Association study of Wnt signaling pathway genes in bipolar disorder.
BACKGROUND
The Wnt signaling pathways promote cell growth and are best known for their role in embryogenesis and cancer. Several lines of evidence suggest that these pathways might also be involved in bipolar disorder.


OBJECTIVE
To test for an association between candidate genes in the Wnt signaling pathways and disease susceptibility in a family-based bipolar disorder study.


METHODS
Two hundred twenty-seven tagging single- nucleotide polymorphisms (SNPs) from 34 genes were successfully genotyped. Initial results led us to focus on the gene PPARD, in which we genotyped an additional 13 SNPs for follow-up.


METHODS
Nine academic medical centers in the United States.


METHODS
Five hundred fifty-four offspring with bipolar disorder and their parents from 317 families.


METHODS
Family-based association using FBAT and HBAT (http://www.biostat.harvard.edu/~fbat/default.html; Harvard School of Public Health, Boston, Massachusetts). Exploratory analyses testing for interactions of PPARD SNPs with clinical covariates and with other Wnt genes were conducted with GENASSOC (Stata Corp, College Station, Texas).


RESULTS
In the initial analysis, the most significantly associated SNP was rs2267665 in PPARD (nominal P < .001). This remained significant at P = .05 by permutation after accounting for all SNPs tested. Additional genotyping in PPARD yielded 4 SNPs in 1 haplotype block that were significantly associated with bipolar disorder (P < .01), the most significant being rs9462082 (P < .001). Exploratory analyses revealed significant evidence (P < .01) for interactions of rs9462082 with poor functioning on the Global Assessment Scale (odds ratio [OR], 3.36; 95% confidence interval [CI], 1.85-6.08) and with SNPs in WNT2B (rs3790606: OR, 2.56; 95% CI, 1.67-4.00) and WNT7A (rs4685048: OR, 1.79; 95% CI, 1.23-2.63).


CONCLUSIONS
We found evidence for association of bipolar disorder with PPARD, a gene in the Wnt signaling pathway. The consistency of this result with one from the Wellcome Trust Case-Control Consortium encourages further study. If the finding can be confirmed in additional samples, it may illuminate a new avenue for understanding the pathogenesis of severe bipolar disorder and developing more effective treatments.
Zandi
Peter P
PP
Department of Mental Health, Bloomberg School of Public Health, Johns Hopkins University, Hampton House, Room 857, 624 N Broadway, Baltimore, MD 21205, USA. pzandi@jhsph.edu
Belmonte
Pamela L
PL
Willour
Virginia L
VL
Goes
Fernando S
FS
Badner
Judith A
JA
Simpson
Sylvia G
SG
Gershon
Elliot S
ES
McMahon
Francis J
FJ
DePaulo
J Raymond
JR
Potash
James B
JB
D001714:Bipolar Disorder / Q000175:diagnosis / Q000235:genetics*; D002896:Chromosomes, Human, Pair 6 / Q000235:genetics; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005500:Follow-Up Studies; D005838:Genotype; D006023:Glycoproteins / Q000235:genetics; D006239:Haplotypes; D006801:Humans; D047494:PPAR delta / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics*; D051153:Wnt Proteins / Q000235:genetics*; D060508:Wnt3 Protein
D006023:Glycoproteins; D047494:PPAR delta; C115496:WNT2B protein, human; C092778:WNT7A protein, human; C110670:WNT9A protein, human; D051153:Wnt Proteins; D060508:Wnt3 Protein