| Objectives To determine the relationship between two DNA polymorphism in β-globin gene cluster, namely the Xmn I polymorphic site at -158 of Gγgene and the nucleotide variations of the DNase I-hypersensitive site 2 of the locus control region (LCR-HS2), and the altered levels of fetal hemoglobin(Hb F) of β-thalassemia trait patients in Guangxi, China. Methods DNA were isolated from the blood samples of 63 unselected patients withβ-thalassemia trait and 7 patients with high Hb Fβ-thalassemia trait. The presence of -158(C→T) mutation (Xmn I +) was determined by amplification of Gγ gene promoter fragments from the DNA, followed by Xmn I restriction enzyme digestion. The direct nucleotide sequencing of β-LCR-HS2 was performed from double-stranded PCR products obtaining by amplification with special primers. Results 10 cases (15.9%) with Xmn I (+) site were found among the 63 unselected patients [15 of them had high Hb F(≥2%), 48 patients' Hb F level were normal (<2%)], and 8 of the ten cases with Xmn I +/- (53.33%) belonged to the group of high Hb F values and only 2 patients with Xmn I +/- were found in the normal Hb F group (4.17%). 2 cases from the 7 high Hb Fβ-thalassemia trait were found carrying Xmn I (+) site too. All of the 12 patients who had Xmn I (+) site were heterozygotes, and most of their Hb F values were 2% to 6%. 9 kinds of (AT)xNy(AT)z motif were detected in our study. (AT)9 N12(AT)11 was the most pattern among the 9 kinds of motif. 5 of 6 patients characterized by Hb F>3% and Xmn I +/- were heterozygotes for (AT)9 N12(AT)10. Conclusion Our study had confirmed the strong relationship between the two DNA polymorphism, Gγ -158(C→T) and (AT)9 N12(AT)10 motif , and the elevation of Hb F in Chineseβ-thalassemia trait patients. (AT)9 N12(AT)10 motif in β-LCR-HS2 was linked to Gγ -158(C→T) mutation. A special motif, (AT)9 N12(AT)11, was possibly the common pattern ofβ-LCR-HS2 (AT)xNy(AT)z motif among the people in Guangxi, China.
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