Coexistence of Southeast Asian ovalocytosis and beta-thalassemia: a molecular and hematological analysis

We describe hematological and molecular characterization of a Thai female who had Southeast Asian ovalocytosis (SAO) associated with beta+-thalassemia trait. The proband had mild microcytosis with Hb 12.9 g/dl, Hct 35.8%, MCV 74.4 fl, MCH 26.8 pg, MCHC 36.0 g/dl, and elevated Hb A2 (5.6%), characteristics of beta-thalassemia trait. Peripheral blood film examination revealed prominent ovalocytosis. However, a one-tube osmotic fragility (OF) test commonly used for thalassemia screening was negative and a normal OF curve was observed. Further polymerase chain reaction (PCR) analyses identified the beta(-28A-G) mutation in the beta-globin gene and a 27 bp deletion in erythrocyte band 3 protein gene, indicating a genetically compound heterozygote. Hematological data of the proband was comparatively presented with those of eight female and 15 male carriers of pure beta-thalassemia with the same mutation. The finding demonstrates that although the association of the SAO and beta-thalassemia does not produce a more severe clinical picture, this could lead to a mis-screening of beta-thalassemia using an OF test as a primary screening test. Additional blood film examination followed by PCR could help in the detection of this unusual genetic interaction in the region.     

Clinical and hematological features of codon 17, A-T mutation of beta-thalassemia in Thai patients

Forty-one patients with codon 17, A-T mutation of beta-thalassemia, which is commonly found in Thailand, were studied to determine whether it is possible to predict phenotypic severity from genetic factors. The clinical phenotype of homozygotes for codon 17, A-T and compound heterozygotes for codon 17, A-T and beta+-thalassemia may be used to predict a severe phenotype with TM. However, the clinical phenotype of compound heterozygotes for codon 17, A-T and beta+-thalassemia or Hb E were variable and could not be accurately predicted. The association of alpha-thalassemia2 and milder disease was and was not evident in patients with codon 17, A-T and Hb E. The association between Hb CS gene or the presence of XmnI-Ggamma polymorphism and a mild clinical phenotype is not apparent, indicating the involvement of other ameliorating determinants or genetic modifications.     

Iron chelators for the treatment of iron overload disease: relationship between structure,redox activity,and toxicity

The success of the iron (Fe) chelator desferrioxamine (DFO) in the treatment of beta-thalassemia is limited by its lack of bioavailability. The design and characterization of synthetic alternatives to DFO has attracted much scientific interest and has led to the discovery of orally active chelators that can remove pathological Fe deposits. However, chelators that access intracellular Fe pools can be toxic by either inhibiting Fe-containing enzymes or promoting Fe-mediated free radical damage. Interestingly, toxicity does not necessarily correlate with Fe-binding affinity or with chelation efficacy, suggesting that other factors may promote the cytopathic effects of chelators. In this review, we discuss the interactions of chelators and their Fe complexes with biomolecules that can lead to toxicity and tissue damage.     

深圳地区血红蛋白G的分子特征与血液学表型

目的分析深圳地区异常血红蛋白G(HbG)病的分子特征和血液学表型,进一步认识异常血红蛋白病的类型,为地中海贫血筛查提供参考数据。方法收集我院进行毛细管电泳法检测的72397例样本,对检出异常血红蛋白者采用Sanger测序法进行DNA测序鉴定,并分析其红细胞参数,采用跨越断裂点聚合酶链反应(Gap-PCR)法和PCR结合反向点杂交(PCR-RDB)法检测并进行地贫基因分型。结果共检出6种HbG,均为杂合子,发生率为0.047%,位于α链异常的为Hb G-Honolulu和Hb G-Waimanalo;位于β链异常的为Hb G-Taipei、Hb G-Coushatta、Hb G-San José和Hb G-Siriraj。除1例Hb G-Honolulu合并β地贫(IVS-Ⅱ-654杂合突变)表现为轻型地贫特征,其余各类型HbG单纯杂合子的血液学表型均正常。新生儿Hb G-Taipei的毛细管电泳结果为HbA(8.6±2.4)%、HbF(89.1±3.1)%和Hb G-Taipei(2.3±0.6)%;Hb G-Coushatta结果为HbA 12.0%、HbF 83.7%和Hb G-Coushatta 4.1%。结论深圳地区HbG以杂合子多见,单纯HbG杂合子可表现为血常规正常,用毛细管电泳分析可发现携带者;合并地贫时可表现为地贫表型,临床应注意鉴别成人和新生儿HbG的毛细管电泳特征。     

重庆地区地中海贫血基因突变类型分析

目的了解重庆地区地中海贫血患者基因突变类型及分布,以指导优生优育。方法采用聚合酶链式反应(PCR)和膜杂交术,进行α-地中海贫血和β-地中海贫血基因检测。结果 2012年9月至2013年9月共检出349例地中海贫血患者,其中α-地中海贫血患者125例,α-地中海贫血患者的基因突变类型以缺失为主,缺失类型主要为东南亚型缺失--SEA/αα(占73.60%)和右侧缺失-3.7/αα(占19.20%)。检出β-地中海贫血患者211例,基因突变热点分别为CD17(A→T)(29.38%)、CD41-42(-TCTT)(28.91%)、IVS-Ⅱ-654(C→T)(27.49%)。α-地中海贫血兼β-地中海贫血13例。结论了解重庆地区地中海贫血基因突变类型及分布可以为该地区地中海贫血的遗传咨询和临床诊疗提供有价值的信息。     

Hb Southern Italy: coexistence of two missence mutations (the Hb Sun Prairie alpha2 130 Ala --> Pro and Hb Caserta alpha2 26 Ala --> Thr) in a single HBA2 gene

This study describes a new molecular condition in the alpha(2)-globin gene (HBA2) found in six unrelated families from Southern Italy (Campania and Sicily). This new double mutant form of haemoglobin is called Hb Southern Italy and originated from the coexistence of two known mutations occurring in the same globin gene, HBA2 26 G-->A (Hb Caserta) and HBA2 130 G-->C (Hb Sun Prairie). Hb Sun Prairie was originally observed in Indian patients in either the homozygous state, with severe hemolytic anemia, and in the heterozygous state with microcytosis, or in asymptomatic cases as an alpha-thalassemia carrier phenotype. Hb Caserta was observed for the first time in a Casertian family (South Italy) that displayed a slowmigrating haemoglobin upon investigation. We report the clinical phenotype and molecular study of this new double mutant form of haemoglobin in heterozygous and homozygous subjects, as well as in association with alpha degrees delectional thalassemia.     

Pulmonary hypertension in thalassemia: association with platelet activation and hypercoagulable state

The pathogenesis of pulmonary hypertension (PAH), a serious complication in thalassemia, is not well understood. Thromboembolism has been postulated as one of the causative factors; however, there are currently limited specific data on its role. To examine whether increased platelet activation and hypercoagulability are linked to PAH, 25 beta-thalassemia major and beta-thalassemia intermedia patients were evaluated with Doppler echocardiograms for estimation of pulmonary artery pressure and with laboratory assays for indications of a prothrombotic state. The association of clinical variables and abnormal coagulation assays with PAH was determined. PAH was identified in 17 (68%) patients; mean pulmonary artery systolic pressure was 39.8 +/- 5.4 mm Hg. PAH was significantly associated with prior splenectomy, older age, and evidence for chronic hemolysis, diagnosed in both transfused (n = 10) and nontransfused (n = 7) patients. Increased platelet activation, measured by P-selectin, was significantly associated with PAH (P = 0.001). Increased thrombin-antithrombin III level was more prevalent in the presence of PAH, but increased fibrinolysis or low protein C levels were not. This study underscores the role of platelet activation in the development of PAH and stresses its occurrence even among patients who are regularly transfused, especially those who are older and have had splenectomies.     

Noninvasive prenatal diagnosis of monogenic diseases by digital size selection and relative mutation dosage on DNA in maternal plasma

Prenatal diagnosis of monogenic diseases, such as cystic fibrosis and β-thalassemia, is currently offered as part of public health programs. However, current methods based on chorionic villus sampling and amniocentesis for obtaining fetal genetic material pose a risk to the fetus. Since the discovery of cell-free fetal DNA in maternal plasma, the noninvasive prenatal assessment of paternally inherited traits or mutations has been achieved. Due to the presence of background maternal DNA, which interferes with the analysis of fetal DNA in maternal plasma, noninvasive prenatal diagnosis of maternally inherited mutations has not been possible. Here we describe a digital relative mutation dosage (RMD) approach that determines if the dosages of the mutant and wild-type alleles of a disease-causing gene are balanced or unbalanced in maternal plasma. When applied to the testing of women heterozygous for the CD41/42 (–CTTT) and hemoglobin E mutations on HBB, digital RMD allows the fetal genotype to be deduced. The diagnostic performance of digital RMD is dependent on interplay between the fractional fetal DNA concentration and number of DNA molecules in maternal plasma. To achieve fetal genotype diagnosis at lower volumes of maternal plasma, fetal DNA enrichment is desired. We thus developed a digital nucleic acid size selection (NASS) strategy that effectively enriches the fetal DNA without additional plasma sampling or experimental time. We show that digital NASS can work in concert with digital RMD to increase the proportion of cases with classifiable fetal genotypes and to bring noninvasive prenatal diagnosis of monogenic diseases closer to reality.     

T-type calcium channel as a portal of iron uptake into cardiomyocytes of beta-thalassemic mice

Objectives: Iron‐overload condition can be found in β‐thalassemic patients with regular blood transfusion, leading to iron deposition in various organs including the heart. Elevated cardiac iron causes iron‐overload cardiomyopathy, a condition that provokes mortality because of heart failure in patients with thalassemia. Previous studies demonstrated that myocardial iron uptake may occur via L‐type calcium channels (LTCCs). However, direct evidence regarding the claimed pathway in thalassemic cardiomyocytes has never been investigated. Methods: Hearts from genetic‐altered β‐thalassemic mice and adult wild‐type mice were used for cultured ventricular cardiomyocytes. Blockers for LTCC, T‐type calcium channel (TTCC), transferrin receptor1 (TfR1), and divalent metal transporter1 (DMT1) were used, and quantification of cellular iron uptake under various iron loading conditions was performed by Calcein‐AM fluorescence assay. Microarray analysis was performed to investigate gene expressions in the hearts of these mice. Results: This study demonstrated that iron uptake under iron‐overload conditions in the cultured ventricular myocytes of thalassemic mice was greater than that of wild‐type cells (P < 0.01). TTCC blocker, efonidipine, and an iron chelator, deferoxamine, could prevent iron uptake into cultured cardiomyocytes, whereas blockers of TfR1, DMT1, and LTCC could not. Microarray analysis from thalassemic hearts demonstrated highly up‐regulated genes of TTCC, zinc transporter, and transferrin receptor2. Conclusions: Our findings indicated that iron uptake mechanisms in cultured thalassemic cardiomyocytes are mainly mediated by TTCC, suggesting that TTCC is the important pathway for iron uptake in this cultured thalassemic cardiomyocyte model.     

对不同基因型地中海贫血儿童全血中9种金属元素的研究

目的：了解不同基因型地中海贫血儿童全血铜、锌、钙、镁、铁、钾、钠、铅、铬9种金属元素含量,为临床对不同类型地贫患儿营养状况的评价并进行针对性地监测、干预治疗提供依据。方法：对选取的240例地贫患儿[21例静止型,108例标准型α地贫,18例H病,81例β地贫杂合子（β＋）,12例β地贫双重杂合子（或纯合子）（β0）]以及70例健康儿童全血的9种元素进行检测和统计学分析。结果：①β0地贫全血铜、钙、钠水平明显高于其他组（P〈0.05）,镁、锌、钾水平明显低于其他组（P〈0.05）。H病全血铜水平与β0地贫相近（P〉0.05）,且明显高于其他组（P〈0.05）;②各地贫组全血铁、镁水平均低于健康对照组（P〈0.05）（血镁静止型α地贫与健康对照组差异无统计学意义）;③铅与铬水平：各组间均差异无统计学意义（P〉0.05）。结论：①地贫患儿体内金属元素的失衡（全血铁除外）主要集中在β地贫纯合子（或双重杂合子）和H病,前者要加强全血镁、钾、锌、钙、铜、钠的监测,后者则着重监测全血铜;②全血铁元素不宜用于评价地贫患儿的铁代谢状况。