RASopathy Cohort of Patients Enrolled in a Brazilian Reference Center for Rare Diseases: A Novel Familial LZTR1 Variant and Recurrent Mutations

Abstract

Natana Chaves Rabelo,1– 3 Maria Eduarda Gomes,1– 3 Isabelle de Oliveira Moraes,1– 3 Juliana Cantagalli Pfisterer,1– 3 Guilherme Loss de Morais,4 Deborah Antunes,5 Ernesto Raúl Caffarena,6 Juan Llerena Jr,1,2,7,8 Sayonara Gonzalez1– 3 1Centro de Genética Médica IFF/Fiocruz, Rio de Janeiro, RJ, Brazil; 2Centro de Referência para Doenças Raras IFF/Fiocruz, Rio de Janeiro, RJ, Brazil; 3Laboratório de Medicina Genômica IFF/Fiocruz, Rio de Janeiro, RJ, Brazil; 4Laboratório Nacional de Computação Científica, Petrópolis, RJ, Brazil; 5Laboratório de Genômica Funcional e Bioinformática, Instituto Oswaldo Cruz/Fiocruz, Rio de Janeiro, RJ, Brazil; 6Grupo de Biofísica Computacional e Modelagem Molecular, Programa de Computação Científica, Fundação Oswaldo Cruz/Fiocruz, Rio de Janeiro, RJ, Brazil; 7Faculdade de Medicina de Petrópolis, FASE, Petrópolis, RJ, Brazil; 8INAGEMP, Rio de Janeiro, RJ, BrazilCorrespondence: Juan Llerena Jr, Email [email protected]: Noonan syndrome and related disorders are genetic conditions affecting 1:1000– 2000 individuals. Variants causing hyperactivation of the RAS/MAPK pathway lead to phenotypic overlap between syndromes, in addition to an increased risk of pediatric tumors. DNA sequencing methods have been optimized to provide a molecular diagnosis for clinical and genetic heterogeneity conditions. This work aimed to investigate the genetic basis in RASopathy patients through Next Generation Sequencing in a Reference Center for Rare Diseases (IFF/Fiocruz) and implement the precision medicine at a public health institute in Brazil.Patients and Methods: This study comprises 26 cases with clinical suspicion of RASopathies. Sanger sequencing was used to screen variants in exons usually affected in the PTPN11 and HRAS genes for cases with clinical features of Noonan and Costello syndrome, respectively. Posteriorly, negative and new cases with clinical suspicion of RASopathy were analyzed by clinical or whole-exome sequencing.Results: Molecular analysis revealed recurrent variants and a novel LZTR1 missense variant: 24 unrelated individuals with pathogenic variants [PTPN11(11), NF1(2), SOS1(2), SHOC2(2), HRAS(1), BRAF(1), LZTR (1), RAF1(1), KRAS(1), RIT1(1), a patient with co-occurrence of PTPN11 and NF1 mutations (1)]; familial cases carrying a known pathogenic variant in PTPN11 (mother-two children), and a previously undescribed paternally inherited variant in LZTR1. The comparative modeling analysis of the novel LZTR1 variant p.Pro225Leu showed local and global changes in the secondary and tertiary structures, showing a decrease of about 1% in the β-sheet content. Furthermore, evolutionary conservation indicated that Pro225 is in a highly conserved region, as observed for known dominant pathogenic variants in this protein.Conclusion: Bringing precision medicine through NGS towards congenital syndromes promotes a better understanding of complex clinical and/or undiagnosed cases. The National Policy for Rare Diseases in Brazil emphasizes the importance of incorporating and optimizing diagnostic methodologies in the Unified Brazilian Health System (SUS). Therefore, this work is an important step for the NGS inclusion in diagnostic genetic routine in the public health system.Keywords: RASopathy, RAS/MAPK pathway, genetic heterogeneity, cancer risk, DNA sequencing

Keywords

• rasopathy
• ras/mapk pathway
• genetic heterogeneity
• cancer risk
• dna sequencing.