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Astroglial cell lines have many applications for advancing neural developmental and functional studies. However, few astroglial cell lines have been reported from fish. In this study, we report the characterization of the immortal cell line TB2 isolated from adult tilapia brain tissue. The cell line was established at 25 degrees C in L15 medium supplemented with 15% fetal bovine serum. Most of the cells displayed a fibrous morphology and were immunoreactive for A2B5 antigen, glial fibrillary acidic protein (GFAP), keratin, vimentin, and the gap junction protein connexin 43 (Cx43). They weakly expressed glutamine synthetase (GS), S100 protein, and the neural stem cell markers Sox2 and brain lipid binding protein (BLBP). In contrast to astroglia in vivo, most TB2 cells also expressed galactocerebroside (GalC), substance P (SP), and tyrosine hydroxylase (TH). By immunoblot and RT-PCR, the cells also expressed myelin basic protein (MBP), proteolipid protein (PLP), and Cx35. On a poly-L-lysine-coated substrate in vitro, TB2 cells showed increases in neuronal dopamine decarboxylase (DDC) and microtubule-associated protein 2 (MAP2), indicating that they can initiate differentiation into neurons. Taken together, the results suggest that TB2 cells are astroglial progenitor cells (neural stem cells) and may develop into oligodendrocytes and neurons in a suitable environment. The present study advances our knowledge of fish astroglia. However, the factors that affect neural development in fish remain unknown, as do the characteristics of the intermediate differentiation stages between stem cells and mature nerve cells. The TB2 cell line will promote these investigations.
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