Defects in ATXN7 are the cause of spinocerebellar ataxia type 7 (SCA7) also known as olivopontocerebellar atrophy III (OPCA III or OPCA3) or olivopontocerebellar atrophy with retinal degeneration. Spinocerebellar ataxia is a clinically and genetically heterogeneous group of cerebellar disorders. Patients show progressive incoordination of gait and often poor coordination of hands, speech and eye movements, due to degeneration of the cerebellum with variable involvement of the brainstem and spinal cord. Ataxin 7 acts as a component of the STAGA transcription coactivator-HAT complex. It mediates the interaction of STAGA complex with the CRX and is involved in CRX-dependent gene activation [taken from the Universal Protein Resource (UniProt) www.uniprot.org/uniprot/O15265].