EXOSC9 encodes a non-catalytic structural component of the RNA exosome complex, a multi-subunit ribonuclease that processes and degrades various RNA species 1. The protein functions in both nuclear and cytoplasmic RNA metabolism, participating in ribosome biogenesis, mRNA turnover, and RNA surveillance pathways 1. EXOSC9 contains an RNA-binding motif essential for its function in stress resistance and P-body formation, which are critical for cellular adaptation to stress conditions 2. The protein also regulates telomeric integrity by degrading long non-coding RNA TERRA in a cell cycle-dependent manner, with recruitment to telomeres mediated by SUMOylated HP1α 3. Disease-causing mutations in EXOSC9 result in pontocerebellar hypoplasia type 1D (PCH1D), characterized by cerebellar atrophy, spinal motor neuronopathy, and severe developmental abnormalities 45. These mutations disrupt the exosome complex integrity and lead to widespread gene expression changes affecting neuronal development 4. The pathogenic mechanism involves increased p53 levels and enhanced apoptosis during development, suggesting EXOSC9-related disorders represent ribosomopathies 6. Higher EXOSC9 activity correlates with poorer prognosis in some cancers, making it a potential therapeutic target 2.