Lineage pathway of human brain progenitor cells identified by JC virus susceptibility

Multipotential human central nervous system progenitor cells, isolated from human fetal brain tissue by selective growth conditions, were cultured as undifferentiated, attached cell layers. Selective differentiation yielded highly purified populations of neurons or astrocytes. This report describes the novel use of this cell culture model to study cell type-specific recognition of a human neurotropic virus, JC virus. Infection by either JC virions or a plasmid encoding the JC genome demonstrated susceptibility in astrocytes and, to a lesser degree, progenitor cells, whereas neurons remained nonpermissive. JC virus susceptibility correlated with significantly higher expression of the NFI-X transcription factor in astrocytes than in neurons. Furthermore, transfection of an NFI-X expression vector into progenitor-derived neuronal cells before infection resulted in viral protein production. These results indicate that susceptibility to JC virus infection occurs at the molecular level and also suggest that differential recognition of the viral promoter sequences can predict lineage pathways of multipotential progenitor cells in the human central nervous system. Neurol 2003;53:636 -646 The differentiation of central nervous system (CNS) stem and progenitor cells into neuronal and glial lineages is accompanied by the expression of specific intracellular molecules involved in the transcription of cell type-specific genes. The selective differentiation of human CNS progenitor cells into neural cell types provides a unique model to study the molecular regulation of cellular phenotypes as well as neurotropic viruses that target specific subpopulations of CNS cells. For example, the human polyomavirus, JC virus (JCV), demonstrates a restricted cellular host range and tropism in the CNS, targeting glial but not neuronal cells. Ann 1,2 Lytic infection of oligodendrocytes results in the fatal demyelinating disease, progressive multifocal leukoencephalopathy. 1,2 JCV infects astrocytes both in vivo and in vitro but does not infect neuronal cells, JCV is unique among most viruses in that viral binding and entry do not predict susceptibility to infection. 7 Therefore, it is hypothesized that the selective tropism of JCV is governed by molecular determinants, namely, nuclear transcription factors located within susceptible cells. The promoter-enhancer region of JCV contains multiple sites for the nuclear factor-1 (NFI) family of transcription factors, 8 -10 which includes four members, NFI-A, NFI-B, NFI-C, and NFI-X 11,12 (also known as NFI-D). NFI has been implicated in the transcriptional regulation of several CNS-specific cellular genes 12-17 and viral replication, 18 -21 including that of JCV. The human CNS multipotential progenitor cells, described in this study, were used as a unique in vitro model to study the molecular regulation of JCV infection and to examine the potential role of NFI transcription factors in initiating viral multiplication in specific subpopulations of CNS cell types. The data presented in this article are the first to our knowledge demonstrating JCV infection of a population of human CNS progenitor cells. These experiments indicate that susceptibility to infection depends not on viral binding and entry, but on intracellular factors. Notably, overexpression of one of the NFI class members, NFI-X, in the neuronal cells initiated JCV susceptibility. These data substantiate the importance of NFI-X recognition in the transcriptional regulation of JCV susceptibility From th