Constitutive heterochromatin of chromosome 1 and Duffy blood group alleles in schizophrenia

Cytogenetic analysis was carried out in unrelated schizophrenic patients, unrelated controls and patients and family members in multiplex families. The size distribution of chromosome 1 heterochromatic region (1qH, C-band variants) among 21 unrelated schizophrenic patients was different from that found in a group of 46 controls. The patient group had 1qH variants of smaller size than the control group (P < 0.01). Incubation of phytohemagglutinin-treated blood lymphocytes with 5-azacytidine (which causes decondensation and extension of the heterochromatin) led to a lesser degree of heterochromatin decondensation in a group of patients than in the controls (7 schizophrenic, 9 controls, P < 0.01). The distribution of phenotypes of Duffy blood group system [whose locus is linked to the 1qH region (Donahue et al.: Proc Natl Acad Sci USA 61:949-955, 1968; Rouleau et al.: Genomics 7:313-318, 1990)] among 28 schizophrenic patients was also different from that in the general population. Cosegregation of schizophrenia with a 1qH (C-band) variant and Duffy blood group allele was observed in one of six multiplex families. The overall results suggest that alterations within the Duffy/1qH region are involved in schizophrenia in some cases. This region contains the locus of D5 dopamine receptor pseudogene 2 (1q21.1), which is transcribed in normal lymphocytes (Takahashi et al.: FEBS Lett 314:23-25, 1992).