Transcriptome of tributyltin-induced apoptosis of the cultured rat mesencephalic neural stem cells.

Exposure to environmental neurotoxic chemicals both in utero and during the early postnatal period can cause neurodevelopmental disorders. To evaluate the disruption of neurodevelopmental programming, we previously established an in vitro neurosphere assay system, using rat mesencephalic neural stem cells (mNSC). Here, we examined the developmental neurotoxicity of tributyltin (TBT) in an in vitro neurosphere assay. A neurosphere was driven from rat E16 mesencephalon and seeded in a poly-l-ornithine/laminin-coated plate. Exposure to TBT increased the number of terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL)-positive cells in time-dependent and dose-dependent manner: it was significantly detectable with treatment of 100pM TBT for 90min, or of 1μM TBT for 30min. Disruption of mitochondrial membrane potential and activation of caspase-3/7 were concomitantly observed. Furthermore, DNA microarray analyses using Affymetrix GeneChip revealed that as early as 0.5h after exposure to the metal (1μM), the expression levels of 71 genes were increased by more than 2-fold, whereas those of 8 genes were decreased by 2-fold or less: it was notably altered in expression of Ca(2+)-mobilizing-related genes, and retinoic-acid signal-related genes, as well as bifunctional apoptosis-related genes. The levels of gene expression of Wnt family were also significantly changed. Thus, we established transcriptome of TBT-induced apoptosis of mNSC. This would help to evaluate developmental neurotoxicity of TBT in vivo, contributing to the risk assessment methods based on infant physiology.