In vitro induction and in vivo expression of bcl-2 in the hNT neurons

Bcl-2 encodes membrane-associated proteins that suppress programmed cell de ath in cells of various origins. Compelling evidence suggests that bcl-2 is also involved in neuronal differentiation and axonal regeneration. The hum an Neuro-Teratocarcinoma (hNT) neurons constitute a terminally differentiat ed human neuronal cell line that is derived from the Ntera-2/clone D1 (NT2) precursors upon retinoic acid (RA) treatment. After transplantation into t he central nervous system (CNS), the hNT neurons survive, engraft, maintain their neuronal identity, and extend long neurite outgrowth. We were partic ularly interested in the intracellular determinants that confer these post- transplant characteristics to the hNT neurons. Thus, we asked whether the h NT neurons express bcl-2 after transplantation into the rat striatum and if RA induction of the neuronal lineage is mediated by bcl-2. The grafted hNT neurons were first identified using three different antibodies that recogn ize human-specific epitopes, anti-hMit, anti-hNuc, and NuMA. After a 1-mont h post-transplant survival time, NuMA immunostaining revealed that 12% of t he hNT neurons survived the transplantation. These neurons extended long ne uritic processes within the striatum, as demonstrated using the human-speci fic antibody against the midsize neurofilament subunit HO14. Importantly, w e found that 85% of the implanted hNT neurons expressed bcl-2 and that the in vitro induction of the neuronal lineage from the NT2 precursors with RA resulted in an upregulation of bcl-2 expression. Together, these data sugge st that the differentiation of the hNT neurons to a neuronal lineage could be mediated at least partially by bcl-2. (C) 2001 Elsevier Science Inc.