Huntingtin inclusions do not down-regulate specific genes in the R6/2 Huntington's disease mouse

Transcriptional dysregulation is a central pathogenic mechanism in Huntington's disease (HD); HID and transgenic mouse models of HID demonstrate down-regulation of specific genes at the level of mRNA expression. Furthermore, neuronal intranuclear inclusions (NIIs) have been identified in the brains of R6/2 mice and HID patients. One possibility is that NIIs contribute to transcriptional dysregulation by sequestering transcription factors. We therefore assessed the relationship between NIIs and transcriptional dysregulation in the R6/2 mouse, using double-label in situ hybridization combined with immunohistochemistry, and laser capture microdissection combined with quantitative real-time PCR. There was no difference in transcript levels of specific genes between NII-positive and Nil-negative neurons. These results demonstrate that NIIs do not cause decreases in D2, PPE and PSS mRNA levels in R6/2 striatum and therefore are not involved in the down-regulation of these specific genes in this HID model. In addition, these observations argue against the notion that NIIs protect against transcriptional dysregulation in HID.