ATXN7 (ataxin 7) is a component of the SAGA transcription coactivator-HAT complex that mediates interactions with the CRX transcription factor for gene activation 1. The protein plays dual roles in nuclear and cytoplasmic functions: it regulates transcription by RNA polymerase II and stabilizes the microtubule cytoskeleton 2, likely through tethering the deubiquitination module within the SAGA complex 3. ATXN7's primary clinical significance relates to spinocerebellar ataxia 7 (SCA7), a neurological repeat expansion disorder caused by CAG repeat expansions in the ATXN7 gene 4. CAG repeat mosaicism in SCA7 increases over time and correlates with disease manifestation, with higher expansion levels in symptomatic versus asymptomatic carriers 4. SCA7 patients demonstrate cerebellar cognitive-affective syndrome in 67% of cases, correlating with ataxia severity and plasma neurofilament light chain levels 5. Beyond ataxia, emerging evidence suggests ATXN7 has broader oncogenic significance; ATXN7 mutations cooperate with RAS in thyroid tumorigenesis 6, and Rad51C-ATXN7 fusion genes appear in colorectal cancers 7. Additionally, ATXN7 genetic variants predict hepatocellular carcinoma prognosis 8.