Detection of splicing aberrations caused by BRCA1 and BRCA2 sequence variants encoding missense substitutions: implications for prediction of pathogenicity.
Missense substitutions in high-risk cancer susceptibility genes create clinical uncertainty in the genetic counseling process. Multifactorial likelihood classification approaches and in vitro assays are useful for the classification of exonic sequence variants in BRCA1 and BRCA2, but these currently rely on the assumption that changes in protein function are the major biological mechanism of pathogenicity. This study investigates the potentially pathogenic role of aberrant splicing for exonic variants predicted to encode missense substitutions using patient-derived RNA. No splicing aberrations were identified for BRCA1c.5054C>T and BRCA2c.7336A>G, c.8839G>A, and c.9154C>T. However, RT-PCR analysis identified a major splicing aberration for BRCA1c.4868C>G(p.Ala1623Gly), a variant encoding a missense substitution considered likely to be neutral. Splicing aberrations were also observed for BRCA2c.7988A>T(p.Glu2663Val) and c.8168A>G(p.Asp2723Gly), but both variant and wildtype alleles were shown to be present in full-length mRNA transcripts, suggesting that variant protein may be translated. BRCA2 protein function assays indicated that BRCA2p.Glu2663Val, p.Asp2723Gly and p.Arg3052Trp missense proteins have abrogated function consistent with pathogenicity. Multifactorial likelihood analysis provided evidence for pathogenicity for BRCA1 c.5054C>T(p.Thr1685Ile) and BRCA2c.7988A>T(p.Glu2663Val), c.8168A>G(p.Asp2723Gly) and c.9154C>T(p.Arg3052Trp), supporting experimentally derived evidence. These findings highlight the need for improved bioinformatic prediction of splicing aberrations and to refine multifactorial likelihood models used to assess clinical significance.
Queensland Institute of Medical Research, Brisbane, Australia.
Logan C
LC
Walker
Phillip J
PJ
Whiley
Fergus J
FJ
Couch
Daniel J
DJ
Farrugia
Sue
S
Healey
Diana M
DM
Eccles
Feng
F
Lin
Samantha A
SA
Butler
Sheila A
SA
Goff
Bryony A
BA
Thompson
Sunil R
SR
Lakhani
Leonard M
LM
Da Silva
Sean V
SV
Tavtigian
David E
DE
Goldgar
Melissa A
MA
Brown
Amanda B
AB
Spurdle
D019313:BRCA1 Protein / Q000235:genetics*; D024682:BRCA2 Protein / Q000235:genetics*; D005091:Exons / Q000235:genetics; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D006801:Humans; D020125:Mutation, Missense; D009369:Neoplasms / Q000235:genetics* / Q000473:pathology; D012326:RNA Splicing / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D019313:BRCA1 Protein; D024682:BRCA2 Protein; D012333:RNA, Messenger