SS18L1 and synovial sarcoma: For example, a polymorphic Alu insertion in the SS18L1 (Synovial sarcoma translocation gene on chromosome 18-like 1) gene locus oriented anti-sense to the transcription of the gene, is associated with increased methylation of nearby CpG sites at the same gene locus (p = 6.67x10-6) (Fig. 5a).