Figure 9. Deletion of JUN increases number of misprojected axons in the Dscam^LOF retina.

A-E, Wild type and mutant genotypes. Dscam and Jun were conditionally deleted using Six3-Cre. F, Quantification of axon misprojection. A significant increase in misprojected axons was detected in all genotypes compared to wild type. An increase in the number of misprojecting axons was detected in the Bax mutant retina compared to Dscam^LOF retinas. A significant increase in the number of misprojecting axons was detected in the Dscam/Jun double mutant retina compared to all other genotypes. G-I, Dscam loss-of-function dendrite clustering phenotype of TH-positive dopaminergic amacrine (DA) cells in the IPL was still observed in the absence of Jun. N=4 (4 retinas). K-P, Nearest neighbor analysis of DA cells was performed in wild type, Dscam^LOF and Dscam/Jun (DKO) mutant retinas. Nearest neighbor index (NNI) values reflect the degree of spacing compared to the most optimal space-filling model, that is a hexagonal organization. Nearest neighbor ratio (NNR) values control for cell density by dividing the actual NNI by the random NNI, generated by randomly distributing a like number of cells averaged over 500 trials. K, Wild type NNI values were significantly increased compared to random simulations (Student's t-test p-value <0.001), indicating a greater degree of spatial organization compared to a random distribution. L, Dscam^LOF DA cell NNI values were significantly decreased compared to random (Student's t-test p-value <0.03). M, DA cells in the Dscam/Jun DKO mutant mice had a significantly lower NNI values compared to controls (Student's t-test p-value <0.01). N, Comparison of NNI values across genotypes. NNI values were significantly increased in wild type compared to single or double mutants (Student's t-test p-value <0.001), while no significant difference was observed comparing Dscam and Dscam/Jun NNI values. O, No significant differences in NNI values were detected when comparing the random simulation of density-matched spacing for each genotype. P, Nearest neighbor ratio (NNR) values, which normalize for cell density, were significantly different comparing wild type to either mutant genotypes (Student's t-test p-value <0.001), but the Dscam^LOF and DKO NNR values were not significantly different from each other. N≥4. P-values for axon misprojection phenotype are listed in Table 1. Scale bar (in A) A-G = 50 μm.