ASPO050 - Characterization of single and double TEKmutations in unifocal and multifocal venous malformations
Saturday, April 30, 2022
4:00 PM – 5:00 PM CT
Location: Landmark B
Kaitlyn Zenner, MD1, Sabrina Wilcox, MD2, Dana M. Jensen, BS3, Victoria Dmyterko, BS3, Randall A. Bly, MD4, Juliana Bonilla-Velez, MD4, John P. Dahl, MD PhD4, Sheila Ganti, PhD3, William B. Dobyns, MD5, James T. Bennett, MD PhD6, Jonathan A. Perkins, DO4;
1Univ. of Washington, Seattle, WA, 2Univ. of Michigan, Ann Arbor, MI, 3Seattle Children's Res. Inst., Seattle, WA, 4Division of Pediatric Otolaryngology, Seattle Children's Hosp., Seattle, WA, 5Division of Genetics and Metabolism, Univ. of Minnesota, Minneapolis, MN, 6Department of Medical Genetics, Univ. of Washington, Seattle, WA.
Resident Physician University of Washington, Washington
Introduction: Venous malformations (VeM) are congenital vascular malformations resulting from abnormal vasculogenesis. Activating mutations in the endothelial receptor tyrosine kinase receptor, TEK, account for 50% of sporadic VeM. A subset of VeM possess multiple somatic TEKmutations. Somatic double mutants in cis (same allele) versus trans (opposite alleles) have implications for protein function and temporal acquisition of mutations. Our objective was to characterize patterns of somatic double TEKmutations in tissue and correlate findings with unifocal or multifocal malformations.
Methods: Individuals with VeM undergoing clinically indicated surgical resection had lesion and adjacent non-lesion samples collected. Samples were sent for whole gene sequencing and patients with somaticTEK mutations were included. Multiplex droplet digital PCR (ddPCR) assays were designed to detect single mutations and double mutations in cis for double mutant pairs identified on whole gene sequencing.
Results: TEK mutations were identified in 22 individuals with 14 (63%) having a single mutation at p.L914F. Double TEK mutations at p.Y897 and either p.R915 or p.R918 were found in 8 individuals (36%). Five multiplex ddPCR assays were developed to screen lesion and non-lesion samples from double mutant VeM. All lesion samples (N = 15) had detectable mutation: 7 double mutation in cis, 3 p.R915/918 mutation alone, and 5 with double mutants in cis and p.R915/918 mutation. Mutations were detected in 50% of non-lesion samples (N= 7/14) with primarily single p.R915/918 mutations (N = 5). The p.Y897 mutation was never identified alone. All individuals with a p.L914F mutation had unifocal malformation while 38% (3/8) of double TEK mutant individuals had multifocal malformations.
Conclusion: Double TEK mutations were found in cis at p.Y897 and either p.R915 or p.R918. The prevalence of p.R915/R918 mutant samples in non-lesion samples and the lack of p.Y897 mutant only samples throughout suggest that there is a temporal acquisition of the mutations with p.Y897 mutations occurring after the p.R915/918 mutation. Multifocal disease may be associated with detection of double TEKmutations. Further work will explore why multifocal disease is more common in double mutant individuals compared to those with single mutations.