Intron 12 in NTRK3 is associated with bipolar disorder

Intron 12 in NTRK3 is associated with bipolar disorder

Psychiatry Research 185 (2011) 358–362 Contents lists available at ScienceDirect Psychiatry Research j o u r n a l h o m e p a g e : w w w. e l s ev...

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Psychiatry Research 185 (2011) 358–362

Contents lists available at ScienceDirect

Psychiatry Research j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / p s yc h r e s

Intron 12 in NTRK3 is associated with bipolar disorder Lavinia Athanasiu a,b,c,⁎, Morten Mattingsdal a,c, Ingrid Melle a,c, Elin Inderhaug a, Trude Lien b, Ingrid Agartz c,d, Steinar Lorentzen c,e, Gunnar Morken f, Ole A. Andreassen a,c, Srdjan Djurovic b,c a

Department of Psychiatry, Oslo University Hospital—Ullevål, Oslo, Norway Department of Medical Genetics, Oslo University Hospital—Ullevål, Oslo, Norway Institute of Psychiatry, University of Oslo, Oslo, Norway d Department of Psychiatric Research, Diakonhjemmet Hospital, Oslo, Norway e Department of Psychiatry, Oslo University Hospital—Aker, Oslo, Norway f Østmarka Psychiatric Department, St. Olavs Hospital and Institute of Neuroscience, Norwegian University of Technology and Science, Trondheim, Norway b c

a r t i c l e

i n f o

Article history: Received 23 December 2009 Received in revised form 19 April 2010 Accepted 11 May 2010 Keywords: NTRK3 SNP Bipolar disorders

a b s t r a c t Based on the important role of neurotrophic factors in brain development and plasticity and reports of association between schizophrenia and the gene neurotrophic tyrosine kinase receptor 3 (NTRK3), we investigated associations of bipolar disorder with polymorphisms in NTRK3. Recently, our group reported evidence for a possible association of NTRK3 polymorphisms with hippocampal function and schizophrenia. In the present study, we used a homogenous Norwegian case–control sample (the TOP study) consisting of 194 patients diagnosed with bipolar disorder and 336 healthy controls genotyped on the Affymetrix Genome-wide Human SNP Array 6.0. In total 149 markers were investigated for SNP-disease association. Polymorphisms in over 20 markers were nominally associated with bipolar disorder, covering intron 5 to intron 12. Interestingly, our markers appeared to be located close or within the linkage regions reported in schizophrenia, early-onset major depressive disorder and eating disorder, supporting the hypothesis that some genes influence risk beyond traditional diagnostic boundaries. © 2010 Elsevier Ireland Ltd. All rights reserved.

1. Introduction Neurotrophins, including NT-3 and the neurotrophic tyrosine kinase receptor (NTRK3), have been implicated in psychiatric disorders. Abnormal expression of NT-3 protein has been observed in schizophrenia (SCZ) (Durany et al., 2001), and associations between NT-3 gene polymorphisms and SCZ have been reported in several (Dawson et al., 1995; Hattori and Nanko, 1995; Jonsson et al., 1997; Nanko et al., 1994; Virgos et al., 2001) but not all studies (Lin and Tsai, 2004; Nimgaonkar et al., 1995). However, it is not known how alterations of NT-3 levels are related to NTRK-3. Reduced gene expression of NTRK3 was reported in patients with SCZ (Schramm et al., 1998; Weickert et al., 2005), but the relationship to SNP variants is not known. We recently reported (Otnaess et al., 2009) evidence for a possible association of NTRK3 gene polymorphisms with hippocampal function in SCZ. Recently, genome-wide significant linkage of chromosome 15q25.3–26.2 with recurrent early-onset major depressive disorder and consecutive sequence analysis revealed NTRK3 as a biologically plausible candidate gene also in affective disorders (Verma et al., 2008). The aim of the present study was to investigate possible ⁎ Corresponding author. Department of Medical Genetics, Oslo University Hospital— Ulleval, Kirkeveien 166, 0407 Oslo, Norway. Tel.: +47 23 02 73 32; fax: +47 22 11 98 99. E-mail address: [email protected] (L. Athanasiu). 0165-1781/$ – see front matter © 2010 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.psychres.2010.05.011

association between genetic variants of NTRK3 and bipolar disorder (BD) in a homogenous Norwegian sample, given the hypothesis of overlap in genetic risk between SCZ and BD (Moskvina et al., 2009), as well as that some genes influence risk beyond traditional diagnostic boundaries (Moskvina et al., 2009).

2. Materials and methods 2.1. Sample description 2.1.1. The TOP study 2.1.1.1. Patients. The subjects participated in a large ongoing study on BD Thematically Organized Psychosis (Top) Study and were recruited from out-patient and in-patient psychiatric units at four University Hospitals in Oslo and Trondheim, Norway, from May, 2003 through July, 2007. The health care system is catchment area based, free of charge, and no other psychiatric health care provider exists. The patients were invited to participate in the study by the clinician responsible for their treatment. All participants gave written informed consent, and the study was approved by the Regional Committee for Medical Research Ethics and the Norwegian Data Inspectorate, and the Biobank was approved by the Health Department.

2.1.1.2. Inclusion criteria. In order to participate in the current study subjects needed to be between 18 and 65 years, obtain an IQ score of above 70, meet the DSM-IV criteria for schizophrenia, schizoaffective or schizophreniform disorder (in the following termed SCZ), Bipolar I disorder, Bipolar II disorder and Bipolar NOS (in the following termed BD), and be willing and able to give informed consent.

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2.1.1.3. Measures. Diagnosis was established using the Structured Clinical Interview for DSM-IV-TR-axis I disorders (SCID-I) (Spitzer et al., 1992). To assess reliability for actual study interviews a stratified random sample was drawn, consisting of cases from each of the raters. Anonymous vignettes describing symptoms and development of the illness were then rated by two experts blind to the study ratings. For the 28 vignettes the overall agreement for the DSM-IV diagnostic categories was 82% and the overall Kappa 0.77 (95% CI: 0.60–0.94). 2.1.1.4. Ethnicity. The majority (90%) of the patients were ethnical Norwegian, i.e. the patient and both parents were born in Norway, while in a minor fraction of the cases (10%) one parent was born outside Norway in another North-western European country. 2.1.2. Healthy controls The healthy controls subjects were randomly selected from statistical records of persons from the same catchments area as the patient groups. Only subjects born in Norway were contacted by letter and invited to participate. All controls were of Caucasian origin; around 85% had two Norwegian parents, the rest one parent from other European origin. Moreover, all participants had to have Norwegian as their first language or have received their compulsory schooling in Norway. The control subjects were screened by interview and with the Primary Care Evaluation of Mental Disorders (PRIME-MD). None of the control subjects had a history of moderate/severe head injury, neurological disorder, mental retardation or an age outside the age range of 18–60 years. Healthy subjects were excluded if they or any of their close relatives had a lifetime history of a severe psychiatric disorder (SCZ, BD and major depression), a history of medical problems thought to interfere with brain function (hypothyroidism, uncontrolled hypertension and diabetes), or significant illicit drug use. 2.2. Genotyping We carried out a genome-wide genotyping using the Affymetrix Genome-wide Human SNP Array 6.0 (Affymetrix Inc, Santa Clara, CA, USA). All chips were subjected to the Birdseed-v2 algorithm developed by Affymetrix Inc. and Broad Inst and implemented in the software respiratory Affymetrix Power Tools (APT v1.10). After calling the raw data, input files for PLINK (Purcell et al., 2007) were made using the NCBI 36.1 genome build. We initialized the following quality control parameters in PLINK: 95% call rate per sample, 95% call rate per marker and a minimum minor allele frequency of 5%. In addition a pair-wise identity-by-state distance matrix was made, using PLINK, in order to detect potential duplicate samples and mix-ups. This pair-wise identity-by-state distance matrix was also used for principal component clustering. Eigenvectors 1 and 2 were used for visualization and identification of genetic outliers was performed in collaboration with database curator. After the application of the above parameters 194 BD and 336 control subjects remained. After frequency and pruning analysis of the genotyping results, 149 markers within NTRK3 (± 20 kb) were ready for association testing. The genomic inflation factor was 1.024. The average call rate was 0.98. 2.3. Association analysis The TOP data were analyzed for NTRK3–BD association using the basic case/control allelic association test and the genotype-based Cochran–Armitage trend test, implemented in PLINK. In addition, logistic regression was used to perform haplotype-based association analyses in intron 12, using the sliding window approach with window-sizes between 2 and 10, also implemented in PLINK. 2.4. In silico analysis of gene expression The associated intronic SNPs were analyzed in silico for effects on the expression of the gene. Transcription factor predicting server PreMod (Ferretti et al., 2007) was used to evaluate the effects. The hg17 coordinates for our high scoring region (rs11631112 to rs4887211), 86,460,660 to 86,556,140 was analyzed.

3. Results Position of the markers genotyped in NTRK3 and the linkage disequilibrium between markers, measured by D′, are presented in Fig. 1. The presented markers covers the area between exons 6 to 12 and are localized in intron 5 (rs3784405) and intron 12 (rs2114252, rs4887364, rs994068, rs991728, rs11630338, rs16941261, rs3784411). The results of the comparison of BD versus controls are displayed in Table 1. Several markers reached nominal significance and their localization was non-random. Of particular interest were 14 neighboring markers (rs16941261–rs3784405), all located in intron 5 to intron 12 (96 kb) in NTRK3. The strongest association signal was obtained for rs3784405 (P = 3.08 × 10− 5). The association signal did

Fig. 1. NTRK3 LD map and polymorphisms. LD map and -log of simulated P-values for SNP vs. BD of NTRK3 using data from bipolar disorder (n = 225) and healthy controls (n = 385) of TOP sample. The figure displays the LD map of NTRK3 on chromosome 15q25.3–26.2, and the localization of the markers that have been linked to BD.

not reach genome-wide significance, but controlling for number of SNPs included in the current study (n = 143), the Bonferroni corrected P-value was 0.004. Strong association signals were also seen for haplotypes in intron 5 to intron 12. The haplotype obtainining the lowest P-value (1.98 × 10− 5) was with window of two markers, rs3784405|rs6496465 (TC) (Supplementary Fig. 1). In addition, we investigated the possible effect the intronic markers could have on gene expression. The best scoring transcription factor modules were a combination of Nkx2.2, Pax6, Zic3 and PUO2F1. 4. Discussion The current systematic gene-wide screen of SNPs within the NTRK3 gene in the TOP sample of patients with BD and healthy controls, revealed a strong association signal in intron 12. To our knowledge, no previous study has investigated the possible association between BD and NTRK3 variants. NTRK3 is localized on 15q25–26, a region found to be duplicated in panic and phobic disorders (Gratacos et al., 2001). Furthermore, NTRK3 has been suggested as a susceptibility gene for: autism (Chagnon 2005), SCZ (McAuley et al., 2009; Shi et al., 2009), earlyonset major depressive disorder (Feng et al., 2008; Verma et al., 2008), eating disorder (Mercader et al., 2008), obsessive–compulsive hoarding (Alonso et al., 2008) and adult attention deficit hyperactivity disorder score in a high-risk male population (Conner et al., 2008) and SCZ (Otnaess et al., 2009). Interestingly, our markers appeared to be located close or within the linkage regions reported in some of the mentioned studies including SCZ (Shi et al., 2009), early-onset major depressive disorder (Verma et al., 2008) and eating disorder (Mercader et al., 2008). These findings support the specific hypothesis that some genes influence risk beyond traditional diagnostic boundaries (Moskvina et al., 2009). Transcription factor binding sites were in silico predicted for Nkx2.2 and Pax6 in the high scoring region using PreMod. These transcription factors are involved in neural system development (Briscoe et al., 1999), connecting these genetic variants, in the intronic regions associated with BD, to be of regulatory nature. Taken together, this provides additional support for the candidacy of NTRK3 as a susceptibility gene in BD. The SNPs investigated in our

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Table 1 Association signals in NTRK3. Results from the allelic and genotypic association tests of BD with polymorphisms in NTRK3. Chr

15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15

SNP

rs1986826 rs9920842 rs1369427 rs7168662 rs4887326 rs11073737 rs7179067 rs1073723 rs717320 rs7166186 rs4887328 rs11632716 rs7165500 rs11073746 rs12591645 rs12903567 rs17842141 rs4887329 rs4243096 rs12907837 rs13313527 rs920067 rs7164376 rs16940895 rs1560977 rs1560976 rs3803409 rs3743165 rs4404039 rs1369417 rs1369416 rs9635402 rs11073752 rs2117655 rs11638486 rs11634388 rs1435403 rs7163473 rs16941001 rs7161806 rs6496455 rs1435397 rs7182329 rs12595693 rs7175941 rs1465747 rs8039186 rs2043516 rs7170062 rs12593792 rs7170215 rs11631508 rs13380271 rs16941070 rs1461214 rs2018052 rs2009966 rs10520671 rs11073758 rs12324332 rs11073759 rs1017757 rs1381112 rs12441487 rs7167737 rs8033409 rs1948066 rs16941174 rs8035265 rs10520673 rs1870736 rs17755717 rs8036369 rs8035178

BP

86128135 86130422 86131261 86141808 86142404 86143459 86143690 86144659 86145464 86146487 86150079 86161287 86161672 86162495 86162626 86163251 86163605 86165434 86167979 86169420 86171266 86191521 86197103 86202124 86204840 86204926 86205395 86206046 86211994 86213813 86213829 86217538 86224055 86229706 86233175 86237621 86238073 86246498 86249170 86253599 86254661 86255830 86258643 86258835 86263503 86265114 86274294 86275791 86284460 86292779 86299145 86299470 86300189 86300437 86312021 86320220 86341728 86347520 86350122 86350155 86351446 86355556 86366855 86385314 86390384 86390784 86391497 86393453 86395443 86418725 86425625 86426100 86433890 86433931

Allelic

P (trend)

A1

Affected

Controls

A2

C T C G A G A C G A T G T G A A T A T C A C T A C G G G T T G C C C T G A C A A A G A A C T T T C T T G T A G T A G G C A G G G C G T A T T G A C C

0.2577 0.2088 0.114 0.1263 0.2435 0.3553 0.3041 0.4763 0.3549 0.2448 0.2655 0.116 0.116 0.3958 0.5156 0.116 0.2181 0.299 0.2474 0.07732 0.3686 0.4021 0.2423 0.07474 0.3582 0.3582 0.3549 0.3413 0.3438 0.2784 0.433 0.2715 0.2906 0.3516 0.2397 0.2603 0.2047 0.2629 0.1166 0.4562 0.134 0.2513 0.3737 0.1414 0.1907 0.4335 0.4249 0.215 0.4768 0.1881 0.4639 0.3325 0.4021 0.3834 0.2036 0.3737 0.4119 0.1469 0.4611 0.1701 0.1443 0.1658 0.1082 0.3325 0.2979 0.0799 0.3196 0.0799 0.4067 0.3921 0.4149 0.232 0.3737 0.482

0.2679 0.2202 0.119 0.125 0.25 0.3807 0.3065 0.4535 0.3769 0.2522 0.2887 0.1146 0.1123 0.4238 0.4836 0.1131 0.2204 0.3015 0.2455 0.0806 0.3408 0.3687 0.253 0.04328 0.3735 0.3735 0.3716 0.3364 0.3398 0.2919 0.4152 0.2857 0.2961 0.3204 0.2411 0.25 0.2087 0.2731 0.0850 0.4836 0.1548 0.1809 0.3284 0.1667 0.1313 0.3854 0.3735 0.2292 0.4286 0.1964 0.4048 0.2619 0.3542 0.3414 0.1771 0.4179 0.3438 0.1176 0.3943 0.1369 0.1183 0.1414 0.1351 0.2649 0.253 0.08482 0.253 0.07508 0.317 0.4092 0.4375 0.1657 0.4196 0.4701

T C T A G A G T A T A C C C G G C G C A G G C C T A A A A C A T T A C C G A T G G A G G T C C C T C A A C C C C G C A G G A A A A A C G G C C G G G

T 0.1297 0.1912 0.06062 0.003723 0.05538 0.6672 0.00681 0.5088 0.506 0.07172 0.658 0.004707 0.03343 0.7801 1.003 0.02023 0.007257 0.007443 0.004719 0.03611 0.8335 1.163 0.1508 4.693 0.2465 0.2465 0.2952 0.02509 0.01675 0.2208 0.32 0.2377 0.0362 1.071 0.002567 0.138 0.02434 0.1311 2.786 0.7432 0.8431 7.316 2.237 1.168 6.681 2.282 2.713 0.282 2.316 0.1082 3.519 5.977 2.416 1.877 1.139 1.997 4.895 1.894 4.494 2.137 1.496 1.146 1.618 5.462 2.517 0.07836 5.445 0.08035 8.688 0.2923 0.5106 7.016 2.157 0.1374

OR

P

0.9491 0.9341 0.952 1.012 0.9654 0.8965 0.9886 1.096 0.9097 0.9612 0.8905 1.014 1.037 0.8908 1.137 1.029 0.9868 0.9881 1.01 0.9559 1.129 1.152 0.9441 1.786 0.9363 0.9363 0.9303 1.022 1.018 0.9356 1.076 0.9317 0.9736 1.15 0.9925 1.056 0.9756 0.9491 1.419 0.8956 0.8452 1.52 1.221 0.8232 1.559 1.22 1.239 0.9214 1.215 0.9481 1.273 1.404 1.226 1.2 1.188 0.8311 1.337 1.293 1.314 1.292 1.258 1.207 0.7769 1.382 1.253 0.9369 1.387 1.07 1.477 0.9312 0.9119 1.521 0.8252 1.048

7.19E−01 6.62E−01 8.06E−01 9.51E−01 8.14E−01 4.14E−01 9.34E−01 4.76E−01 4.77E−01 7.89E−01 4.17E−01 9.45E−01 8.55E−01 3.77E−01 3.17E−01 8.87E−01 9.32E−01 9.31E−01 9.45E−01 8.49E−01 3.61E−01 2.81E−01 6.98E−01 3.03E−02 6.20E−01 6.20E−01 5.87E−01 8.74E−01 8.97E−01 6.39E−01 5.72E−01 6.26E−01 8.49E−01 3.01E−01 9.60E−01 7.10E−01 8.76E−01 7.17E−01 9.51E−02 3.89E−01 3.59E−01 6.83E−03 1.35E−01 2.80E−01 9.75E−03 1.31E−01 9.96E−02 5.95E−01 1.28E−01 7.42E−01 6.07E−02 1.45E−02 1.20E−01 1.71E−01 2.86E−01 1.58E−01 2.69E−02 1.69E−01 3.40E−02 1.44E−01 2.21E−01 2.84E−01 2.03E−01 1.94E−02 1.13E−01 7.80E−01 1.96E−02 7.77E−01 3.20E−03 5.89E−01 4.75E−01 8.08E−03 1.42E−01 7.11E−01

7.13E−01 6.59E−01 8.03E−01 9.52E−01 8.06E−01 4.14E−01 9.35E−01 4.59E−01 4.78E−01 7.85E−01 4.12E−01 9.45E−01 8.55E−01 3.60E−01 3.13E−01 8.87E−01 9.31E−01 9.31E−01 9.43E−01 8.52E−01 3.61E−01 2.89E−01 7.01E−01 3.46E−02 6.20E−01 6.20E−01 5.86E−01 8.72E−01 8.93E−01 6.31E−01 5.76E−01 6.16E−01 8.44E−01 3.01E−01 9.59E−01 7.06E−01 8.73E−01 7.11E−01 1.03E−01 3.78E−01 3.71E−01 8.12E−03 1.37E−01 2.84E−01 1.01E−02 1.17E−01 9.50E−02 5.90E−01 1.29E−01 7.47E−01 6.23E−02 1.32E−02 1.17E−01 1.66E−01 2.96E−01 1.62E−01 2.83E−02 1.80E−01 3.42E−02 1.50E−01 2.34E−01 2.92E−01 2.06E−01 1.97E−02 1.14E−01 7.81E−01 2.21E−02 7.79E−01 3.64E−03 5.85E−01 4.85E−01 4.66E−03 1.59E−01 7.18E−01

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Table 1 (continued) Chr

15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15

SNP

rs6496461 rs4887205 rs16941252 rs7175493 rs12148667 rs12901745 rs16941261 rs11631112 rs4887364 rs11630338 rs9806762 rs991728 rs2114252 rs994068 rs3784410 rs12911150 rs10163123 rs7165979 rs3784406 rs3784405 rs6496465 rs16941328 rs16941331 rs17830422 rs10520676 rs8025158 rs12591487 rs6496466 rs13329385 rs4887376 rs1105442 rs1346164 rs6496469 rs17831280 rs4887211 rs4887382 rs2349054 rs2081556 rs4887212 rs1863482 rs3963196 rs7169789 rs12591318 rs1559822 rs11073768 rs8026216 rs1075891 rs1863490 rs744994 rs744993 rs4887401 rs998636 rs17765281 rs7164988 rs11635754 rs16941593 rs11073771 rs16941599 rs16941600 rs12441513 rs894291 rs894290 rs873897 rs7178884 rs8023765 rs958699 rs958700 rs4887408 rs12443330 rs4392026

BP

86434102 86436684 86439010 86452753 86454854 86455529 86456524 86460910 86461119 86462636 86462743 86463950 86465680 86467650 86468952 86469695 86476492 86478392 86486334 86489014 86490648 86492235 86494637 86510061 86510642 86514696 86515555 86518712 86519246 86520227 86525651 86530483 86536314 86543516 86555895 86555933 86556014 86556308 86557205 86560748 86560842 86561203 86562798 86564157 86566368 86585243 86586302 86586842 86603939 86604269 86604847 86612334 86615136 86615213 86620063 86621433 86621794 86623520 86623678 86624785 86625511 86625685 86654296 86676795 86684852 86686111 86686322 86686855 86690150 86692501

Allelic

P (trend)

A1

Affected

Controls

A2

T

OR

P

C T T C T T C T C C G G A C T G G C T C A A C C A A C C C G T C G T G C A T T A G A T A A A T G A A T C A G G A A A T A A G A A A G A T G C

0.129 0.3683 0.08505 0.3854 0.3776 0.3658 0.3047 0.2964 0.3247 0.299 0.3135 0.299 0.3247 0.3247 0.3918 0.268 0.2565 0.263 0.4866 0.2809 0.4227 0.1959 0.2345 0.06701 0.1727 0.2062 0.1701 0.299 0.232 0.4948 0.2927 0.2747 0.268 0.09896 0.1062 0.1053 0.1057 0.1057 0.4401 0.09896 0.1094 0.09948 0.1057 0.1057 0.1108 0.1218 0.1186 0.1186 0.3568 0.1553 0.2036 0.2268 0.0799 0.2306 0.2963 0.1186 0.2786 0.1469 0.2912 0.1302 0.1859 0.1917 0.3099 0.1371 0.1495 0.1414 0.171 0.1755 0.2912 0.2409

0.08663 0.4006 0.08036 0.4147 0.4122 0.4048 0.2009 0.2054 0.2217 0.2009 0.4018 0.2009 0.2188 0.2217 0.409 0.203 0.3313 0.3144 0.4303 0.1771 0.369 0.1324 0.2619 0.07313 0.2262 0.2321 0.2113 0.2021 0.253 0.4345 0.197 0.3354 0.1722 0.04655 0.1299 0.1375 0.1295 0.1295 0.3994 0.1272 0.1306 0.1231 0.1284 0.1295 0.1414 0.1392 0.1403 0.1399 0.3468 0.1602 0.1801 0.2009 0.07143 0.2024 0.2628 0.128 0.2425 0.1205 0.2634 0.1057 0.1772 0.1949 0.3207 0.1274 0.1369 0.1307 0.1622 0.1636 0.2776 0.2081

T C C T G C G G T T A C C G C T C G C T G G A T G G T T T T C G A C A T C A C G C G C G G C C C G C C T G A T C T C C G G A T T G C G G C G

4.668 1.043 0.07195 0.8666 1.219 1.546 14.49 11.22 13.59 13.09 8.207 13.09 14.45 13.59 0.3023 5.929 6.409 3.088 3.041 15.71 2.978 7.531 0.9778 0.1399 4.297 0.9576 2.648 12.71 0.587 3.607 12.6 3.979 13.73 10.9 1.284 2.258 1.312 1.312 1.654 1.89 1.021 1.331 1.197 1.312 2.027 0.6475 1.012 0.9758 0.1054 0.04392 0.8911 0.9942 0.2557 1.164 1.351 0.2002 1.673 1.511 0.9596 1.452 0.1239 0.01638 0.13 0.1956 0.3204 0.2359 0.137 0.2435 0.225 1.538

1.562 0.8722 1.064 0.8852 0.8651 0.8479 1.743 1.63 1.688 1.696 0.6798 1.696 1.718 1.688 0.9308 1.438 0.6964 0.7784 1.255 1.816 1.252 1.596 0.8635 0.9102 0.7141 0.8591 0.765 1.684 0.8918 1.275 1.687 0.7506 1.761 2.25 0.7964 0.738 0.7945 0.7945 1.182 0.7533 0.8173 0.7869 0.8024 0.7945 0.757 0.8572 0.8242 0.827 1.044 0.9637 1.164 1.167 1.129 1.181 1.181 0.9165 1.207 1.256 1.149 1.267 1.06 0.9795 0.9513 1.089 1.108 1.095 1.065 1.089 1.069 1.208

3.07E−02 3.07E−01 7.89E−01 3.52E−01 2.70E−01 2.14E−01 1.41E− 04 8.10E− 04 2.28E− 04 2.97E− 04 4.17E− 03 2.97E− 04 1.44E− 04 2.28E− 04 5.82E− 01 1.49E− 02 1.14E− 02 7.89E− 02 8.12E− 02 7.38E− 05 8.44E−02 6.06E−03 3.23E−01 7.08E−01 3.82E−02 3.28E−01 1.04E−01 3.63E−04 4.44E−01 5.75E−02 3.87E−04 4.61E−02 2.11E−04 9.63E−04 2.57E−01 1.33E−01 2.52E−01 2.52E−01 1.98E−01 1.69E−01 3.12E−01 2.49E−01 2.74E−01 2.52E−01 1.55E−01 4.21E−01 3.15E−01 3.23E−01 7.46E−01 8.34E−01 3.45E−01 3.19E−01 6.13E−01 2.81E−01 2.45E−01 6.55E−01 1.96E−01 2.19E−01 3.27E−01 2.28E−01 7.25E−01 8.98E−01 7.18E−01 6.58E−01 5.71E−01 6.27E−01 7.11E−01 6.22E−01 6.35E−01 2.15E−01

study are located in intronic regions of NTRK3. Therefore, it is difficult to achieve a full understanding of the effect of the different SNPs on the level of diagnosis, and functional studies are now warranted.

2.84E−02 3.21E−01 7.84E−01 3.72E−01 2.89E−01 2.29E−01 5.73E− 05 4.62E− 04 8.95E− 05 1.61E− 04 5.11E− 03 1.61E− 04 5.58E− 05 8.95E− 05 5.93E− 01 1.32E− 02 1.20E− 02 8.85E− 02 8.50E− 02 3.08E− 05 8.93E−02 6.12E−03 3.38E−01 7.14E−01 3.53E−02 3.37E−01 1.07E−01 2.34E−04 4.57E−01 6.28E−02 2.36E−04 4.96E−02 8.44E−05 1.78E−03 2.45E−01 1.26E−01 2.40E−01 2.40E−01 2.00E−01 1.65E−01 2.99E−01 2.36E−01 2.62E−01 2.40E−01 1.55E−01 4.00E−01 2.93E−01 3.01E−01 7.37E−01 8.31E−01 3.33E−01 3.23E−01 6.08E−01 2.86E−01 2.38E−01 6.45E−01 1.95E−01 2.27E−01 3.23E−01 2.24E−01 7.30E−01 9.01E−01 7.23E−01 6.62E−01 5.81E−01 6.23E−01 7.10E−01 6.21E−01 6.27E−01 2.11E−01

Studies using transgenic mice have revealed that over-expression of NTRK3 results in enhanced anxiety-related behaviour (AmadorArjona et al., 2010; Dierssen et al., 2006), dissociation between

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hippocampal (CA3–CA1) synaptic plasticity and associative learning (Sahun et al., 2007), as well as altered circadian rhythm (AmadorArjona et al., 2010). In conclusion, using a gene-wide approach we report specific NTRK3 allelic variants that may contribute to BD risk. These results need to be replicated, and international efforts such as the Psychiatric GWAS Consortium (Cichon et al., 2009) that is soon to be available with extended simulations of 50,000 case and control pairs will help in elucidation of the involvement of NTRK3 in psychiatric disorders. Acknowledgements We thank patients and controls for their participation in the study, and the health professionals who facilitated our work. We also wish to thank Knut-Erik Gylder, Thomas Bjella, and Eivind Bakken for skillful technical and administrative assistance. The study was supported by grants from: the Research Council of Norway (#167153/ V50, #163070/V50, and #175345/V50), Eastern Norway Health Authority (#1232004), and Sigurd K. Thoresen's legat.

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