A new gene deletion involving the alpha 2-, alpha 1-, and theta 1-globin genes in a black family with Hb H disease.

A new deletion of approximately 8.5 kb that includes the alpha 2-, alpha 1-, and theta 1-globin genes was detected in a father and newborn son of a black family from Georgia. In the newborn baby the chromosome with the deletion occurred together with a rightward (-alpha 3.7) deletion chromosome. The resulting Hb H disease was detected at birth by the high level of Hb Bart's; a moderate anemia with severe microcytosis and hypochromia was present at the age of 5 months. A review of cord blood testing results for a period of over 20 years, involving at least 200,000 black newborns, indicated that this baby was the first with a level of Hb Bart's in excess of 10-15%; this underscores the rarity of alpha-thalassemia-1 in this population.     

Alpha thalassaemia in Zambian newborn

The umbilical cord blood from 109 consecutive Zambian neonates (excluding those found to be anti-HIV positive) were analysed for haemoglobin (Hb) Bart's and for alpha thalassaemia by restriction endonuclease analysis. This showed that 52.3% had the genotype alpha alpha/alpha alpha, 38.5% had -alpha 3.7/alpha alpha, 7.3% had -alpha 3.7/-alpha 3.7 and 1.8% had alpha alpha alpha/alpha alpha. The alpha thalassaemia gene (-alpha) frequency was 0.27. There were no apparent differences in gene frequency between six major Zambian ethnic groups. Detection of Hb Bart's identified all alpha-thalassaemia homozygotes (-alpha/-alpha), but fewer than 10% of heterozygotes (-alpha/alpha alpha). alpha-thalassaemia was associated with slight but significant anaemia and microcytosis.     

First Description in Tunisia of a Point Mutation at Codon 119 (CCT→TCT) in the α1-Globin Gene: Hb Groene Hart in Association with the − α3.7 Deletion

Herein we describe the case of a Tunisian girl who presented with 3% Hb Bart's (γ₄) at birth. At the age of 3 years, she showed microcytosis and hypochromia in the absence of iron deficiency. The first step of molecular analysis was to test for the common Mediterranean mutations and the classical ? α^3.7 deletion was found in the heterozygous state. Since this finding could not explain the level of Hb Bart's at birth, or the hypochromia and microcytosis, all the α-globin genes were sequenced. This revealed a rare point mutation at codon 119 (CCT→TCT) in the α1-globin gene, identified for the first time in Tunisia, and which has previously been described as an unstable hemoglobin (Hb) variant named Hb Groene Hart [α119(H2)Pro→Ser (α1)]. Here the ? α^3.7/αα^{119(CCT→TCT)} genotype is responsible for the α-thalassemia (thal) trait phenotype.     

The first case of Hb Groene Hart [alpha119(H2)Pro-->Ser, CCT-->TCT (alpha1)] homozygosity confirms that a thalassemia phenotype is associated with this abnormal hemoglobin variant

Hb Groene Hart [alpha119(H2)Pro-->Ser, CCT-->TCT (alpha1)] has been reported in heterozygotes of Moroccan origin and also in association with the common -alpha(3.7) deletion. In all cases, the mutated protein was not detectable but was apparently associated with a mild alpha-thalassemia (thal) phenotype, presumably due to a modification of the alpha-globin chain domain that is recognized by the a hemoglobin stabilizing protein (AHSP). The present case of Hb Groene Hart homozygosity, confirms that the alpha-thal phenotype is associated with this alpha-globin chain. Hb Groene Hart must be quite frequent not only in Morocco but probably also among the northern African coastal population.     

Molecular spectrum of alpha-thalassemia in Tunisia: epidemiology and detection at birth

We present the characterization of the molecular spectrum and frequency data of alpha-thal (thal) defects in Tunisia, and an evaluation of the efficacy and limitations of Hb Bart's (gamma4) measurement for the screening of alpha-thal at birth. Cord blood samples were collected from two different areas: the northeast of the country, an area where Hb H (beta4) disease frequently occurs, and Tunis, the capital city, representative of the average Tunisian population. From the first group, 110 samples with Hb Bart's and/or microcytosis at birth were selected from 1270 randomly collected samples. Two additional population samples, one from the same northeastern region (n = 90), the other from Tunis (n = 104) were collected randomly. Nine common deletional alpha-thal defects and nondeletional mutations were screened. In the northeastern samples, selected for the presence of Hb Bart's and microcytosis, the -alpha3.7 deletion was the most common defect (4.5% allele frequency) followed by a polyadenylation (poly A) signal mutation (1.8%), the five nucleotide (nt) deletion and the -alpha4.2 deletion (both 0.9%). The African polymorphism (G-->TCGGCCC at position 7238 and T-->G at 7174) was found with an allele frequency of 11% in the selected northeastern samples. In the random population samples, the overall alpha-thal allele frequency was 4% in the northeast region, against 2% in the average Tunisian population. The +14 (G-->C) polymorphism in the 5'UTR (untranslated region) of the alpha2 gene and the African polymorphism in the second intron of the same gene, were found in 3.5% of the alleles. No alpha0-thal alleles were found among the 304 blood samples studied at the DNA level during this survey.     

Combinations of three different forms of alpha-thalassemia in a large Indian family from Durban, South Africa: hematological observations.

We have identified three types of alpha-thalassemia in 28 members of an Indian family from Durban, South Africa. The rare South African (SA) type of alpha-thalassemia-1, which is characterized by an approximately 23-kb deletion involving the psi zeta, psi alpha 2, psi alpha 1, alpha 2, alpha 1, and theta 1 genes, was present in 13 members [6 simple heterozygotes, 5 with Hb H disease of the --(SA)/-alpha(-3.7 kb) type, and 2 with Hb H disease of the --(SA)/-alpha(-4.2 kb) type]. Seven others were heterozygotes for alpha-thalassemia-2 (-3.7 kb), 1 was homozygous for this deletion, and 1 was a compound heterozygote [-alpha(-3.7 kb/-alpha(-4.2 kb)]. Hematological and hemoglobin composition data indicated a moderate anemia in all 7 patients with Hb H disease with severe microcytosis and hypochromia, no elevation of gamma-chain synthesis, low levels of Hb A2 (0.3-0.7%), and low levels of Hb H. The most severe disease was present in 2 teenagers with the --(SA)/-alpha(-4.2 kb) combination.     

A novel alpha-thalassemia nonsense mutation in codon 23 of the alpha2-globin gene (GAG-->TAG) in a Tunisian family

Herein we describe a novel alpha-thalassemia (thal) point mutation in the alpha2-globin gene, found in a 3-year-old Tunisian girl who had Hb Bart's (gamma4) at birth, later on presenting with moderate anemia, microcytosis and hypochromia. She had a normal Hb A2 level and no abnormal hemoglobin (Hb) fraction. After excluding most of the common Mediterranean mutations, the alpha2-globin gene was sequenced and found to have a point mutation in the heterozygous state that creates a premature stop signal for translation (GAG-->TAG or Glu-->Term) at codon 23. The same mutation was also found in the mother in the heterozygous state, while the father had a normal sequence. The presence of the mutation was also confirmed by nucleotide sequencing of the opposite strand. Since the mutation creates a restriction site for the BfaI enzyme, a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP)-based assay was established for screening purposes.     

Molecular basis of Hb H disease in southwest Iran

Although alpha0-thalassemia (thal) defects are not very frequent in the Iranian population, Hb H disease does occur in the country. We have analyzed the alpha gene cluster of 13 patients showing the presence of Hb H to establish the molecular background of this disease in southwest Iran (Shiraz and Hormozgan provinces). Using gap-polymerase chain reaction (gap-PCR) and direct DNA sequencing we have found the --MED-I deletion, the polyadenylation signal (poly A) mutations alphaT-Saudi alpha and alphaT-Turkish alpha and Hb Constant Spring (Hb CS) in association with the common -alpha3.7 deletion. This study has revealed that: 1) at least six genotypes are responsible for Hb H disease in the area: .-alpha3.7/ --MED-I; -alpha3.7/alphaT-Saudi alpha; alphaT-Saudi alpha/alphaT-Saudi alpha; alphaCSalpha/--MED-I; --MED-I/alphaT-Turkish alpha; and the atypical forms of Hb H disease -alpha3.7/alphaCSalpha. 2) The molecular background of Hb H disease in the southwest area of Iran is more similar to the Mediterranean type than to the Southeast Asian. 3) Hb Bart's hydrops fetalis syndrome and mild, intermediate or severe postnatal Hb H disease conditions can be expected, but at a relatively low incidence. 4) The diagnostic flowchart for patients with microcytic hypochromic anemia should include iron deficiency, beta-thal, alpha+- and alpha0-thal analyses.     

Alpha thalassaemia in Sardinian newborns

In this study we describe the correlation between the haematological parameters (red cell indices and Hb Bart's levels) and the α-globin genotype in Sardinian newborns. Increased Hb Bart's levels at birth always indicates α-thalassaemia, either of the deletion or non-deletion variety. Infants with two α-globin genes deleted (-α/ -α and - -/act genotypes) had microcytosis, low MCH and Hb Bart's in the 2.0-7.1% range. A minority (38.9%) of infants with the (-α/αα) globin genotype had detectable Hb Bart's, in the 0.78-2 '5% range, frequently associated with minimal microcytosis while the remainder (61 e l %) were completely silent. Infants carriers of a non-deletion type of α-thalassaemia showed Hb Bart's levels within the range found in the (- α/αα) genotype. The association of heterozygous Po-thalassemia seems to have no effect on the expression of any of these α-thalassaemia lesions at birth.     

Hb Bart's levels in cord blood and alpha-thalassemia mutations in Cyprus

The purpose of this study was to examine the frequency of alpha-thalassemia in the population of Cyprus using cord blood samples. The levels of Hb Bart's were compared with the hematological indices and the results correlated with the presence of alpha-thalassemia mutations. The protocols for the polymerase chain reaction detection of the six most common alpha-globin mutations encountered in Cyprus were optimized, and the frequency of each mutation was determined through the screening of 495 random cord blood samples. The total allele frequency for the mutations examined was 10.6%, of which 1% is due to the triplication of the alpha-globin genes. The -alpha(3.7 kb) deletion accounts for 72.8% of all detectable mutations, while the--MED-I and -(alpha)-20.5 kb mutations account for 7.8%. The level of Hb Bart's and the MCV and MCH values in cord blood samples were found to correlate closely with the severity of alpha-thalassemia, although the -alpha(3.7 kb) deletion and perhaps other mild alpha-thalassemia mutations may not give detectable Hb Bart's levels. A reasonably accurate estimate of the alpha-thalassemia carrier frequency may be obtained from cord blood studies if Hb Bart's estimates are combined with hematological indices. When molecular methods are added, these give the best way to use cord bloods to survey populations for alpha-thalassemia.     

A new gene deletion involving the α2-, α1 -, and 81-globin genes in a black family with Hb H disease

A new deletion of ∽ 8.5 kb that includes the α2-, α1-, and θ1-globin genes was detected in a father and newborn son of a black family from Georgia. In the newborn baby the chromosome with the deletion occurred together with a rightward (-α^3.7) deletion chromosome. The resulting Hb H disease was detected at birth by the high level of Hb Bart's; a moderate anemia with severe microcytosis and hypochromia was present at the age of 5 months. A review of cord blood testing results for a period of over 20 years, involving at least 200,000 black newborns, indicated that this baby was the first with a level of Hb Bart's in excess of 10-15%; this underscores the rarity of α-thalassemia-1 in this population. © 1992 Wiley-Liss, Inc.     

Two new beta-chain variants: Hb Tripoli [beta26(B8)Glu-->Ala] and Hb Tizi-Ouzou [beta29(B11)Gly-->Ser

Two new beta-globin chain variants: Hb Tripoli: codon 26, GAG-->GCG [beta26(B8)Glu-->Ala] and Hb Tizi-Ouzou: codon 29, GGC-->AGC [beta29(B11)Gly-->Ser] are described on the first exon of the beta-globin gene. The two variants are characterized by DNA sequencing and mass spectrometry (MS). Hematological abnormalities were found in the two carriers. The presence of microcytosis and hypochromia is explained by an additional homozygous 3.7 kb alpha(+) thalassemic deletion for the carrier of Hb Tizi-Ouzou. Hb Tizi-Ouzou showed a slight instability in vitro. The same hematological abnormalities associated with anemia are difficult to explain for Hb Tripoli's carrier in the absence of an alpha-globin genes abnormality and could suggest a possible abnormal splicing.     

PCR-Based Analysis of α-Thalassemia in Southern Taiwan

The Southeast Asia type deletion of alpha-thalassemia-1 (--SEA) is the most common type of alpha-thalassemia-1 in Taiwan. There are 2 less common types, Filipino type (--FIL) and Thai type (--THAI). In the current study, we screened 754 cases of alpha-thalassemia-1 in Southern Taiwan using a polymerase chain reaction (PCR)-based method. Our results show that the prevalence of the (--SEA) type is 90.6%, followed by the (--FIL) type (8.6%), the (--THAI) type (0.5%), and the (-alpha(3.7/-alpha(3.7)) type (0.3%). We also analyzed the genotypes of 96 patients with hemoglobin (Hb) H disease and 48 cases of hydrops fetalis with Hb Bart's. The frequencies of the genotypes of the alpha-thalassemia-1 allele in Hb H disease are in accordance with the results of analyses of alpha-thalassemia-1 cases. The alpha-thalassemia-2 allele includes alpha(4.2), alpha(G), alpha(CS), and alpha(QS)alpha. Forty-one cases, 6 cases, and 1 case of hydrops fetalis with Hb Bart's were caused by --SEA/--SEA, --SEA/--FIL and --SEA/--THAI respectively. The genotypes and frequencies of alpha-thalassemia in this study are different from those in previous studies in Taiwan and Hong Kong. These differences may be attributed to the diverse genetic origin among different ethnic groups and the extensive inclusion of the (--FIL) and (--THAI) alpha-thalassemia-1 types.     

Molecular spectrum of alpha-thalassemia in the Iranian population of Hormozgan: three novel point mutation defects

We describe the molecular spectrum of alpha-thalassemia mutations in a population sample of newborns in the South-Iranian province of Hormozgan. Out of 660 randomly collected blood samples 218 (33%) had visibly elevated Hb Bart's. DNA was extracted from 78 samples out of this selection (n=156), of which 114 alleles were found to carry an alpha-thalassemia defect. Besides the common -alpha3.7 (79.1%), -alpha4.2 (1.7%), and alpha-5nt alpha alleles (4.3%), three novel nondeletional alpha-thalassemia mutations were found; the alpha2 cd19 (-G) frameshift mutation (12.2%), the alpha1 IVS1-148(A-->G) (0.9%) affecting the splice acceptor site consensus sequence and the cd14 (TGG-->TAG) (0.9%), which creates a premature stop codon in the first exon of the alpha1-gene. A fourth mutation in the alpha1-gene, the IVS1-38 (C-->T) (0.9%) of undetermined effect, was found in an individual heterozygous for the alpha2 cd19(-G) mutation.     

Hb Sun Prairie or alpha(2)130(H13)Ala----Pro beta 2, a new unstable variant occurring in low quantities

A severe hemolytic anemia with microcytosis and hypochromia was present in a young adopted Indian patient. Reversed phase high performance liquid chromatographic methodology and heat stability tests detected an unstable alpha chain which was present in 3 to 5% of the total hemoglobin. A larger quantity of the alpha X chain was obtained by preparative reversed phase high performance liquid chromatography. Structural analyses identified an Ala----Pro replacement at position 130 of the alpha chain. The instability of the variant, named Hb Sun Prairie, is comparable to that of Hb Bibba [alpha 136 (H19)Leu----Pro]. Gene mapping failed to detect an alpha-thalassemia deletion (alpha alpha/alpha alpha), while dot-blot analysis of amplified DNA with synthetic probes localized a G----C mutation in codon 130 (resulting in the Ala----Pro mutation) of the alpha 2-globin genes of both chromosomes. These results suggest a homozygosity for the G----C mutation and the condition alpha 2(G----C)alpha 1/alpha 2(G----C)alpha 1 adequately explains the rather severe clinical status of this child, including the marked microcytosis and hypochromia. Unfortunately, family studies to exclude the presence of a large deletion involving all zeta- and alpha-globin genes were not possible.     

Alpha thalassaemia in an Italian population

The incidence of alpha-thalassaemia in an Italian population has been determined by a survey of random cord bloods for the presence of Hb Bart's. 144 out of 4730 (3%) had detectable amounts of Hb Bart's. Furthermore, alpha-globin gene analysis of 100 random cord bloods showed that five out of 100 had the common type of alpha-thalassaemia caused by a single alpha-globin gene deletion (-alpha). The molecular basis of alpha-thalassaemia was also determined in a selected group of 34 newborns with detectable levels of Hb Bart's. 25 of these cases had the -alpha 3.7 deletion type of alpha-thalassaemia and nine had nondeletion types of alpha-thalassaemia in four of which the molecular defect was detectable directly by restriction enzyme analysis.     

A new G(gamma) chain variant: Hb F-Bron [gamma20(B2)val-->Ala

A new G(gamma) hemoglobin (Hb) variant, Hb F-Bron [gamma20(B2)Val-->Ala] on the first exon of the G(gamma)-globin gene is described. The variant was characterized by DNA sequencing and mass spectrometry (MS). Hematological abnormalities included hypochromia and microcytosis and were probably caused by an interaction with an alpha-thalassemia (thal) (3.7 kb) deletion in the heterozygous state.     

A New Gγ Chain Variant: Hb F-Bron [γ20(B2)Val→Ala]

A new ^Gγ hemoglobin (Hb) variant, Hb F-Bron [γ20(B2)Val→Ala] on the first exon of the ^Gγ-globin gene is described. The variant was characterized by DNA sequencing and mass spectrometry (MS). Hematological abnormalities included hypochromia and microcytosis and were probably caused by an interaction with an α-thalassemia (thal) (3.7 kb) deletion in the heterozygous state.     

Alpha-gene deletions in black newborn infants with Hb Bart's

The presence of increased Hb Bart's (gamma 4) in cord blood is believed to be an indication of alpha-thalassemia. We have used restriction endonuclease nalyses of DNA to compare the number of alpha-genes with the percentage of Hb Bart's in 6 older children who had Hb Bart's at birth and 17 newborns. Four children with > 2% Hb Bart's had Eco R1 alpha-gene patterns and hematologic data consistent with the presence of two alpha-genes, one per chromosome. Of the remaining 19 children, all of whom had < 2% Hb Bart's, 8 had 3, while 11 had 4 alpha-genes. Three infants with Hb Bart's between 1% or less Hb Bart's. infants with 3 alpha-genes may therefore have elevated or normal levels of Hb Bart's at birth. DNA analysis is the definitive method for the determination of heterozygous alpha-thalassemia syndromes in newborns.     

Molecular Characterization of α-Thalassemia in the Dohuk Region of Iraq

The molecular basis of α-thalassemia (α-thal) has been addressed by several studies from the eastern Mediterranean region, but not from Iraq. To address this issue, we studied 51 individuals with unexplained hypochromia and/or microcytosis, as well as nine patients with documented Hb H disease from the Dohuk region in northern Iraq. We used multiplex gap-polymerase chain reaction (gap-PCR), reverse hybridization, and sequencing for this purpose. It was found that the most common genotypes in those with unexplained hypochromia and/or microcytosis were ?α^3.7/αα, followed by ? ?^MED-I/αα, then ?α^3.7/?α ^3.7, respectively, detected in 84.3% of the above individuals. Other genotypes identified sporadically were ?α^4.2/αα, α^{poly A1}α/αα (AATAAA>AATAAG), α^Adanaα/αα [Hb Adana, codon 59 (Gly→Asp) or HBA1:c.179G>A], and α^Evanstonα/αα [Hb Evanston, codon 14 (Trp→Arg) or HBA1:c.43 T>C]. Three cases (5.88%) remained uncharacterized even after sequencing. All nine Hb H cases carried the ?α^3.7/? ?^MED-I genotype. Such findings are rather different from those in other eastern Mediterranean populations, particularly with relevance to an Hb H molecular basis.