NO EVIDENCE FOR LINKAGE OF CHROMOSOME-22 MARKERS TO SCHIZOPHRENIA IN SOUTHERN AFRICAN BANTU-SPEAKING FAMILIES

Previous studies have demonstrated possible linkage between chromosome 22 and one of the hypothesized schizophrenia susceptibility genes. In terpretation of these data, however, is not straightforward: although not significant at the level traditionally accepted to demonstrate lin kage, reported led scores were greater than should have occurred by ch ance for an unlinked marker based on simulation studies. Further, thes e studies used sample populations which were either of mixed nationali ty and ethnicity, or mixed ethnic ancestry from one country. We theref ore tested for linkage between highly polymorphic chromosome 22 marker s and schizophrenia in a sample of southern African Bantu-speaking bla ck families, a population known to have diverged within the last 2,000 years. We also tested one candidate locus, the gene for the soluble f orm of catechol-O-methyl transferase (COMT) located at 22q11, which ha s been suggested as the cause of psychiatric symptoms observed in velo -cardio-facial syndrome (VCFS, including DiGeorge syndrome), and which is known to be functionally as well as genetically polymorphic. There is no evidence to support the linkage of markers on chromosome 22 to susceptibility to schizophrenia in this population, using either param etric or nonparametric analysis. (C) 1996 Wiley-Liss, Inc.