by the branched arbors, the number of branching points, or the total branch length. To normalize for slight differences in developmental stages, both are plotted as the ratio of the top arbor versus the bottom one, which appears to follow a normal developmental course in all animals. The ratio of the area, points, or lengths in the wild type is 1.41 ± 0.24, 1.16 ± 0.34, or 1.27 ± 0.22, respectively, whereas the ratio in the mutant is 0.69 ± 0.30, 0.61 ± 0.36, or 0.56 ± 0.23, respectively.
D
,
E
, The ophthalmic projections from the Robo1;Robo2 cross are stained with neurofilament antibodies as in
A
and
B
. The embryos shown here are slightly younger than those in
A
and
B
to illustrate the requirement of Robo signaling in early branch formation. Scale bars, 500 μm.
F
, Quantification of the difference in Robo1;Robo2 animals as in
C
. The ratio of branching area, points, or length drops from 1.94 ± 0.26, 1.42 ± 0.22, or 1.57 ± 0.28 in the wild type to 0.79 ± 0.22, 0.59 ± 0.11, or 0.71 ± 0.21 in the mutant, respectively.