Functional redundancy of exon 12 of BRCA2 revealed by a comprehensive analysis of the c.6853A>G (p.I2285V) variant.
Variants of unknown significance (VUS) in BRCA1 and BRCA2 are common, and present significant challenges for genetic counseling. We observed that BRCA2: c.6853A>G (p.I2285V) (Breast Cancer Information Core [BIC] name: 7081A>G; http://research.nhgri.nih.gov/bic/) co-occurs in trans with the founder mutation c.5946delT (p.S1982RfsX22) (BIC name: 6174delT), supporting the published classification of p.I2285V as a neutral variant. However, we also noted that when compared with wild-type BRCA2, p.I2285V resulted in increased exclusion of exon 12. Functional assay using allelic complementation in Brca2-null mouse embryonic stem cells revealed that p.I2285V, an allele with exon 12 deleted and wild-type BRCA2 were all phenotypically indistinguishable, as measured by sensitivity to DNA-damaging agents, effect on irradiation-induced Rad51 foci formation, homologous recombination, and overall genomic integrity. An allele frequency study showed the p.I2285V variant was identified in 15 out of 722 (2.1%) Ashkenazi Jewish cases and 10 out of 475 (2.1%) ethnically-matched controls (odds ratio, 0.99; 95% confidence interval: 0.44-2.21; P=0.97). Thus the p.I2285V variant is not associated with an increased risk for breast cancer. Taken together, our clinical and functional studies strongly suggest that exon 12 is functionally redundant and therefore missense variants in this exon are likely to be neutral. Such comprehensive functional studies will be important adjuncts to genetic studies of variants.
Program in Cancer Genetics, Departments of Oncology and Human Genetics, McGill University, Montreal, Quebec, Canada.
Lili
L
Li
Kajal
K
Biswas
Laura Anne
LA
Habib
Sergey G
SG
Kuznetsov
Nancy
N
Hamel
Tomas
T
Kirchhoff
Nora
N
Wong
Susan
S
Armel
George
G
Chong
Steven A
SA
Narod
Kathleen
K
Claes
Kenneth
K
Offit
Mark E
ME
Robson
Stacey
S
Stauffer
Shyam K
SK
Sharan
William D
WD
Foulkes
D000818:Animals; D024682:BRCA2 Protein / Q000737:chemistry / Q000235:genetics / Q000502:physiology; D004252:DNA Mutational Analysis; D005091:Exons; D005787:Gene Frequency; D024522:Genes, BRCA2; D014644:Genetic Variation; D006801:Humans; D051379:Mice; D012326:RNA Splicing; D012333:RNA, Messenger / Q000737:chemistry
D024682:BRCA2 Protein; D012333:RNA, Messenger