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A report of Hb Fontainebleau [α21 (B2) Ala > Pro] as a result of founder effect phenomenon
Abstract
Objective
To date, more than 400 alpha chain variants or point mutations in the α-globin genes that lead to single amino acid substitutions have been described. Here, we state a rare alpha-globin gene variant Hb Fontainebleau [a21 (B2) Ala>Pro] identified in heterozygote state in two families from the north of Iran during premarital thalassemia screening program.
Material
Two first cousin couples with reduced hematological indices compatible with α-thalassemia were referred to Lab for premarital screening of thalassemia. At first CBC and capillary electrophoresis tests were applied. For molecular investigation genomic DNA was isolated from peripheral blood samples. Then, multiplex-Gap PCR and Sanger sequencing techniques were applied to discover common α- globin deletions and probable point mutations, respectively.
Results
In the capillary electrophoresis results, one unknown peak was observed to the left of Hb A. Sanger sequencing results revealed that all cases are heterozygote for Hb Fontainebleau (HBA2: c.64G4C, p.Ala21Pro). Family history analysis has shown that all presented cases have belonged to the families which are originally from India.
Conclusion
The presence of Hb Fontainebleau in Mazandaran province and in subjects with Indian origin may indicate the founder effect phenomenon. DNA analysis of subjects with reduced hematological indices is recommended for finding common and rare mutations to predict childbirth with thalassemia in premarital screening programs.
... According to the results of their study, the -3.7 deletion (44.9%), polyadenylation signal 2 (α Poly A2 ) (AATAAA > AATGAA) (18.2%), -4.2 deletion (9.1%), α-5nt (6.5%), --MED (4.3%), and α codon 19 (-G) (4%) were the most frequent mutations observed in the region [13]. Moreover, several variants of hemoglobin, such as Hb D [14], Hb J-Toronto [15], Hb Setif [16], Hb Fontainebleau [17], Hb Daneshgah-Tehran [18], and Hb S [19], have also been reported from that region. Since Mazandran is located in the south of the Caspean Sea, which has a subtropical climate as well as a high prevalence of malaria having been observed in the region in the past, a high frequency of thalassemia is reported from there. ...
... The presented case was originally from Mazandaran province. There were several migrations of minor ethnic groups, such as Kurds, Turks, Georgians, and small groups of Indian origin, to Mazandaran province throughout history [17] that may have resulted in a high diversity of α-globin gene variants in the region. ...
Background: Alpha thalassemia is one of the most common human genetic abnormalities. More than 400 different variations of the α-globin protein have been introduced, most of which are not associated with noticeable clinical manifestations. The identification of all variants of Hb in different regions helps in acquiring comprehensive knowledge concerning thalassemia disease, and it can be used in preventive programs as well as prenatal diagnosis (PND). Aims: In the present study, we describe a new α1 gene mutation that leads to a frameshift after codon 83. Methods: As a plan for a national screening program of thalassemia, routine cell blood count (CBC) and Hb capillary electrophoresis tests were applied. After taking written informed consent, genomic DNA was extracted, and, for identifying common Mediterranean α-Globin gene deletion, multiplex Gap-PCR was performed; for detecting other mutations on α- and β-Globin genes, a DNA sequencing method was used. Results: The results of CBC and capillary electrophoresis tests showed microcytosis in a female subject. The sequencing of the α-Globin gene showed that the case is heterozygote for a single-nucleotide deletion at codon 83 of the α1-Globin Gene. We named this mutation Hb Adrian (α1: c.251–T), which is a novel mutation. The mentioned mutation was also detected in the subject’s mother. Conclusions: The introduced mutation (Hb Adrian) leads to a frameshift change that produces a protein with 100 amino acids, which in comparison to a normal α-chain is shorter, and its amino acids are altered after codon 83. This hemoglobin is undetectable via the use of electrophoresis. Although no major hematological abnormalities were observed in the carriers, Hb Adrian should be considered in screening programs to help prevent Hb H disease in high-risk couples.
... Mazandaran is a province of Iran located on the southern coastline of the Caspian Sea, and thalassemia is a common hereditary genetic disorder in that region [6]. Several variants of Hb, such as Hb D [7], Hb J-Toronto [8], Hb Fontainebleau [9], and Hb S [10], have also been reported in Mazandaran. In the present study, we report a novel variant of the α1globin gene, Hb Mazandaran (α1) α51 Gly > Cys(CE9), c.154 GGC > TGC, detected in a family from Mazandaran, Iran. ...
... Mazandaran is a province of Iran located on the southern coastline of the Caspian Sea, and thalassemia is a common hereditary genetic disorder in that region [6]. Several variants of Hb, such as Hb D [7], Hb J-Toronto [8], Hb Fontainebleau [9], and Hb S [10], have also been reported in Mazandaran. In the present study, we report a novel variant of the α1-globin gene, Hb Mazandaran (α1) α51 Gly > Cys(CE9), c.154 GGC > TGC, detected in a family from Mazandaran, Iran. ...
This is a report of a novel variant of the α1-globin gene—(α1) α51 Gly > Cys (CE9), c.154 GGC > TGC, named Hb Mazandaran, which was observed in an Iranian family. This variant gives rise to a previously undescribed haemoglobin variant that was undetectable by capillary haemoglobin electrophoresis (CE). This variant was detected in two cases in combination with β-globin mutation, and it does not seem to be associated with severe haematological abnormalities in the carriers.
We read with great interest the paper on ‘A report of Hb Fontainebleau [α21 (B2) Ala > Pro] as a result of founder effect Phenomenon’ that appeared in a recent issue of the journal by Jalalia et al. However, although they discussed extensively the data on the very rare hemoglobin variant Fontainebleau (a 21(B2) Ala-Pro), they did not mention the existence of this variant in Turkish population.
Several types of hemoglobin D (Hb D) are distinguishable by DNA analysis, and the aim of this study was to identify the types of Hb D variant and β-globin gene haplotypes linked to Hb D in Mazandaran Province, northern Iran. Fifty five individuals were identified as Hb D carriers, and PCR-RFLP analysis revealed that all 55 had the Hb D-Los Angeles type. To identify haplotypes associated with the βD allele, family linkage analysis, using the PCR-RFLP method for seven polymorphisms in the β-globin gene cluster, was carried out on families of 23 of these 55 individuals. We observed three different haplotypes in association with Hb D-Los Angeles. In most cases (91.4%) βD alleles were linked to haplotype I [+ – – – – + +]. Haplotype II [– + + – + + +] and an atypical haplotype [– + + – – + –] were each in association with the βD allele in only one case (4.3%). This is the first report worldwide of the [– + + – – + –] haplotype in association with Hb D-Los Angeles. We conclude that more than 90% of the evaluated Hb D-Los Angeles alleles in Mazandaran have the same origin, and the two rare haplotypes may represent different genetic origins and/or other molecular events, such as gene conversion or recombination, in the region.
Hb Setif is a rare type of hemoglobinopathy resulting from an aspartic acid to tyrosine substitution at codon 94 (GAC>TAC) of the α2-globin gene. In manual and automated hemoglobin (Hb) electrophoresis examination of the case, an unusual band was detected and the result of subsequent capillary electrophoresis suggested that to be Hb Setif. Carrying out polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and DNA sequencing, a typical Hb Setif mutation (GAC>TAC) was identified. The haplotype of the α cluster was + + - M PZ + - - - -. This is the first report of such a hemoglobinopathy in North Iran. Various reports of such Hb variants in Iran and countries in the Mediterranean region and North Africa, suggest that the mutation may have occurred around 6,000 years ago, prior to colonization of Aryans on the Iranian plateau.
α-Thalassemia (α-thal) is one of the most common inherited hemoglobin (Hb) disorders in the world. In addition to large deletions, over 50 different α-thal point mutations were detected around the world, thus, patients showed different phenotypes with regard to genotype. This study evaluated the genetic frequency of α-thal in Khuzestan Province, Southwest Iran, to help implement premarital and prenatal screening programs. The study was conducted on couples proposing to get married and parents who were referred to the genetic center of Shafa Hospital, Ahvaz, Iran, for prenatal diagnosis (PND) in 2012. Genomic DNA was purified by the salting-out method and tested using multiplex gap-polymerase chain reaction (gap-PCR), amplification refractory mutation system-PCR (ARMS-PCR), reverse hybridization test strips and DNA sequencing. Overall, 11 mutations were found on the α-globin genes. Based on gene frequency, the most common mutant allele was –α3.7 (rightward) (71.3%) followed by the two gene deletion – –MED (9.7%). Other common mutations were αcodon 19α (GCG>GC–, α2) (8.4%), the polyadenylation (polyA1) site αpolyA1α (AATAAA>AATAAG) (2.8%), and α–5 ntα (–TGAGG) (2.0%). In addition, an extremely rare mutation at αcodon 21α [Hb Fontainebleau, HBA2: c.64G > C (or HBA1)] was also found. The results of this study are critical for correct diagnosis of α-thal carriers, premarriage counseling and PND. This study suggests that the distribution of mutations on the α-globin genes differs among the ethnic groups in Khuzestan Province as well as in other provinces.
Abstract Hb Fontainebleau (HBA2: c.64G > C) is a rare α-globin variant, which has previously been described in only 10 individuals worldwide. We report here 12 additional cases identified in our laboratory. These included the first case of a homozygosity for Hb Fontainebleau and cases in which Hb Fontainebleau occurred in combination with deletional and nondeletional α-thalassemia (α-thal). The prevalence of Hb Fontainebleau in the samples submitted to our laboratory for premarital hemoglobinopathy screening was 0.24%, the highest reported prevalence to date, indicating that this is a comparatively common variant in the United Arab Emirates (UAE).
Alpha thalassemia is one of the most prevalent disorders worldwide and carrier frequency of the disease is varied in different parts of the world. Although different studies in Iran and Mazandaran province have been carried out to identify different mutations of alpha globin gene among people with low hematological indices, frequencies of these mutations were unknown in general population, and thus the aim of this study was to evaluate the carrier frequencies of alpha globin gene mutations among neonates in Mazandaran.
Four hundred and twelve neonates were collected from a delivery ward of a hospital in Sari. DNA was extracted from their cord blood samples using phenol-chloroform-based method. For the detection of five common alpha thalassemia gene mutations, multiplex-GAP-PCR and PCR-RFLP methods were applied.
Sixty three (15.29%, confidence interval, CI 95%: 11.81-18.77) of investigated neonates had at least one of the five evaluated mutations. The -α(3.7) deletion had the highest frequency (9.7%, CI 95%: 6.84-12.56) and none of the neonates had -(Med) double gene deletion. The -α(4.2) deletion, ααα(anti3.7) triplication, and α(-5nt) mutations had frequencies of 4.1% (CI 95%: 2.19-36.01), 2.2% (CI 95%: 0.78-3.62), and 0.49% (CI 95%: -0.18-1.16), respectively.
Our study showed that in most of the alpha thalassemia carriers just one copy of alpha globin gene was absent and they are not at risk of having children with Hb H disease or hydrops fetalis; however, up to 2.2% of neonates were carriers for ααα(anti3.7) triplication and they will be at risk for having a child with thalassemia intermediate if they marry a person which is a carrier of beta thalassemia.
A new α chain hemoglobin variant (Hb Daneshgah Tehran) discovered in a 57 yr old Iranian man is described. No hematologic abnormality is produced in the heterozygote. One of the propositus' 3 children was also found to be heterozygous for this hemoglobin variant. It migrates on cellulose acetate electrophoresis at pH 8.6 with the same mobility as Hb S, but it moves with Hb A at pH 6.2 on agar gel. The histidine residue at position 72 of the α chain is replaced by an arginine residue. The location of this substitution is in an external non helical segment of the α chain, not involved in haem or interchain contacts. Therefore, Hb Daneshgan Tehran is stable and identical to Hb A with respect to haem binding and O2 dissociation. Although arginine substitution for histidine has been described previously in β chain variants (Hb Zurich; Hb P), this is the first example of this mutation in the α chain. (Van Slyck - Detroit, Mich.)
Building on the pioneering efforts of Professor Huisman, several different databases of hemoglobin variants have been developed, each with progressively increased capacity for sophisticated queries and prompt updating. These resources are reviewed in the context of a larger plan for providing related resources on hemoglobins, benign and pathological variation in these proteins and the genes that encode them, and the regulation of the globin genes.
Hb Fontainebleau [α21(B2)Ala→Pro] was found in a family of Italian origin. This new variant has electrophoretic properties identical to those of Hb A with the exception of isoelectrofocusing in which it migrates like Hb A1c. The introduction of a prolyl residue at the beginning of the B helix in the α chain does not lead to a change in the stability or oxygen binding properties of the hemoglobin molecule.
We report of an Iranian family with history of a rare haemoglobin variant, Haemoglobin J associated with alpha thalassemia, discovered while performing premarital thalassemia screening. In the present study we report the first case of haemoglobin J-Toronto [alpha 5 (A3) Ala > Asp] on -globin gene, found in a 16-year-old female from Mazandaran Province, North of Iran. Further investigation characterized the same mutation for mother and brother of the proband, whilst mother was also a carrier of an alpha thalassemia gene mutation (-alpha3.7). Haemoglobin J-Toronto was previously just reported from Canada and has not been found in any part of Iran.
To evaluate the significance of non-deletional α gene variants identified in neonates during newborn screening for sickle cell disorders.
1534 newborn babies were screened in the last 2 years for sickle cell disease using a targeted screening approach. Investigations included a complete blood count, high performance liquid chromatography analysis, cellulose acetate electrophoresis (pH 8.9), heat stability test, restriction digestion and Amplified Refractory Mutation System for confirmation of sickle haemoglobin (Hb S), α genotyping by multiplex PCR and DNA sequencing.
Three non-deletional α gene variants, Hb Fontainebleau, Hb O Indonesia and Hb Koya Dora, were identified in heterozygous condition in newborns. This is the first report of Hb Fontainebleau in association with Hb S. The baby had anaemia at birth (Hb 11.4 g/dl) with no cyanosis, icterus or need for transfusion. She had occipital encephalocoele and was operated on day 24 to remove the mass. The baby diagnosed with Hb O Indonesia in combination with Hb S also had a low haemoglobin level of 12.7 g/dl.
Newborn screening for sickle cell disorders also enabled us to identify three α globin chain variants. Two babies who inherited Hb Fontainebleau and Hb O Indonesia along with Hb S had reduced Hb levels at birth and need to be followed up.
The identification of a second case of Hb Fontainbleau [alpha21(B2)Ala-->Pro] allowed us to re-examine its association with microcytosis, explore the effects of the mutation on protein stability and define the mutation at a DNA level. Although slightly unstable, the variant was expressed at 28-29% of the total and was caused by a heterozygous mutation in the alpha2 gene. There was no evidence for concomitant alpha-thalassemia (alpha-thal); both alpha-globin gene deletion analysis and sequencing of the alpha-globin locus failed to detect any additional mutations that might explain the relatively high expression level.
Cyprus, located at the eastern end of the Mediterranean region, has been a place of eastern and western civilizations, and the presence of various hemoglobin (Hb) variants can be considered a testimony to past colonizations of the island. In this study, we report the structural Hb variants identified in the Cypriot population (Greek Cypriots, Maronites, Armenians, and Latinos) during the thalassemia screening of 248,000 subjects carried out at the Thalassaemia Centre, Nicosia, Cyprus, over a period of 26 years. A sample population of 65,668 people was used to determine the frequency and localization of several of the variants identified in Cyprus. The localization of some of the variants in regions where the presence of foreign people was most prevalent provides important clues to the origin of the variants. Twelve structural variants have been identified by DNA sequencing, nine concerning the beta-globin gene and three concerning the alpha-globin gene. The most common beta-globin variants identified were Hb S (0.2%), Hb D-Punjab (0.02%), and Hb Lepore-Washington-Boston (Hb Lepore-WB) (0.03%); the most common alpha-globin variant was Hb Setif (0.1%). The presence of some of these variants is likely to be directly linked to the history of Cyprus, as archeological monuments have been found throughout the island which signify the presence for many years of the Greeks, Syrians, Persians, Arabs, Byzantines, Franks, Venetians, and Turks.
Neonatal identification of sickle cell disease can significantly reduce mortality and morbidity during the first 5 years of life. During a 10-year period, 414,801 neonates were screened by isoelectric focusing. The most common variants detected were haemoglobins S, C, D and E. Two hundred and fifty of the samples tested were homozygotes or compound heterozygotes, and 6554 samples were heterozygotes for the common variants. The gene frequencies in the population tested were calculated from this data for the most common variants. They were: S, 0.0057; C, 0.0014; D(Punjab(Los Angeles)), 0.0007; E, 0.0005. Additionally, 16 babies had beta thalassaemia major and 405 had rarer variants, of which six had never previously been described. Knowledge of the distribution of these inherited diseases is useful in healthcare planning and appropriate allocation of resources, while counselling targeted at appropriate couples enables informed parental choice and may prevent disease.