Analysis of chromosome 22 markers in nine schizophrenia pedigrees

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Abstract
Previous results of a genome-wide survey for schizophrenia susceptibility genes in nine multiplex families indicated a possible region of linkage on chromosome 22. We therefore tested for linkage using ten highly polymorphic chromosome 22 DNA markers. Lod score analyses were suggestive of linkage for several markers on the distal end of the chromosome; however, no lod score exceeded 3 assuming either autosomal dominant or autosomal recessive transmission. The highest lod score was 2.09 (theta = 0.10) for marker D22S276 under autosomal recessive inheritance. Based on simulation analyses, this result is unlikely to represent a false positive. Analyses using information from affected individuals only resulted in reduced lod scores, with a maximum of 1.40 (theta = 0.05) for D22S276 assuming autosomal recessive inheritance. Two nonparametric methods, sib pair analysis and the Affected-Pedigree-Member method, also yielded suggestive but inconclusive findings; results were positive, but strict thresholds of significance were not met. Additionally, we tested one candidate gene, the Arylsulfatase A gene, located in the region of 22q13.31-qter. Results were again inconclusive, though the DNA marker available for this gene was a 2-allele RFLP with heterozygosity of 0.5, and therefore not maximally informative. Further investigation of this chromosomal region and this and other candidate genes may be warranted.