Novel SMARCA4::VEZF1 Rearrangement in Pediatric Sarcomas

The SMARCA4 gene encodes a key ATPase subunit of the SWI/SNF (BAF) chromatin-remodeling complex, which plays an essential role in regulating transcription and cellular differentiation. Loss-of-function alterations of SMARCA4 are common in various human cancers, including sarcomas; however, rare SMARCA4 fusion events, presumably resulting in gain of function, have also been reported. We present two pediatric soft-tissue sarcomas harboring a novel, recurrent in-frame fusion between SMARCA4 and VEZF1 (Vascular Endothelial Zinc Finger 1), a transcription factor important for vascular development and angiogenesis. The predicted fusion protein contains the N-terminal QLQ protein interaction domain of SMARCA4 and preserves most of VEZF1's C2H2 zinc-finger DNA-binding domains. Interestingly, another component of the BAF complex, SS18, has also been reported to be fused to VEZF1 in uterine sarcoma. We propose that fusion of BAF complex components to VEZF1 leads to aberrant recruitment of chromatin-remodeling activity to VEZF1 target loci, resulting in altered chromatin architecture, dysregulated VEZF1-dependent transcription, and tumorigenesis.