An Assiociation Study of Interleukin-2 Receptor beta-Chain Gene Polymorphism on Chromosome 22 in Korean Schizophrenic Patients

Kim, Yong Ku; Lee, Min Soo; Kim, Leen; Kwak, Dong Il; Suh, Kwang Yoon

Abstract

BACKGROUND: While a significant genetic predisposition to schizophrenia has been proposed, the mode of inheritance or nature of etiological factors is unknown. Previous reports of a genome-wide survey for schizophrenia susceptibility genes have indicated a possible region of linkage on chromosome 22. In order to test the possibility that the interleukin-2 recepto beta chain(IL-2R beta ) gene on chromosome 22 is of etiological importance in schizophrenia, a case-control association study was conducted.
METHODS
Subjects were ninety-three schizophrenic patients with a diagnosis of schizophrenia by DSM- III -R criteria and ninety-seven normal controls. Schizophrenic patients were divided by clinical phenotypes such as DSM- III -R diagnostic subtypes, positive and negative symptoms, and family history so as to increase the homogeneity of schizophrenics. Genomic DNA was extracted from whole blood lymphocytes according to standard procedures. The DNA was used to study a dinucleotide repeat in the IL-2R beta gene. To reveal the dinucleotide polymorphism, genomic DNA of subjects was amplified by polymerase chain reactions(PCR).
RESULTS
At the IL-2R beta gene locus, all the previously reported alleles (eight different alleles) of a dinucleotide polymorphism were identified. There was no significant difference between number of heterozygosity in schizophrenic patients and in normal controls. There was no significant difference in the distribution of frequencies of alleles between schizophrenics and normal controls. In addition, there was no significant difrfrence in the allele frequencies among subtypes of schizophrenic patients according to DSM- III -R diagnostic subtypes, positive and negative symptoms, and family history.
CONCLUSIONS
The present study did not detect a difference in frequencies of alleles of a dinucleotide polymorphism at the IL-2R beta gene locus between schizophrenic patients and normal controls. These results do not support an evidence that IL-2R beta gene plays, a major role in the etiology of schizophrenia.