6P24-22 REGION AND MAJOR PSYCHOSES IN THE EASTERN QUEBEC POPULATION

Recent reports of a linkage trend in 6p24-22 for schizophrenia (SZ), i n different samples, were tempered by the concurrent evidence of negat ive reports in other samples. In the studies showing positive results, different definitions of affection and a wide spectrum of diagnoses w ere used. Our objectives were not only to test for linkage at 6p24-22 in the Eastern Quebec population, but also to test whether this putati ve vulnerability locus was either selectively linked to schizophrenia (SZ), or to bipolar disorder (BP), or to both major psychoses. Paramet ric and nonparametric linkage analyses with 12 microsatellite markers in 6p24-p22 were performed on a sample of 18 large multigenerational p edigrees (N = 354) either affected by SZ, or by BP, or equally affecte d by both major psychoses (i.e., mixed pedigrees). Three affection def initions were usually tested in our program: one on schizophrenia (SZ) , one an bipolar disorder (BP), and one that comprised SZ and BP under the hypothesis of a susceptibility locus common to both in major psyc hoses (common locus, CL). The results of parametric analyses did not s upport a major gene hypothesis. However, in one large mixed pedigree ( #151), we observed with the common locus phenotype (CL) lad scores of 2.49 and 2.15, respectively, at the D6S296 and D6S277 loci under a dom inant model. Our data suggest the presence of a potential vulnerabilit y locus at 6p24-22 that could be related to both schizophrenia and bip olar affective disorder. These results may be seen as congruent with f ormer studies that used schizoaffective as well as schizophrenia diagn oses as entry criteria for the affected families, and used an affectio n definition that comprised affective psychoses as web as schizophreni a. Am. J. Med. Genet. 74:311-318, 1997. (C) 1997 Wiley-Liss, Inc.