Estudio de variantes genéticas recurrentes y priorización de variantes de significado clínico desconocido asociadas al síndrome de cáncer de mama y ovario hereditario en familias de la Región de Murcia

Abstract

The prevalence study of Hereditary Breast and Ovarian Cancer (HBOC) carried out in 2928 families in the Region of Murcia has identified the recurrent pathogenic variants and founder mutations, mainly associated with the BRCA1 and BRCA2 genes. The variants c.68_69del, c.212+1G > A, and c.5123C > A were detected in 30% of BRCA1 carriers while exon 2 deletion along with c.3264dupT, c.3455T > G and c.9117G > A have been found in 30% of BRCA2 carriers. The genotype-phenotype correlation did not show differences with respect to what was previously reported in the literature for BRCA1/2 carriers. In addition, this thesis demonstrates the founder effect of c.1918C > T (BRCA1) and c.8251_8254del (ATM) in the Murcian population and exon2 deletion (BRCA2) as a Spanish founder mutation. The incorporation of genetic panels through massive sequencing in healthcare practice has led to a significant increase in detected variants of unknown clinical significance. The implementation of a VUS prioritization algorithm in Genomics Laboratory of University Hospital Virgen de la Arrixaca, based on the clinical actionability of the genes and the predictions estimated by the computational tools, has made it possible to prioritize 16 variants susceptible to pathogenicity (15%). The study of prioritized VUS through reverse transcription-polymerase chain reaction, RT-PCR/capillary electrophoresis and RT-PCR/Sanger, has allowed us to characterize the prioritized variants susceptible to aberrant or alternative splicing. The presence of 1 aberrant splicing event has been demonstrated, classifying the variant c.3402+3A < C (ATM) as probably pathogenic. The presence of 2 alternative splicing events of the variants c.8488-1_8489delinsTCCATTACA (BRCA2) and c.320-5T > A (CHEK2) has been evidenced. Likewise, it has been proven that the variant c.1008G > A (CHEK2) does not modify the constitutive splicing pattern. Therefore, the probability that they are pathogenic variants is reduced, and it is appropriate to consider them as VUS.