Fetuin in neurons of the retina and cerebellum during fetal and postnatal development of the rat

Although long known to be a liver-derived fetal plasma glycoprotein, fetuin has more recently been shown to be present in sub-populations of neurons i n the developing nervous system of a number of mammalian species. We have e xtended these observations to examine the fetuin immunoreactivity (IR) in d eveloping rat retina and cerebellum. Fetuin-IR was first seen in the retina on embryonic day (E) 19 in a sub-population of cells in the retinal gangli on cell layer and a small proportion of cells in the neuroblastic layer. Th e proportion of cells in the ganglion layer exhibiting fetuin-IR increased until postnatal day (P)10 when all cells in this layer were strongly immuno reactive. From P14 onwards fetuin-IR was absent or very weak and restricted to a small proportion of ganglion cells. In the developing cerebellum, the outer and inner granule cell layers, the deep nuclei and cells in the sub- cortical white matter exhibited fetuin-IR from E19 to P10. There was little fetuin-IR in the cerebellum at ages P14 and older, and Purkinje cells did not exhibit fetuin-IR at any lime. The results show that fetuin appears in many neurons in the retina and cerebellum that are differentiating during t he period from E19 to P10. The concentration of fetuin in cerebrospinal flu id is at its highest in this same period which suggests that some sub-popul ations of neurons could obtain fetuin from extracellular fluid during this period; however, the lack of fetuin-IR in other neuronal populations sugges ts that fetuin uptake is not a general property of developing neurons. (C) 1999 ISDN. Published by Elsevier Science Ltd. All rights reserved.