**Mutational analysis of the *BRCA1*-interacting genes *ZBRK1* and
*BRIP1* among *BRCA1/2*-negative probands from breast-ovarian cancer
families and among early-onset breast cancer cases and reference
individuals**

 

 

 

Joni L Rutter^1^, Amelia M Smith^1^, Michael R Dávila^1^, Alice J
Sigurdson^2^, Ruthann M. Giusti^4^, Marbin A. Pineda^1^, Michele M
Doody^2^, Margaret A Tucker^3^, Mark H Greene^4^, Jinghui Zhang^1^,
Jeffery P Struewing^1^

 

 

 

^1^Laboratory of Population Genetics, Center for Cancer Research;
^2^Radiation Epidemiology Branch, ^3^Genetic Epidemiology Branch, &
^4^Clinical Genetics Branch, Division of Cancer Epidemiology and
Genetics; National Cancer Institute, Bethesda, MD

# Abstract

 

Two potential breast cancer susceptibility genes, encoding the
BRCA1-interacting proteins ZBRK1 and BRIP1, have recently been
identified in yeast two-hybrid screens(Zheng et al. 2000; Cantor et al.
2001). We sequenced these genes in probands from 21 families with
potentially inherited breast/ovarian cancer, all of whom were negative
for *BRCA1/2* mutations. Families had at least 1 case of male breast
cancer, 2 cases of ovarian cancer, or 3 or more cases of breast and
ovarian cancer. In addition, 58 early-onset (before age 35) breast
cancer cases and 30 reference individuals were analyzed. Of 17 variants
detected in *ZBRK1*, a missense mutation Val524Ile was identified in one
proband but no other family members were available for testing. Of 25
variants identified in *BRIP1*, in addition to four common silent or
missense mutations, we identified Gln540Leu, a non-conservative amino
acid change, in a single proband with inflammatory breast cancer, but it
was not present in her three relatives with breast cancer. Haplotype
analysis suggests that all *ZBRK1* SNPs fall within a single block with
two SNPs capturing 92% of the haplotype diversity, while the *BRIP1*
SNPs fall in two blocks, with five SNPs capturing 89% of the haplotype
diversity. Based on sequencing of *ZBRK1* and *BRIP1* in 21
*BRCA1/2*-negative probands from inherited breast/ovarian cancer
families, it appears unlikely that mutations in these genes account for
a large fraction of inherited forms of breast cancer. Further analysis
in unselected cases will be required to know whether the identified
variants play a role in genetic predisposition to breast cancer in
general.

Introduction

 

Among clearly inherited breast and ovarian cancer families (those with 5
or more early-onset cases of breast cancer, ovarian cancer, or male
breast cancer), approximately 2/3 have germline mutations in the *BRCA1*
or *BRCA2* genes that are detectable using PCR-based techniques(Szabo
and King 1997). While some additional families may have abnormalities in
*BRCA1* or *BRCA2*, such as large genomic rearrangements or regulatory
mutations, a sizeable fraction appear to be unexplained by mutations in
these two genes. Linkage analyses of large collections of families
without *BRCA1/2* mutations are ongoing, but it does not appear that
mutations in a single gene will account for a large proportion of the
remaining families.

 

The *BRCA1* and *BRCA2* genes encode large, multi-functional proteins
that do not share significant homology to other well-characterized
proteins or to each other(Venkitaraman 2002). Biochemical studies have
identified a large number of interacting proteins and upstream and
downstream targets, many relating to DNA damage repair or
transcriptional regulation. Two novel proteins that interact with BRCA1
were recently identified in yeast two-hybrid assays(Zheng et al. 2000;
Cantor et al. 2001). We studied whether mutations in the genes *ZBRK1*
and *BRIP1* (originally termed *BACH1*) that encode these
BRCA1-interacting proteins might account for some proportion of
*BRCA1/2*-negative probands from potentially inherited breast/ovarian
cancer families. In addition, we screened for variants in an anonymized
series of early-onset breast cancer cases and reference individuals to
identify variants that could be studied as lower-penetrance
susceptibility alleles in other studies. We also studied linkage
disequilibrium and haplotypes derived from the single nucleotide
polymorphism (SNP) discovery and genotyping results emanating from this
work.

 

 

## Materials and Methods

*BRCA1/2*-negative probands

Within the NCI's Family Cancer Registry, after excluding the families
with identified *BRCA1* or *BRCA2* mutations, there were 21 probands
with breast or ovarian cancer who were negative upon full sequencing of
the *BRCA1* and *BRCA2* genes. The *BRCA1/2*-negative families had
slightly fewer ovarian cancers (average 1.0 per family) compared to
mutation positive families (2.8 per family), but similar numbers of
breast cancer cases (3.1 vs 3.3)(Struewing et al. 1995). Each
*BRCA1/2*-negative family in the present study had at least 1 case of
male breast cancer, 2 cases of ovarian cancer, or 3 or more cases of
breast and ovarian cancer. All families were of European ancestry.

 

Early-onset breast cancer cases and reference individuals

Among all 61 subjects diagnosed with breast cancer before age 35 from a
national cohort of radiologic technologists, the 58 who were negative
after limited *BRCA1/2* mutation testing were included in this
study(Struewing et al. 1996; Mohan et al. 2002). These samples are
linked only to limited epidemiologic information, and the ethnicity of
individual subjects is not known, but most are of European ancestry. In
addition, samples from 30 unrelated individuals of European ancestry
(subjects 01 and 02 from families 1328, 1331, 1332, 1333, 1341, 1344,
1346, 1347, 1349, 1362, 1400, 1408, 1413, 1416, 1423 from the CEPH
family collection) were obtained from the Coriell Repository. Analysis
of these 88 subjects was performed blinded as to case or comparison
status.

 

Sequence analysis

The intron-exon boundaries of *ZBRK1* and *BRIP1* were determined by
aligning Genbank mRNA records (AF295096 and AF360549, respectively) with
genomic sequence records (NT_010757 and NT_011091). *ZBRK1* spans
approximately 10kb and is composed of 4 exons, while *BRIP1* spans
approximately 180kb and is composed of 20 exons. PCR amplicons were
designed to amplify the entire mRNA encoding portions and flanking
intronic sequence from genomic DNA, using 9 primer pairs ranging in size
from 208 bp to 428 bp for *ZBRK1* and 23 primer pairs ranging in size
from 250 bp to 549 bp for *BRIP1*. Primer sequences and thermal cycling
conditions are available upon request from the authors
(http://lpgws.nci.nih.gov:...)

The 21 *BRCA1/2*-negative probands were analyzed by sequencing all PCR
products with both the forward and reverse primers used for
amplification. The sequencing reaction included 2 microliters of PCR
product as template in an 8 microliter reaction using 20 pmoles of
primer and Big Dye Terminator Ready Reaction Mix (Applied Biosystems,
Foster City, CA) at 0.8X concentration. The reactions were cleaned up
using Microcon 96-well spin plates, dried down, resuspended in 10
microliters of deionized formamide and analyzed on an ABI 3100
sequencer. All sequence tracings were inspected by two reviewers, with
the forward and reverse reads aligned using Vector NTI.

 

Analysis of the early-onset breast cancer cases and CEPH reference
individuals included both denaturing high performance liquid
chromatography (dHPLC) and sequencing. dHPLC analysis was performed on a
WAVE System (Transgenomic, Inc.) using the same PCR primers as for
sequencing (gradients and dHPLC protocols are available at
http://lpgws.nci.nih.gov:...). For amplicons in which there were no
polymorphisms, only dHPLC analysis was performed. For amplicons with 1
or more common polymorphisms, both dHPLC and sequencing in one direction
were usually performed, because distinguishing among the several
possible genotype combinations in the dHPLC chromatograms alone was not
always possible. Variants observed in the dHPLC chromatograms were
sequenced as above to determine the exact nucleotide change. STAR
software (Varian, Inc.) was also used to group the dHPLC chromatograms
into clusters based on their patterns as an aid in identifying samples
requiring sequencing, or to determine a subject's genotype for common
polymorphisms.

 

Statistical analysis

No formal statistical comparisons of variant allele frequencies between
the early-onset breast cancer cases and reference individuals were made
because the base populations for the two groups are likely to be
dissimilar. Nucleotide diversity was calculated separately for the amino
acid coding nucleotides (n=1599 for *ZBRK1* and n=3750 for *BRIP1*) and
non-coding nucleotides (n=1084 for *ZBRK1* and n=5115 for *BRIP1*) that
were analyzed(Hartl and Clark 1997). We used the publicly available
computer algorithms PHASE and SNPHAP to predict haplotypes, as
implemented in the HapScope suite of programs(Johnson et al. 2001;
Stephens et al. 2001; Zhang et al. 2002). Haplotypes were estimated
after excluding variants with allele frequencies below 1% (and before
block boundaries were estimated), and the minimum set of variants
required to distinguish all haplotypes with a frequency above 2% was
calculated using a greedy partition algorithm as implemented in
HapScope(Zhang et al. 2002). The normalized measure of linkage
disequilibrium, D', and exact *P* values for allelic association, were
calculated for all pair-wise combinations of markers using Arlequin
Version 2.001 software (<http://anthro.unige.ch/arlequin>).

 

## Results

A total of 12 nucleotide variants were identified in *ZBRK1* and 11
variants were identified in *BRIP1* among the 21 *BRCA1/2*-negative
probands. (Tables 1 & 2 and Figure 1) The *ZBRK1* mutations Q393Q and
V524I and a variant in the 3'UTR (1845c\>t) were identified in one
proband each, but no other affected family members were available to
determine whether these variants segregated with cancer in the family.
Neither the silent nor the missense mutation was observed in the 58
early-onset breast cancer cases or 30 reference individuals, but the
3'UTR variant was present in 7% and 8% of these subjects, respectively.
The other variants observed in the probands had allele frequencies of
10% or greater and were observed in the 88 other individuals analyzed
and are unlikely to be related to the cancer clustering in these
families. (Table 1) The missense mutation Q540L and an intronic variant
IVS14+26delT were identified in *BRIP1* in one proband each and were not
observed in the early-onset breast cancer cases or reference
individuals. Another intronic variant, IVS5-31g\>c was identified in two
probands and in none of the other 88 individuals, but the other 6
variants identified in the probands were common and had allele
frequencies of 25% or greater in the reference individuals. (Table 2)

 

The glutamine to leucine change at residue 540 (Q540L) in *BRIP1* is a
non-conservative change that does not fall within any of the helicase
domains of this protein. Samples from additional family members were
available for analysis, but neither the proband's daughter nor her two
nieces who had breast cancer, carried this mutation. No other family
members were available for analysis of the *BRIP1* IVS14+26delT variant
nor for one family with the IVS5-31g\>c. In the second family with the
intron 5 variant, all three relatives with breast or ovarian cancer also
carried it. One other female over age 50 without cancer from this family
was available for analysis, and she also carried the IVS5-31g\>c.

 

Analysis of the early-onset breast cancer cases and reference
individuals revealed five *ZBRK1* variants not observed in the
*BRCA1/2*-negative probands and 14 additional *BRIP1* variants. (Tables
1 & 2) Of seven additional *BRIP1* missense mutations identified, four
were identified in the 30 reference individuals and not the early-onset
breast cancer cases. Four breast cancer cases carried both the T385T and
S472P variants in *ZBRK1* while none of the reference individuals did,
but the frequencies of most variants were similar between the breast
cancer cases and reference individuals.

 

The extensive genetic analysis of these two genes in 218 chromosomes
allowed us to examine diversity and linkage disequilibrium measures. The
calculated amino acid encoding nucleotide diversity was approximately
twice as high for *ZBRK1* (8.6 X 10^-4^) compared to *BRIP1* (4.4 X
10^-4^), while for non-coding regions the values were 1.2 X 10^3^ and
4.9 X 10^-4^, respectively. The SNPHAP and PHASE programs resulted in
nearly identical *ZBRK1* haplotype predictions for each the 109
subjects, with only 1 difference when excluding variants at 1% allele
frequency or below, and no differences when excluding variants at 10%
frequency or lower. For *BRIP1*, in which there were no variants with
allele frequencies between 1% and 10%, the predicted haplotypes differed
for 6 subjects when variants below 1% allele frequency were excluded.

There were only three *ZBRK1* haplotypes with estimated frequencies of
2% or greater, with two variants, namely D35D (or alternatively
IVS3+18a\>g or IVS3+62g\>a) and L66P (or alternatively IVS3+46a\>t)
capturing all of this variability. (Figure 2) *BRIP1* showed much more
haplotype diversity, with nine haplotypes at 2% frequency or greater,
and no single haplotype had an estimated frequency above 25%. (Figure 2)
Five variants would need to be analyzed to capture the common haplotype
diversity in this gene. By graphical inspection of the pair-wise D' and
*P* values for the *ZBRK1* variants that span approximately 10
kilobases, they appear to fall within a single haplotype block, while
there appear to be two haplotype blocks across *BRIP1*, which spans
approximately 180 kilobases. (Figures 2 & 3)

 

## Discussion

 

Approximately 1/3 of families with inherited forms of breast and ovarian
cancer do not segregate mutations in *BRCA1* or *BRCA2*, two genes
identified through linkage analysis in multiple-case families.
Additional linkage studies in families that are negative for *BRCA1/2*
suggest that mutations in no single gene account for a large proportion
of families. If mutations in several genes account for small subsets of
these *BRCA1/2*-negative families, identifying such genes by linkage
analyses and positional cloning will be difficult. An alternative
approach is to analyze candidate genes for mutations that segregate with
cancer in a family and that alter the normal biological function of the
gene or its product, and some breast cancer families have been
attributed to such mutations(Vahteristo et al. 2001; Chenevix-Trench et
al. 2002).

 

The biological basis of the cancer predisposition in *BRCA1* and *BRCA2*
mutation carriers has not been clearly identified. BRCA1 and BRCA2 are
large, multi-functional proteins, involved in DNA damage sensing and
repair, transcriptional regulation, and transcription-coupled repair,
but whether these or other functions account for their carcinogenic
effect are not known. They interact with many different proteins,
including two that were identified through yeast two-hybrid analyses.
The *ZBRK1* gene is a novel gene identified using an N-terminal fragment
of *BRCA1* as bait(Zheng et al. 2000). This gene encodes a protein with
a KRAB domain and eight zinc fingers that is involved in repression of
*GADD45* and potentially other targets. No mutational analysis has been
published, but there are four SNPs in dbSNP that map to the mRNA. The
*BRIP1* gene, originally termed *BACH1*, was identified using a
C-terminal fragment of *BRCA1* as bait(Cantor et al. 2001). *BRIP1*
contains six DEAH-helicase homology regions and interacts with the BRCT
domains of *BRCA1*. Mutations within the helicase domains of BRIP1
interfered with double-strand DNA break repair in a BRCA1-binding
dependent manner, and two germline missense mutations in *BRIP1* were
identified among 65 breast cancer cases(Cantor et al. 2001). One of
these, P47A, identified in a patient with a strong family history of
breast and ovarian cancer who was negative for *BRCA1/2* mutations,
affected a conserved residue in the helicase domain and produced an
unstable protein. No other family members from the two missense-carrying
cases were available for analysis, but this raised the possibility that
mutations in *BRIP1* may account for some fraction of inherited breast
cancer cases.

 

We screened the *ZBRK1* and *BRIP1* genes in a series of individuals at
high risk of genetic forms of breast cancer, including 21 probands from
families with multiple cases of breast and/or ovarian cancer who were
negative for *BRCA1/2* mutations, and 58 individuals who were diagnosed
with breast cancer before age 35(Struewing et al. 1995; Struewing et al.
1996; Mohan et al. 2002). We did not identify any mutations that were
clearly related to breast cancer. For *BRIP1* we did not observe the two
previously reported mutations P47A and M299I, but we did identify a
non-conservative missense mutation, Q540L, in an individual with breast
cancer. Analysis of seven additional relatives, however, suggested that
this mutation was not the underlying cause of the breast cancer in this
family, as none of the three other relatives with breast cancer carried
this mutation. The conservative *ZBRK1* missense mutation V524I was
identified in a *BRCA1/2*-negative proband and in none of the early
onset breast cancer cases or reference individuals, but no other family
members were available for analysis and it is unclear whether this is
related to the cancer occurrence. There were only two other *ZBRK1* or
*BRIP1* variants observed in *BRCA1/2*-negative probands but not in the
other 88 individuals analyzed, but one was a silent mutation and the
other an intronic variant that appear unlikely to be causative
mutations. If we assume none of the 21 probands carries a
disease-related mutation, the upper 95% confidence limit on this
proportion (0/21) would be 13%.(Hanley and Lippman-Hand 1983)

 

We identified many sequence variants in the two genes, including two
silent mutations in *ZBRK1* and two silent and one missense mutation in
*BRIP1* that had allele frequencies of at least 10% but are not in dbSNP
(as of September 2002). The observed nucleotide diversity was about
twice as high for *ZBRK1* as *BRIP1*, but in comparison to 15 other
genes analyzed in 93 subjects of worldwide distribution, only 4 genes
had higher amino-acid coding diversity than *BRIP1*, suggesting that
neither gene is under strong functional contstraint. (Thorstenson et al.
2001)Our linkage disequilibrium and haplotype analysis appears to be
consistent with recent evidence suggesting that SNPs fall within blocks
of extended disequilibrium(Rioux et al. 2001; Gabriel et al. 2002). All
*ZBRK1* variants were in strong linkage disequilibrium, and analyzing
the D35D and L66P variants would capture the common haplotype diversity
across this gene, which appears to fall within a single block. While
less diverse at the nucleotide level, *BRIP1* showed considerably more
haplotype diversity, with the variants in *BRIP1* falling within two
haplotype blocks.

 

Our SNP discovery effort in the early-onset breast cancer cases and
reference individuals identified several common variants that may
warrant further study in breast cancer or other cancer case-control
studies. Within *ZBRK1*, the two non-conservative missense mutations
L66P and R501S are common (allele frequencies of 10% or greater), and
another non-conservative mutation, S472P, was present in 7% of
early-onset breast cancer cases but none of the reference individuals.
Two *BRIP1* variants, the non-conservative missense mutation (P919S)
that is very common (allele frequency \>30%), and a newly described,
common variant 64 nucleotides upstream from the transcription start site
(-64g\>a) that might affect gene regulation, may warrant further
investigation as susceptibility alleles.

 

In summary, we performed mutational analysis of the genes *ZBRK1* and
*BRIP1*, encoding two recently identified BRCA1-interacting proteins, as
possible explanations for inherited breast and ovarian cancer clustering
in families that are negative for mutations in *BRCA1* and *BRCA2*. We
did not identify any mutations that appear to be causative in these
families and it appears unlikely that mutations in these genes account
for a large fraction of inherited forms of breast cancer (upper
confidence limit 13%). Additional analysis in early-onset breast cancer
cases and reference individuals identified several newly described
variants that make attractive candidates as susceptibility alleles for
breast and other cancers.

Accession numbers and supplementary material.

Genomic records used were AC011460.1 and NT_035426.1 and mRNA records
used were NM_021632.1 and NM_032043.1 for *ZBRK1* and *BRIP1*,
respectively. All identified variants not previously deposited into
dbSNP have been submitted as accession numbers rs-NNNNNNN to rs-NNNNNNN.
Primer sequences, PCR and dHPLC conditions, and the genetic data for
each subject are available at http://lpgws.nci.nih.gov/?????.

![](media/image1.wmf)

![](media/image2.wmf)

![](media/image3.wmf){width="8.89375in" height="6.496527777777778in"}

Figure 1. Schematic diagram showing the genomic structure and position
of identified genetic variants. Introns are shown as a thin horizontal
line and are not drawn to scale; exons are shown as thick horizontal
lines and are drawn roughly to scale, with selected ones numbered. A)
*ZBRK1* gene showing 4 exons with 17 genetic variants. The KRAB, C2H2
zinc finger, and BRCA1-interacting domains are indicated by rectangles
below the gene. B) *BRIP1* gene showing 20 exons with 25 genetic
variants. The DEAH helicase domains are shown as circles and the
BRCA1-interacting domain as a rectangle below the gene. The two
mutations identified previously in early-onset breast cancer cases^1^
are indicated with small circles above the gene.

![](media/image4.png){width="8.679166666666667in"
height="6.495138888888889in"}

Figure 2. Schematic representation of calculated haplotypes as displayed
by HapScope, with minor modifications. The exons and introns are drawn
to scale (different for each gene) at the top of the diagram as
horizontal lines, with nucleotide positions of the genomic record
indicated by the ruler. Repetitive elements are shown as blackened areas
in the genomic record bar. Symbols (diamonds = nucleotide substitutions,
triangles = insertion/deletion) below the ruler represent the SNPs and
their relative location indicated by lines connecting to the ruler.
Small squares below a SNP symbol indicate a minimum set required to
identify all haplotypes with a frequency greater than 2%. Numbers
immediately below some SNP symbols correspond to the variant numbers
from Tables 1 & 2, for cross-reference). Haplotypes are shown in the
lower half of the figure, with each SNP used to calculate the haplotypes
represented by a circle; darkened circles represent the common allele;
open circles represent the variant allele. The number of occurrences and
percent frequency are shown to the left of each haplotype. A) *ZBRK1*
showing the 12 SNPs with allele frequencies greater than 1% used to
estimate haplotypes. D35D and P373P are indicated with small squares as
the minimum SNPs required to identify the three haplotypes with a
frequency greater than 2%. B) *BRIP1* showing the nine SNPs with allele
frequencies greater than 1% used to estimate haplotypes, and the two
estimated haplotype blocks.

![](media/image5.png){width="5.425694444444445in"
height="8.993055555555555in"}

 

Figure 3. Graphical representation of measures of linkage disequilibrium
between SNPs with allele frequencies greater than 1%. The relative
location of SNPs are indicated by lines connecting to the linear
representation of the genomic structure of the gene, which are drawn to
a different scale for each gene; a 500bp line above the gene line
indicates the scale. For each pair-wise comparison, the upper half of
the square indicates the magnitude of D', with dark shading representing
values \> 0.9, light shading representing values between 0.8 and 0.9,
and open rectangles representing values \< 0.8; the lower half
represents the exact *P* value for the 2 X 2 association between SNPs,
with dark shading representing values \< 0.001, light shading
representing values between 0.05 and 0.001, and open rectangles
representing values \> 0.05. A) *ZBRK1*. B) *BRIP1*.

 

 

 

References

Cantor SB, Bell DW, Ganesan S, Kass EM, Drapkin R, Grossman S, Wahrer
DC, Sgroi DC, Lane WS, Haber DA, Livingston DM (2001) Bach1, a novel
helicase-like protein, interacts directly with brca1 and contributes to
its dna repair function. Cell 105:149-60.

Chenevix-Trench G, Spurdle AB, Gatei M, Kelly H, Marsh A, Chen X, Donn
K, Cummings M, Nyholt D, Jenkins MA, Scott C, Pupo GM, Dork T, Bendix R,
Kirk J, Tucker K, McCredie MR, Hopper JL, Sambrook J, Mann GJ, Khanna KK
(2002) Dominant negative ATM mutations in breast cancer families. J Natl
Cancer Inst 94:205-15

Gabriel SB, Schaffner SF, Nguyen H, Moore JM, Roy J, Blumenstiel B,
Higgins J, DeFelice M, Lochner A, Faggart M, Liu-Cordero SN, Rotimi C,
Adeyemo A, Cooper R, Ward R, Lander ES, Daly MJ, Altshuler D (2002) The
structure of haplotype blocks in the human genome. Science 296:2225-9

Hanley JA, Lippman-Hand A (1983) If nothing goes wrong, is everything
all right? Interpreting zero numerators. JAMA 249:1743-5

Hartl DL, Clark AG (1997) Principles of population genetics. Sinauer
Associates, Inc., Sunderland, MA

Johnson GC, Esposito L, Barratt BJ, Smith AN, Heward J, Di Genova G,
Ueda H, Cordell HJ, Eaves IA, Dudbridge F, Twells RC, Payne F, Hughes W,
Nutland S, Stevens H, Carr P, Tuomilehto-Wolf E, Tuomilehto J, Gough SC,
Clayton DG, Todd JA (2001) Haplotype tagging for the identification of
common disease genes. Nat Genet 29:233-7

Mohan AK, Hauptmann M, Linet MS, Ron E, Lubin JH, Freedman DM, Alexander
BH, Boice JD, Jr., Doody MM, Matanoski GM (2002) Breast cancer mortality
among female radiologic technologists in the United States. J Natl
Cancer Inst 94:943-8

Rioux JD, Daly MJ, Silverberg MS, Lindblad K, Steinhart H, Cohen Z,
Delmonte T, et al. (2001) Genetic variation in the 5q31 cytokine gene
cluster confers susceptibility to Crohn disease. Nat Genet 29:223-8

Stephens M, Smith NJ, Donnelly P (2001) A new statistical method for
haplotype reconstruction from population data. Am J Hum Genet 68:978-89

Struewing JP, Brody LC, Erdos MR, Kase RG, Giambarresi TR, Smith SA,
Collins FS, Tucker MA (1995) Detection of eight *BRCA1* mutations in 10
breast/ovarian cancer families, including 1 family with male breast
cancer. Am J Hum Genet 57:1-7

Struewing JP, Tarone RE, Brody LC, Li FP, Boice JD, Jr. (1996) *BRCA1*
mutations in young women with breast cancer. Lancet 347:1493

Szabo CI, King MC (1997) Population genetics of BRCA1 and BRCA2. Am J
Hum Genet 60:1013-20

Thorstenson YR, Shen P, Tusher VG, Wayne TL, Davis RW, Chu G, Oefner PJ
(2001) Global analysis of ATM polymorphism reveals significant
functional constraint. Am J Hum Genet 69:396-412

Vahteristo P, Tamminen A, Karvinen P, Eerola H, Eklund C, Aaltonen LA,
Blomqvist C, Aittomaki K, Nevanlinna H (2001) p53, CHK2, and CHK1 genes
in Finnish families with Li-Fraumeni syndrome: Further evidence of CHK2
in inherited cancer predisposition. Cancer Research 61:5718-5722

Venkitaraman AR (2002) Cancer susceptibility and the functions of BRCA1
and BRCA2. Cell 108:171-82

Zhang Z, Rowe WL, Struewing JP, Buetow KH (2002) HapScope: A software
system for automated and visual analysis of functionally annotated
haplotypes. Nucleic Acids Res (In Press)

Zheng L, Pan H, Li S, Flesken-Nikitin A, Chen LP, Boyer GT, Lee HW
(2000) Sequence-specific transcriptional corepressor function for BRCA1
through a novel zinc finger protein, ZBRK1. Mol Cell 6:757-68.