Molecular diagnosis of the Portuguese founder mutation BRCA2 c.156_157insAlu

Peixoto, Ana; Santos, Catarina; Rocha, Patrícia; Pinto, Pedro; Bizarro, Susana; Teixeira, Manuel R.

doi:10.1007/s10549-008-0214-z

Cited by 10 publications

(14 citation statements)

References 8 publications

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“…We recently evaluated the contribution of the c.156_157insAlu BRCA2 mutation to inherited predisposition to breast/ovarian cancer in families originated mostly from northern/central Portugal (Peixoto et al, 2009a) and found that this rearrangement is responsible for more than half of all deleterious BRCA2 mutations and about one-fourth of all deleterious mutations in HBOC families. Additionally, in light of some doubts raised about the pathogenic effect of BRCA2 exon 3 skipping (Diez et al, 2007), we demonstrated its pathogenic effect by showing that the BRCA2 full length transcript is produced almost exclusively from the wildtype allele in patients carrying the c.156_157insAlu BRCA2 rearrangement and that this mutation co-segregates with the disease in HBOC families and is absent in healthy blood donors, although residual exon 3 skipping in BRCA2 mRNA can be found in negative controls (Peixoto et al, 2009a;Peixoto et al, 2009b).…”

Section: Introductionmentioning

confidence: 87%

“…From Portugal, 149 new suspected HBOC families were selected for BRCA1 and BRCA2 mutation screening using previously described criteria (Peixoto et al, 2006;Peixoto et al, 2009a) after written informed consent. Molecular testing at the Department of Genetics of the Portuguese Oncology Institute, Porto, Portugal (IPO-Porto) started by looking for the c.156_157insAlu BRCA2 mutation, followed by full BRCA1 and BRCA2 mutation screening with the previously reported methodology (Peixoto et al, 2006;Peixoto et al, 2009a;Peixoto et al, 2009b). The c.156_157insAlu BRCA2 mutation was additionally screened in 5,291 suspected HBOC families living in countries other than Portugal in whom no deleterious BRCA1/BRCA2 mutations had previously been found, with the following Additionally, predictive testing was performed in four individuals from two additional families (two relatives from each family living in Rhode Island, USA, and in Villejuif, France, respectively) with the c.156_157insAlu BRCA2 mutation identified elsewhere.…”

Section: Familiesmentioning

confidence: 99%

“…Screening for the c.156_157insAlu BRCA2 mutation was performed using two independent PCRs (Peixoto et al, 2009a;Peixoto et al, 2009b), one for exon 3 amplification and another specific for the Alu rearrangement. Using this strategy, we expect two bands in positive cases in the first PCR (one band if negative) and one band in the second PCR (none if negative).…”

Section: Screening For the C156_157insalu Brca2 Mutationmentioning

confidence: 99%

“…This strategy of two independent PCRs, followed by sequencing of the genomic fragments in positive cases, allows the unambiguous detection of the c.156_157insAlu BRCA2 mutation (Peixoto et al, 2009a;Peixoto et al, 2009b). Positive and negative controls were used in all runs and all positive cases were confirmed in a second independent sample.…”

Section: Screening For the C156_157insalu Brca2 Mutationmentioning

confidence: 99%

“…Although all reported c.156_157insAlu BRCA2 mutations have so far been identified in Portuguese HBOC families (Teugels et al, 2005;Machado et al, 2007;Peixoto et al, 2009a), this mutation is not detected using the commonly used screening methodologies and must be specifically sought (Teugels et al, 2005;Peixoto et al, 2009b), so one can not currently rule out its presence in other populations. To gain insight into the ancestral origin and population spread of the c.156_157insAlu BRCA2 mutation, we screened for this rearrangement in 5,440 suspected HBOC patients from several countries and performed an extensive haplotype study using closely linked microsatellite markers and single nucleotide polymorphisms (SNPs) in carrier families.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

International distribution and age estimation of the Portuguese BRCA2 c.156_157insAlu founder mutation

Peixoto

Santos

Pinheiro

et al. 2010

Breast Cancer Res Treat

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The c.156_157insAlu BRCA2 mutation has so far only been reported in hereditary breast/ovarian cancer (HBOC) families of Portuguese origin. Since this mutation is not detectable using the commonly used screening methodologies and must be specifically sought, we screened for this rearrangement in a total of 5,440 suspected HBOC families from 22 labs from 13 countries from several continents. Whereas the c.156_157insAluBRCA2 mutation was detected in 11 of 149 suspected HBOC families from Portugal, representing 37.9% of all deleterious mutations, in other countries it was detected only in one proband living in France and in four individuals requesting predictive testing living in France and in the USA, all having in common the fact that they are relatively recent immigrants of Portuguese origin in those countries. After performing an extensive haplotype study in carrier families, we estimate that this founder mutation has occurred 558±215 years ago. We further demonstrate significant quantitative differences regarding the production of the BRCA2 full length RNA and the transcript with exon 3 skipping in c.156_157insAlu BRCA2 mutation carriers and in controls, indicating that disruption of alternative transcript ratios is the mechanism causing hereditary breast/ovarian cancer associated with this BRCA2 rearrangement. We further show that the cumulative incidence of breast cancer in c.156_157insAlu BRCA2 mutation carriers does not differ from that of other BRCA2 and BRCA1 pathogenic mutations, further strengthening its role as the major contributor to hereditary predisposition to breast cancer in Portugal. We recommend that all suspected HBOC families from Portugal or with Portuguese ancestry are specifically tested for this rearrangement, ideally prior to screening of the entire coding regions of BRCA1 and BRCA2.3

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Section: Introductionmentioning

confidence: 87%

Section: Familiesmentioning

confidence: 99%

Section: Screening For the C156_157insalu Brca2 Mutationmentioning

confidence: 99%

Section: Screening For the C156_157insalu Brca2 Mutationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

International distribution and age estimation of the Portuguese BRCA2 c.156_157insAlu founder mutation

Peixoto

Santos

Pinheiro

et al. 2010

Breast Cancer Res Treat

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Portuguese c.156_157insAlu BRCA2 founder mutation: gastrointestinal and tongue neoplasias may be part of the phenotype

et al. 2012

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We have screened BRCA2 c.156_157insAlu founder mutation in a cohort of 168 women with diagnosis of breast cancer referred for genetic counseling because of risk of being carriers of hereditary breast and ovarian cancer syndrome. Portuguese founder mutation BRCA2 c.156_157insAlu was identified in three unrelated breast cancer probands. Genotyping identified a common haplotype between markers D13S260 and D13S171, and allele sizes were compatible to those described in the Portuguese families. Allele sizes of marker D13S1246, however, were concordant in two families, suggesting that the haplotype may be larger in a subset of families. Tumor phenotypes in Brazilian families seem to reinforce the high prevalence of breast cancer among affected males. However, an apparent excess of gastrointestinal and tongue neoplasias were also observed in these families. Although these tumors are not part of the phenotypic spectrum of hereditary breast and ovarian cancer syndrome, they might be accounted for by other risk alleles contained in the founder haplotype region.

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Pathogenicity Evaluation of BRCA1 and BRCA2 Unclassified Variants Identified in Portuguese Breast/Ovarian Cancer Families

Santos

Peixoto

Rocha

et al. 2014

The Journal of Molecular Diagnostics

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Hereditary breast/ovarian cancer syndrome is caused by germline deleterious mutations in BRCA1 and BRCA2. A major problem of genetic testing and counseling is the finding of variants of uncertain significance (VUS). We sought to ascertain the pathogenicity of 25 BRCA1 and BRCA2 VUS identified in Portuguese families during genetic testing. We performed cosegregation analysis of VUS with cancer in families, evaluated their frequency in unaffected controls, and looked for loss of heterozygosity in tumors. In addition, three different bioinformatic algorithms were used (Interactive Biosoftware, ESEfinder, and PolyPhen). Finally, six VUS located in exon-intron boundaries were analyzed by RT-PCR. We found that seven variants segregated with the disease, six variants co-occurred with a pathogenic mutation in the same gene, and four variants co-occurred with a deleterious mutation in the other BRCA gene. By RT-PCR, we observed that four variants (BRCA1 c.4484G>T, BRCA2 c.682-2A>C, BRCA2 c.8488-1G>A, and BRCA2 c.8954-5A>G) disrupted splicing. After the combined analysis, we were able to classify 4 splicing variants as pathogenic mutations, 16 variants as neutral, and 3 variants as polymorphisms; only 2 variants remained classified as VUS. This work highlights the contribution of DNA, RNA, and in silico data to assess the pathogenicity of BRCA1/2 VUS, which, in turn, allows more accurate genetic counseling and clinical management of the families carrying them.

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Molecular diagnosis of the Portuguese founder mutation BRCA2 c.156_157insAlu

Cited by 10 publications

References 8 publications

International distribution and age estimation of the Portuguese BRCA2 c.156_157insAlu founder mutation

International distribution and age estimation of the Portuguese BRCA2 c.156_157insAlu founder mutation

Portuguese c.156_157insAlu BRCA2 founder mutation: gastrointestinal and tongue neoplasias may be part of the phenotype

Pathogenicity Evaluation of BRCA1 and BRCA2 Unclassified Variants Identified in Portuguese Breast/Ovarian Cancer Families

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