Molecular pathway analysis towards understanding tissue vulnerability in spinocerebellar ataxia type 1

Purpose: The goals of this study were to identify the molecular alterations in the SCA1 inferior olive, and determine whether these changes are found in other affected tissues. Methods: mRNA profiling was conducted in two different SCA1 mouse models (Atxn1 154Q/2Q KI and ATXN1-82Q Tg), in two different affected tisues (inferior olive and cerebellum) during early disease initiation and progression (5 week and 12 week time-points). All analyses were conducted relative to appropriate wild-type controls. TopHat2 v2.1.0 was utilized to align reads to the mouse reference genome (mm10) before quantification and differential expression analysis with Cufflinks v2.2.1. Normalized expression values were generated using Cuffnorm. Results: Differentially regulated genes identified in the SCA1 inferior olive segregated into several enriched biological pathways, including the Defense Response at 12 weeks of age. Our study demonstrates that vulnerable tissues in SCA1 are not uniform in their gene expression changes, and express discrete and commonly enriched biological pathways. In addition, we found that brain region-specific differences occur early in disease initiation and progression at 5 weeks of age. Conclusions: The findings from this study suggest that different mechanisms of neurodegeneration are at work in the SCA1 inferior olive and cerebellum. Overall design: mRNA profiling was conducted on an Illumina HiSeq 2500. Three biological replicates were sequenced for each genotype (Atxn1 154Q/2Q KI mice and wild-type controls; ATXN1-82Q Tg mice and wild-type controls) in each brain region (inferior olive and cerebellum) at each time-point (5 weeks old and 12 weeks old), yielding a total of 48 biological samples.

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Driessen TM, Lee PJ, Lim J