Gene and protein expression profiling of a presymptomatic type III spinal muscular atrophy mouse model

Abstract

In order to determine the molecular events leading up to motor neuron degeneration in SMA this study profiled the changes at the mRNA and protein levels in spinal cords of Smn+/- mice with those of Smn+/- littermates. The Smn+/- mice show 50% motor neuron loss by 6 months of age and are used as a model for mild SMA in humans. We have isolated RNA from spinal cords of 5-week-old mice in order to perform representational difference analysis (RDA) and microarray analysis using Affymetrix MOE430 arrays. Subtle but reproducible changes occur in the transcriptome of SMA mice. Genes involved in RNA metabolism, apoptosis regulation and transcriptional regulation were shown to be the most affected in the Smn +/- mice. These changes in expression were characterized by semi-quantitative RT-PCR and Western blot analysis at various timepoints. The differences in protein levels in 5-week-old Smn +/- and Smn+/+ spinal cords were examined using apoptosis and kinase protein screens from Kinetworks Bioinformatics. Results demonstrated similar protein expression levels in the Smn +/- and Smn+/+ samples. Although the signaling pathways and apoptotic protein levels do not seem to be significantly altered in the SMA mouse spinal cord at the 5-week presymptomatic stage we believe that the cells present the first signs of the apoptotic process indicating that they are responding to the stress of Smn depletion.