Transcriptome sequencing reveals aberrant alternative splicing in Huntington's disease

Huntington’s disease (HD) is an autosomal dominant neurodegenerative disorder caused by a CAG expansion in the gene encoding Huntingtin (HTT). Transcriptome dysregulation is a major feature of HD pathogenesis, as revealed by a large body of work on gene expression profiling of tissues from human HD patients and mouse models. These studies were primarily focused on transcriptional changes affecting steady-state overall gene expression levels using microarray based approaches. A major missing component however has been the study of transcriptome changes at the post-transcriptional level, such as alternative splicing. Alternative splicing is a critical mechanism for expanding regulatory and functional diversity from a limited number of genes, and is particularly complex in the mammalian brain. Here we carried out a deep RNA-seq analysis of 7 human HD brains and 7 controls to systematically discover aberrant alternative splicing events and characterize potential associated splicing factors in HD. We identified 593 differential alternative splicing events between HD and control brains. Using an expanded panel of 54 brain tissues from patients and controls, we also identified 9 splicing factors exhibiting significantly altered expression levels in HD patient brains. Moreover, follow-up molecular analyses of one splicing factor PTBP1 revealed its impact on disease-associated splicing patterns in HD. Collectively, our data provide genomic evidence for widespread splicing dysregulation in HD brains, and suggest the role of aberrant alternative splicing in the pathogenesis of HD RNA-seq analysis of the BA4 motor cortex of 7 control and 7 Huntington's disease patients. 1.5 ug of total RNA was used for RNA-seq library preparation using the TruSeq™ Stranded mRNA LT Sample Prep Kit (Illumina). 100x2 bp paired-end RNA-seq reads were generated on a HiSeq 2000 sequencer.