Proliferation, cell death and reelin expression during development of the retina in a teleost, the common trout (Salmo trutta fario)

We have analysed the spatiotemporal pattern of cell proliferation and apopt osis during the development of the retina in a teleost. Distribution of pro liferating cells in different developmental stages (embryos, alevins, and j uveniles) was analysed with an antibody against proliferating cell nuclear antigen (PCNA). After establishment of the retinal lamination, PCNA-immunor eactive (PCNA-ir) cells were frequently observed in all cell layers, with a high majority of proliferating cells located at the marginal (growing) ret ina. Clusters of PCNA-ir cells were characteristic of the inner nuclear lay er (INL). The distribution of apoptotic cells was studied by the TUNEL meth od, which has revealed significant cell death before completion of the reti nal lamination. We have also used an antibody against Reelin (RELN) as a ma rker for retinal cells that secrete this glycoprotein to the extracellular space. The pattern of RELN expression, as well as that of proliferating and dying cells was very similar to that described in tetrapods, suggesting th at this protein regulates the cell migration and synaptogenesis in the diff erent developmental stages of the retina.