Linkage results on 11Q21-22 in Eastern Quebec pedigrees densely affected by schizophrenia

The 11q21-22 region is of interest for schizophrenia because several candidate genes are located in this section of the genome. The 11q21-22 region, including DRD2, was surveyed by linkage analysis in a sample (N = 242) made of four large multigenerational pedigrees densely affected by schizophrenia (SZ) and eight others by bipolar disorder (BP). These pedigrees were ascertained in a large area of Eastern Quebec and Northern New Brunswick and are still being extended. Family members were administered a "consensus best-estimate diagnosis procedure" (DSM-III-R criteria) blind to probands and relatives' diagnosis and to pedigree assignment (SZ or BP). For linkage analysis, 11 microsatellite polymorphism (CA repeat) markers, located at 11q21-22, and comprising DRD2, were genotyped. Results show no evidence of a major gene for schizophrenia. However, a maximum lod score of 3.41 at the D11S35 locus was observed in an affected-only analysis of one large SZ family, pedigree 255. Whether or not the positive linkage trend in pedigree 255 reflects a true linkage for a small proportion of SZ needs to be confirmed through the extension of this kindred and through replication.