Pulver et al. [1994a] reported modest linkage evidence for a dominantly (D) inherited ''schizophrenia gene'' in the vicinity of IL2RB on chromosome 22q12, and Coon et al. [1994] adduced moderate evidence under a recessive (R) model. We report here a replication study to test the hypothesis that one of these two models (or a third, intermediate (I) model) adequately describes the cosegregation of schizophrenia and chromosome 22q12 markers in an independent sample of 23 multiplex families. Altogether nine transmission models were evaluated.
The models differed depending on whether the 15 family members with a diagnosis of schizophrenia spectrum disorders were considered unaffected (a ''narrow'' (N) definition), affected (a ''wide'' (W) definition), or declared ''unknown'' (U). The entire region between D22S268 and D22S307 is excluded (i.e., lod <-2) for models RN, RW, RU, and IW. Lod scores for the remaining models are uniformly negative; albeit, equivocal with respect to the dominant hypothesis over a small region between D22S268 and IL2RB. Nonparametric analysis under both diagnostic criteria also failed to yield any evidence for a susceptibility locus in this region of chromosome 22. Am. J. Med. Genet. 74:361-364, 1997.