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.

The incidence of JAK2 V617F mutation in bcr/abl-negative chronic myeloproliferative disorders: assessment by two different detection methods.

A recurrent specific JAK2 V617F mutation has been reported in bcr/abl-negative chronic myeloproliferative diseases (cMPD), including polycythemia vera (PV), essential thrombocythemia (ET) and idiopathic myelofibrosis (IMF). The mutation is detectable in a variable proportion of neoplastic clones, depending on the molecular methods employed. In this study, we attempted to establish the JAK2 V617F mutation frequency in two partially overlapping cMPD patient series by two different PCR-based techniques. Using an allele-specific polymerase chain reaction assay (AS-PCR), the JAK2 V617F mutation was detected in 124/158 (78.5%) cMPD patients; in particular, 90.2, 72.1, 63.2 and 50% of PV, ET, IMF and unclassified (U)-MPD cases, respectively, showed the mutation. Employing a semiquantitative 5' fluorogenic TaqMan assay, the JAK2 V617F mutation was identified in a much larger percentage of cMPDs patients (118/127: 92.9%). Rates of mutation in PV, ET, IMF and U-MPD cases were 95.9, 85.7, 91.7 and 92.9%, respectively. Furthermore, a statistically higher percentage of JAK2 mutated alleles was detected by TaqMan assay in PV (68+/-3.5, mean value+/-SEM) and IMF (64+/-9.3) cases as compared with ET (35+/-5.4). Finally, a significant correlation between JAK2 V617F mutational status and hematocrit (Ht), white blood cell and platelet counts in PV patients, and Ht values in ET cases, was observed by AS-PCR. Overall, these data indicate that TaqMan technology significantly improved sensitivity in detecting the JAK2 mutation in cMPD patients and may be worth of further evaluations as a clinically useful tool for detection of small amounts of mutated clones.