Several studies have shown effects of diesel exhaust (DE) on the central nervous 
system, but the mechanism is unclear. Fetal mice were exposed to whole DE 
(contains gases and particles) in an inhalation chamber, and cerebrum gene 
expression changes were examined by gene assay (microarray and quantitative 
real-time PCR). By microarray, upregulation of Xist, B-raf and Drwms2 were 
detected. Especially, mRNA expression of Xist was increased in a 
concentration-dependent manner in male and female mice. Xist (X-inactive 
specific transcript) is a major effector of the X-inactivation process, and 
X-linked genes are highly expressed in brain tissue and consistent with a role 
in brain developments. By quantitative real-time PCR, Tsix (crucial noncoding 
antisense partner of Xist) and other X-linked genes (Mecp2, Hprt1, and Sts) were 
examined; Tsix was upregulated, and other X-linked genes were unaffected in the 
male and female mice. Our findings suggest that exposure to DE increases Xist 
and Tsix gene expression in utero without influencing X-linked gene expression. 
An examination of Xist gene expression changes may provide an important 
biomarker for DE-induced effects. The possibility of avoiding X-chromosome 
inactivation (XCI) mechanisms by minimizing exposure to DE is expected.