Application of MLPA assay to characterize unsolved α-globin gene rearrangements.

α-thalassemia belongs to those inherited diseases in which large genomic deletions/duplications represent a significant proportion of causative mutations. Until recently, large α-globin gene cluster rearrangements have been mainly detected by gap-PCR and Southern blotting, methods that have significant drawbacks. We tested the recently developed multiplex ligation-dependent probe amplification (MLPA) assay for deletional screening of the α-globin gene cluster in a cohort of 25 individuals suspected of having α-globin alteration(s), in which no or doubtful mutations had been found using conventional methods. In 13 out of 18 α-thalassemia carriers and in all 5 patients with HbH we found the causative α-globin defects. In 2 thalassemia intermedia patients, carriers of heterozygous ß-globin mutations, the co-inheritance of homozygous α-genes triplication was detected. MLPA results were subsequently confirmed by real-time PCR. This study shows that MLPA can effectively identify different and unknown types of α-globin gene rearrangements, to allow characterizing previously unsolved α-thalassemia genotypes.

Hb L'Aquila [beta106(G8)Leu-->Val, CTG-->GTG]: a novel thalassemic hemoglobin variant.

A new beta-globin variant at codon 106 (CTG-->GTG), and which we named Hb L'Aquila [beta106(G8)Leu-->Val], was detected by DNA analysis. The proband and her father presented with the features of a mild beta(+)-thalassemia (thal), confirmed by their alpha/beta-globin chain biosynthesis ratios.

Detection of a rare beta-globin nonsense mutation [codon 59 (AAG-->TAG)] in an Italian family.

In this study we report on the hematological and molecular findings of a family from Central Italy, whose 33-year-old male proband presented with a beta0-thalassemia (thal) trait associated to a relevant Hb F level. The proband and his family (parents and a sister) were investigated by hematological analysis. The two beta-thal carriers of the beta-globin nonsense mutation [codon 59 (AAG-->TAG)] (the proband and his father) showed the hematological picture of a beta0-thal trait: the only hematological difference between the two beta-thal carriers was in the Hb F level (3.3% in the proband and 1% in his father).

Rapid detection of six common Mediterranean and three non-Mediterranean alpha-thalassemia point mutations by reverse dot blot analysis.

We describe the implementation of reverse dot blot (RDB) hybridization as a rapid nonradioactive method for the identification of six frequent globin gene point mutations in the Mediterranean population: alpha(Hph)alpha: alpha2 IVS I donor site GGTGAGG --> GG-----; alpha(NcoI)alpha: alpha2 initiation codon ATG --> ACG; alpha(TSaudi)alpha: alpha2Poly A signal AATAA --> AATAAG; alpha(Icaria)alpha: alpha2 termination codon TAA --> AAA (Ter --> LYS); alpha(CS)alpha: alpha2 termination codon TAA --> CAA (Ter --> gly); alphaalpha(NcoI): alpha1 initiation codon ATG --> GTG; and three alpha2 globin gene point mutations found in immigrants in Italy: alpha(T-Quongsze)alpha: alpha2 codon 12 CTG --> CCG (Leu --> Pro); alpha(Seal Rock)alpha: alpha2 termination codon TAA --> GAA (TER --> GLU); and alpha(Koyadora)alpha: alpha2 termination codon TAA --> TCA (TER --> SER). The method uses the principle of allele-specific oligonucleotide (ASO) hybridization, but it is a nonradioactive method and permits rapid and simultaneous typing of point mutations and small deletions.

Factors regulating Hb F synthesis in thalassemic diseases.

BACKGROUND: The thalassemic syndromes originate from mutations of the globin genes that cause, besides the characteristic clinical picture, also an increased Hb F amount. It is not yet clear if there are more factors, besides the beta globin genotype, determining the Hb F production. We have tried to find out if there are relations between total Hb and Hb F, between erythropoietin (Epo) and Hb F, between Hb F and point mutations of the gamma gene promoters. MATERIALS AND METHODS: Hematologic parameters, iron status, alpha/non-alpha globin ratio, Epo level, and thalassemic defects of the alpha-, beta-, and gamma-globin genes were explored using standard methods in patients affected by thalassemic diseases. Ninety-five non thalassemic individuals have been examined as controls. RESULTS: Two clinical variants of beta-thalassemia intermedia referred to as beta-thal int sub-silent and evident are associated with distinct sets of mutations of the beta-globin gene. Silent beta thal mutations are invariably associated with sub-silent beta thal int; beta degrees or severe beta+ thal mutations are associated with evident beta thal int (88%) and almost invariably (98%) with thalassemia major. A positive correlation was observed between the severity of the disease and the Hb F level, but no correlation was found between the Hb F and erythropoietin (Epo) level. The mutation Ggamma -158 C→T was detected in 26.9% of patients affected by beta-thal int sub-silent and evident, respectively, but only in 2% of patients with thalassemia major. CONCLUSIONS: The severity of beta-thal int and the increased Hb F level are strictly dependent from the type of beta-globin gene mutations. No relation is found between Hb F synthesis and Epo secretion. The mutation Ggamma -158 C→T, common among patients affected by beta-thal int and very rare in thal major patients, does not seem, in this study, to influence the Hb F content in beta thal int patients.