Molecular characterization of a novel form of (A gamma delta beta)zero thalassemia deletion in a Chinese family.
We have identified and molecularly characterized a novel deletion in the beta-globin gene cluster that is associated with elevated fetal hemoglobin in the adult. The propositus is a homozygote from the Yunnan province of China. The deletion spans about 90 kb of DNA and removes the A gamma, delta, and beta-globin genes. The 5' breakpoint of the deletion is located about 0.13 kb upstream from the A gamma-globin gene, whereas the 3' breakpoint is located about 66 kb downstream from the beta-globin gene, about 13 kb upstream from the breakpoint of the Chinese (A gamma delta beta)zero-thalassemia. Heterozygotes for this Yunnanese form of (A gamma delta beta)zero-thalassemia express between 9% and 17% of fetal hemoglobin, whereas the homozygote present with a mild anemia (Hb = 10.7 g/dl). Comparison of the sites of 3' breakpoints of the Yunnanese and the Chinese (A gamma delta beta)zero-thalassemia mutants is compatible with the hypothesis that an enhancer element is located between the 3' breakpoints of these two mutants. Juxta-position to the G gamma gene of this element may be responsible for the efficient gamma-gene expression in the Yunnanese mutant.
Zhang
J W
JW
Department of Biochemistry and Molecular Biology, Chinese Academy of Medical Sciences, Beijing.
Song
W F
WF
Zhao
Y J
YJ
Wu
G Y
GY
Qiu
Z M
ZM
Wang
F N
FN
Chen
S S
SS
Stamatoyannopoulos
G
G
D000293:Adolescent; D000328:Adult; D002874:Chromosome Mapping; D005260:Female; D005319:Fetal Hemoglobin / Q000235:genetics; D017353:Gene Deletion; D005914:Globins / Q000235:genetics*; D006801:Humans; D008297:Male; D013789:Thalassemia / Q000235:genetics*
D005914:Globins; D005319:Fetal Hemoglobin