FAM120C (family with sequence similarity 120 member C) is an X-linked gene located at Xp11.22 that encodes a putative transmembrane protein with 1096 amino acids 1. The protein contains five predicted transmembrane domains and belongs to a family of novel transmembrane proteins that evolved during early chordate development 1. FAM120C demonstrates RNA binding capacity and localizes to the nucleus [GO annotations], with functional roles identified in chrX organization and interactions with the Fragile X Mental Retardation Protein (FMRP) network through association with CYFIP1 2. In cell structure mapping, FAM120C functions within pre-ribosomal RNA processing assemblies involved in rRNA maturation 3. Clinically, FAM120C deletions are associated with autism spectrum disorder (ASD), intellectual disability, and craniofacial abnormalities. Complete deletion of FAM120C was identified in two brothers with ASD, intellectual disability, and cleft lip/palate 4, while a discontiguous deletion encompassing FAM120C correlated with syndromic autism in another patient 2. The gene shows enriched expression in brain tissues including pituitary, cerebellum, and cortex, with a cortical expression pattern similar to Fmr1 2. However, resequencing of FAM120C in 87 male autism patients identified no novel mutations, suggesting deletions rather than point mutations may be primary pathogenic mechanisms 2.