Polymorphisms of (AC)n (AT)xTy in the upstream of β-globin gene in patients with mild β-thalassemia / 中华检验医学杂志

ABSTRACT

ObjectiveTo explore linkage relationship between polymorphisms of (AC)n (AT)xTy and mutations in the β-globin gene in patients with mild β-thalassemia.MethodsThe subjects were 89 mild β-thalassemia patients with known mutations and 110 healthy subjects from People's Hospital of Baoan District of Shenzhen from February 2009 to July 2010.Genomic DNA was extracted from peripheral leukocytes.Sequence of the BP1 binding site upstream of the β-globin gene was amplified by polymerase chain reaction,polymorphisms of (AC)n (AT)xTy were determined by DNA sequencing.Allelic frequencies of (AC)n (AT)xTy between mild β-thalassemia patients and healthy subjects were compared using x2 test.Mutation rates between two groups were also compared using x2 test for subjects carrying same haplotype. Linkage relationship was conducted according to allelic frequencies and mutations. Results Analysis of the (AC)n(AT) xTy polymorphisms of the BP1 binding site upstream of the β-globin gene showed 9 different genotypes (AC)2( AT)7T7,( AC)2( AT)8T5,( AC)3( AT)7T5,( AC)2( AT)9T5,( AC)2(AT)8T9,(AC)3(AT)8T5,(AC)2(AT)10T3,(AC)2(AT)7T5 and (AC)2(AT)11T3.The (AC)2(AT)7T7 and (AC)2 (AT)8T5 genotypes were common for patients with mild β-thalassemia.Allele frequencies of (AC)2(AT)7T7,(AC)3 ( AT)7T5 and ( AC)2( AT)8T9 were 38.8％ (69/178),11.8％(21/178),9.0％ ( 16/178 ) for mild β-thalassemia patients,and 24.1％ ( 53/220),5.4％ ( 12/220),3.2％(7/220)for healthy subjects, respectively, there were significant differences between mild β-thalassemia patients and healthy subjects (x2 =9.966,4.371,6.093,P ＜ 0.05 ).Allele frequency of (AC)2(AT)9T5 was 10.1％ (18/178) and 33.2％ (73/220) for mild β-thalassemia patients and healthy subjects,frequency of (AC)2 (AT)9T5 was significandy lower in mild β-thalassemia patients than in healthy subjects (x2 =29.691,P ＜0.01 ).Allele frequency of (AC)2(AT)8T5 was 25.3％ (45/178) and 29.1％(64/220) for mild β-thalassemia patients and healthy subjects,there wasn't significant difference between patients and healthy subjects (x2 =0.718,P ＞0.05).The mutation rates of codon41/42(-TTCT) and IVSⅡ-654(C→T) were 59％ (10/17) and 29％ (5/17) for mild β-thalassemia patients carrying (AC)2(AT)7T7 allele,and 29％ (4/14) and 57％ (8/14) for patients carrying ( AC)2 (AT)8T5 allele.There were not significant differences between codon41/42(-TTCT) mutation rate and IVS-Ⅱ-654(C→T) mutation rate (x2 =2.982,2.333,P ＞ 0.05 ) for mild β-thalassemia patients carrying ( AC)2 ( AT)7T7 and ( AC)2(AT)8T5 allele.ConclusionsAllele of (AC)2(AT)7T7,(AC)3(AT)7T5 and (AC)2(AT)8T9 are in linkage disequilibrium with β-thalassemia.Most mild β-thalassemia patients carrying (AC)2 (AT)7T7 allele are caused by codon41/42 (-TTCT) mutation in the β-globin gene,and IVS-Ⅱ-654 (C→T) is a major mutation for patients carrying (AC)2(AT)8T5 allele.