Developmental distribution of GFAP and vimentin in the Brazilian opossum brain

Cells of glial origin are involved in the morphogenesis of the mammalian central nervous system (CNS). Characterization of glial-associated proteins during neurogenesis and differentiation may aid in understanding the complexity of CNS development. We have utilized immunoblotting and immunohistochemistry to characterize the developmental profiles of glial fibrillary acidic protein (GFAP) and vimentin (VIM) in the brain of the Brazilian opossum, Monodelphis domestica. Typical of marsupials, CNS morphogenesis and neurogenesis in the opossum extend well into the postnatal period. Opossum GFAP and VIM were found as single bands at molecular weights consistent with those reported for other species, thus indicating conservation of the VIM and GFAP proteins through mammalian evolution. Differential developmental trends were observed for both proteins with relative VIM levels decreasing and GFAP levels increasing with age. Vimentin-like immunoreactivity (VIM-IR) was present at day 1 of postnatal life throughout the brain. The density of VIM-IR was maximal at 10 and 15 days postnatal (especially in radial glial elements) and decreased slightly by 25 days postnatal. In the adult brain, VIM-IR was markedly reduced compared to that of younger ages. In contrast, GFAP-like immunoreactivity (GFAP-IR) in the brain of Monodelphis increased dramatically with age. No GFAP-IR was observed in the 1 and 5 day postnatal brains. By 25 days postnatal, the pattern of GFAP-IR in the brainstem resembled that of the adult. In the forebrain, more GFAP-IR was present than at younger ages. The adult distribution of GFAP-IR was very similar to that reported for other mammalian species. These results indicate that GFAP and VIM are reciprocally related during periods of morphogenesis and differentiation of the opossum brain.