title: Evidence for the multigenic inheritance of schizophrenia.
abstract: Schizophrenia is assumed to have complex inheritance because of its high prevalence and sporadic familial transmission. Findings of linkage on different chromosomes in various studies corroborate this assumption. It is not known whether these findings represent heterogeneous inheritance, in which various ethnic groups inherit illness through different major gene effects, or multigenic inheritance, in which affected individuals inherit several common genetic abnormalities. This study therefore examined inheritance of schizophrenia at different genetic loci in a nationally collected European American and African American sample. Seventy-seven families were previously genotyped at 458 markers for the NIMH Schizophrenia Genetics Initiative. Initial genetic analysis tested a dominant model, with schizophrenia and schizoaffective disorder, depressed type, as the affected phenotype. The families showed one genome-wide significant linkage (Z = 3.97) at chromosome 15q14, which maps within 1 cM of a previous linkage at the alpha 7-nicotinic receptor gene. Chromosome 10p13 showed suggestive linkage (Z = 2.40). Six others (6q21, 9q32, 13q32, 15q24, 17p12, 20q13) were positive, with few differences between the two ethnic groups. The probability of each family transmitting schizophrenia through two genes is greater than expected from the combination of the independent segregation of each gene. Two trait-locus linkage analysis supports a model in which genetic alleles associated with schizophrenia are relatively common in the general population and affected individuals inherit risk for illness through at least two different loci.
authors.affiliation: Department of Psychiatry, Denver VA Medical Center and University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. robert.freedman@uchsc.edu
authors.forename: R
authors.initials: R
authors.lastname: Freedman
authors.forename: S
authors.initials: S
authors.lastname: Leonard
authors.forename: A
authors.initials: A
authors.lastname: Olincy
authors.forename: C A
authors.initials: CA
authors.lastname: Kaufmann
authors.forename: D
authors.initials: D
authors.lastname: Malaspina
authors.forename: C R
authors.initials: CR
authors.lastname: Cloninger
authors.forename: D
authors.initials: D
authors.lastname: Svrakic
authors.forename: S V
authors.initials: SV
authors.lastname: Faraone
authors.forename: M T
authors.initials: MT
authors.lastname: Tsuang
mesh_terms: D000483:Alleles; D002879:Chromosomes, Human, Pair 10 / Q000235:genetics; D002882:Chromosomes, Human, Pair 13 / Q000235:genetics; D002884:Chromosomes, Human, Pair 15 / Q000235:genetics; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics; D002890:Chromosomes, Human, Pair 20 / Q000235:genetics; D002896:Chromosomes, Human, Pair 6 / Q000235:genetics; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics; D005192:Family Health; D005787:Gene Frequency; D008040:Genetic Linkage; D005838:Genotype; D006801:Humans; D008126:Lod Score; D018895:Microsatellite Repeats; D020412:Multifactorial Inheritance; D012559:Schizophrenia / Q000235:genetics*