α-Thalassemia associated with hb instability: a tale of two features. the case of Hb Rogliano or α1 Cod 108(G15)Thr→Asn and Hb Policoro or α2 Cod 124(H7)Ser→Pro.

We identified two new variants in the third exon of the α-globin gene in families from southern Italy: the Hb Rogliano, α1 cod108 ACC>AAC or α1[α108(G15)Thr→Asn] and the Hb Policoro, α2 cod124 TCC>CCC or α2[α124(H7)Ser→Pro]. The carriers showed mild α-thalassemia phenotype and abnormal hemoglobin stability features. These mutations occurred in the G and H helices of the α-globin both involved in the specific recognition of AHSP and ß1 chain. Molecular characterization of mRNA, globin chain analyses and molecular modelling studies were carried out to highlight the mechanisms causing the α-thalassemia phenotype. The results demonstrated that the α-thalassemia defect associated with the two Hb variants originated by different defects. Hb Rogliano showed an intrinsic instability of the tetramer due to anomalous intra- and inter-chain interactions suggesting that the variant chain is normally synthesized and complexed with AHSP but rapidly degraded because it is unable to form the α1ß1 dimers. On the contrary in the case of Hb Policoro two different molecular mechanisms were shown: the reduction of the variant mRNA level by an unclear mechanism and the protein instability due to impairment of AHSP interaction. These data highlighted that multiple approaches, including mRNA quantification, are needed to properly identify the mechanisms leading to the α-thalassemia defect. Elucidation of the specific mechanism leads to the definition of a given phenotype providing important guidance for the diagnosis of unstable variants.

Serum YKL-40 levels and chitotriosidase activity in patients with beta-thalassemia major.

BACKGROUND: YKL-40 association with human disease has been the object of many years of investigation. ß-thalassemia patients are affected by hepatic siderosis, which determines a fibrotic process and tissue remodelling. Chitotriosidase has been found to be increased in thalassemic patients returning to normal in patients submitted to bone marrow transplantation. YKL-40 is associated with macrophage activation in liver and in other tissues. The aim of the study was to analyse the level of serum YKL-40 and plasma chitotriosidase activity of patients with beta-thalassemia to assess whether their expression correlates with liver disease and degree of liver siderosis. METHODS: Expression of YKL-40 and chitotriosidase as a marker of inflammation in 69 thalassemic patients were evaluated. We sought to investigate whether these two chitinases could be considered as a significant biomarker to evaluate therapy effectiveness. RESULTS: Surprisingly we found normal value of YKL-40. We, also, analysed chitotriosidase activity in the same patients that was slightly increased as a consequence of macrophage activation. CONCLUSIONS: These data would suggest a good treatment for these patients.

Genotype-phenotype relationship of the δ-thalassemia and Hb A(2) variants: observation of 52 genotypes.

The increase of Hb A(2) (α2δ2) beyond the upper limit [2.0-2.2/3.3-3.4% of the total hemoglobin (Hb)] is an invaluable tool in the hematological screening of ß-thalassemia (ß-thal) carriers. Factors decreasing Hb A(2) percentages can hinder correct diagnosis. In order to analyze the genotype-phenotype relationship, we characterized δ-, ß- and α-globin genotypes in 190 families where the probands had Hb A(2) values of ≤2.0% or were ß-thal heterozygotes with normal Hb A(2) levels. Hb A(2) was measured with cation exchange high performance liquid chromatography (HPLC). Mutations were detected with allele-specific methods or DNA sequencing; two multiplex-ARMS (amplification refractory mutation system) assays were set up. The molecular basis underlying the decrease in Hb A(2) was extremely heterogeneous. Nineteen δ-globin alleles (Hb A(2)-S.N. Garganico was new) were detected; their interaction with α- or ß-globin alleles (10 and eight, respectively) led us to observe 52 genotypes in 261 carriers. The type of δ-globin mutations, the relative genotypes, the interaction with α(0)-thal traits, are the most important factors in decreasing the Hb A(2) percentage. These results are extremely useful in addressing the molecular diagnosis of hemoglobinopathies and thalassemias.

HbA2-Partinico or delta(A2)Pro-->Thr, a new genetic variation in the delta-globin gene in cis to the beta(+) thal IVS-I-110 G>A, and the heterogeneity of delta-globin alleles in double heterozygotes for beta- and delta-globin gene defects.

The study of the alleles of the delta-globin gene is relevant to the prevention of beta-thalassemia homozygosis; in fact, the increase of the HbA2 is an invaluable hematological marker of the beta-thalassemia heterozygosis and the double heterozygosis for alleles of delta- and beta-globin genes can cause the decrease of the HbA2 up to normal or borderline values. We carried out the characterization of alleles of the delta- and beta-globin genes, restriction fragment length polymorphism (RFLP) haplotype background, and hematologic phenotype in 23 double heterozygotes belonging to 18 unrelated families. A wide heterogeneity of the delta-globin alleles was detected; seven known alleles in trans to the beta-globin gene defects were revealed in 17 out of 18 families, while a new allele in cis to a beta-thalassemia allele was detected in one family. Moreover, the relative frequency of the delta-mutants was quite different from that found among heterozygotes. The new allele delta-cod 5 CCT>ACT, in cis to the allele beta(+) thal IVS-I-110 G>A, was found in five carriers of a Sicilian family. The new variant delta5(A2)Pro-->Thr, named HbA2-Partinico upon the origin of the family, was detected with high-performance liquid chromatography; it overlapped the HbA2 peak which was partially split. The double in cis heterozygotes had increased percentage of normal and variant HbA2 of comparable size. The variant originated most likely from a new mutational event because it was associated with RFLP haplotype I, commonly found with the beta(+) thal IVS-I-110 G>A, even if crossing over or gene conversion cannot be excluded.

Molecular evidences of single mutational events followed by recurrent crossing-overs in the common delta-globin alleles in the Mediterranean area.

The human delta-globin gene (HBD) is one of the beta-like globin genes expressed in adults. In the Mediterranean countries the carriers of delta-thalassemia defects or Hb A2-variants are >1% and about 40/70 known alleles have been found in families with this ethnic origin. The scope of this study was to investigate the variability of the gene and of the chromosomal background in order to highlight the origin and spreading of the delta-globin gene alleles in the Mediterranean area. We carried out the characterization of the delta-globin gene alleles and of RFLP-haplotypes, SNPs and one microsatellite associated with them in 231 carriers originating principally from East Sicily. Seventeen alleles were identified, of which five were new. The chromosomes associated with mutated alleles from unrelated carriers were 158; the allele Hb A2-Yialousa accounted for about 75% of relative frequency, Hb A2-Mitsero for about 8%. The alleles were associated with RFLP 5'-haplotypes "- - - -" or "+ - + +", prevalent in the Mediterranean area, except Hb A2-Mitsero associated with the 5'-haplotype "Benin" "- - - +" and the Hb A2' associated with "+ - - +", both of African origin. Each allele showed linkage with one haplotype with these exceptions. The Hb A2-Yialousa showed heterogeneity of the 5'-haplotype in 2/58 chromosomes; the Hb A2-Mitsero showed SNPs and (A)gamma-microsatellite typical of a "Benin" haplotype found associated with the Hb C and Hb S chromosomes; the Hb A2-Yialousa (14/58 chromosomes), Hb A2-Mitsero, Hb A2-Pylos, Hb A2-Fitzroy showed heterogeneity in the 3'-haplotypes and beta-globin gene SNPs. The Hb A2-Coburg was found associated with the haplotype "+ - + +/+ +" different from that already reported "- - - -/+ -". With the exception of this last allele, the linkage of each mutation with a core of RFLPs or SNPs around or inside the delta-globin locus suggested the unicentric origin of the mutations followed by recurrent recombination events causing the chromosomal background heterogeneity.

Hb G-San Josè variant levels correlate with alpha-thalassemia genotypes.

Hb G-San Josè or beta7(A4)Glu-->Gly has been reported in Southern Italian or Mexican families. We have studied four families from Sicily and Campania, Southern Italy. In six carriers, the hemoglobin variant level ranged from 32 to 38%. In four double heterozygotes for Hb G-San Josè and alpha-thalassemia the variant level showed a strong correlation with the alpha-thalassemia genotype. In fact, the variant level was 15% when interacting with the - (alpha)20.5/alphaalpha, 19.6% with the alphaalpha/alphaPoly Aalpha, and 24.8% with alphaalpha/alpha(-5) ntalpha genotypes. In two double heterozygotes for Hb G-San Josè and beta+ -IVS-I-6 (T-->C) the hemoglobin variant level was 67%. These data show that the reduced synthesis of alpha chains causes drastic reduction of probability to form Hb G-San Josè in favor of the formation of Hb A. Moreover, this reduction, (i) correlates with the type of alpha-thalassemia genotype and with the degree of the alpha chain deficiency, and (ii) is, most probably, more marked than the degree of alpha chain reduction. The minor affinity of the beta chain variant for the alpha chains associated with the reduced synthesis of the alpha chains is probably the principal cause of the variant hemoglobin reduction. Moreover, the rapid removal of the abnormal chains by proteolytic enzymes must have an essential role in order to reduce the chain variant pool. These conclusions are in agreement with the results obtained in reticulocyte and in vitro recombination experiments.