Hb Beograd [beta121(GH4)Glu-->Val, GAA-->GTA] in the Turkish population

Hb Beograd [beta121(GH4)Glu-->Val, GAA-->GTA] is a rare variant first reported in Yugoslavia and then in Turkey, Australia and New Zealand. We report two further unrelated cases from Turkey. The importance of identifying Hb Beograd at the molecular level, especially in regions where Hb D-Los Angeles [beta121(GH4)Glu-->Gln, GAA-->CAA] is prevalent, is emphasized.     

Hb Buffalo [alpha89(FG1)His-->Gln (alpha1)], observed solely and in the presence of an Hb S [beta6(A3)Glu-->Val] heterozygosity

The hemoglobin (Hb) pattern of a 32-year-old Somali male living in The Netherlands, during routine diabetes mellitus monitoring, showed two more peaks in addition to the characteristic heterozygous Hb A/S pattern. A major peak of 15% faster than Hb A, and a minor one of 10.8%, overlapping Hb A2 and the glycated Hb S1c fraction were present. The patient was not anemic or microcytic but had a low haptoglobin level, possibly indicating a slightly elevated red blood cell (RBC) turnover. Hb S was confirmed by a sickle test and at the DNA level. The DNA sequence of the alpha1 gene revealed a C-->G transversion at position 89, changing the local positively charged histidine to a neutral glutamine. This mutant has been previously described in a Yemenite woman and two apparently unrelated Somali males. Our case is the first showing Hb Buffalo in combination with Hb S and a G6PD deficiency, and is again observed in a Somali. No functional abnormalities associated with mutations at this amino acid residue are reported in the literature. Also, in this case no sign of any hematological abnormalities that could not be explained by the Hb S heterozygosity G6PD deficiency was found. The abnormal alpha chain is expressed at the expected rate and without thalassemic effect or instability. The mutated alpha chain seems to associate with a slight preference to the beta(A) (15%) rather than with the beta(S) counterpart. The sum of both Hb A(Buffalo) and Hb S(Buffalo) results in about 19-20% of total Hb. This figure is in agreement with a stable mutant of the alpha1 gene.     

Hb Hope [beta136(H14)Gly-->Asp (GGT-->GAT)]: interactions with Hb S [beta6(A3)Glu-->Val (GAG-->GTG)], other variant hemoglobins and thalassemia

Hb Hope [beta136(H14)Gly-->Asp (GGT-->GAT)] was first described in an African-American family in 1965. Since then, it has been found in combination with several different globin gene mutations in many other families of divergent ethnic backgrounds. The basis for its relatively frequent occurrences remains unexplained. This variant hemoglobin (Hb) is mildly unstable and has reduced oxygen affinity, but is generally innocuous clinically. This variant Hb can present as a confounding factor in arriving at a correct diagnosis by either electrophoresis or high performance liquid chromatography (HPLC), particularly during the neonatal period. DNA-based diagnostics can help solve this potential problem.     

Surface plasmon resonance-based molecular detection of Hb S [beta6(A3)Glu-->Val, GAG-->GTG] at the gene level

The surface plasmon resonance (SPR) approach, being a relatively novel biophysical method, is used to detect many different targets by biomolecular interaction. The SPR system uses optical and evanescent wave phenomenon. This approach does not need any labels, such as enzymes or isotopes, and the monitored interactions are in real time. In DNA-DNA interaction, the SPR approach is Tm-independent. Here we report our preliminary results for the molecular detection of the Hb S (GAG -->GTG) mutation at codon 6 of the human beta-globin gene. Our preliminary results show that the SPR approach could be applied as an inexpensive and fast routine test system for the molecular diagnosis of abnormal hemoglobins (Hbs), especially in premarital screening programs.     

Molecular characterization of Hb D-Punjab [beta121(GH4)Glu-->Gln] in Thailand

We describe the hematological and DNA characterization of Hb D-Punjab [beta121(GH4)Glu-->Gln] in Thailand. Nine patients from five unrelated families were studied; four patients were simple carriers of Hb D-Punjab, two were compound heterozygotes for Hb D-Punjab/beta+-thalassemia; another two patients were double heterozygotes for Hb D-Punjab and alpha-thalassemia-2, and one patient was a compound heterozygote for Hb D-Punjab and Hb E [beta26(B8)Glu-->Lys]. Typical thalassemic indices with hypochromic microcytosis were observed in compound Hb D-Punjab/ beta+-thalassemia and Hb D-Punjab/Hb E but normal hematological profiles were observed in the remaining cases. DNA sequencing of the beta-globin gene identified the GAA-->CAA substitution at codon 121 causing Hb D-Punjab in all cases, and the -28 (A-->G) mutation for the beta+-thalassemia alleles. beta-Globin gene haplotype analysis demonstrated, for the first time, that all these Asian beta(D-Punjab) globin genes were associated with haplotype [-++-+++], previously undescribed in other populations. The finding of Hb D-Punjab in Thailand is compatible either with an independent origin of this abnormal hemoglobin or a spread of the Hb D-Punjab gene with a single origin among Asians.     

Five variants of the beta-globin gene without clinical or hematological effects: Hb Maryland [beta 47(CD6)Asp-->His], Hb Kent [beta 37(C3)Trp-->Cys], Hb Visayan [beta 136(H14)Gly-->Cys], Hb Cutlerville [beta 138(H16)Ala-->Val] and Hb Hornchurch [beta 43(CD2)Glu-->Lys

We report on five hemoglobin (Hb) beta chain variants that were initially identified either by electrophoretic, chromatographic or isoelectric focusing (IEF) methods. These variants do not appear to be associated with clinical or hematological abnormalities. All variants were confirmed by DNA sequence analysis.     

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.     

Molecular characterization of Hb D-Ibadan [beta87(F3)Thr-->Lys] in combination with Hb S [beta6(A3)Glu-->Val] and with beta+-Thalassemia: report of two cases

Hb D-Ibadan [beta87(F3)Thr-->Lys] is a common variant in the Nigerian population, which has been reported in association with Hb S [beta6(A3)Glu-->Val] and with beta-thalassemia. Unlike the Hb S/Hb D-Los Angeles [beta121(GH4)Glu-->Gln] combination, compound heterozygosity for Hb D-Ibadan and Hb S does not result in a sickling disorder. We report the first case of a combination of Hb D-Ibadan with beta+-thalassemia, and the first observation of Hb S/Hb D-Ibadan in the African-American population. In both cases, the characterization of Hb D-Ibadan was achieved by sequencing of the genomic DNA. Although protein based methods such as isoelec-trofocusing and high performance liquid chromatography may suggest that the "D-like" variant is different from Hb D-Los Angeles, the definitive identification of the variant by structural analysis or molecular genetic methods should be undertaken, particularly in newborn screening programs when the variant is found in combination with Hb S.     

Genetic studies suggest a multicentric origin for Hb G-Coushatta [beta22(B4)Glu-->Ala

Hb G-Coushatta [beta22(B4)Glu-->Ala] is found in geographically separated ethnic groups. Commonest along the Silk Road region of China but also present in the North American Coushatta, we sought to determine whether this variant had a unicentric or multicentric origin. We examined the haplotype of the beta-globin gene cluster in two Chinese families and in five Louisiana Coushatta heterozygous for this mutation. Chinese and Louisiana Coushatta had different haplotypes associated with the identical Hb G mutation. These haplotypes were defined by the presence of a HindIII restriction site in the Agamma-globin gene and AvaII restriction site in the beta-globin gene in Chinese subjects and their absence in the Louisiana Coushatta. We found a CAC at codon beta2 (beta-globin gene framework 1 or 2) linked to the Hb G-Coushatta gene in Chinese, and a CAT (framework 3) in Louisiana Coushatta, indicating different beta-globin gene frameworks. Both the Hb G-Coushatta mutation (GAA-->GCA) and the codon 2 CAC-->CAT polymorphism are normal delta-globin gene sequences, suggesting the possibility of gene conversion. We conclude that Hb G-Coushatta had at least two independent origins. This could be due to separate mutations at codon beta22 in Chinese and Louisiana Coushatta, a mutation at this codon and a beta-->delta conversion, or two beta-->delta gene conversion events.     

Hb Jeddah [alpha68(E17)Asn-->His (alpha1)]: a newly recognized alpha chain variant, seen in combination with Hb S [beta6(A3)Glu-->Val], and found in three separate families of middle eastern origin

We report a previously unrecognized alpha chain variant identified in three families from Saudi Arabia, Yemen and Abu Dhabi. The index patient presented for hemoglobinopathy screening and was identified to have both this novel alpha chain variant and Hb S [beta6(A3)Glu-->Val, GAG(-->)GTG]. Hb Jeddah results from a point mutation (AAC(-->)CAC) at codon 68 in exon 2 of the alpha1 gene. There were no apparent hematological abnormalities or clinical symptoms in the three individuals identified as heterozygotes for Hb Jeddah, as well as the index case with both Hb S and Hb Jeddah. As we have found this variant in three separate families, the incidence may be greater than currently recognized.     

Hb G-Makassar [beta6(A3)Glu-->Ala; codon 6 (GAG-->GCG)]: molecular characterization,clinical, and hematological effects

We report a Thai family in which five members are Hb G-Makassar heterozygotes and one member is, in addition, a heterozygote for beta0-thalassemia (IVS-I-1, G-->T). We confirm that the previously presumed mutation at codon 6 of the beta-globin gene is GAG-->GCG. Hb G-Makassar heterozygotes are asymptomatic and hematologically normal. The Hb G-Makassar/beta0-thalassemia compound heterozygote has features of thalassemia minor. A simple and rapid polymerase chain reaction-restriction fragment length polymorphism for the detection of Hb G-Makassar is described.