TSEN54 encodes a non-catalytic subunit of the tRNA splicing endonuclease (TSEN) complex, which is essential for removing introns from precursor tRNAs 1. The complex recognizes the mature tRNA body structure and positions splice sites into catalytic centers for cleavage, releasing introns and two tRNA half-molecules with defined termini 2. TSEN54 cooperatively recognizes pre-tRNA through unique structural regions and helps trap the scissile phosphate for catalytic activity 2. Beyond tRNA processing, TSEN54 associates with pre-mRNA 3'-end processing factors, linking tRNA splicing to mRNA biogenesis. TSEN54 mutations cause pontocerebellar hypoplasia (PCH) types 2A, 4, and 5—rare autosomal recessive neurodegenerative disorders 3. Loss-of-function mechanisms underlie disease pathogenesis, with TSEN54 knockdown in zebrafish increasing brain cell death and causing structural abnormalities 3. Recent organoid models show PCH2a cerebellar organoids have reduced growth with altered proliferation kinetics 4. The cerebellum and pons show region-specific vulnerability, and prenatal MRI can differentiate PCH phenotypes based on vermis and cerebellar involvement patterns 5. Beyond neurological disease, TSEN54 upregulation in hepatocellular carcinoma associates with poor prognosis and altered immune cell infiltration 6.