Hydroxyurea differentially modulates activator and repressors of γ-globin gene in erythroblasts of responsive and non-responsive patients with sickle cell disease in correlation with Index of Hydroxyurea Responsiveness.

Hydroxyurea (HU), the first of two drugs approved by the US Food and Drug Administration for treating patients with sickle cell disease (SCD), produces anti-sickling effect by re-activating fetal γ-globin gene to enhance production of fetal hemoglobin. However, approximately 30% of the patients do not respond to HU therapy. The molecular basis of non-responsiveness to HU is not clearly understood. To address this question, we examined HU-induced changes in the RNA and protein levels of transcription factors NF-Y, GATA-1, -2, BCL11A, TR4, MYB and NF-E4 that assemble the γ-globin promoter complex and regulate transcription of γ-globin gene. In erythroblasts cultured from peripheral blood CD34+ cells of patients with SCD, we found that HU-induced changes in the protein but not the RNA levels of activator GATA-2 and repressors GATA-1, BCL11A and TR4 correlated with HU-induced changes in fetal hemoglobin (HbF) levels in the peripheral blood of HU high and low responders. However, HU did not significantly induce changes in the protein or RNA levels of activators NF-Y and NF-E4. Based on HU-induced changes in the protein levels of GATA-2, -1 and BCL11A, we calculated an Index of Hydroxyurea Responsiveness (IndexHU-3). Compared to the HU-induced fold changes in the individual transcription factor protein levels, the numerical values of IndexHU-3 statistically correlated best with the HU-induced peripheral blood HbF levels of the patients. Thus, IndexHU-3 can serve as an appropriate indicator for inherent HU responsiveness of patients with SCD.

Hemoglobin F Only Syndrome at Birth: A Case of Maternal HbA2' Complicating the Diagnosis of ß-Thalassemia.

An asymptomatic infant of Ghanaian descent had hemoglobin F only detected on newborn screening. ß-globin gene sequencing identified the intervening sequence (IVS)-II-849 (A → G) mutation with no normal ß-globin gene. ß-globin/δ-globin gene sequencing showed that both parents were heterozygous for the IVS-II-849 (A → G) mutation. The mother was heterozygous for the HbA2' δ-globin mutation (δ16 (A13) Gly → Arg), thus ß-thalassemia trait was unrecognized due to coinheritance of HbA2'. The infant developed anemia, splenomegaly, and began transfusion therapy by the age 6 of months. This is the first report of ß-thalassemia major with homozygous IVS-II-849 (A → G) mutations. This case highlights the importance of δ-globin gene mutations in prenatal testing.

Coagulation activation in sickle cell trait: an exploratory study.

Recent epidemiologic data suggest that sickle cell trait (HbAS; AS) is a risk factor for venous thromboembolism. We conducted an exploratory study of healthy subjects with AS under baseline conditions to determine whether a chronic basal hyperactivation of coagulation exists, and if so, what mechanism(s) contribute to this state. Eighteen healthy AS individuals were compared to 22 African-American controls with a normal haemoglobin profile (HbAA; AA) and 17 patients with sickle cell disease (HbSS; SS). Plasma thrombin-antithrombin complexes and D-dimer levels were elevated in AS relative to AA patients (P = 0·0385 and P = 0·017, respectively), and as expected, were much higher in SSversusAA (P < 0·0001 for both). Thrombin generation in platelet poor plasma was indistinguishable between AA and AS subjects, whereas a paradoxical decrease in endogenous thrombin potential was observed in SS (P ≤ 0·0001). Whole blood tissue factor was elevated in SS compared to AA (P = 0·005), but did not differ between AA and AS. Plasma microparticle tissue factor activity was non-significantly elevated in AS (P = 0·051), but was clearly elevated in SS patients (P = 0·004) when compared to AA controls. Further studies in larger cohorts of subjects with sickle cell trait are needed to confirm the results of this preliminary investigation.

A new Aγ-globin chain variant: Hb F-Sykesville MD [Aγ113(G15)Val → Ile; HBG1: c.340G>A] detected in a Caucasian baby.

The total number of hemoglobin (Hb) variants currently included in the globin gene server database is 1626 (November 12 2014), of which 131 are fetal Hb variants. These variants are observed as two different subunits of fetal Hb, (G)γ- and (A)γ-globin chains. Of the 131 documented fetal Hb variants, 73 are (G)γ- and 58 are (A)γ-globin chain variants. Although they are easily detected at birth, as the quantity of γ chains progressively decreases over the first few months of life, they are essentially undetectable after 6 months of age. In this report we discuss the molecular characteristics and diagnostic criteria of a new (A)γ chain variant that was detected during newborn screening and named Hb F-Sykesville MD [(A)γ113(G15)Val → Ile; HBG1: c.340G>A].

Two new γ chain variants: Hb F-Augusta GA [(G)γ59(E3)Lys → Arg; HBG2: c.179A > G] and Hb F-Port Royal-II [(A)γ125(H3)Glu → Ala; HBG1: c.377A > C].

The total number of hemoglobin (Hb) variants so far reported to the HbVar database is 1598 (April 9 2014) and 130 of them are fetal Hb variants. Fetal Hb are categorized as two different subunits, (G)γ- and (A)γ-globin chains, and γ chain variants can be observed in both subunits. There are 72 (G)γ- and 58 (A)γ-globin chain variants. Most of them are clinically silent and detected during newborn screening programs in the USA and outside the USA. In this report, we discuss the molecular characteristics and diagnostic difficulties of two new γ-globin chain variants found in an African American baby with no clinical symptoms. One is a new (G)γ-globin chain variant, Hb F-Augusta GA [(G)γ59(E3)Lys → Arg; HBG2: c.179A > G] and the other one is Hb F-Port Royal-II [(A)γ125(H3)Glu → Ala; HBG1: c.377A > C].

Two new hemoglobin variants: Hb Tallahassee [α3(A1)Ser→Tyr; HBA2: c.11C>A] and Hb madison-NC [ß119(GH2)Gly→Ser; HBB: c.358G>A].

Of the 1570 reported hemoglobin (Hb) variants detected to date, 390 are α2-globin chain (some variants have yet to be identified by DNA analyses and are therefore presumed) and 827 are the result of mutations of the ß-globin chain. Due to their location on the Hb structure, only a minority of these variants result in a clinical phenotype; most are silent and are detected during routine surveillance, are found incidentally during other disease-related investigations or following newborn screening programs. In this report we discuss phenotype/genotype and molecular characteristics of two new Hb variants, both of which were clinically silent. One is an α2-globin chain variant located at codon 3 [α3(A1)Ser→Tyr; HBA2: c.11C > A] named Hb Tallahassee and the other is a ß-globin chain variant located at codon 119 [ß119(GH2)Gly→Ser; HBB: c.358G > A] called Hb Madison-NC.

Pomalidomide augments fetal hemoglobin production without the myelosuppressive effects of hydroxyurea in transgenic sickle cell mice.

Pharmacologic induction of fetal hemoglobin (HbF) expression is an effective treatment strategy for sickle cell disease (SCD) and ß-thalassemia. Pomalidomide is a potent structural analog of thalidomide and member of a new class of immunomodulatory drugs. Recent reports demonstrated that pomalidomide reduced or eliminated transfusion requirements in certain hematologic malignancies and induced HbF ex vivo in CD34(+) progenitor cells from healthy and SCD donors. We investigated the effects of pomalidomide on erythropoiesis and hemoglobin synthesis in a transgenic mouse model of SCD. We found that 8 weeks of treatment with pomalidomide induced modest increases of HbF with similar efficacy as hydroxyurea. However, in stark contrast to hydroxyurea's myelosuppressive effects, pomalidomide augmented erythropoiesis and preserved bone marrow function. Surprisingly, combinatory therapy with both drugs failed to mitigate hydroxyurea's myelotoxic effects and caused loss of HbF induction. These findings support further evaluation of pomalidomide as a novel therapy for SCD.

Hb Fulton-Georgia [α20(B1)His→Pro; HBA1: c.62A>C]: a new α-globin variant coinherited with α-thalassemia-2 (3.7 kb deletion) and Hb SC disease.

We report a novel hemoglobin (Hb) variant that we named Hb Fulton-Georgia, caused by a point mutation in exon 1/codon 20 of the α-globin gene [α20(B1)His→Pro; HBA1: c.62A>C]. This α chain variant was identified in an adult African-American female with Hb SC disease who was also heterozygous for the α-thalassemia-2 (α-thal-2) (3.7 kb deletion or αα/-α(3.7)). The Hb Fulton-Georgia mutation was located on the intact α1-globin gene not involved by α-thal-2. Molecular models indicated that the α20 residue of Hb Fulton-Georgia was the first amino acid of the B helix, and was not involved in α1/ß1 or α1/ß2 contacts in Hb S [ß6(A3)Glu→Val; HBB: c.20A>T] or Hb C [ß6(A3)Glu→Lys; HBB: c.19G>A] tetramers. Furthermore, the histidine→proline substitution at α20 did not disrupt the helical structure. High performance liquid chromatography (HPLC) detected Hb Fulton-Georgia in 16.0% of total Hb, consistent with inheritance on the α1 gene. Coinheritance of Hb Fulton-Georgia, heterozygous α-thal-2 and Hb SC disease was associated with a mild phenotype, consisting of microcytosis and anisocytosis, but no anemia or other hematological abnormality.

Thalassemia-like phenotype in a novel complex hemoglobinopathy with α, ß, δ globin chain abnormalities.

The occurrence of multiple abnormalities of α, ß, δ, and γ globin genes may lead to unusual and complex phenotypes when they arise simultaneously in the same individual. Here, we report the findings of an African American boy who coinherited 3 heterozygous globin gene abnormalities: the unstable ß-globin chain variant; hemoglobin (Hb) Showa-Yakushiji [ß110(G12) Leu→Pro], the δ-globin chain variant; HbB2 [δ16(A13) Gly→Arg] and α-thalassemia (α-thal); (α-/αα). Hb Showa-Yakushiji had been previously described in Japanese, Indian, and European populations. We report its first occurrence in a child of African ancestry who presented with anemia not responsive to iron and an incomplete ß-thalassemia minor phenotype. Although the clinical and laboratory features of Hb Showa-Yakushiji mimic those of a ß-thalassemia, the coinheritance of the δ-globin chain variant Hb B2 suppressed the relative increase in Hb A2 usually observed in heterozygotes for the Hb Showa-Yakushiji mutation. Protein-based methods detected only a trace amount of HbB2 and failed to reveal presence of Hb Showa-Yakushiji and α-thal. The latter were only identified through DNA analyses. The diagnostic difficulties, molecular characteristics, and genotype/phenotype correlations of this novel complex hemoglobinopathy syndrome are reviewed.

A new sickling variant 'Hb S-Wake ß[(Glu6Val-Asn139 Ser)]' found in a compound heterozygote with Hb S ß(Glu6Val) coinherited with homozygous α-thalassemia-2: phenotype and molecular characteristics.

We report the case of a 14-year-old African-American boy who was diagnosed with sickle cell disease. Laboratory tests showed that the patient was a compound heterozygote for a novel Hb variant with a double mutation detected on ß(S) allele, Hb S ßGlu6Val, and ßAsn139Ser substitution, i.e. a ß-chain variant named 'Hb S-Wake'. The patient also carried a single Hb S mutation in trans allele, leading to Hb SS-Wake disease. He had coinherited homozygous α(+)-thalassemia (-α(3.7)/-α(3.7)) simultaneously which resulted in multiple globin gene abnormalities.

Rare occurrence of Hb Lepore-Baltimore in African Americans: molecular characteristics and variations of Hb Lepores.

Hb Lepore is the hybrid hemoglobin (Hb) composed of two alpha-globin chains and two deltabeta hybrid chains and is associated with the clinical findings of thalassemia minor in its heterozygous form. Hb Lepore can be found in many ethnic groups, commonly in southern European countries, but rarely in African Americans. The first Hb Lepore case in an African-American individual was named Hb Lepore-The Bronx (Hb Lepore-Boston). Hb Lepore-Washington-Boston and Hb Lepore-Baltimore with a breakpoint of (delta50Ser/beta86Ala) were later reported. In this paper, we describe an Hb Lepore-Baltimore (delta68Leu/beta84Thr) deltabeta-fusion gene with a different breakpoint detected for the first time in an African-American female. We have used state-of-the-art technology, combining protein- and DNA-based methods, in the analysis of the hybrid hemoglobin and discuss its molecular characteristics.

Acute splenic complications and implications of splenectomy in hemoglobin SC disease.

Splenectomy indications and outcome were evaluated in 124 adults with hemoglobin SC disease (Hb SC). Twelve patients (9.6%) required splenectomy. There was a significant difference between the splenectomy group and the non-splenectomy group, respectively, regarding Hb levels (median 7.2 g/dL vs. 12.5 g/dL, P < 0.0001), platelet counts (median 146 x 10(6)/L vs. 275 x 10(6)/L, P = 0.031), palpable spleen rate (66% vs. 16%, P = 0.0003%), acute chest syndrome frequency (75% vs. 12%P = 0.0004) and cholecystectomy rate (66% vs. 13%, P = 0.0004). No significant morbidity or mortality occurred postsplenectomy. There is a subgroup of Hb SC patients requiring splenectomy, in which splenectomy is effective. Although it appears to be safe regarding short-term complications of surgery, long-term adverse effects such as infections have to be evaluated cautiously.

Compound heterozygosity for hemoglobin S [beta6(A3)Glu6Val] and hemoglobin Korle-Bu [beta73(E17)Asp73Asn].

We report a case of compound heterozygous hemoglobins S [beta6(A3)Glu6Val] and Korle-Bu [beta73(E17)Asp73Asn] in a 2-year-old girl. This hemoglobin genotype is associated with a benign clinical course, much like the sickle cell trait; however, its laboratory characteristics are very similar to compound heterozygous hemoglobin S and hemoglobin D-Los Angeles [beta121(GH4)Glu121Gln], which produces severe sickling hemolytic anemia. We describe laboratory data used to resolve this important differential diagnosis and review the interactions between hemoglobin S and the variant hemoglobins that may account for the different clinical phenotypes in compound heterozygotes.

Two new hemoglobin variants: Hb Sinai-Greenspring [beta34(B16)Val-->Ile, GTC > ATC] and Hb Sinai-Bel Air [beta53(D4)Ala-->Asp, GCT > GAT].

Neonatal screening for hemoglobinopathies occasionally results in the detection of novel hemoglobin (Hb) variants. Two heterozygous infants were found with different beta chain mutations, neither of which produced obvious clinical or laboratory abnormalities on routine examinations. The variants were characterized by cation exchange high performance liquid chromatography (HPLC), reversed phase HPLC, and sequencing of amplified beta-globin genes. Functional studies could not be performed at this time.

Neonatal cyanosis due to a novel fetal hemoglobin: Hb F-Circleville [Ggamma63(E7)His-->Leu, CAT>CTT].

Neonatal cyanosis can result from a multitude of acquired and inherited causes. Cyanosis resulting from fetal M hemoglobin (Hb) variants is very rare. Only two (G)gamma variants causing methemoglobinemia and cyanosis in the newborn have been reported to date. Here we describe a novel fetal Hb variant, Hb F-Circleville [Ggamma63(E7)His-->Leu], associated with methemoglobinemia and cyanosis in the newborn. The patient's sister also had neonatal cyanosis at birth.

Missense mutation of the last nucleotide of exon 1 (G->C) of beta globin gene not only leads to undetectable mutant peptide and transcript but also interferes with the expression of wild allele.

Hemoglobin Monroe (beta globin G->C, codon 30) is a missense mutation. We could not detect either the mutant peptide or transcript in reticulocyte-enriched preparation and in expanded erythroid progenitor cells. By quantitative gene expression assay beta globin mRNA was found to be reduced by more than 70% in all heterozygous subjects with different haplotypes. We conclude that this mutation also interferes with expression of wild type allele.

Hb J- Meerut [alpha 120 (H3) Ala ->Glu (alpha1)] in a Turkish male.

Hb J Meerut is an infrequently found alpha-globin variant. It has previously been reported in various populations around the world. One particular case reported in 1994 included a Turkish family. In this report, details of a second case of Hb J Meerut in a Turkish male who is unrelated to the first family are described. In the present case a slight increase in the oxygen affinity of Hb J Meerut, relative to that of the normal control, has been observed as detected by low p50 values in arterial whole blood. Additionally, a slight increase in red blood cell count, as compared against a normal individual, was observed.

Genetic risk factors for cerebrovascular disease in children with sickle cell disease: design of a case-control association study and genomewide screen.

BACKGROUND: The phenotypic heterogeneity of sickle cell disease is likely the result of multiple genetic factors and their interaction with the sickle mutation. High transcranial doppler (TCD) velocities define a subgroup of children with sickle cell disease who are at increased risk for developing ischemic stroke. The genetic factors leading to the development of a high TCD velocity (i.e. cerebrovascular disease) and ultimately to stroke are not well characterized. METHODS: We have designed a case-control association study to elucidate the role of genetic polymorphisms as risk factors for cerebrovascular disease as measured by a high TCD velocity in children with sickle cell disease. The study will consist of two parts: a candidate gene study and a genomewide screen and will be performed in 230 cases and 400 controls. Cases will include 130 patients (TCD > or = 200 cm/s) randomized in the Stroke Prevention Trial in Sickle Cell Anemia (STOP) study as well as 100 other patients found to have high TCD in STOP II screening. Four hundred sickle cell disease patients with a normal TCD velocity (TCD < 170 cm/s) will be controls. The candidate gene study will involve the analysis of 28 genetic polymorphisms in 20 candidate genes. The polymorphisms include mutations in coagulation factor genes (Factor V, Prothrombin, Fibrinogen, Factor VII, Factor XIII, PAI-1), platelet activation/function (GpIIb/IIIa, GpIb IX-V, GpIa/IIa), vascular reactivity (ACE), endothelial cell function (MTHFR, thrombomodulin, VCAM-1, E-Selectin, L-Selectin, P-Selectin, ICAM-1), inflammation (TNFalpha), lipid metabolism (Apo A1, Apo E), and cell adhesion (VCAM-1, E-Selectin, L-Selectin, P-Selectin, ICAM-1). We will perform a genomewide screen of validated single nucleotide polymorphisms (SNPs) in pooled DNA samples from 230 cases and 400 controls to study the possible association of additional polymorphisms with the high-risk phenotype. High-throughput SNP genotyping will be performed through MALDI-TOF technology using Sequenom's MassARRAY system. DISCUSSION: It is expected that this study will yield important information on genetic risk factors for the cerebrovascular disease phenotype in sickle cell disease by clarifying the role of candidate genes in the development of high TCD. The genomewide screen for a large number of SNPs may uncover the association of novel polymorphisms with cerebrovascular disease and stroke in sickle cell disease.