Characterization of an Italian Founder Mutation in the RING-Finger Domain of BRCA1

Abstract

The identification of founder mutations in cancer predisposing genes is important to improve risk assessment in geographically defined populations, since it may provide specific targets resulting in cost-effective genetic testing. Here, we report the characterization of the BRCA1 c.190T>C (p.Cys64Arg) mutation, mapped to the RING-finger domain coding region, that we detected in 43 hereditary breast/ovarian cancer (HBOC) families, for the large part originating from the province of Bergamo (Northern Italy). Haplotype analysis was performed in 21 families, and led to the identification of a shared haplotype extending over three BRCA1-associated marker loci (0.4 cM). Using the DMLE+2.2 software program and regional population demographic data, we were able to estimate the age of the mutation to vary between 3,100 and 3,350 years old. Functional characterization of the mutation was carried out at both transcript and protein level. Reverse transcriptase-PCR analysis on lymphoblastoid cells revealed expression of full length mRNA from the mutant allele. A green fluorescent protein (GFP)-fragment reassembly assay showed that the p.Cys64Arg substitution prevents the binding of the BRCA1 protein to the interacting protein BARD1, in a similar way as proven deleterious mutations in the RING-domain. Overall, 55 of 83 (66%) female mutation carriers had a diagnosis of breast and/or ovarian cancer. Our observations indicate that the BRCA1 c.190T>C is a pathogenic founder mutation present in the Italian population. Further analyses will evaluate whether screening for this mutation can be suggested as an effective strategy for the rapid identification of at-risk individuals in the Bergamo area.

Haplotype analyses of the c.1027C>T and c.2167_2168delAT recurrent truncating mutations in the breast cancer-predisposing gene PALB2

“…Its limited range to this specific area in Northern Italy may reflect limited migration of the local population, possibly due to territory geographical conformation characterized by several secluded valleys that may have caused genetic isolation [4]. Consistent with this hypothesis, the BRCA1 c.190T>C (p.Cys64Arg) founder mutation is only found in breast cancer families from Bergamo, and was estimated to be more than 3,000 years old [16]. There are too few families and family members with the PALB2 c.1027C>T to estimate the age of the mutation.…”

BRCA1 and BRCA2 mutations in ovarian cancer patients from China: ethnic‐related mutations in BRCA1 associated with an increased risk of ovarian cancer

“…Although the majority of the pathogenic mutations were previously reported, 32 novel mutations were identified in our study, which were not described in the literature [20][21][22][23][24][25][26][27][28][29][30][31] nor recorded in public databases, such as BIC, ClinVar or LOVD. Two novel pathogenic mutations in BRCA1: c.283_286delCTTG and c.4573C > T, were both identified in two unrelated EOC patients (Table 2).…”

Homologous Recombination and Human Health: The Roles of BRCA1, BRCA2, and Associated Proteins

“…By contrast, the cancer-associated C61G RING domain mutant, which disrupts the interaction with BARD1 rather than specifically impairing interaction with E2 enzymes, causes tumor susceptibility in mice as well as in patients (Wu et al 1996; Drost et al 2011). Another deleterious mutant, BRCA1 C64R, also has impaired interaction with BARD1 (Caleca et al 2014). Thus, while integrity of the BRCA1 RING domain region is critical for tumor suppression, apparently because of its interaction with BARD1, the physiological role of the E3 ligase activity itself is uncertain.…”