Graham, Katie – Identifying a low complexity domain within residues 1-197 of Ataxin-1 (Dr. Ray Truant)

Identifying a low complexity domain within residues 1-197 of Ataxin-1

Spinocerebellar ataxia type 1 (SCA1) is one of nine polyglutamine (polyQ) diseases, which are characterized by the expansion of CAG, an unstable trinucleotide within the coding region of the gene. The causative protein for SCA1, Ataxin-1 (ATXN1), is a nuclear protein with unknown normal function, despite the understanding of the ability of the mutated protein to cause degeneration of Purkinje cells in the cerebellar cortex. ATXN1 has been shown to aggregate in nuclear inclusions,  a process essential for SCA1 pathogenesis. The ability of ATXN1 to form nuclear aggregates implies the presence of a low complexity domain (LCD), although an LCD has not been characterized within the protein.

Present research has primarily focused on regions following the CAG tract, however no studies have analyzed the 197 amino acids preceding this expansion. This study aims to characterize an LCD within the first 197 residues of ATXN1. Polymerase chain reactions and recombinant technology were used to isolate, amplify, and insert seven specific ATXN1 fragments into a green fluorescently tagged plasmid, which was then transfected into RPE1 cells for imaging. The latter experiment assessed the ability of the ATXN1 fragments to form nuclear aggregates based on visual aggregation of fluorescent signals to regions in the nucleus, resulting in the identification of an LCD. Due to the high concentration of cytosine and guanine in the fragments, they were not obtained in high enough yields for transfection, and thus further research is needed to characterize an LCD in Ataxin-1.