Fig. 7. The lak gene is not required within ACs for dendrite morphogenesis or sublaminar targeting. (A-C) Normal morphology and monostratification of line 220 GFP⁺ ACs situated in wild-type retinas, as revealed by transplantation into non-GFP hosts. (A) Wild-type ACs in a wild-type host. Reconstructions of confocal stacks are shown en face and rotated 40° and 90°. Cell 1 has a symmetrical dendritic field and tightly packed processes, while Cell 2 has a larger, asymmetric dendritic field (note in the 90° rotation that the primary dendrite is already projecting to the left) and sparse, highly branched processes. Both cells are monostratified in the same IPL sublayer (see 90° rotation). (B) Two more monostratified ACs from a different wild type into wild type chimera. (C) A large-field symmetrical AC derived from a lak mutant develops normally in a wild-type host retina. A 90° rotation shows that its arbors are monostratified. (D-F) Projection errors of ACs situated in lak mutant retinas. A wild-type-derived AC in a lak mutant retina (D) projects diffusely into the IPL, resembling the projection errors (arrows) made by lak mutant ACs in mutant retinas (E,F). (G-J) Sections through chimeric retinas, cut perpendicular to the IPL. When the host retina is wild type (G,H), donor-derived GFP⁺ AC processes are confined to specific sublayers (1), regardless of whether the donor is wild type (G) or lak mutant (H). Wild-type ACs in a lak mutant retina (I) show local perturbations of sublaminar targeting, similar to the phenotype of lak-into-lak chimeras (J). Arrow 1, normal stratification; arrow 2, disrupted stratification.