Exonic DNA Sequencing of ERBB4 in Bipolar Disorder
Fernando S. Goes1*, Michael Rongione1, Yun-Ching Chen2, Rachel Karchin2, Eran Elhaik3, the Bipolar
Genome Study", James B. Potash1
1Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America, 2Department of Biomedical
Engineering and the Institute for Computational Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America, 3McKusick-Nathans Institute of
Genetic Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
The Neuregulin-ErbB4 pathway plays a crucial role in brain development and constitutes one of the most biologically
plausible signaling pathways implicated in schizophrenia and, to a lesser extent, in bipolar disorder (BP). However, recent
genome-wide association analyses have not provided evidence for common variation in NRG1 or ERBB4 influencing
schizophrenia or bipolar disorder susceptibility. In this study, we investigate the role of rare coding variants in ERBB4 in BP
cases with mood-incongruent psychotic features, a form of BP with arguably the greatest phenotypic overlap with
schizophrenia. We performed Sanger sequencing of all 28 exons in ERBB4, as well as part of the promoter and part of the
39UTR sequence, hypothesizing that rare deleterious variants would be found in 188 cases with mood-incongruent
psychosis from the GAIN BP study. We found 42 variants, of which 16 were novel, although none were non-synonymous or
clearly deleterious. One of the novel variants, present in 11.2% of cases, is located next to an alternative stop codon, which is
associated with a shortened transcript of ERBB4 that is not translated. We genotyped this variant in the GAIN BP case-control
samples and found a marginally significant association with mood-incongruent psychotic BP compared with controls
(additive model: OR=1.64, P-value=0.055; dominant model: OR=1.73. P-value=0.039). In conclusion, we found no rare
variants of clear deleterious effect, but did uncover a modestly associated novel variant that could affect alternative splicing
of ERBB4. However, the modest sample size in this study cannot definitively rule out a role for rare variants in bipolar
disorder and studies with larger sample sizes are needed to confirm the observed association.
Citation: Goes FS, Rongione M, Chen Y-C, Karchin R, Elhaik E, et al. (2011) Exonic DNA Sequencing of ERBB4 in Bipolar Disorder. PLoS ONE 6(5): e20242.
Editor: Katharina Domschke, University of Muenster, Germany
Received December 14, 2010; Accepted April 28, 2011; Published May 26, 2011
Copyright: ? 2011 Goes et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: The study was funded by my NIMH grant (K99 MH086049).The funders had no role in study design, data collection and analysis, decision to publish, or
preparation of the manuscript.
Competing Interests: The authors have declared that no competing interests exist.
* E-mail: firstname.lastname@example.org
" Membership of the Bipolar Genome Study is provided in the Acknowledgments.
Mounting evidence suggests that the major psychoses share, to
some degree, a common genetic susceptibility [1–3]. In particular,
we and others have proposed that within the broad bipolar
disorder spectrum, the subtype of bipolar disorder with mood-
incongruent psychotic features is likely to be the subphenotype
most closely aligned with schizophrenia [4,5]. Among candidate
genes implicated in the pathogenesis of both psychotic disorders,
those in the Neuregulin1-ErbB4 signaling pathway have been
frequently supported by association, copy number variation, and
expression studies , although these findings have not always
In the CNS, NRG1 functions primarily as a signaling molecule
that binds to ERBB4, a tyrosine kinase receptor predominantly
expressed in inhibitory neurons . The ERBB4 gene spans over
1.16 Mb and consists of 28 exons. Alternative splicing of exons
15/16 and exon 26 results in the formation of at least four protein
isoforms that differ in their susceptibility to extra-cellular and
intracellular cleavage . Bound ERBB4 auto-phosphorylates
several intracellular tyrosine residues, leading to the activation of
key intracellular messengers such as phosphatidyl-inositol 3-kinase
(PI3K) and AKT . These proteins, among many functions,
inhibit glycogen synthase kinase-3 (GSK-3), which is arguably the
protein most strongly implicated in lithium’s mechanism of action
. Post-mortem studies have also provided initial evidence for a
functional interaction of ERBB4 with the NMDA receptor ,
also a promising therapeutic target for both mood disorders and
Although ERBB4 has been far less studied than NRG1,
preliminary evidence suggests a possible association with schizo-
phrenia. Among the initial candidate gene studies of ERBB4,
Silberberg et al. found an association between schizophrenia and
three highly linked markers surrounding exon 3 of the gene (best
allelic P-value=0.0049) . However, the sample size was small
(total N=199) and these findings have not been replicated.
Subsequent studies have focused on the interactions between
NRG1 and ERBB4; while significant interactions between various
markers werereported byeachstudy,there was littleoverlap among
the actual interacting markers across studies [13–16]. Moreover, in
genome-wide association studies (GWAS) of Caucasians with
schizophrenia or bipolar disorder, neither NRG1 nor ERBB4 have
featured among the top hits in the original studies or in subsequent
meta-analyses [17,18]. By contrast, the most highly associated SNP
in the only GWAS of schizophrenia in African-Americans was
found in ERBB4 (rs1851196, P-value=2.1461026), though the
PLoS ONE | www.plosone.org1May 2011 | Volume 6 | Issue 5 | e20242
sample size was relatively modest by GWAS standards and the
findings fell short of genome-wide significance.
The above studies of ERBB4 have focused almost exclusively on
common variants. However, increasing evidence indicates that rare
variants might also play a role in the etiology of complex diseases
such as bipolar disorder and schizophrenia . Indeed, a large
deletion (,400 kb)of the39 region of ERBB4 has been reported in a
subject withschizophrenia , but,to ourknowledge,no study has
performed comprehensive sequencing of ERBB4.
While most of the evidence for association in the NRG1-ERBB4
pathway comes from studies of schizophrenia, we hypothesized
that variation in the pathway might also be involved in
susceptibility to bipolar disorder with mood-incongruent psychosis,
where symptoms can often be indistinguishable from those of
schizophrenia. In this study we have performed comprehensive
sequencing of all 28 exons of ERBB4 in cases with mood-
incongruent psychosis from the GAIN BP sample . While we
did not find an excess of functional rare variants, we discovered a
novel, potentially functional, common variant, which was
additionally genotyped in a case-control association experiment.
We demonstrate a modest excess of this variant that appears to be
specific to the mood-incongruent form of BP.
We analyzed 5.9 kb of DNA sequence representing all the 28
exons and surrounding sequences, as well as approximately
600 bp of the promoter sequence, all the 59 UTR, and 400 bp
of the 39 UTR sequence in 188 BP subjects with mood-
incongruent psychotic features. We found 42 variants; of these,
26 were single nucleotide variants (SNVs) present in dbSNP 132,
including 17 common polymorphisms present in the HapMap
CEU sample (Fig. 1). We discovered 16 novel variants across
ERBB4 (Table 1), and while no novel variant was non-
synonymous, several were found to have bioinformatic evidence
of a potential functional effect. There were two synonymous SNVs
predicted to change splice site enhancers and silencers, as well as
three variants in the 39 UTR sequence.
Among the 16 novel variants, our power analyses indicated that
only two variants (SNVs 7 and 8) had allele frequencies sufficiently
high enough (MAF.0.03) to warrant additional genotyping in our
available 999 independent controls. Of these, the potentially most
interesting finding was SNV 7 (G.A), which was absent in dbSNP
132, butwaspresentin21out of188 cases(11.2%prevalence,MAF
of 5.6%). As shown in Fig.2, this SNV is 40 bp downstream of exon
20 and is located next to an alternate ‘‘bleeding’’ form of exon 20
that is associated with a prematurely truncated transcript of ERBB4,
with no evidence of being translated (http://genome.ucsc.edu/).
To determine whether this novel SNV was associated with
mood-incongruent psychotic BP, we performed an association
study by genotyping additional controls (N=999) and the
remaining (non mood-incongruent psychotic) BP cases (N=806)
from the GAIN BP sample (Table 2). The novel marker was in
Hardy-Weinberg equilibrium in both cases (P-value=1.0) and
controls (P-value=0.36), and was present in 6.9% of controls,
with a MAF of 3.6%. Using logistic regression with principal
components as covariates we found an association of the novel
SNV in cases with mood-incongruent psychotic BP compared with
controls that was statistically significant in a dominant model
(OR=1.73, P-value=0.039) and close to significance in an
additive model (OR=1.64, P-value=0.055). This association
appeared to be specific to cases with mood-incongruent psychotic
BP, since a case-only analysis found an enrichment of the putative
risk allele in cases with mood-incongruent psychosis compared
with all other BP cases (Table 2). The second variant tested for
association was a common A/- insertion-deletion polymorphism
(SNV 8). This variant was genotyped in the 999 controls and 806
non-mood incongruent BP cases, but showed no evidence of
association in either the case-control (P-value=0.87) or the case-
only analyses (P-value=0.86).
In this study we sequenced all coding regions of ERBB4, a
candidate gene withstrongbiological plausibility,aswell as suggestive
evidence for geneticassociation with schizophrenia. Wehypothesized
over-represented in BP cases with mood-incongruent psychotic
features, a subset of BP with phenotypic similarities to schizophrenia.
Although sequencing of 188 cases revealed no evidence of a non-
synonymous or loss of function variant, we identified an intriguing
variant with a possible functional effect, and found an association of
Figure 1. Variants identified by sequencing in ERBB4.
Exonic DNA Sequencing of ERBB4 in Bipolar Disorder
PLoS ONE | www.plosone.org2 May 2011 | Volume 6 | Issue 5 | e20242
this variant with the mood-incongruent psychotic form of BP
There are at least five alternatively spliced transcripts of ERBB4
documented in the UCSC Genome Browser, including one
transcript that ends just after exon 20 and has no associated protein
product. This transcript includes a retained 140 bp sequence of
intron 20 (hg 19 coordinates 212,426,487–212,426,626), which, as
shown in Fig. 2, leads to the transcription of a ‘‘bleeding’’ exon with
an alternative stop codon. The newly identified single nucleotide
variant is one base downstream of the alternative stop codon and, if
functional, may have an impact on transcription of the shorter and
non-functional ERBB4 isoform. Although this hypothesis remains to
be experimentally validated, it raises the possibility that risk alleles
may, among other mechanisms, disrupt the normal isoform
‘‘balance’’ of alternatively spliced genes [28,29].
The major psychotic syndromes are likely to be heterogeneous
categories with many underlying etiologies. Clinical subpheno-
types like mood-incongruent psychosis may help mitigate this
Table 1. Description of novel variants identified by sequencing in ERBB4.
number Location (bp)SNP reference allelenew allele
1 213,403,857WTA 0.00359 upstream / in unspliced EST
2 213,403,847SGC 0.00359 upstream / in unspliced EST
3 212,590,021MAC 0.003 intron 102 bp 59 of exon 7
4 212,566,810YCT 0.003 exon 12 Synonymous; Loss of
exon splice enhancer
5 212,543,982KGT 0.003 intron 73 bp 59 of exon 13
6 212,488,828SCG 0.003 intron 59 bp 59 of exon 18
7 212,426,588RGA 0.056intron 40 bp 39 of exon 20Adjacent to
8 212,295,591 A indel
A/-0.247intron 80 bp 39 of exon 21
9212,293,120-2 CTT indelCTT/CTTCTT/-0.003 intron 85 bp 59 of exon 22
10212,286,804RAG 0.003exon 24 Synonymous;Gain of
exon splice silencer
11 212,251,910YCT 0.008intron 35 bp 59 of exon 27
12212,251,550RGA0.003intron 28 bp 39 of exon 27
13212,251,537MCA0.003intron 41 bp 39 of exon 27
14212,248,283MCA0.00839 UTR (57 bp)
15212,248,281SCG0.00539 UTR (59 bp)
16212,248,219RGA0.00339 UTR (121 bp)
Figure 2. ERBB4 gene structure with a focus on a novel variant within a ‘‘bleeding’’ exon 20.
Exonic DNA Sequencing of ERBB4 in Bipolar Disorder
PLoS ONE | www.plosone.org3May 2011 | Volume 6 | Issue 5 | e20242
complexity. If the BP phenotype is composed of multiple
subphenotypes with partially distinct genetic causes, then any
particular genetic variant might contribute to causation of one or
several subphenotypes, but not all. Subphenotypes of the disorder
might be more informative for purposes like gene mapping if the
increased effect size of a risk allele due to genetic homogeneity
within the subgroup outweighs the reduction in power from a
smaller sample size . In this study, the association of a novel
SNP with mood-incongruent BP yielded a larger effect size
(OR,1.6–1.7) than those typically seen in GWAS of psychiatric
This study has several limitations, perhaps the most important
being the relatively small sample size. Assuming a binomial
distribution, our sample of 188 sequenced cases had an 80%
probability to find a mutation with a case frequency .0.4%,
which is likely to miss many rare variants, particularly if extensive
allelic heterogeneity is present. In our genotyped case-control
sample we had 80% power to detect OR$1.9, but only ,55%
power to detect ORs in the range found in this study (ORs$1.6).
Modest sample sizes such as these are also more likely to produce
inflated effect size estimates and are vulnerable to chance findings
(type I error). A further limitation which may increase type I
error stems from our strategy to sequence cases, while only
genotyping potentially functional variants in controls ,
although this is likely lessened by our tested variant being
uncommon rather than rare, and by the control sample size being
over five times larger than the case sample size. Additional
limitations include the limited coverage of the promoter and the
39 UTR sequences and the very restricted coverage of the introns.
Given the length of ERBB4 (1.16 MB) full sequencing of the gene
is likely to be feasible only in the context of whole genome
sequencing. Finally, we note that although the discovered SNV
may potentially affect splicing, experimental validation is
necessary to test this hypothesis.
In conclusion, we find no evidence of unambiguous loss of
function mutations in 188 cases with mood-incongruent psychotic
BP. We discovered a novel variant present in 11% of cases and 6%
of controls that may have functional importance, but additional
studies are necessary to replicate this association and to study the
impact of the variant on splicing of ERBB4.
All samples were collected from study participants after
obtaining written informed consent under clinical research
protocols approved by the Johns Hopkins University School of
Medicine institutional review board.
Cases were selected from the 1,001 BP cases and 1,033 controls
of European-American descent genotyped through the GAIN
consortium by the Bipolar Genome Study (BiGS) . All cases
were interviewed with the Diagnostic Interview for Genetic
Studies (DIGS) and best-estimate diagnoses were made by two
research psychiatrists or PhD psychologists. Among the BP cases,
we initially selected for sequencing the 189 subjects from
the GAIN BP sample who had a lifetime history of mood-
incongruent psychosis as previously defined . Briefly, subjects
were classified as cases with mood-incongruent psychotic bipolar
disorder if they had a lifetime history of running commentary
auditory hallucinations, or passivity delusions such as delusions of
being controlled, or delusions of thought insertion, withdrawal, or
broadcasting. Subjects were also included if their psychotic
symptoms during their most severe depression or mania were
judged by the interviewer to be ‘‘inconsistent’’ with typical
depressive or manic themes. Of the 189 subjects, one subject was
sequenced in duplicate, and DNA for one subject was
unavailable, leading to a final count of 188 subjects sequenced
across the ERBB4 gene.
In our association study we genotyped all 189 cases as well as
810 non mood-incongruent BP cases and 999 healthy controls
from the GAIN BP consortium sample. These controls were
previously ascertained using an Internet based adaption of the
Composite International Diagnostic Interview-Short Form (CIDI-
SF) . Controls were selected to have no self-reported history of
hallucinations, bipolar disorder, or schizophrenia, and no history
of sufficient lifetime depressive symptoms to meet DSM-IV criteria
for major depressive disorder.
Conventional PCR amplification and Sanger sequencing were
performed by Polymorphic DNA technologies Inc. (Alameda, CA,
USA). Primers were designed based on the NCBI36/hg18
reference sequence of the longest ERBB4 transcript (RefSeq
NM_005235; CCDS 2394). The sequenced regions included all 28
exons, 1 kb of the promoter region, the 59UTR, and 400 bp of the
7.9 kb 39UTR. Sequencing was performed on both strands and
chromatograms were aligned and visualized using CodonCode
Aligner (CodonCode Corporation, Dedham, MA, USA). One
sample was sequenced in duplicate across all PCR amplifications
and showed 100% concordance. Sequencing of the promoter
region was divided into five PCR amplicons; however, the first
three amplicons yielded poor sequence quality in all samples and
were excluded from the analysis. The remaining two amplicons
(closest to the promoter) yielded approximately 600 bp of high
Table 2. Association analysis of a novel SNV (chr2:212426588).
(N subjects) OR
Mood-incongruent psychotic BP 5.6% (189)
vs. vs.1.64 0.0551.73 0.039
Controls 3.6% (999)
Mood-incongruent psychotic BP 5.6% (189
vs.vs.1.650.063 1.65 0.063
All other BP cases3.6% (806)
Exonic DNA Sequencing of ERBB4 in Bipolar Disorder
PLoS ONE | www.plosone.org4May 2011 | Volume 6 | Issue 5 | e20242
All novel single nucleotide variants (SNVs) were confirmed
either with bidirectional sequencing, or, if the complimentary
strand was of poor sequencing quality, with additional genotyping
Genotyping was performed by pyrosequencing using the
PyroMark MD system (QIAGEN). To confirm the novel variants
that were seen only on one strand we genotyped nine novel SNVs,
validating seven of these nine variants. In the case-control
association, we genotyped 995 BP cases (189 with and 806
without mood-incongruent psychosis) and 999 controls from the
BiGS study. Among this sample, 23 individuals were genotyped in
duplicate and showed 100% concordance.
To account for potential population stratification between cases
and controls, we used Eigensoft  to derive principal
components from the available GWAS data for all samples. Based
on a scree plot, we selected the top two principal components to
include as covariates in our association analysis. We performed
association analyses using additive and dominant models.
Novel variants were visualized in the UCSC genome browser
(GRCh37/hg19) with all available annotation tracks. RESCUE-
ESE was used to identify potential exonic splicing enhancers .
We queried UTR variants for disruption of miRNA binding sites
with miRBase , and for changes in RNA secondary structure
with RNAFold .
Probability and power calculations
For the sequenced sample size of 188, we calculated the smallest
minor allele frequency (MAF) that could be detected with a
probability of 80% using an integral over a cumulative binomial
distribution. Power for the association analysis of 188 cases and
999 controls was calculated using the Genetic Power Calculator
 with the following assumptions: (1) full linkage disequilibrium
with the pathogenic mutation; (2) an additive model; and (3) an
a=0.05. With the above parameters and a hypothesized effect size
of OR=2.0, our sample had 80% power to detect an association
with variants of minor allele frequencies .0.03.
The authors express their appreciation to the families who participated in
this project, and to the many clinicians who facilitated the referral of
participants to the study. Genome-wide SNP genotyping of the NIMH
samples was performed through the Genetic Association Information
Network under the direction of the Bipolar Genome Study (BiGS). The
principal investigators and co-investigators were: John R. Kelsoe, Tiffany
A. Greenwood, Caroline M. Nievergelt, Rebecca McKinney, Paul D.
Shilling, Nicholas Schork, Erin N. Smith, Cinnamon Bloss, John
Nurnberger, Howard J. Edenberg, Tatiana Foroud, Daniel L. Koller,
Elliot Gershon, Chunyu Liu, Judith A. Badner, William A. Scheftner,
William B. Lawson, Evaristus A. Nwulia, Maria Hipolito, William Coryell,
John Rice, William Byerley, Francis McMahon, Thomas G. Schulze,
Wade Berrettini, James B. Potash, Peter P. Zandi, Pamela B. Mahon,
Melvin G. McInnis, Sebastian Zo ¨llner, Peng Zhang, David W. Craig,
Szabolcs Szelinger, Thomas B. Barrett.
Data and biomaterials for the NIMH samples were collected as part of
10 projects that participated in the NIMH Bipolar Disorder Genetics
Initiative. From 1991 to 1998, the principal investigators and co-
investigators were: John Nurnberger, Marvin Miller, Elizabeth Bowman,
Theodore Reich, Allison Goate, John Rice, J. Raymond DePaulo Jr.,
Sylvia Simpson, Colin Stine, Elliot Gershon, Diane Kazuba, Elizabeth
Maxwell. From 1999 to 2003, the principal investigators and co-
investigators were: John Nurnberger, Marvin J. Miller, Elizabeth S.
Bowman, N. Leela Rau, P. Ryan Moe, Nalini Samavedy, Rif El-Mallakh,
Husseini Manji, A. Glitz, Eric T. Meyer, Carrie Smiley, Tatiana Foroud,
Leah Flury, Danielle M. Dick, Howard Edenberg, John Rice, Theodore
Reich, Allison Goate, Laura Bierut, Melvin McInnis, J. Raymond DePaulo
Jr., Dean F. MacKinnon, Francis M. Mondimore, James B. Potash, Peter
P. Zandi, Dimitrios Avramopoulos, Jennifer Payne, Wade Berrettini,
William Byerley, Mark Vawter, William Coryell, Raymond Crowe, Elliot
Gershon, Judith Badner, Francis McMahon, Chunyu Liu, Alan Sanders,
Maria Caserta, Steven Dinwiddie, Tu Nguyen, Donna Harakal, John R.
Kelsoe, Rebecca McKinney, William Scheftner, Howard M. Kravitz,
Diana Marta, Annette Vaughn-Brown, Laurie Bederow, Layla Kassem,
Sevilla Detera-Wadleigh, Lisa Austin, Dennis L. Murphy. Control subjects
from the National Institute of Mental Health Schizophrenia Genetics
Initiative (NIMH-GI), data and biomaterials were collected by the
‘‘Molecular Genetics of Schizophrenia II’’ (MGS-2) collaboration. The
investigators and co-investigators are: Pablo V. Gejman, Alan R. Sanders,
Farooq Amin, Nancy Buccola, William Byerley, C. Robert Cloninger,
Raymond Crowe, Donald Black, Robert Freedman, Douglas Levinson
Bryan Mowry, Jeremy Silverman.
Conceived and designed the experiments: FSG JBP. Performed the
experiments: FSG MR. Analyzed the data: FSG Y-CC RK EE. Wrote the
paper: FSG JBP.
1. Lichtenstein P, Yip BH, Bjork C, Pawitan Y, Cannon TD, et al. (2009) Common
genetic determinants of schizophrenia and bipolar disorder in Swedish families:
A population-based study. Lancet 373(9659): 234–239.
2. Potash JB, Bienvenu OJ (2009) Neuropsychiatric disorders: Shared genetics of
bipolar disorder and schizophrenia. Nat Rev Neurol 5(6): 299–300.
3. Williams HJ, Craddock N, Russo G, Hamshere M, Moskvina V, et al. (2011)
Most genome-wide significant susceptibility loci for schizophrenia and bipolar
disorder reported to date cross traditional diagnostic boundaries. Hum Mol
Genet 20(2): 387–391.
4. Green EK, Raybould R, Macgregor S, Gordon-Smith K, Heron J, et al. (2005)
Operation of the schizophrenia susceptibility gene, neuregulin 1, across
traditional diagnostic boundaries to increase risk for bipolar disorder. Arch
Gen Psychiatry 62(6): 642–648.
5. Goes FS, Zandi PP, Miao K, McMahon FJ, Steele J, et al. (2007) Mood-
incongruent psychotic features in bipolar disorder: Familial aggregation and
suggestive linkage to 2p11-q14 and 13q21-33. Am J Psychiatry 164(2): 236–247.
6. Buonanno A (2010) The neuregulin signaling pathway and schizophrenia: From
genes to synapses and neural circuits. Brain Res Bull 83(3–4): 122–131.
7. Fazzari P, Paternain AV, Valiente M, Pla R, Lujan R, et al. (2010) Control of
cortical GABA circuitry development by Nrg1 and ErbB4 signaling. Nature
8. Birchmeier C (2009) ErbB receptors and the development of the nervous system.
Exp Cell Res 315(4): 611–618.
9. Mei L, Xiong WC (2008) Neuregulin 1 in neural development, synaptic
plasticity and schizophrenia. Nat Rev Neurosci 9(6): 437–452.
10. Beaulieu JM, Sotnikova TD, Yao WD, Kockeritz L, Woodgett JR, et al. (2004)
Lithium antagonizes dopamine-dependent behaviors mediated by an AKT/
glycogen synthase kinase 3 signaling cascade. Proc Natl Acad Sci U S A 101(14):
11. Hahn CG, Wang HY, Cho DS, Talbot K, Gur RE, et al. (2006) Altered
neuregulin 1-erbB4 signaling contributes to NMDA receptor hypofunction in
schizophrenia. Nat Med 12(7): 824–828.
12. Silberberg G, Darvasi A, Pinkas-Kramarski R, Navon R (2006) The involvement
of ErbB4 with schizophrenia: Association and expression studies. Am J Med
Genet B Neuropsychiatr Genet 141B(2): 142–148.
13. Norton N, Moskvina V, Morris DW, Bray NJ, Zammit S, et al. (2006) Evidence
that interaction between neuregulin 1 and its receptor erbB4 increases
susceptibility to schizophrenia. Am J Med Genet B Neuropsychiatr Genet
14. Benzel I, Bansal A, Browning BL, Galwey NW, Maycox PR, et al. (2007)
Interactions among genes in the ErbB-neuregulin signalling network are
associated with increased susceptibility to schizophrenia. Behav Brain Funct
15. Shiota S, Tochigi M, Shimada H, Ohashi J, Kasai K, et al. (2008) Association
and interaction analyses of NRG1 and ERBB4 genes with schizophrenia in a
Japanese population. J Hum Genet 53(10): 929–935.
Exonic DNA Sequencing of ERBB4 in Bipolar Disorder
PLoS ONE | www.plosone.org5 May 2011 | Volume 6 | Issue 5 | e20242
16. Nicodemus KK, Law AJ, Radulescu E, Luna A, Kolachana B, et al. (2010) Download full-text
Biological validation of increased schizophrenia risk with NRG1, ERBB4, and
AKT1 epistasis via functional neuroimaging in healthy controls. Arch Gen
Psychiatry 67(10): 991–1001.
17. Shi J, Levinson DF, Duan J, Sanders AR, Zheng Y, et al. (2009) Common
variants on chromosome 6p22.1 are associated with schizophrenia. Nature
18. Ferreira MA, O’Donovan MC, Meng YA, Jones IR, Ruderfer DM, et al. (2008)
Collaborative genome-wide association analysis supports a role for ANK3 and
CACNA1C in bipolar disorder. Nat Genet 40(9): 1056–1058.
19. Cirulli ET, Goldstein DB (2010) Uncovering the roles of rare variants in
common disease through whole-genome sequencing. Nat Rev Genet 11(6):
20. Walsh T, McClellan JM, McCarthy SE, Addington AM, Pierce SB, et al. (2008)
Rare structural variants disrupt multiple genes in neurodevelopmental pathways
in schizophrenia. Science 320(5875): 539–543.
21. Smith EN, Bloss CS, Badner JA, Barrett T, Belmonte PL, et al. (2009) Genome-
wide association study of bipolar disorder in European American and African
American individuals. Mol Psychiatry 14(8): 755–763.
22. Sanders AR, Levinson DF, Duan J, Dennis JM, Li R, et al. (2010) The internet-
based MGS2 control sample: Self report of mental illness. Am J Psychiatry
23. Patterson N, Price AL, Reich D (2006) Population structure and eigenanalysis.
PLoS Genet 2(12): e190.
24. Fairbrother WG, Yeh RF, Sharp PA, Burge CB (2002) Predictive identification
of exonic splicing enhancers in human genes. Science 297(5583): 1007–1013.
25. Griffiths-Jones S, Saini HK, van Dongen S, Enright AJ (2008) miRBase: Tools
for microRNA genomics. Nucleic Acids Res 36(Database issue): D154–8.
26. Bindewald E, Shapiro BA (2006) RNA secondary structure prediction from
sequence alignments using a network of k-nearest neighbor classifiers. RNA
27. Purcell S, Cherny SS, Sham PC (2003) Genetic power calculator: Design of
linkage and association genetic mapping studies of complex traits. Bioinformatics
28. Johnson MB, Kawasawa YI, Mason CE, Krsnik Z, Coppola G, et al. (2009)
Functional and evolutionary insights into human brain development through
global transcriptome analysis. Neuron 62(4): 494–509.
29. Wang GS, Cooper TA (2007) Splicing in disease: Disruption of the splicing code
and the decoding machinery. Nat Rev Genet 8(10): 749–761.
30. Potash JB, Toolan J, Steele J, Miller EB, Pearl J, et al. (2007) The bipolar
disorder phenome database: A resource for genetic studies. Am J Psychiatry
31. Li B, Leal SM (2009) Discovery of rare variants via sequencing: Implications for
the design of complex trait association studies. PLoS Genet 5(5): e1000481.
Exonic DNA Sequencing of ERBB4 in Bipolar Disorder
PLoS ONE | www.plosone.org6 May 2011 | Volume 6 | Issue 5 | e20242