Shin Ihda

Publications (2)0 Total impact

• Article: Association study between schizophrenia and dopamine D3 receptor gene polymorphism

  Toshihisa Tanaka, Shuichi Igarashi, Osamu Onodera, Hajime Tanaka, Makoto Takahashi, Masaya Maeda, Kensuke Kameda, Shoji Tsuji, Shin Ihda
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  ABSTRACT: Crocq et al. [1992: J Med Genet 29:858–860] reported the existence of an association between schizophrenia and homozygosity of a BalI polymorphism in the first exon of the dopamine D3 receptor (DRD3) gene. In response to this report, further studies were conducted; however, these studies yielded conflicting results. In the present study, we examined 100 unrelated Japanese schizophrenics and 100 normal controls to determine any association between this polymorphism and schizophrenia. Results suggest that neither allele nor genotype frequencies of the DRD3 gene in the schizophrenics as a whole are significantly different from those of the controls. Further, we found no association between any allele or genotype and any clinical subtype based on family history of schizophrenia and age-at-onset. A significantly high frequency of homozygosity of a dopamine D3 receptor gene allele was not observed in the schizophrenics as a whole, or in clinical subtypes. Our results suggest that an association between the dopamine D3 receptor gene and schizophrenia is unlikely to exist. © 1996 Wiley-Liss, Inc.
  American Journal of Medical Genetics 12/1998; 67(4):366 - 368.
• Article: Lack of association between dopamine D2 receptor gene Cys311 variant and schizophrenia

  Toshihisa Tanaka, Shuichi Igarashi, Osamu Onodera, Hajime Tanaka, Noboru Fukushima, Makoto Takahashi, Kensuke Kameda, Shoji Tsuji, Shin Ihda
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  ABSTRACT: Itokawa et al. [1993] reported identifying one missense nucleotide mutation from C to G resulting in a substitution of serine with cysteine at codon 311 in the third intracellular loop of the dopamine D2 receptor in schizophrenics. Arinami et al. [1994] reported finding a positive association between the Cys311 variant and schizophrenia. In response to the report by Arinami et al. [1994] we examined 106 unrelated Japanese schizophrenics and 106 normal controls to determine if there is any association of the Cys311 variant with schizophrenia. However, we found no statistically significant differences in allelic frequencies of Cys311 between schizophrenia and normal controls. The present results as well as those of all previous studies except for that of Arinami et al. [1994] indicated that an association between the dopamine D2 receptor gene and schizophrenia is unlikely to exist. © 1996 Wiley-Liss, Inc.
  American Journal of Medical Genetics 12/1998; 67(2):208 - 211.