Fetuin expression in the dorsal root ganglia and trigeminal ganglia of perinatal rats.

Fetuin, a fetal plasma glycoprotein, has been shown previously to be present in sub-populations of neurons in the developing central and peripheral nervous system. To gain a more complete description of the time course of the appearance of fetuin during neurogenesis we have examined fetuin immunoreactivity, and the presence of fetuin mRNA, in the developing rat trigeminal and dorsal root ganglia. Fetuin immunoreactivity and its mRNA were first seen at embryonic day 15 in the trigeminal ganglia, and at embryonic day 16 in dorsal root ganglia. In both trigeminal and dorsal root ganglion, fetuin appeared to be present up until around the time of birth, and then again between postnatal days 3 and 16. The results suggest that fetuin first appears at around the time that ganglion cell axons reach their central targets, which is also approximately when the cell-death period begins. The proportion of ganglion neurons that were fetuin immunoreactive at different ages was inversely related to the amount of cell death that is known to occur in these populations, thus it seems that fetuin is more likely to be associated not with dying cells, but with those that survive the cell-death period.