title: Search for a genetic event in monozygotic twins discordant for schizophrenia.
abstract: When monozygotic twins are discordant for the diagnosis of schizophrenia, this discordance has been traditionally attributed to environmental factors acting upon a genome susceptible for the schizophrenia phenotype. The study presented here was designed to examine the occurrence of a genetic event, such as a postzygotic mitotic crossover, that could account for the discordance. Such a postzygotic event could affect cis-acting sequences and result in a phenotype of variable severity. We used molecular genetic methods to evaluate such an event with 94 microsatellite repeat polymorphic markers distributed on all autosomes and the X chromosome in five pairs of monozygotic twins discordant for schizophrenia. In this search, no genetic marker discordances were identified between the co-twins. The lack of a genetic difference may implicate nongenetic factors that are responsible in eliciting or suppressing the phenotype. However, the experiments performed in this study cannot eliminate the possibility that a tissue-specific mitotic crossover might have occurred in one of the discordant twins, which could not have been detected in our current study.
authors.affiliation: Laboratory of Biochemical Genetics, National Institute of Mental Health, Neuroscience Center at St. Elizabeths, Washington, DC 20032.
authors.forename: M H
authors.initials: MH
authors.lastname: Polymeropoulos
authors.forename: H
authors.initials: H
authors.lastname: Xiao
authors.forename: E F
authors.initials: EF
authors.lastname: Torrey
authors.forename: L E
authors.initials: LE
authors.lastname: DeLisi
authors.forename: T
authors.initials: T
authors.lastname: Crow
authors.forename: C R
authors.initials: CR
authors.lastname: Merril
mesh_terms: D000328:Adult; D002874:Chromosome Mapping; D004200:Diseases in Twins / Q000235:genetics*; D005260:Female; D005819:Genetic Markers / Q000235:genetics; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic / Q000235:genetics; D012559:Schizophrenia / Q000175:diagnosis / Q000235:genetics*; D012563:Schizophrenia, Paranoid / Q000175:diagnosis / Q000235:genetics / Q000523:psychology; D012565:Schizophrenic Psychology; D014430:Twins, Monozygotic / Q000235:genetics
chemical_list: D005819:Genetic Markers