Cytochemical heterogeneity of the C-band in human chromosome 1

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).

Identification of marker chromosomes by restriction endonucleases/Giemsa technique in neoplastic cells

The most recent addition to the various selective staining methods is the technique using restriction endonucleases to digest the metaphase chromosomes and subsequent staining by Giemsa (endonuclease/Giemsa technique). One of the endonucleases, AluI, which induces a characteristic modified C-band pattern is evaluated for its application in cancer cytogenetics using malignant lymphoid cells. The pattern obtained by AluI/Giemsa has been routinely useful in identifying some of the unusual markers that are difficult by routine banding. The centromeric regions are found to be far more heterogeneous by AluI resulting in frequent heteromorphic markers on several chromosomes. This has provided additional information to detect the donor cells in grafts after bone marrow transplantation.