Fig. 4. kra and shot synergistically interact to affect CNS
midline repulsion. (A-K) The CNS of embryos stained with mAb 1D4
(anti-Fasciclin II). (A-C) Early stage 13 embryos. (D-K) Stage 16-17 embryos.
(A-I) Both kra and shot are required for midline axon
repulsion. (A) In wild-type embryos, the pCC axon extends anteriorly and
slightly away from the midline (arrow). (B,C) In
kra1/kra2 (B) and
shot3/shot3 (C) mutant embryos, the pCC axon
abnormally crosses the midline (arrows). (D) The Fas II-positive axons show
three parallel longitudinal pathways on each side of the midline in wild-type
embryos. (E,G) The innermost pathway ectopically crosses the midline in
kra1/kra2 (E) and
shot3/shot3 (G) mutants. (F) The
kra1/kra2 mutant phenotype is rescued
by expressing the UAS-HA-KraWT transgene in all
neurons. (H,I) The indicated transgenes are expressed in all neurons in
shot3 as described
(Lee and Kolodziej, 2002b).
(H) The midline phenotype of shot is rescued by the
UAS-Shot L(A)-
GAS2-GFP transgene. (I) The
UAS-Shot L(C)-GFP transgene fails to rescue the midline
phenotype of shot. (J,K) Heterozygosity for kra and
shot enhances the phenotypes of the shot and kra
homozygotes, respectively, resulting in multiple crossing defects in
shot3/+; kra1/kra2
(J) and shot3/shot3;
kra2/+ (K) embryos. Anterior is to the top. (L)
Quantification of midline crossing defects per segments in each of the
indicated genotypes (wild-type, n=60 segments;
shot3/+; kra2/+, n=240;
kra1/kra2, n=504;
C155-GAL4/+;
kra1,UAS-HA-kraWT/kra2,
n=440; shot3/shot3, n=272;
shot3,1407-GAL4/shot3;
UAS-Shot L(A)-GFP/+, n=192;
shot3,1407-GAL4/shot3,UAS-Shot
L(A)-GAS2-GFP, n=264;
shot3,1407-GAL4/shot3,UAS-Shot
L(A)- EF-GFP, n=640;
shot3,1407-GAL4/shot3,UAS-Shot
L(C)-GFP, n=816; shot3/+;
kra1/kra2, n=184;
shot3/shot3;
kra2/+, n=120;
shot3/shot3;
kra1/kra2, n=298). Statistically
significant differences, as determined by Student's t-test, are
denoted by an asterisk (control, wild-type; P<0.001), double
asterisk (control, kra1/kra2;
P<0.017) or triple asterisk (control,
shot3/shot3; P<0.001).
Scale bar: 10 µm.