Identification and quantification of differentially expressed proteins in plasma of spinocerebellar ataxia type 12

Spinocerebellar ataxia 12 (SCA12) is a unique dominant type of ataxia characterized by early and prominent action tremors, memory deficit, neuropathy, dysarthria, etc. The expansion of DNA triplet (CAG) repeats in 5′UTR of PPP2R2B gene appears to be the cause for the pathogenesis of the neurodegenerative disorder, SCA12. The objective of the current study was to identify the aberrantly expressed plasma proteins for their potential application in therapy or diagnosis/prognosis of SCA12. Sixty-two clinically suspected patients were assessed using International Co-operative Ataxia Rating Scale (ICARS) and genetic confirmation was done using PCR followed by DNA sequencing. Twenty patients who were genetically confirmed were included in the study. 2D-DIGE analyses of plasma proteins of SCA12 patients revealed 14 differentially expressed protein spots, which were confirmed as nine proteins by LC–MS/MS. The 6 downregulated and 3 upregulated proteins are known to have physiological role in transport (thyroxin and retinol to brain), lipid metabolism, memory, scavenging of free haemoglobin, etc. Altered expression of some of the proteins of interest, transthyretin, haptaglobin, apolipoprotein C-II, apolipoprotein C-III are indicative of clinical manifestations such as neuropathy, cognitive impairment and altered lipid metabolism in SCA12.

► High prevalence of SCA12 in north India.
► Plasma proteomics identified 9 differentially expressed proteins.
► Low transthyretin levels indicate neuropathy in SCA12 patients.
► Oxidative stress and memory deficit linked with over-expression of haptaglobin.