Transcriptional profile of muscle following acute induction of symptoms in a mouse model of Kennedy's disease/SBMA

Kennedy’s disease/Spinobulbar muscular atrophy (KD/SBMA) is a degenerative neuromuscular disease affecting males. This disease is caused by polyglutamine expansion mutations of the androgen receptor (AR) gene. Although KD/SBMA has been traditionally considered a motor neuron disease, emerging evidence points to a central etiological role of muscle. We previously reported a microarray study of genes regulated in muscle of three genetically unique mouse models of KD/SBMA but were unable to those which are androgen-dependent or are associated with onset of symptoms. Methodology/principal findings: In the current study we examined the time course and androgen-dependence of transcriptional changes in the HSA-AR transgenic (Tg) mouse model, in which females have a severe phenotype after acute testosterone treatment. Using microarray analysis we identified regulated genes at the onset and peak of muscle weakness in testosterone-treated Tg females. We found both transient and persistent groups of regulated genes and analysis of gene function indicated functional groups such as mitochondrion, ion and nucleotide binding, muscle development, and sarcomere maintenance. By comparing the current results with those from the three previously reported models we were able to identify KD/SBMA candidate genes that are androgen dependent, and occur early in the disease process, properties which are promising for targeted therapeutics. We used microarray (38.5K oligo mouse array, which contain 35,302 of 70mer oligonucleotide probes largely derived from constitutively expressed exons and 3,482 of controls) to analyze gene expression in limb muscles of transgenic mice. Five sample groups of 3 animals each were performed: Tg female 3 days testosterone treatment; Tg female 7d T treatment; WT untreated; WT 3d T treatment; and WT 7d T treatment. We additionally used microarray data from HSA-AR males to compare with HSA-AR females. A universal RNA reference sample made from WT (C57BL/6J) mice was utilized on each array. Triplicate arrays using RNA samples from the different experimental animals (i.e., 3 of Tg female with 3d T treatment, 3 of Tg female with 7d T treatment, 3 of untreated WT females, 3 of WT female with 3d T treatment, 3 of WT female with 7d T treatment) were performed. Log2 ratios of experimental samples (Cy5) versus reference RNA (Cy3) were obtained. The log2 ratios of Tg mice samples were then subtracted from log2 ratios of WT to find differentially regulated genes (3d T-treated Tg subtracted from 3d T-treated WT, 7d T-treated Tg subtracted from 7d T-treated WT). log2 ratios of T-treated WT were subtracted from log2 ratio of untreated WT.