Graded ephrin-A2 expression in the developing hamster superior colliculus

During development, ephrin gradients guide retinal ganglion cell axons to their appropriate topographic locations in the superior colliculus (SC). Expression of ephrin-A2, assessed immunohistochemically in the developing hamster SC, revealed a rostrallow to caudalhigh gradient that is most prominent at postnatal days (P)4 and P7 when topography is established. Double-labelling immunohistochemistry for ephrin-A2 and cell speciWc markers revealed that ephrin-A2 is expressed exclusively by a subset of neurons. The expression pattern has implications for mechanisms underlying establishment of topography during development and following injury.