Cis- and trans- loci influence expression of the schizophrenia susceptibility gene DTNBP1.

Susceptibility to complex disease appears to be partly mediated by heritable differences in gene expression. Where cis-acting effects on a gene's expression influence disease susceptibility, other genes containing polymorphism with a trans-acting effect on expression of that gene may also be expected to modulate risk. Use of the expression of an identified disease gene as an endophenotype for quantitative linkage analysis may therefore provide a powerful method for mapping loci that modulate disease susceptibility. We performed genome-wide linkage analysis on expression of dystrobrevin binding protein 1 (DTNBP1), a well-supported susceptibility gene for schizophrenia, in large CEPH pedigrees. We observed genome-wide significant evidence for linkage at the DTNBP1 locus on chromosome 6p22, and demonstrated that this reflects variable cis-acting effects on DTNBP1 expression. In addition, we observed genome-wide suggestive evidence for linkage of DTNBP1 expression to chromosome 8p, suggesting a locus that exerts a trans-acting effect on DTNBP1 expression. The region of linkage to DTNBP1 expression on chromosome 8 is contiguous with linkage findings based upon the clinical schizophrenia phenotype, and contains another well-supported schizophrenia susceptibility gene, neuregulin-1 (NRG1). Our data provide complementary evidence for chromosome 8p as a susceptibility locus for schizophrenia, and suggest that genetic variation within this region may influence risk, at least in part, through effects on DTNBP1 expression.

Regional and cellular gene expression changes in human Huntington's disease brain.

Huntington's disease (HD) pathology is well understood at a histological level but a comprehensive molecular analysis of the effect of the disease in the human brain has not previously been available. To elucidate the molecular phenotype of HD on a genome-wide scale, we compared mRNA profiles from 44 human HD brains with those from 36 unaffected controls using microarray analysis. Four brain regions were analyzed: caudate nucleus, cerebellum, prefrontal association cortex [Brodmann's area 9 (BA9)] and motor cortex [Brodmann's area 4 (BA4)]. The greatest number and magnitude of differentially expressed mRNAs were detected in the caudate nucleus, followed by motor cortex, then cerebellum. Thus, the molecular phenotype of HD generally parallels established neuropathology. Surprisingly, no mRNA changes were detected in prefrontal association cortex, thereby revealing subtleties of pathology not previously disclosed by histological methods. To establish that the observed changes were not simply the result of cell loss, we examined mRNA levels in laser-capture microdissected neurons from Grade 1 HD caudate compared to control. These analyses confirmed changes in expression seen in tissue homogenates; we thus conclude that mRNA changes are not attributable to cell loss alone. These data from bona fide HD brains comprise an important reference for hypotheses related to HD and other neurodegenerative diseases.