Evidence for common ancestral origin of a recurring BRCA1 genomic rearrangement identified in high-risk Hispanic families.
BACKGROUND
Large rearrangements account for 8% to 15% of deleterious BRCA mutations, although none have been characterized previously in individuals of Mexican ancestry.


METHODS
DNA from 106 Hispanic patients without an identifiable BRCA mutation by exonic sequence analysis was subjected to multiplexed quantitative differential PCR. One case of Native American and African American ancestry was identified via multiplex ligation-dependent probe amplification. Long-range PCR was used to confirm deletion events and to clone and sequence genomic breakpoints. Splicing patterns were derived by sequencing cDNA from reverse transcription-PCR of lymphoblastoid cell line RNA. Haplotype analysis was conducted for recurrent mutations.


RESULTS
The same deletion of BRCA1 exons 9 through 12 was identified in five unrelated families. Long-range PCR and sequencing indicated a deletion event of 14.7 kb. A 3-primer PCR assay was designed based on the deletion breakpoints, identified within an AluSp element in intron 8 and an AluSx element in intron 12. Haplotype analysis confirmed common ancestry. Analysis of cDNA showed direct splicing of exons 8 to 13, resulting in a frameshift mutation and predicted truncation of the BRCA1 protein.


CONCLUSIONS
We identified and characterized a novel large BRCA1 deletion in five unrelated families-four of Mexican ancestry and one of African and Native American ancestry, suggesting the possibility of founder effect of Amerindian or Mestizo origin. This BRCA1 rearrangement was detected in 3.8% (4 of 106) of BRCA sequence-negative Hispanic families. An assay for this mutation should be considered for sequence-negative high-risk Hispanic patients.
Weitzel
Jeffrey N
JN
Department of Clinical Cancer Genetics, City of Hope, 1500 East Duarte Road, Duarte, CA 91010, USA. jweitzel@coh.org
Lagos
Veronica I
VI
Herzog
Josef S
JS
Judkins
Thaddeus
T
Hendrickson
Brant
B
Ho
Jason S
JS
Ricker
Charité N
CN
Lowstuter
Katrina J
KJ
Blazer
Kathleen R
KR
Tomlinson
Gail
G
Scholl
Tom
T
D000328:Adult; D001741:Black or African American / Q000235:genetics; D000368:Aged; D017398:Alternative Splicing / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D001943:Breast Neoplasms / Q000235:genetics; D003001:Cloning, Molecular; D018388:Codon, Terminator / Q000235:genetics; D015331:Cohort Studies; D053960:DNA Breaks; D005091:Exons / Q000235:genetics; D005260:Female; D018703:Founder Effect; D016368:Frameshift Mutation / Q000235:genetics; D015321:Gene Rearrangement / Q000235:genetics*; D019398:Genes, BRCA1; D006239:Haplotypes / Q000235:genetics; D006630:Hispanic or Latino / Q000235:genetics*; D006801:Humans; D007198:Indians, North American / Q000235:genetics; D007438:Introns / Q000235:genetics; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D010051:Ovarian Neoplasms / Q000235:genetics; D017384:Sequence Deletion / Q000235:genetics
D018388:Codon, Terminator