The structure and function of normal and abnormal haemoglobins

Heterozygous variants in ZBTB7A cause a neurodevelopmental disorder associated with symptomatic overgrowth of pharyngeal lymphoid tissue, macrocephaly, and elevated fetal hemoglobin

By clinical whole exome sequencing, we identified 12 individuals with ages 3 to 37 years, including three individuals from the same family, with a consistent phenotype of intellectual disability (ID), macrocephaly, and overgrowth of adenoid tissue. All 12 individuals harbored a rare heterozygous variant in ZBTB7A which encodes the transcription factor Zinc finger and BTB-domain containing protein 7A, known to play a role in lympho- and hematopoiesis. ID was generally mild. Fetal hemoglobin (HbF) fraction was elevated 2.2%-11.2% (reference value <2% in individuals > 6 months) in four of the five individuals for whom results were available. Ten of twelve individuals had undergone surgery at least once for lymphoid hypertrophy limited to the pharynx. In the most severely affected individual (individual 1), airway obstruction resulted in 17 surgical procedures before the age of 13 years. Sleep apnea was present in 8 of 10 individuals. In the nine unrelated individuals, ZBTB7A variants were novel and de novo. The six frameshift/nonsense and four missense variants were spread throughout the gene. This is the first report of a cohort of individuals with this novel syndromic neurodevelopmental disorder.

Screening Readthrough Compounds to Suppress Nonsense Mutations: Possible Application to β-Thalassemia

Several types of thalassemia (including β⁰39-thalassemia) are caused by nonsense mutations in genes controlling globin production, leading to premature translation termination and mRNA destabilization mediated by the nonsense mediated mRNA decay. Drugs (for instance, aminoglycosides) can be designed to suppress premature translation termination by inducing readthrough (or nonsense suppression) at the premature termination codon. These findings have introduced new hopes for the development of a pharmacologic approach to cure this genetic disease. In the present review, we first summarize the principle and current status of the chemical relief for the expression of functional proteins from genes otherwise unfruitful for the presence of nonsense mutations. Second, we compare data available on readthrough molecules for β⁰-thalassemia. The examples reported in the review strongly suggest that ribosomal readthrough should be considered as a therapeutic approach for the treatment of β⁰-thalassemia caused by nonsense mutations. Concluding, the discovery of molecules, exhibiting the property of inducing β-globin, such as readthrough compounds, is of great interest and represents a hope for several patients, whose survival will depend on the possible use of drugs rendering blood transfusion and chelation therapy unnecessary.

Clinical method evaluation of hemoglobin S and C identification by top-down selected reaction monitoring and electron transfer dissociation

Background

Biological diagnosis of hemoglobin disorders is a complex process relying on the combination of several analytical techniques to identify Hb variants in a particular sample. Currently, hematology laboratories usually use high-performance liquid chromatography (HPLC), capillary electrophoresis and gel-based methods to characterize Hb variants. Co-elution and co-migration may represent major issues for precise identification of Hb variants, even for the most common ones such as Hb S and C.

Methods

We adapted a top-down selected reaction monitoring (SRM) electron transfer dissociation (ETD) mass spectrometry (MS) method to fit with a clinical laboratory environment. An automated analytical process with semi-automated data analysis compatible with a clinical practice was developed. A comparative study between a reference HPLC method and the MS assay was performed on 152 patient samples.

Results

The developed workflow allowed to identify with high specificity and selectivity the most common Hb variants (Hb S and Hb C). Concordance of the MS-based approach with HPLC was 71/71 (100%) for Hb S and 11/11 (100%) for Hb C.

Conclusions

This top-down SRM ETD method can be used in a clinical environment to detect Hb S and Hb C.

Hemoglobin E, malaria and natural selection

It is known that there has been positive natural selection for hemoglobin S and C in humans despite negative health effects, due to its role in malaria resistance. However, it is not well understood, if there has been natural selection for hemoglobin E (HbE), which is a common variant in Southeast Asia. Therefore, we reviewed previous studies and discussed the potential role of natural selection in the prevalence of HbE. Our review shows that in vitro studies, evolutionary genetics studies and epidemiologic studies largely support an involvement of natural selection in the evolution of HbE and a protective role of HbE against malaria infection. However, the evidence is inconsistent, provided from different regions, and insufficient to perform an aggregated analysis such as a meta-analysis. In addition, few candidate gene, genome-wide association or epistasis studies, which have been made possible with the use of big data in the post-genomic era, have investigated HbE. The biological pathways linking HbE and malaria infection have not yet been fully elucidated. Therefore, further research is necessary before it can be concluded that there was positive natural selection for HbE due to protection against malaria.

Lay summary: Our review shows that evidence largely supports an involvement of natural selection in the evolution of HbE and a protective role of HbE against malaria. However, the evidence is not consistent. Further research is necessary before it is concluded.

Investigation of the effect of hemoglobin F and A levels on development of retinopathy of prematurity

PURPOSE

To investigate the effect of hemoglobin F (HbF) and hemoglobin A (HbA) levels on development of retinopathy of prematurity (ROP) in premature infants.

METHODS

In this prospective study, blood samples were collected from the side of the heel of 49 premature infants at postnatal months 0, 1, 2, and 3. HbF and HbA levels were measured in all samples and analyzed statistically. Furthermore, correlation analysis was performed regarding development of ROP, blood transfusion, and HbF and HbA levels.

RESULTS

A total of 49 infants were included. The mean gestational age of the premature infants was 30.9 ± 2.7 weeks (range, 25-35 weeks); mean birth weight, 1542 ± 582 g (range, 520-3240 g). Of the 49 premature infants, stage 1 ROP or above developed in 26 (53%). Mean HbF levels were lower at postnatal months 1 and 2 in premature infants with ROP compared to those without ROP (P = 0.013 and 0.02, respectively); however, mean HbA levels were higher in the infants with ROP than the others (P = 0.034 and 0.029, respectively). Analysis of covariance that ignored transfusion revealed no difference between the means of Hb variants in the infants with and without ROP (P = 0.572 and 0.486).

CONCLUSIONS

Blood transfusion significantly altered the levels of HbF and HbA in premature infants, and Hb variants have no direct effect on development of ROP.

Laboratory parameters provided by Advia 2120 analyser identify structural haemoglobinopathy carriers and discriminate between Hb S trait and Hb C trait

BACKGROUND

Haemoglobinopathies have spread owing to human migration, and the number of people needing diagnosis and management of these conditions is increasing. Clinicians need to accurately identify carriers and provide adequate genetic counselling in order to prevent the occurrence of homozygous or compound heterozygous offspring.

OBJECTIVES

To identify red blood cell (RBC) laboratory parameters that discriminate between structural haemoglobinopathy carriers and healthy subjects, and to compare RBC laboratory indices between HbAS and HbAC individuals.

METHODS

Samples of 500 variant Hb carriers (355 HbAS, 104 HbAC, 19 HbAD, 7 HbAE, 7 HbAO-Arab, 4 α-chain variants and 4 Hb Lepore) and 251 normal controls were run on an Advia 2120 analyser (Siemens). Classic haematological parameters and RBC populations were assessed in all subjects. A multivariable binary logistic regression model was created to predict the probability of a subject carrying any structural haemoglobinopathy. HbAS (n=355, 71%) and HbAC (n=104, 20.8%) subjects were compared.

RESULTS

A clinical prediction rule was developed by assigning one point to each of the most efficient variables: mean corpuscular volume (MCV) <88.4 fL, RBC distribution width >13.4%, percentage of microcytic RBCs (%MICRO) >0.7% and the ratio of microcytic RBCs to hypochromic RBCs >0.8. A score of 0, 1, 2, 3 or 4, resulted in a probability of 9.6%, 36.3%, 66.7%, 85.2% or 98.3%, respectively. Among the most frequent variant Hb, HbAC subjects had lower values of parameters related to cell size (MCV, %MICRO) and higher values of parameters related to haemoglobin concentration (MCHC, %HYPER) than HbAS subjects. Coexistence of α-thalassaemia in both HbAS and HbAC individuals resulted in decreased Hb, MCV, MCH and MCHC.

CONCLUSIONS

Structural haemoglobinopathy should be investigated in subjects belonging to ethnic groups with high prevalence of variant Hb and with a score of 3 or 4. Erythrocytes of HbAC subjects are smaller and denser than those of HbAS subjects.

Prenatal programming of pulmonary hypertension induced by chronic hypoxia or ductal ligation in sheep

Pulmonary hypertension of the newborn is caused by a spectrum of functional and structural abnormalities of the cardiopulmonary circuit. The existence of multiple etiologies and an incomplete understanding of the mechanisms of disease progression have hindered the development of effective therapies. Animal models offer a means of gaining a better understanding of the fundamental basis of the disease. To that effect, a number of experimental animal models are being used to generate pulmonary hypertension in the fetus and newborn. In this review, we compare the mechanisms associated with pulmonary hypertension caused by two such models: in utero ligation of the ductus arteriosus and chronic perinatal hypoxia in sheep fetuses and newborns. In this manner, we make direct comparisons between ductal ligation and chronic hypoxia with respect to the associated mechanisms of disease, since multiple studies have been performed with both models in a single species. We present evidence that the mechanisms associated with pulmonary hypertension are dependent on the type of stress to which the fetus is subjected. Such an analysis allows for a more thorough evaluation of the disease etiology, which can help focus clinical treatments. The final part of the review provides a clinical appraisal of current treatment strategies and lays the foundation for developing individualized therapies that depend on the causative factors.

Antenatal hypoxia and pulmonary vascular function and remodeling

This review provides evidence that antenatal hypoxia, which represents a significant and worldwide problem, causes prenatal programming of the lung. A general overview of lung development is provided along with some background regarding transcriptional and signaling systems of the lung. The review illustrates that antenatal hypoxic stress can induce a continuum of responses depending on the species examined. Fetuses and newborns of certain species and specific human populations are well acclimated to antenatal hypoxia. However, antenatal hypoxia causes pulmonary vascular disease in fetuses and newborns of most mammalian species and humans. Disease can range from mild pulmonary hypertension, to severe vascular remodeling and dangerous elevations in pressure. The timing, length, and magnitude of the intrauterine hypoxic stress are important to disease development, however there is also a genetic-environmental relationship that is not yet completely understood. Determining the origins of pulmonary vascular remodeling and pulmonary hypertension and their associated effects is a challenging task, but is necessary in order to develop targeted therapies for pulmonary hypertension in the newborn due to antenatal hypoxia that can both treat the symptoms and curtail or reverse disease progression.

Erythrocytosis in a child due to Hb Andrew-Minneapolis [β144(HC1)Lys→Asn (AAG>AAT or AAC)] associated with a Spanish (δβ)(0)-thalassemia

We report a rare association of δβ-thalassemia (δβ-thal) and a hemoglobin (Hb) variant with high oxygen affinity in a Spanish newborn. The proband had no Hb A and showed microcytosis and hypochromia; the peripheral blood smear was compatible with a thalassemia trait. Molecular studies revealed that the proband had a Spanish (δβ)(0)-thal (inherited from his father) and also carried a de novo variant (Hb Andrew-Minneapolis) because from the point of hematology, his mother was quite normal. The hemoglobinopathies with high affinity for oxygen constitute an infrequent cause of secondary congenital erythrocytosis. The degree of erythrocytosis and the resulting clinical manifestations are highly variable, depending on the degree of altered oxygen affinity and the presence of thalassemic genes. Thus, when these variants are associated with β(0)- or δβ-thal, as in our case, the proportion of abnormal Hb is ∼100.0%, which may cause polycythemia, hyperviscosity, and iron deficiency. This type of association is very rare and few have been described, especially in children, as they would normally be detected in adults as the increased packed cell volume (PCV) also increases blood viscosity and causes the typical symptoms (cephalalgia, drowsiness, dizziness). The association of a high oxygen affinity Hb and a δβ-thal presents a greater degree of erythrocytosis than when this same variant is associated with a β(0)-thal, mainly because the Hb F percentage is usually greater in the δβ-thal, and Hb F normally shows a greater affinity for oxygen and a reduced P(50), although one must always take into account the degree of oxygen affinity of the Hb variant. Familial erythrocytosis and an abnormal electrophoresis finding are indicative of a high affinity Hb. However, the absence of these findings does not reject the possibility of hemoglobinopathies, and in these cases, functional and molecular studies would be justified and should be mandatory for the differential diagnosis of erythrocytosis.

What influences Hb fetal production in adulthood?

Human hemoglobin genes are located in α and β globin gene clusters in chromosomes 16 and 11, respectively. Different types of hemoglobin are synthesized according to the stage of development with fetal hemoglobin (α(2)γ(2)) (Hb F) being the main hemoglobin in the fetal period. After birth, there is a reduction (to about 1%) in Hb F levels and adult hemoglobin, Hb A (2α(2)β(2)), increases to more than 96% of total hemoglobin. However, some genetic conditions whether linked to the β-globin gene cluster or not are associated with high Hb F levels in adults. Among those linked to β-globin are hereditary persistence of fetal hemoglobin, delta-beta thalassemia (δβ-Thalassemia) and the XmnI polymorphism (-158 C = T). Other polymorphisms not related to β-globin gene cluster are known to influence the γ-globin gene expression in adulthood. The most relevant polymorphisms that increase concentrations of Hb F are the HMIP locus on chromosome 6, the BCL11A locus on chromosome 2, the Xp22.2 region of the X chromosome and the 8q region on chromosome 8. Findings from our research group studying genetic factors involved in γ-globin gene regulation in adults without anemia in the northwestern region of São Paulo State showed that high Hb F levels are influenced by the presence of hereditary persistence of fetal hemoglobin mutations and the XmnI polymorphism, suggesting that both genetic alterations characterize the molecular basis of the evaluated population.

Control of human beta-globin mRNA stability and its impact on beta-thalassemia phenotype

Messenger RNA (mRNA) stability is a critical determinant that affects gene expression. Many pathways have evolved to modulate mRNA stability in response to developmental, physiological and/or environmental stimuli. Eukaryotic mRNAs have a considerable range of half-lives, from as short as a few minutes to as long as several days. Human globin mRNAs constitute an example of highly stable mRNAs. However, a wide variety of naturally occurring mutations that result in the clinical syndrome of thalassemia can trigger accelerated mRNA decay thus controlling mRNA quality prior to translation. Distinct surveillance mechanisms have been described as being targeted for specific defective globin mRNAs. Here, we review mRNA stability mechanisms implicated in the control of β-globin gene expression and the surveillance pathways that prevent translation of aberrant β-globin mRNAs. In addition, we emphasize the importance of these pathways in modulating the severity of the β-thalassemia phenotype.

Identification of the First Japanese Family Harboring a Novel Hemoglobin Variant "Perpignan", Which Caused Low HbA1c Measurement During Diabetic Follow-Up

Hemoglobin A1c (HbA1c) is an important parameter for evaluating long-term (6-8 weeks) control of blood glucose levels in patients with diabetes mellitus. We report a Japanese diabetic case who harbored abnormal Hb and demonstrated falsely low HbA1c levels in the regular ion exchange HPLC-based assay. His abnormal β-globin chain had an amino acid replacement that corresponded to glycine to serine substitution at amino acid position 136 of the β-globin chain (Hb Perpignan). Accordingly, a heterozygotic point mutation replacing guanine by adenine at nucleotide position 406 (β136G > S) was identified in the β-globin gene of the proband and his son. These results indicate that the patient had Hb Perpignan, and this abnormal Hb interfered with the HPLC-based HbA1c assay commonly used in the clinic. The cases presented are the first report of patients in the Japanese population harboring Hb Perpignan (β136G > S).

Parathyroid and calcium status in patients with thalassemia

Thirty patients with thalassemia major receiving repeated blood transfusion were studied to see their serum parathyroid hormone (PTH) and calcium status. Serum PTH, serum and 24 h urinary calcium, and serum alkaline phosphatase, phosphorus, and albumin-corrected calcium levels were determined. Half of these patients, in addition to transfusion, were also supplemented with vitamin D (60,000 IU for 10d) and calcium (1500 mg/day for 3 months). Serum PTH, and serum and 24 h urinary calcium concentrations of the patients receiving transfusions were found to be significantly reduced while their serum alkaline phosphatase, phosphorus, and albumin-corrected calcium levels were not significantly altered when compared to the respective mean values for the control group. Vitamin D and calcium supplementation significantly increased their serum PTH and calcium levels. Supplementations also increased urinary excretion of calcium. The results thus suggest that patients with thalassemia have hypoparathyroidism and reduced serum calcium concentrations that in turn were improved with vitamin D and calcium supplementation.

Partial glutathione reductase deficiency as a cause of diverse clinical manifestations in a family with unstable hemoglobin (Hemoglobin Haná, β63(E7) His-Asn)

Hemoglobin Haná [β63(E7) His-Asn] is an unstable hemoglobin variant that was described in a Czech proband and her sister with Heinz body hemolytic anemia. The mother bearing the same mutation was asymptomatic; nevertheless, all three carriers had the same proportion of the mutant globin chains. Assessment of several erythrocyte antioxidant parameters revealed that both symptomatic children, unlike their asymptomatic mother, had significantly decreased glutathione reductase (GR) activity. Their GR activities were restorable in vitro by flavin adenine dinucleotide. The riboflavin supplementation improved their glutathione metabolism and ameliorated their hemolysis. Pre- and post-treatment assessment of the B(2) vitamers indicated suboptimal pre-treatment vitamin B(2) status in both children. This study provides evidence that partial GR deficiency may alter the clinical manifestation of an unstable hemoglobinopathy.

Ontogeny of haematopoiesis: recent advances and open questions

Unravelling the embryonic origins of the haematopoietic system has been the subject of sustained research for more than a century. Nevertheless, many important questions are still either unanswered or remain a matter of intense debate. Recent progress in mouse and embryonic stem cell model systems as well as imaging and post-genomic technologies has provided new insights into many of these open questions. Here we place into context recent reports on the anatomical site of blood stem cell emergence and, using red blood cells as an example, illustrate how the development of stem cells and the other blood lineages is both temporally and spatially decoupled. In addition, we outline how embryonic stem cell assays are increasingly used as a powerful surrogate for studying lineage relationships and developmental potential of early embryonic blood progenitors. Finally, we review how recent progress in the reconstruction of transcriptional regulatory networks is beginning to define the connectivity between key regulators that control early blood development. In light of these rapid recent advances, research into the embryonic origins of the haematopoietic system should remain one of the most vibrant disciplines within the wider field of haematology for the foreseeable future.

[Hemoglobin Stanleyville II [alpha78(EF7)Asn --> Lys]. First case described in Spain]

BACKGROUND AND OBJECTIVE

Structural hemoglobinopathies are the result of mutations in the genes of globin, which determine a qualitative alteration in the expression of these genes. Most alterations do not originate any significant change, and correspond to silent or asymptomatic forms. This study proves a new case of hemoglobin (Hb) Stanleyville II.

PATIENTS AND METHOD

The propositus was a 72 years old Caucasian woman, from the Canary Islands. Her hematological data were: Hb 14.3 g/dl; hematocrit 44.4%; mean corpuscular volume 85.8 fl; mean corpuscular hemoglobin 27.7 pg; red cell distribution width 15.1%; reticulocytes 1.2%; HbA2 3.1% and HbF 1.6%. Electrophoretic studies in cellulose acetate electrophoresis at alkaline pH = 8.6 and isoelectrofocusing showed an anomalous Hb similar to HbS. The anomalous Hb did not appear in agar citrate electrophoresis (pH 6.0). The analysis by reverse phase high performance liquid chromatography for globin chains showed an X anomalous after A.

RESULTS

Molecular analysis by sequentiation of the polymerase chain reaction products genes 1 and 2 showed the mutation AAC --> AAA at CD78 of second gene 2 in heterozygote state, which leads the change of asparagine to lysine.

CONCLUSIONS

The substitution of an amino acid with neutral charge like asparagine for another one with positive charge like lysine in the segment EF, which corresponds to the external surface of the tertiary structure of the chain of globin, determines the change of charge in the chain. This allows an easy differentiation by electrophoretic and chromatographic methods. Nevertheless, owing to its position in the chain, which is not critique for the stability, solubility and affinity for the oxygen allows for silent or asymptomatic forms. The Hb Stanleyville II had been described before in black families of the Congo, Uganda, USA, Alsace and Brazil. This case represents the first case described in Spain.

Haemoglobinopathies with high oxygen affinity. Experience of Erythropathology Cooperative Spanish Group

Haemoglobinopathies are the world's most frequently found monogenic disorders. In the cases with high oxygen affinity, the decrease in the liberation of the oxygen determines a secondary erythrocytosis. In this work, we present 17 unrelated families of Caucasian race and of Spanish origin, with ten variants of haemoglobin or haemoglobinopathies with high oxygen affinity which were diagnosed in our laboratory. Of the ten haemoglobinopathies, in four (the Hb San Diego, the Hb Johnstown, the Hb Malmö and the Hb Columbia-Missouri), the change of amino acid affects zones of the contact alpha(1)beta(2); in two variants (the Hb Strasbourg and the Hb Syracuse), it affects the unions with 2,3-DPG in the central cavity; in the other two (the Hb Badalona and the Hb La Coruña), the cavity of contact with the group haem is affected; in one (Hb Bethesda), it affects the zone of contact alpha(1)beta(1;) and in one (Hb Olympia), the position 20 of the chain in the helix B in the surface of the protein is affected. In all cases, the change of amino acid, though of different form, facilitates that the quaternary structure of the haemoglobin becomes stable in its relaxed configuration so the transfer of oxygen and the P(50) value are decreased. All cases were sent to our laboratory because of shown erythrocytosis. In the majority of them, the diagnosis was done during an analysis of routine or for being relatives of the first ones.

Hemoglobina Fannin-Lubbock II [β111(G13)Val → Leu y β119(GH2)Gly → Asp]: descripción de 4 nuevos casos

BACKGROUND AND OBJECTIVE

The aim of this work is the molecular description of a 4 new cases of the hemoglobin Fannin-Lubbock II, which presents the substitution of 2 amino acids in the same beta globin chain.

PATIENT AND METHOD

Four cases belonging to 3 families all of white race and from Spain are studied. The molecular analysis was done with the sequence of the products of amplification for polymerase chain reaction of the beta globin gene.

RESULTS

The molecular study demonstrated the mutation GTC -> CTC in the codon 111 that determines a change of valine for leucine and the mutation GGC -> GAC in the codon 119 that determines a change of glycine for aspartic acid, both in heterozygote state.

CONCLUSIONS

Until the present time 17 hemoglobin variants have been described with 2 substitutions of amino acids in the beta globin chain. The hemoglobin Fannin-Lubbock II had been described in 5 Spanish families; therefore, the communication of these new cases suggests it could be a haemoglobin variant relatively frequent and circumscribed to our population.

The thalassaemia syndromes

The thalassaemia syndromes, endemic in the Mediterranean area, the Middle East, the Indian subcontinent, the Far East and in tropical Africa, are the most common hereditary disorders in humans, and millions of people are affected by diseases. Due to a widespread population flow between continents in recent past centuries, the thalassaemias are now occurring with relatively high frequency in many non-endemic areas. In the Nordic countries, homozygous thalassaemia is still relatively rare, and most health-care personnel are not familiar with these diseases. This article focuses on two important issues, namely the biological and the clinical aspects of thalassaemia.

In vivo rates of erythrocyte glutathione synthesis in adults with sickle cell disease

Despite reports of lower GSH concentration in sickle cell disease (SCD), the in vivo kinetic mechanism(s) responsible for GSH deficiency is unknown. To determine whether suppressed synthesis was responsible for the lower erythrocyte GSH concentration, we used a primed intermittent infusion of [(2)H(2)]glycine to measure erythrocyte GSH synthesis in vivo in 23 individuals with homozygous beta(s) SCD and 8 healthy controls. Erythrocyte cysteine concentration, the rate-limiting precursor for GSH synthesis, plasma markers of oxidant damage, and dietary intakes of energy and protein were also measured. Compared with values of controls, SCD subjects had significantly lower erythrocyte GSH (P < 0.04) and cysteine concentrations (P < 0.004) but significantly faster fractional rates of GSH synthesis (P < 0.02). The absolute rates of GSH synthesis in SCD subjects compared with control subjects was greater by approximately 57% (P = 0.062). However, the concentrations of markers of oxidative damage, plasma derivatives of reactive oxygen metabolites, plasma nitrotyrosine, urinary isoprostane-to-creatinine ratio, and GSH-to-GSSG ratio, as well as dietary intakes of energy, protein, and GSH precursor amino acids, were not different between SCD subjects and controls. The findings of this study suggest that the lower erythrocyte GSH of SCD patients is not due to suppressed synthesis or impaired regeneration but rather to increased consumption. In addition, the lower erythrocyte cysteine concentration plus the faster rate of GSH synthesis strongly suggest that the endogenous cysteine supply is not sufficient to meet all anabolic demands; hence, cysteine may be a conditionally essential amino acid in individuals with SCD.

Asociación de hemoglobinopatía S y alfatalasemia. Análisis de 45 casos

BACKGROUND AND OBJECTIVE

Hemoglobin S (HbS) alpha-thalassemia together with ss-thalassemia and hemoglobins C, E and D are named common hemoglobinopathies. In this study, we analyzed the frequency of the association between alpha-thalassemia and HbS and its phenotypic expression.

PATIENTS AND METHOD

Since January 1995 to March 2003 we studied 83 cases of HbS, which were diagnosed by electrophoretic and chromatographic criteria. The molecular study was carried out by Southern blot with the restriction enzymes Bam HI and Bgl II and a (1.5 Kb Pst) and z (1.8 Kb Sac Y) probes.

RESULTS

45 cases (54.2%) had a-thalassemia (36 -alpha3,7/aa; 1-alpha4,2/alphaalpha; 6 -alpha3,7/-alpha3,7; 1-alpha4,2/-alpha4,2); 36 had not alpha-thalassemia and in two cases there were a triplication of a genes. The patients with HbS heterozygote associated with alpha-thalassemia showed a percentage of HbS (p < 0.0001), CMV (p = 0.004), MCH (p = 0.002) and MCHC (p = 0.02) significantly lower than the cases of HbS without this association. However, no differences between both groups were found with regard to the rest of parameters analyzed (Hb p = 0.56; PVC p = 0.84; RDW p = 0.06; Reticulocytes p = 0.26; HbF p = 0.76; HbA2 p = 0.13). In the cases with a severe form of disease (HbS homozygote; HbS/Hb C; HbS/beta-thalassemia), patients with alpha-thalassemia had a number of leukocytes that was significantly lower than that of patients without alpha-thalassemia (p = 0.034).

CONCLUSION

An association between HbS and alpha-thalassemia was common (> 50%). Screening for this association is of great interest because the clinical expression in the cases of HbS homozigote will be modulated. This association must be suspected in cases of homozygous HbS in which levels of HbS are lower than expected.

Hb H hydrops foetalis syndrome: a case report and review of literature

Haemoglobin H (Hb H) disease is caused by deletion or inactivation of three alpha-globin genes, leaving only one intact and active alpha-globin gene. People with Hb H disease usually have moderate anaemia, but are generally thought to be asymptomatic. Some Hb H disease patients require transfusions, and there are reports of fetuses with Hb H disease who have severe anaemia in utero resulting in fatal hydrops foetalis syndrome. We now report a case of Hb H hydrops foetalis syndrome, caused by the inheritance of a hitherto novel alpha-globin gene point mutation (codon 35 TCC-->CCC or Serine-->Proline) and an alpha-thalassaemia deletion of the Filipino type removing all zeta-alpha-globin genes on the other chromosome 16. The infant was delivered prematurely because of pericardial effusion and fetal distress, and was found to have severe anaemia and congenital anomalies. A review of the relevant literature on this syndrome is presented, and serves to underscore the phenotypic variations of Hb H disease and the need for surveillance for this condition among newborns and genetic counselling in communities with a high proportion of at-risk populations.

Glutathione in disease

Altered glutathione metabolism in association with increased oxidative stress has been implicated in the pathogenesis of many diseases. However, whether strategies aimed at restoring glutathione concentration and homeostasis are effective in ameliorating or modifying the natural history of these states is unknown. In this review we discuss the pathogenic role for altered glutathione metabolism in such diseases as protein energy malnutrition, seizures, Alzheimer's disease, Parkinson's disease, sickle cell anaemia, chronic diseases associated with ageing and the infected state. In addition, we discuss the efficacy of glutathione precursors in restoring glutathione homeostasis both in vitro and in vivo.

A rapid combined immunocytochemical and fluorescence in situ hybridisation method for the identification of human fetal nucleated red blood cells

Fetal nucleated red blood cells are found in the maternal circulation during pregnancy. If a simple routine method of detection of these cells was developed, it could be used as the basis of non-invasive prenatal diagnosis of fetal genetic disorders. Fetal male and adult female blood were mixed to mimic maternal blood in pregnancy and used to establish a simple technique to unequivocally detect fetal nucleated red blood cells. These were identified by combined immunocytochemistry using a human fetal haemoglobin antibody and a rapid and simple-to-use fluorescence in situ hybridisation method using X and Y chromosome probes. Initial studies using the alkaline phosphatase anti-alkaline phosphatase technique as the first procedure showed that the stain was unstable and unsuitable for in situ hybridisation. An immunoperoxidase technique was found to produce a stable stain resistant to harsh fixation steps required in subsequent in situ hybridisation. This enabled the simultaneous visualisation of immunopositivity and in situ hybridisation signals on the same cell with neither procedure affecting the other's signal quality. We are currently using this procedure to detect a range of endoplasmic reticulum proteins in fetal nucleated red blood cells from maternal blood in an attempt to diagnose disorders of liver protein expression in early pregnancy.

Diagnosis of sickle-cell disease with a universal heteroduplex generator

A new diagnostic technique, universal heteroduplex generator screening, has been developed to detect homozygosity and heterozygosity for sickle-cell disease. Since it is a polymerase chain reaction-based technique, it may be used to detect haemoglobin S and haemoglobin C genotypes in adults, neonates, or from coelocentesis during the first 10 weeks of pregnancy. beta-globin gene nucleotide sequences are amplified by the polymerase chain reaction, and are heteroduplexed with a beta-globulin universal heteroduplex generator. Haemoglobins S and C mutations are identified by characteristic polyacrylamide minigel banding patterns. The technique is simple and rapid to do, even by nonspecialist laboratories, and is applicable to large-scale screening for haemoglobin S and C mutations as well as prenatal diagnosis of sickle cell disease.