Topographic map in Isl2/EphA3 knockin mice. (A) Distribution of the EphA receptors in the retina of wild-type (left), heterozygous (center), and homozygous (right) knockins. (B) Results of anterograde tracing of axons after temporal, central, and nasal injections for these three animals adopted with slight modifications from . In homozygous knockins (ki/ki, right column) the map is doubled for all three retinal locations. In heterozygous knockins (ki/+, central column) the map is doubled after nasal and central injection, but is single-valued after temporal injection (dashed circle).