Abstract 2559: Functional characterization of a RECQL4 mutation in Rothmund Thomson Syndrome

Abstract

Abstract Osteosarcoma (OS) is the most common malignancy of the bone, typically diagnosed during the adolescent years. Despite early advances in treatment, OS survival rates have not improved in recent times. Targeted treatment remains elusive because OS is a genetically complex and heterogeneous disease and the low incidence of sporadic OS presents a challenge in dissecting the causes and drivers of tumor development. Type II Rothmund-Thomson Syndrome (RTS), a cancer predisposition disorder, presents a potential model for studying OS pathogenesis as roughly 30% of Type II RTS patients are eventually diagnosed with OS. Type II RTS is associated with germline mutations of the DNA helicase RECQL4 that exclusively target the C-terminal helicase domain thought to be involved in various cellular mechanisms of DNA repair. The N-terminal SLD2-homology domain, required for the assembly of the CMG complex at origins of replication, is spared. We used CRISPR/Cas9 gene editing to generate cell lines containing a common RECQL4 mutation identified in Type II RTS patients to further study its effects. Unexpectedly, a mutation previously reported as a nonsense mutation instead upregulates the activation of a known cryptic splice site in exon 14. This splice variant results in the in-frame deletion of the final 66 amino acids of exon 14. Our cell lines exhibit a mildly increased sensitivity to the DNA double-strand break inducing agent neocarzinostatin consistent with RECQL4’s reported functions in DNA damage repair. We will use next generation sequencing techniques to further characterize DNA damage repair signatures in RTS RECQL4 mutant cell lines. Citation Format: Tianyi Wu, Robert L. Walker, Marbin Pineda, MiYoung Lee, Yuelin Zhu, Ashok R. Venkitaraman, Paul S. Meltzer. Functional characterization of a RECQL4 mutation in Rothmund Thomson Syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2559.