Technical Report No. 5-89
A chromosome study of 6-thioguanine-resistant mutants in T lymphocytes of Hiroshima atomic bomb survivors
Kodama Y, Hakoda M, Shimba H, Awa AA, Akiyama MEditor’s note: A publication based on this report was published in Mutat Res 227:31-8, 1989.
Summary
Cytogenetic characterizations were made of lymphocyte colonies established from somatic mutation assays for 6-thioguanine (TG) resistance in Hiroshima atomic bomb survivors. G-banded chromosomes were analyzed in both TG-resistant (TGr) and wild-type (not TG-selected) colonies. Included were 45 TGr and 19 wild-type colonies derived from proximally exposed A-bomb survivors, as well as colonies from distally exposed control individuals who were not exposed to a significant level of A-bomb radiation (18 TGr and 9 wild-type colonies). Various structural and numerical abnormalities of chromosomes were observed in both TGr and wild-type colonies. Aberrations of the X chromosome, on which the hypoxanthine guanine phosphoribosyltransferase (HPRT) locus is present, were found in six colonies: two resistant colonies from controls [45,X/46,XX; 46,X,ins(X)], three resistant colonies [45,X/46, XX/46,X+mar; 46,X,t(Xq+;14q-); 46,Y,t(Xq-; 5q+)], and one wild-type colony [45,X/47,XXX] from proximally exposed persons. In cases with exchange aberrations, each of the break points on the X chromosome was situated proximally to band q26 where the HPRT locus is known to be assigned. DNA replicating patterns were also studied, and it was found that abnormal X chromosomes showed early replicating patterns, while normal X chromosomes showed late replicating patterns.
Cytogenetic characterizations were made of lymphocyte colonies established from somatic mutation assays for 6-thioguanine (TG) resistance in Hiroshima atomic bomb survivors. G-banded chromosomes were analyzed in both TG-resistant (TGr) and wild-type (not TG-selected) colonies. Included were 45 TGr and 19 wild-type colonies derived from proximally exposed A-bomb survivors, as well as colonies from distally exposed control individuals who were not exposed to a significant level of A-bomb radiation (18 TGr and 9 wild-type colonies). Various structural and numerical abnormalities of chromosomes were observed in both TGr and wild-type colonies. Aberrations of the X chromosome, on which the hypoxanthine guanine phosphoribosyltransferase (HPRT) locus is present, were found in six colonies: two resistant colonies from controls [45,X/46,XX; 46,X,ins(X)], three resistant colonies [45,X/46, XX/46,X+mar; 46,X,t(Xq+;14q-); 46,Y,t(Xq-; 5q+)], and one wild-type colony [45,X/47,XXX] from proximally exposed persons. In cases with exchange aberrations, each of the break points on the X chromosome was situated proximally to band q26 where the HPRT locus is known to be assigned. DNA replicating patterns were also studied, and it was found that abnormal X chromosomes showed early replicating patterns, while normal X chromosomes showed late replicating patterns.