Genomic discordance between monozygotic twins discordant for schizophrenia.

Abstract

Genomic DNA of monozygotic twins discordant for schizophrenia was analyzed to determine whether their genomes were truly identical. The subjects were monozygotic male twins, one of whom had DSM-III-R schizophrenia, undifferentiated type. Genomic DNA was extracted from leukocytes and was applied to restriction landmark genome scanning analysis, which was developed for a high-speed survey of restriction sites throughout a genome and measurement of their copy number in each locus. After comparisons of patterns with approximately 2,000 spots, the authors detected at least two spots with autoradiographic intensities that obviously differed in the two twins. The discrepancies likely were generated either by differences in the methylation status at NotI sites between the twins or by submicroscopic changes occurring at NotI-flanking sites in one twin after (or simultaneous with) twinning. In either case, the difference may influence the transcription level of one or more genes.