Linkage of familial schizophrenia to chromosome 13q32

Over the past 4 years, a number of investigators have reported findings sug gestive of linkage to schizophrenia, with markers on chromosomes 13q32 and 8p21, with one recent study by Blouin et al. reporting significant linkage to these regions. As part of an ongoing genome scan, we evaluated microsate llite markers spanning chromosomes 8 and 13, for linkage to schizophrenia, in 21 extended Canadian families. Families were analyzed under autosomal do minant and recessive models, with broad and narrow definitions of schizophr enia. All models produced positive LOD scores with markers on 13q, with hig her scores under the recessive models. The maximum three-point LOD scores w ere obtained under the recessive-broad model: 3.92 at recombination fractio n (theta) .1 with D13S793, under homogeneity, and 4.42 with alpha=.65 and t heta=0 with D13S793, under heterogeneity. Positive LOD scores were also obt ained, under all models, for markers on 8p. Although a maximum two-point LO D score of 3.49 was obtained under the dominant-narrow model with D8S136 at theta = 0.1, multipoint analysis with closely flanking markers reduced the maximum LOD score in this region to 2.13. These results provide independen t significant evidence of linkage of a schizophrenia-susceptibility locus t o markers on 13q32 and support the presence of a second susceptibility locu s on 8p21.