FIGURE 2. Arborization and mosaic patterning of dopaminergic amacrine cells in control and Dscam^-/- retinas.

a, A wild-type P6 retina stained with anti-TH. Dopaminergic amacrine cell processes have little proximal contact and rarely self-cross. b, DRP analysis of cell-body spacing identified an exclusion zone surrounding dopaminergic neurons in wild-type retinas. c, A P6 Dscam^-/- retina stained with anti-TH. Individual dopaminergic amacrine cells frequently self-cross. Error bars in all figures represent s.d. d, DRP analysis of Dscam^-/- dopaminergic amacrine cells indicates normal soma spacing at P6. e, f, Representative isolated P6 wild-type (e) and Dscam^-/- (f) dopaminergic amacrine cells are shown; insets contain traces of the neurites. g–j, Analysis of 20 isolated dopaminergic amacrine neurons from either wild-type or Dscam^-/- retinas. g, No significant difference in the total neurite length was observed between wild-type and Dscam^-/- neurons (t-test, P = 0.55). h, Similarly, no significant difference in neurite branches per unit length was observed (P = 0.38). i, j, A significant increase in the number of self-crossings per length of neurite (i) or per number of branches (j) was observed for the Dscam^-/- neurons over controls (P = 0.003 and 0.015, respectively). k–n, Whole adult (6–8 weeks) wild-type (k, l) or Dscam^-/- (m, n) retinas stained with anti-TH. TH-positive neurite fascicles run throughout the Dscam^-/- retina (m) in contrast to the wild-type retina (k), in which neurites arborize evenly. l, DRP analysis indicates that dopaminergic amacrine cells in the adult wild-type retina maintain and expand their mosaic spacing and exclusion zones. n, DRP analysis of adult Dscam^-/- retinas indicates aggregation of dopaminergic amacrine neurons. o, Schematic of arborization and mosaic formation in wild-type (left) and Dscam^-/- (right) retinas. At P6, both wild-type and Dscam^-/- dopaminergic amacrine cells are organized in a mosaic pattern; however, wild-type neurites arborize, whereas Dscam^-/- neurites self-cross. By P10, wild-type dopaminergic amacrine cells have an increased exclusion zone, whereas Dscam^-/- dopaminergic amacrine neurons aggregate along bundled fascicles. Scale bars: a, c, e, f, 133 m; k, m, 388 m.