Fig. 6. DCas functions with integrins to regulate axon fasciculation during development. (A-E) Dominant (transheterozygous) genetic LOF interactions between DCas and the ß1, 1 or 2 integrin genes (ß1Int, 1Int or 2Int). (A) ISNb axons in ß1 integrin (mys¹) heterozygous embryos (ß1Int/+) innervate muscles 6/7 and 12/13 (open arrows). (B-D) ISNb axons in embryos heterozygous for both ß1 integrin (mys¹) (B), or 1 integrin (mew^M6) (C), or 2 integrin (if^K27E) (D) and DCas^{Df(3L)Exel6083} fail to innervate their muscle targets (arrows), exhibiting increased axonal fasciculation (arrowheads). (E) The percentage of defective ISNb, SNa and CNS pathways in embryos heterozygous for either DCas, ß1Int, 1Int or 2Int, or in embryos heterozygous for both DCas and ß1Int, 1Int or 2Int. (F-H) Expression of one copy of ^MycDCas and one copy of the ELAV-GAL4 pan-neuronal driver results in axon guidance phenotypes that are suppressed by heterozygosity at the ß1 integrin locus. (F) ISNb axon innervation of muscles 6/7 (black arrow) is absent in embryos expressing one copy of ^MycDCas in all neurons in a wild-type background. (G) Normal ISNb axon innervation of muscles 6/7 and 12/13 (open arrows) in an embryo in which one copy of ^MycDCas is expressed in all neurons in combination with heterozygosity at ß1 integrin. (H) The percentage of defective ISNb, SNa and CNS pathways in embryos expressing low levels of neuronal DCas (Neuronal DCas GOF: UAS-^MycDCas/+, ELAV-GAL4/+), in embryos expressing low levels of neuronal DCas that are also heterozygous for DCas LOF (Neuronal DCas GOF; DCas/+: UAS-^MycDCas, ELAV-GAL4/+; DCas^{Df(3L)Exel6083}/+), and in embryos expressing low levels of neuronal DCas that are also heterozygous for ß1 integrin LOF (Neuronal DCas GOF; ß1Int/+: mys¹/+; UAS-^MycDCas, ELAV-GAL4/+). The differences in the percentage of defective guidance phenotypes observed between Neuronal DCas GOF; DCas/+ or Neuronal DCas GOF; ß1Int/+ and Neuronal DCas GOF for each axon pathway are statistically significant (^*, P<0.05; ² test). Scale bar: 15 µm in A-D; 15 µm in F,G.