- Email: [email protected]
Failure to confirm the association between the FEZ1 gene and schizophrenia in a Japanese population
Neuroscience Letters 417 (2007) 326–329
Failure to confirm the association between the FEZ1 gene and schizophrenia in a Japanese population Minori Koga a,b , Hiroki Ishiguro a,b , Yasue Horiuchi a,b , Talal Albalushi a , Toshiya Inada b,c , Nakao Iwata b,d , Norio Ozaki b,e , Hiroshi Ujike b,f , Tatsuyuki Muratake b,g , Toshiyuki Someya b,g , Tadao Arinami a,b,∗ a
Department of Medical Genetics, Doctoral Program in Social and Environmental Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan b CREST, Japan Science and Technology Agency, Kawaguchi-shi, Saitama 332-0012, Japan c Department of Psychiatry, Teikyo University School of Medicine, Chiba Medical Center, Anesaki 3426-3, Ichihara-shi, Chiba 299-0111, Japan d Department of Psychiatry, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan e Department of Psychiatry, School of Medicine, Nagoya University, Nagoya 466-8550, Aichi, Japan f Department of Neuropsychiatry, Okayama University, Graduate School of Medicine, Dentistry & Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8558, Japan g Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8510, Japan Received 1 December 2006; received in revised form 21 February 2007; accepted 22 February 2007
Abstract Fasciculation and elongation of protein zeta-1 (FEZ1) is a binding partner of Disrupted-In-Schizophrenia 1 (DISC1). Because the DISC1 gene is shown to be a causative gene for psychosis in a Scottish family, the FEZ1 gene may well have importance in mental disease. A previous association study that analyzed polymorphisms of the FEZ1 gene in Japanese patients with schizophrenia and control subjects found significant association of the Asp123Glu polymorphism with schizophrenia. In the present study, we examined two polymorphic markers, rs559668 and rs597570 (Asp123Glu), in the FEZ1 gene to confirm the association in 1920 Japanese patients with schizophrenia and 1920 control subjects. The power to detect an association was more than 0.98. However, we did not detect genotypic associations of either of these two single nucleotide polymorphisms with schizophrenia (p = 1 and 0.79, respectively). We concluded that the missense mutation Asp123Glu of the FEZ1 gene is unlikely to play a substantial role in the genetic susceptibility to schizophrenia. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Schizophrenia; FEZ1; DISC1; Japanese; Case-control study
Schizophrenia is a chronic, severe and disabling brain disorder that affects approximately 1% of the world’s population. A large body of data collected from family, twin and adoption studies over many years has consistently supported the involvement of a major, complex genetic component in susceptibility to schizophrenia. A heritability of schizophrenia is estimated at about 80% [2]. Although the ultimate biological cause is ∗
Corresponding author at: Department of Medical Genetics, Doctoral Program in Social and Environmental Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan. Tel.: +81 298 53 3352; fax: +81 298 53 3333. E-mail address: [email protected] (T. Arinami). 0304-3940/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2007.02.055
unknown, schizophrenia is believed to be of neurodevelopmental origin. The Disrupted-in-Schizophrenia 1 (DISC1) gene on human chromosome 1 was first identified as a disrupted gene by a balanced (1;11) (q42.1;q14.3) translocation that segregated with major mental illnesses in a large Scottish family [6]. DISC1 may be involved in psychiatric symptoms that cross diagnostic boundaries. In addition, it has been reported that some single nucleotide polymorphisms in the DISC1 gene are associated with schizophrenia [4]. Therefore, the DISC1 gene is a candidate gene for schizophrenia. To investigate the function of DISC1 protein, investigators sought to identify proteins that interact with DISC1 protein [6].
M. Koga et al. / Neuroscience Letters 417 (2007) 326–329
327
Fig. 1. Genomic structure and location of polymorphic markers for FEZ1 gene. Exons are indicated by boxes, with translated regions in filled boxes and untranslated regions in open boxes. Size of exons and introns are also shown. Two SNPs (rs559668 and rs597570) which were confirmed in the present study are shown above.
Recently, fasciculation and elongation protein zeta-1 (FEZ1) was identified as an interacting partner of DISC1 by yeast twohybrid analysis with the C terminus of human DISC1 as bait [7]. FEZ1 is a mammalian homologue of the Caenorhabditis elegans UNC-76 protein, which is involved in axonal outgrowth and fasciculation. It was reported that DISC1 participates in the neurite extension machinery through its interaction with FEZ1 [7]. In translocation carriers in the Scottish family, DISC1 is disrupted within intron 8, likely generating a truncated protein that lacks the C-terminal 200 amino acids. This truncated DISC1 may have to reduce potential to interact with FEZ1. Cellular dysregulation induced by disruption of DISC1 may be transmitted to a downstream cascade via FEZ1. The FEZ1 gene is located at 11q24.2, where linkage to schizophrenia was revealed by meta-analysis, although results from different sample populations are inconsistent [5]. The FEZ1 may offer a compelling candidate gene for psychiatric disorders from both functional and positional perspectives. A study was done to investigate genetic variants of FEZ1 to evaluate the contribution of the gene to the risk of developing schizophrenia and bipolar disorder [9]. In that study, two tightly linked SNPs, rs559668 and rs597570, were associated significantly with schizophrenia. Homozygotes for the minor alleles were found only in the 360 schizophrenia patients and not in the 360 age- and sex-matched control subjects [9]. SNP rs597570 causes an Asp123Glu substitution and Asp123 is conserved between humans and rodents [9]. This residue lies within a region shown to be responsible for the axonal targeting of the unc-76 protein [1]. Because replication of reported findings in other populations is important for genetic association studies, we examined the associations of these FEZ1 SNPs with schizophrenia in a Japanese population with sufficient power to detect an association. All subjects were of Japanese descent and were recruited from the main island of Japan. A total of 1920 unrelated patients with schizophrenia (mean age ± S.D., 48.9 ± 14.5 years; 1056 men and 864 women) were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSMIV). To provide best-estimate lifetime diagnosis, we obtained consensus from at least two experienced psychiatrists. All available medical records and family information were also taken into consideration. Control subjects were 1920 mentally healthy, unrelated subjects (mean age ± S.D., 49.0 ± 14.3 years; 1017 men and 903 women) with family a self-reported history of mental illness within second-degree relatives. The present study
was approved by the Ethics Committees of the University of Tsukuba, Niigata University, Fujita Health University, Nagoya University, Okayama University and Teikyo University, and all participants provided written informed consent. We assessed gene and haplotype associations of two SNPs, rs559668 and rs597570 that were reported to have significant association with schizophrenia. These SNPs are located in the FEZ1 gene (Fig. 1). SNPs were genotyped by TaqMan® assay (Applied Biosystems, Foster City, CA, USA). The genomic DNA for genotyping analysis was prepared from the blood of patients and controls by phenol extraction and ethanol precipitation. Genotyping assays were carried out with qPCRTM Mastermix Plus Quick Gold Star (WAKO Japan) with 5 ng amplified DNA. Alleles were discriminated with an ABI PRISM 7900HT Sequence Detection System with SDS 2.1 software (Applied Biosystems). Association was evaluated by chi-square test. Hardy– Weinberg equilibrium was evaluated by exact test [8]. Haplotype frequencies were estimated with the expectation maximization algorithm. Haploview program (http://www.broad. mit.edu/mpg/haploview/) was used to detect the haplotype block. The level for significance was 0.05. The genomic power in this study was calculated with the Genetic Power Calculator (http://pngu.mgh.harvard.edu/∼purcell/gpc/cc2.html). The two SNPs, rs559668 and rs597570, were in almost complete linkage disequilibrium, as reported previously [9]. The genotype distributions of these two SNPs in the control subjects were in Hardy–Weinberg equilibrium; however, they were not in Hardy–Weinberg equilibrium in schizophrenia patients (rs559668, p = 0.01; rs597570, p = 0.01) (Table 1). No significant difference in the genotype frequencies of the ressesive model or allele distribution was found between patients with schizophrenia and control subjects (rs559668, p = 1 and p = 0.28, respectively; rs597570, p = 0.79 and 0.41, respectively) (Table 1). Yamada et al. [9] found that homozygotes with the Glu123 allele comprised 2% of the schizophrenia patients but none of the control subjects. In the present study, 1% of each of the two groups were homozygous for Glu123 (p = 0.78; odds ratio, 1.13; 95% confidence interval, 0.65–1.96). A significant haplotype association was not observed (Table 2). The sample size of the present study had a power of 0.98 (α = 0.05) to detect the genotype associations reported previously by Yamada et al. [9]. We performed a replication study for possible association between FEZ1 polymorphisms and schizophrenia in a large pop-
M. Koga et al. / Neuroscience Letters 417 (2007) 326–329 Table 2 Frequencies of haplotypes in the FEZ1 gene
0.01 0.20
0.01 0.05
HWEd
328
1.07 (0.92–1.24) 0.41 A 361 (0.09) 382 (0.10) A/A 27 (0.01) 24 (0.01) T/A 307 (0.16) 334 (0.17) T/T 1579 (0.83) 1553 (0.81)
c
d
rs number: http://www.ncbi.ntm.gov/SNP. p-Value in the case of ressesive model. CI: confidential interval. HWE: Hardy–Weinberg equilibrium. a
b
Affected Controls rs597570
T/A
1913 1911
296 (0.15) 321 (0.17) Affected Controls rs559668
G/A
1913 1911
1592 (0.83) 1564 (0.82)
25 (0.01) 26 (0.01)
0.79
T 3465 (0.91) 3440 (0.90)
346 (0.09) 373 (0.10) 1.00
3480 (0.91) 3449 (0.90)
A G G/A G/G
Genotype count (frequency)
Ratio
p-Value
Schizophrenia
Control
0.905 0.090
0.899 0.096
0.383 0.310
There are two different haplotypes which are above 1% in ratio are shown in this table.
Population
n
GT AA
Polymorphism Markera
Table 1 Genotypic and allelic distributions of the FEZ1 gene polymorphisms
A/A
Pb
Allele count (frequency)
P
0.28
1.09 (0.93–1.27)
Odds ratio (95% CIc )
Haplotype
ulation with sufficient statistical power to confirm the association reported previously. All subjects were of Japanese descent, as were those reported by Yamada et al. [9]. Recently, association between the Asp123Glu polymorphism and schizophrenia was examined in Caucasian and African–American populations; however, no significant association was detected in these populations [3]. Our failure to replicate the association of this polymorphism with schizophrenia is consistent with the results of the studies of Caucasian and African–American populations. Although the Asp123Glu residue is a missense polymorphism and Asp123 is conserved in mammalian species, the residue is not conserved in Gallus gallus and Caenorhabditis elegans. It is unclear whether Asp123Glu causes a functional change. In the present study, the genotype distributions deviated from the Hardy–Weinberg prediction in schizophrenia patients but not control subjects. The most frequent cause of deviation from Hardy–Weinberg equilibrium is typing error. In the present study, genotyping the two SNPs in almost complete in linkage disequilibrium yielded similar results (Table 1). Therefore, the deviations from Hardy–Weinberg equilibrium of these two SNPs in our patients with schizophrenia are not likely due to typing error. Deviation from Hardy–Weinberg equilibrium was also observed in the patients with schizophrenia studied by Yamada et al. [9]. The deviations observed in these two schizophrenia patient populations appeared to be due mainly to overrepresentation of homozygotes. However, significant deviation from Hardy–Weinberg equilibrium was not observed in schizophrenia in the Caucasian or African–American populations [3]. Therefore, the deviation from Hardy–Weinberg equilibrium observed in two Japanese schizophrenia patient populations may be chance findings. Other possibility is that the deviation was caused by the microdeletion of the genetic region containing rs597570 in some schizophrenia patients of Japanese populations. In conclusion, we failed to replicate the previously reported association of a missense polymorphism of the FEZ1 gene with schizophrenia in our present analysis in almost 4000 Japanese case-control subjects and this was consistent with published findings in Caucasians and African–American populations [3]. Taking together, these findings indicate that the Asp123Glu missense polymorphism of the FEZ1 gene does not play a significant role in vulnerability to schizophrenia. Acknowledgements The present study was supported by Grant-in-Aid for Scientific Research (C) (17590285); Grant-in-Aid for Scientific
M. Koga et al. / Neuroscience Letters 417 (2007) 326–329
Research on Priority Areas-Research on Pathomechanisms of Brain Disorders (18023009) from the Ministry of Education, Culture, Sports, Science and Technology of Japan, a grant from the Mitsubishi Foundation; Grant-in-Aid for Young Scientists (B) (18790823). References [1] L. Bloom, H.R. Horvitz, The Caenorhabditis elegans gene unc-76 and its human homologs define a new gene family involved in axonal outgrowth and fasciculation, Proc. Natl. Acad. Sci. U.S.A. 94 (1997) 3414–3419. [2] T.D. Cannon, J. Kaprio, J. Lonnqvist, M. Huttunen, M. Koskenvuo, The genetic epidemiology of schizophrenia in a Finnish twin cohort. A population-based modeling study, Arch. Gen. Psychiatry 55 (1998) 67–74. [3] C.A. Hodgkinson, D. Goldman, F. Ducci, P. Derosse, D.A. Caycedo, E.R. Newman, J.M. Kane, A. Roy, A.K. Malhotra, The FEZ1 gene shows no association to schizophrenia in Caucasian or African American populations, Neuropsychopharmacology (2006). [4] C.A. Hodgkinson, D. Goldman, J. Jaeger, S. Persaud, J.M. Kane, R.H. Lipsky, A.K. Malhotra, Disrupted in schizophrenia 1 (DISC1): association with schizophrenia, schizoaffective disorder, and bipolar disorder, Am. J. Hum. Genet. 75 (2004) 862–872. [5] C.M. Lewis, D.F. Levinson, L.H. Wise, L.E. DeLisi, R.E. Straub, I. Hovatta, N.M. Williams, S.G. Schwab, A.E. Pulver, S.V. Faraone, L.M. Brzustowicz,
[6]
[7]
[8] [9]
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C.A. Kaufmann, D.L. Garver, H.M. Gurling, E. Lindholm, H. Coon, H.W. Moises, W. Byerley, S.H. Shaw, A. Mesen, R. Sherrington, F.A. O’Neill, D. Walsh, K.S. Kendler, J. Ekelund, T. Paunio, J. Lonnqvist, L. Peltonen, M.C. O’Donovan, M.J. Owen, D.B. Wildenauer, W. Maier, G. Nestadt, J.L. Blouin, S.E. Antonarakis, B.J. Mowry, J.M. Silverman, R.R. Crowe, C.R. Cloninger, M.T. Tsuang, D. Malaspina, J.M. Harkavy-Friedman, D.M. Svrakic, A.S. Bassett, J. Holcomb, G. Kalsi, A. McQuillin, J. Brynjolfson, T. Sigmundsson, H. Petursson, E. Jazin, T. Zoega, T. Helgason, Genome scan meta-analysis of schizophrenia and bipolar disorder, part II: schizophrenia, Am. J. Hum. Genet. 73 (2003) 34–48. J.K. Millar, J.C. Wilson-Annan, S. Anderson, S. Christie, M.S. Taylor, C.A. Semple, R.S. Devon, D.M. Clair, W.J. Muir, D.H. Blackwood, D.J. Porteous, Disruption of two novel genes by a translocation co-segregating with schizophrenia, Hum. Mol. Genet. 9 (2000) 1415–1423. K. Miyoshi, A. Honda, K. Baba, M. Taniguchi, K. Oono, T. Fujita, S. Kuroda, T. Katayama, M. Tohyama, Disrupted-In-Schizophrenia 1, a candidate gene for schizophrenia, participates in neurite outgrowth, Mol. Psychiatry 8 (2003) 685–694. J.E. Wigginton, D.J. Cutler, G.R. Abecasis, A note on exact tests of Hardy–Weinberg equilibrium, Am. J. Hum. Genet. 76 (2005) 887–893. K. Yamada, K. Nakamura, Y. Minabe, Y. Iwayama-Shigeno, H. Takao, T. Toyota, E. Hattori, N. Takei, Y. Sekine, K. Suzuki, Y. Iwata, K. Miyoshi, A. Honda, K. Baba, T. Katayama, M. Tohyama, N. Mori, T. Yoshikawa, Association analysis of FEZ1 variants with schizophrenia in Japanese cohorts, Biol. Psychiatry 56 (2004) 683–690.
Failure to confirm the association between the FEZ1 gene and schizophrenia in a Japanese population Minori Koga a,b , Hiroki Ishiguro a,b , Yasue Horiuchi a,b , Talal Albalushi a , Toshiya Inada b,c , Nakao Iwata b,d , Norio Ozaki b,e , Hiroshi Ujike b,f , Tatsuyuki Muratake b,g , Toshiyuki Someya b,g , Tadao Arinami a,b,∗ a
Department of Medical Genetics, Doctoral Program in Social and Environmental Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan b CREST, Japan Science and Technology Agency, Kawaguchi-shi, Saitama 332-0012, Japan c Department of Psychiatry, Teikyo University School of Medicine, Chiba Medical Center, Anesaki 3426-3, Ichihara-shi, Chiba 299-0111, Japan d Department of Psychiatry, Fujita Health University School of Medicine, Toyoake, Aichi 470-1192, Japan e Department of Psychiatry, School of Medicine, Nagoya University, Nagoya 466-8550, Aichi, Japan f Department of Neuropsychiatry, Okayama University, Graduate School of Medicine, Dentistry & Pharmaceutical Sciences, 2-5-1 Shikata-cho, Okayama 700-8558, Japan g Department of Psychiatry, Niigata University Graduate School of Medical and Dental Sciences, Niigata 951-8510, Japan Received 1 December 2006; received in revised form 21 February 2007; accepted 22 February 2007
Abstract Fasciculation and elongation of protein zeta-1 (FEZ1) is a binding partner of Disrupted-In-Schizophrenia 1 (DISC1). Because the DISC1 gene is shown to be a causative gene for psychosis in a Scottish family, the FEZ1 gene may well have importance in mental disease. A previous association study that analyzed polymorphisms of the FEZ1 gene in Japanese patients with schizophrenia and control subjects found significant association of the Asp123Glu polymorphism with schizophrenia. In the present study, we examined two polymorphic markers, rs559668 and rs597570 (Asp123Glu), in the FEZ1 gene to confirm the association in 1920 Japanese patients with schizophrenia and 1920 control subjects. The power to detect an association was more than 0.98. However, we did not detect genotypic associations of either of these two single nucleotide polymorphisms with schizophrenia (p = 1 and 0.79, respectively). We concluded that the missense mutation Asp123Glu of the FEZ1 gene is unlikely to play a substantial role in the genetic susceptibility to schizophrenia. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Schizophrenia; FEZ1; DISC1; Japanese; Case-control study
Schizophrenia is a chronic, severe and disabling brain disorder that affects approximately 1% of the world’s population. A large body of data collected from family, twin and adoption studies over many years has consistently supported the involvement of a major, complex genetic component in susceptibility to schizophrenia. A heritability of schizophrenia is estimated at about 80% [2]. Although the ultimate biological cause is ∗
Corresponding author at: Department of Medical Genetics, Doctoral Program in Social and Environmental Medicine, Graduate School of Comprehensive Human Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8575, Japan. Tel.: +81 298 53 3352; fax: +81 298 53 3333. E-mail address: [email protected] (T. Arinami). 0304-3940/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.neulet.2007.02.055
unknown, schizophrenia is believed to be of neurodevelopmental origin. The Disrupted-in-Schizophrenia 1 (DISC1) gene on human chromosome 1 was first identified as a disrupted gene by a balanced (1;11) (q42.1;q14.3) translocation that segregated with major mental illnesses in a large Scottish family [6]. DISC1 may be involved in psychiatric symptoms that cross diagnostic boundaries. In addition, it has been reported that some single nucleotide polymorphisms in the DISC1 gene are associated with schizophrenia [4]. Therefore, the DISC1 gene is a candidate gene for schizophrenia. To investigate the function of DISC1 protein, investigators sought to identify proteins that interact with DISC1 protein [6].
M. Koga et al. / Neuroscience Letters 417 (2007) 326–329
327
Fig. 1. Genomic structure and location of polymorphic markers for FEZ1 gene. Exons are indicated by boxes, with translated regions in filled boxes and untranslated regions in open boxes. Size of exons and introns are also shown. Two SNPs (rs559668 and rs597570) which were confirmed in the present study are shown above.
Recently, fasciculation and elongation protein zeta-1 (FEZ1) was identified as an interacting partner of DISC1 by yeast twohybrid analysis with the C terminus of human DISC1 as bait [7]. FEZ1 is a mammalian homologue of the Caenorhabditis elegans UNC-76 protein, which is involved in axonal outgrowth and fasciculation. It was reported that DISC1 participates in the neurite extension machinery through its interaction with FEZ1 [7]. In translocation carriers in the Scottish family, DISC1 is disrupted within intron 8, likely generating a truncated protein that lacks the C-terminal 200 amino acids. This truncated DISC1 may have to reduce potential to interact with FEZ1. Cellular dysregulation induced by disruption of DISC1 may be transmitted to a downstream cascade via FEZ1. The FEZ1 gene is located at 11q24.2, where linkage to schizophrenia was revealed by meta-analysis, although results from different sample populations are inconsistent [5]. The FEZ1 may offer a compelling candidate gene for psychiatric disorders from both functional and positional perspectives. A study was done to investigate genetic variants of FEZ1 to evaluate the contribution of the gene to the risk of developing schizophrenia and bipolar disorder [9]. In that study, two tightly linked SNPs, rs559668 and rs597570, were associated significantly with schizophrenia. Homozygotes for the minor alleles were found only in the 360 schizophrenia patients and not in the 360 age- and sex-matched control subjects [9]. SNP rs597570 causes an Asp123Glu substitution and Asp123 is conserved between humans and rodents [9]. This residue lies within a region shown to be responsible for the axonal targeting of the unc-76 protein [1]. Because replication of reported findings in other populations is important for genetic association studies, we examined the associations of these FEZ1 SNPs with schizophrenia in a Japanese population with sufficient power to detect an association. All subjects were of Japanese descent and were recruited from the main island of Japan. A total of 1920 unrelated patients with schizophrenia (mean age ± S.D., 48.9 ± 14.5 years; 1056 men and 864 women) were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSMIV). To provide best-estimate lifetime diagnosis, we obtained consensus from at least two experienced psychiatrists. All available medical records and family information were also taken into consideration. Control subjects were 1920 mentally healthy, unrelated subjects (mean age ± S.D., 49.0 ± 14.3 years; 1017 men and 903 women) with family a self-reported history of mental illness within second-degree relatives. The present study
was approved by the Ethics Committees of the University of Tsukuba, Niigata University, Fujita Health University, Nagoya University, Okayama University and Teikyo University, and all participants provided written informed consent. We assessed gene and haplotype associations of two SNPs, rs559668 and rs597570 that were reported to have significant association with schizophrenia. These SNPs are located in the FEZ1 gene (Fig. 1). SNPs were genotyped by TaqMan® assay (Applied Biosystems, Foster City, CA, USA). The genomic DNA for genotyping analysis was prepared from the blood of patients and controls by phenol extraction and ethanol precipitation. Genotyping assays were carried out with qPCRTM Mastermix Plus Quick Gold Star (WAKO Japan) with 5 ng amplified DNA. Alleles were discriminated with an ABI PRISM 7900HT Sequence Detection System with SDS 2.1 software (Applied Biosystems). Association was evaluated by chi-square test. Hardy– Weinberg equilibrium was evaluated by exact test [8]. Haplotype frequencies were estimated with the expectation maximization algorithm. Haploview program (http://www.broad. mit.edu/mpg/haploview/) was used to detect the haplotype block. The level for significance was 0.05. The genomic power in this study was calculated with the Genetic Power Calculator (http://pngu.mgh.harvard.edu/∼purcell/gpc/cc2.html). The two SNPs, rs559668 and rs597570, were in almost complete linkage disequilibrium, as reported previously [9]. The genotype distributions of these two SNPs in the control subjects were in Hardy–Weinberg equilibrium; however, they were not in Hardy–Weinberg equilibrium in schizophrenia patients (rs559668, p = 0.01; rs597570, p = 0.01) (Table 1). No significant difference in the genotype frequencies of the ressesive model or allele distribution was found between patients with schizophrenia and control subjects (rs559668, p = 1 and p = 0.28, respectively; rs597570, p = 0.79 and 0.41, respectively) (Table 1). Yamada et al. [9] found that homozygotes with the Glu123 allele comprised 2% of the schizophrenia patients but none of the control subjects. In the present study, 1% of each of the two groups were homozygous for Glu123 (p = 0.78; odds ratio, 1.13; 95% confidence interval, 0.65–1.96). A significant haplotype association was not observed (Table 2). The sample size of the present study had a power of 0.98 (α = 0.05) to detect the genotype associations reported previously by Yamada et al. [9]. We performed a replication study for possible association between FEZ1 polymorphisms and schizophrenia in a large pop-
M. Koga et al. / Neuroscience Letters 417 (2007) 326–329 Table 2 Frequencies of haplotypes in the FEZ1 gene
0.01 0.20
0.01 0.05
HWEd
328
1.07 (0.92–1.24) 0.41 A 361 (0.09) 382 (0.10) A/A 27 (0.01) 24 (0.01) T/A 307 (0.16) 334 (0.17) T/T 1579 (0.83) 1553 (0.81)
c
d
rs number: http://www.ncbi.ntm.gov/SNP. p-Value in the case of ressesive model. CI: confidential interval. HWE: Hardy–Weinberg equilibrium. a
b
Affected Controls rs597570
T/A
1913 1911
296 (0.15) 321 (0.17) Affected Controls rs559668
G/A
1913 1911
1592 (0.83) 1564 (0.82)
25 (0.01) 26 (0.01)
0.79
T 3465 (0.91) 3440 (0.90)
346 (0.09) 373 (0.10) 1.00
3480 (0.91) 3449 (0.90)
A G G/A G/G
Genotype count (frequency)
Ratio
p-Value
Schizophrenia
Control
0.905 0.090
0.899 0.096
0.383 0.310
There are two different haplotypes which are above 1% in ratio are shown in this table.
Population
n
GT AA
Polymorphism Markera
Table 1 Genotypic and allelic distributions of the FEZ1 gene polymorphisms
A/A
Pb
Allele count (frequency)
P
0.28
1.09 (0.93–1.27)
Odds ratio (95% CIc )
Haplotype
ulation with sufficient statistical power to confirm the association reported previously. All subjects were of Japanese descent, as were those reported by Yamada et al. [9]. Recently, association between the Asp123Glu polymorphism and schizophrenia was examined in Caucasian and African–American populations; however, no significant association was detected in these populations [3]. Our failure to replicate the association of this polymorphism with schizophrenia is consistent with the results of the studies of Caucasian and African–American populations. Although the Asp123Glu residue is a missense polymorphism and Asp123 is conserved in mammalian species, the residue is not conserved in Gallus gallus and Caenorhabditis elegans. It is unclear whether Asp123Glu causes a functional change. In the present study, the genotype distributions deviated from the Hardy–Weinberg prediction in schizophrenia patients but not control subjects. The most frequent cause of deviation from Hardy–Weinberg equilibrium is typing error. In the present study, genotyping the two SNPs in almost complete in linkage disequilibrium yielded similar results (Table 1). Therefore, the deviations from Hardy–Weinberg equilibrium of these two SNPs in our patients with schizophrenia are not likely due to typing error. Deviation from Hardy–Weinberg equilibrium was also observed in the patients with schizophrenia studied by Yamada et al. [9]. The deviations observed in these two schizophrenia patient populations appeared to be due mainly to overrepresentation of homozygotes. However, significant deviation from Hardy–Weinberg equilibrium was not observed in schizophrenia in the Caucasian or African–American populations [3]. Therefore, the deviation from Hardy–Weinberg equilibrium observed in two Japanese schizophrenia patient populations may be chance findings. Other possibility is that the deviation was caused by the microdeletion of the genetic region containing rs597570 in some schizophrenia patients of Japanese populations. In conclusion, we failed to replicate the previously reported association of a missense polymorphism of the FEZ1 gene with schizophrenia in our present analysis in almost 4000 Japanese case-control subjects and this was consistent with published findings in Caucasians and African–American populations [3]. Taking together, these findings indicate that the Asp123Glu missense polymorphism of the FEZ1 gene does not play a significant role in vulnerability to schizophrenia. Acknowledgements The present study was supported by Grant-in-Aid for Scientific Research (C) (17590285); Grant-in-Aid for Scientific
M. Koga et al. / Neuroscience Letters 417 (2007) 326–329
Research on Priority Areas-Research on Pathomechanisms of Brain Disorders (18023009) from the Ministry of Education, Culture, Sports, Science and Technology of Japan, a grant from the Mitsubishi Foundation; Grant-in-Aid for Young Scientists (B) (18790823). References [1] L. Bloom, H.R. Horvitz, The Caenorhabditis elegans gene unc-76 and its human homologs define a new gene family involved in axonal outgrowth and fasciculation, Proc. Natl. Acad. Sci. U.S.A. 94 (1997) 3414–3419. [2] T.D. Cannon, J. Kaprio, J. Lonnqvist, M. Huttunen, M. Koskenvuo, The genetic epidemiology of schizophrenia in a Finnish twin cohort. A population-based modeling study, Arch. Gen. Psychiatry 55 (1998) 67–74. [3] C.A. Hodgkinson, D. Goldman, F. Ducci, P. Derosse, D.A. Caycedo, E.R. Newman, J.M. Kane, A. Roy, A.K. Malhotra, The FEZ1 gene shows no association to schizophrenia in Caucasian or African American populations, Neuropsychopharmacology (2006). [4] C.A. Hodgkinson, D. Goldman, J. Jaeger, S. Persaud, J.M. Kane, R.H. Lipsky, A.K. Malhotra, Disrupted in schizophrenia 1 (DISC1): association with schizophrenia, schizoaffective disorder, and bipolar disorder, Am. J. Hum. Genet. 75 (2004) 862–872. [5] C.M. Lewis, D.F. Levinson, L.H. Wise, L.E. DeLisi, R.E. Straub, I. Hovatta, N.M. Williams, S.G. Schwab, A.E. Pulver, S.V. Faraone, L.M. Brzustowicz,
[6]
[7]
[8] [9]
329
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