THOC2 encodes the largest subunit of the evolutionarily conserved TREX (Transcription-Export) complex, which plays a critical role in coupling transcription to mRNA processing and nuclear export 12. The protein functions in multiple RNA processing steps including 3'-end processing, 5' capping, transcriptional regulation, R-loop resolution, and splicing, facilitating the export of mRNA from nucleus to cytoplasm 2. THOC2 also regulates stem cell properties by facilitating nuclear export of key transcription factors like SOX2 and NANOG 3. Loss-of-function variants in THOC2 cause severe neurodevelopmental disorders characterized by intellectual disability, seizures, movement disorders, and cerebellar hypoplasia 45. The molecular mechanism involves R-loop accumulation, DNA damage, and consequent cell death when THOC2 function is compromised 1. THOC2 mutations are associated with X-linked intellectual developmental disorder and arthrogryposis multiplex congenita, with affected individuals showing growth delays, hypotonia, and microcephaly 67. The protein's essential role in mRNA export makes it critical for normal brain development and function, establishing THOC2 as an important target for understanding neurodevelopmental diseases 2.