Hb Bab-Saadoun or alpha 2 beta (2)48(CD7)Leu----Pro, a mildly unstable variant found in an Arabian boy from Tunisia

Hb Bab-Saadoun which has a Leu----Pro substitution at position 48 of the beta chain was detected in a young Arabian boy living in Tunisia. His parents did not have the variant which suggests that it occurred as a spontaneous mutation. The substitution is located in the interhelical CD segment; leucine at beta 48 is an invariable amino acid that may be important as part of a spacer sequence between the two helices and its replacement by proline may affect the stability of the hemoglobin molecule. Hb Bab-Saadoun is unstable in heat and isopropanol stability tests and its chain was best isolated by parachloromercuribenzoate precipitation. It appears unlikely that the presence of Hb Bab-Saadoun results in a hemolytic anemia.

The unstable Hb Hammersmith or alpha 2 beta 2(42)(CD1)Phe----Ser observed in an Indian child; identification by HPLC and by sequence analysis of amplified DNA

We have identified the unstable hemoglobin variant present in a Chipewayan Indian patient with severe hemolytic anemia as Hb Hammersmith or alpha 2 beta 2(42)(CD1)Phe----Ser. Her parents were normal. Identification was greatly facilitated by the use of reversed phase high performance liquid chromatography for the isolation of the beta X chain and its tryptic fragments, and of sequence analysis of amplified DNA which readily identified a TTT(Phe)----TCT(Ser) mutation at codon 42.

Types of thalassemia among patients attending a large university clinic in Kuala Lumpur, Malaysia

We have identified the beta-thalassemia mutations in 59 patients with thalassemia major and 47 patients with Hb E-beta-thalassemia, and the deletional and nondeletional alpha-thalassemia determinants in 23 out of 24 patients with Hb H disease. All persons were attending the Haematology Clinic at the National University of Malaysia in Kuala Lumpur (Malaysia). Most patients (76) were of Malay descent, while 52 patients were Chinese, and two came from elsewhere. The most frequently occurring beta-thalassemia alleles among the Malay patients were IVS-I-5 (G----C) and G----A at codon 26 (Hb E), while a few others were present at lower frequencies. The Chinese patients carried the mutation characteristic for Chinese [mainly codons 41/42 (-TTCT) and IVS-II-654 (C----T)]; Malay mutations were not observed among Chinese and Chinese mutations were virtually absent in the Malay patients. The large group of patients with Hb E-beta-thalassemia and different beta-thalassemia alleles offered the opportunity of comparing hematological data; information obtained for patients with Hb E-beta-thalassemia living in other countries was included in this comparison. Twenty-three patients with Hb H disease carried the Southeast Asian (SEA) alpha-thalassemia-1 deletion; 13 had the alpha CS alpha (Constant Spring) nondeletional alpha-thalassemia-2 determinant, while the deletional alpha-thalassemia-2 (-3.7 or -4.2 kb) was present in 10 subjects. The --/alpha CS alpha condition appeared to be the most severe with higher Hb H values. Both deletional and nondeletional types of alpha-thalassemia-2 were seen among Malay and Chinese patients.

A new variant, HB Muscat [alpha 2 beta (2)32(B14)Leu----Val] observed in association with HB S in an Arabian family

The silent Hb Muscat with a Leu----Val replacement at position beta 32 was discovered by reversed phase high performance liquid chromatography in two members of an Arabian family from Oman; in one person Hb Muscat occurred with Hb S and in the other with Hb A. Hb Muscat is slightly unstable but its presence has no apparent adverse effect on the health of its carriers. Additional hemoglobin abnormalities observed in this family were a common alpha-thalassemia-2 (-3.7 kb) and Hb S. The beta S haplotypes in the heterozygous carriers and the two sickle cell anemia patients were #19 (Benin) and #20 (Bantu); the latter likely originated from an East African population.

Hb Graz or alpha 2 beta 2(2)(NA2)His-->Leu; a new beta chain variant observed in four families from southern Austria

Two abnormal hemoglobins were accidentally detected by cation exchange high performance liquid chromatography with the Diamat system of Bio-Rad Laboratories; the variants eluted together with the fast-moving Hb A1c. Structural analysis of isolated beta chains and sequence analysis of amplified DNA identified a new variant, i.e. Hb Graz that has a His-->Leu replacement at position 2 of the beta chain, in four healthy, apparently unrelated, adults. The second variant was identical to Hb Sherwood Forest or alpha 2 beta 2(104)(G6)Arg-->Thr; it is believed that this may be the second observation of this abnormal hemoglobin.

A second observation of the fetal methemoglobin variant Hb F-M-Fort Ripley or alpha 2G gamma 2(92)(F8)His----Tyr

We have identified a second baby with the fetal methemoglobin F-M-Fort Ripley. It was observed in a Caucasian infant from Canada; at least eleven additional members of that family were known to have had a neonatal cyanosis similar to that seen in the propositus and in a previously described baby (2). Sequencing of amplified DNA that included (part of) the G gamma gene greatly facilitated the characterization. The G gamma X chain was readily isolated by reversed phase high performance liquid chromatography; its quantity was approximately 12.5% of total gamma. Interestingly, the baby also carried the A gamma T mutation on one chromosome, either in cis or in trans to the G gamma X mutation. Hb F-M-Fort Ripley could be isolated in reasonably pure form by DEAE-cellulose chromatography. The isolated Hb FX was unstable, had spectral changes characteristic for the M-hemoglobins, while its methemoglobin derivative reacted rapidly with cyanide. Oxygen affinity data could not be obtained. It is suggested that the formation of a rather large amount (approximately 25%) of mixed hybrids (alpha 2G gamma X.gamma) with low oxygen affinity is the main cause for the occurrence of the neonatal cyanosis.

Vaginal delivery after previous cesarean section in a rural West African hospital

Two hundred twenty women with prior cesarean section were delivered at our institution between January 1987 and February 1990. Vaginal delivery was achieved in 111 (66%) of 169 patients given a trial of labor (TOL). Success of TOL correlated positively with the number of prior vaginal deliveries (P less than 0.05) and inversely with the number of prior cesarean sections (P less than 0.005). Maternal and fetal outcome were not significantly different between the TOL and non-TOL groups.

Dominant beta-thalassaemia trait in a Portuguese family is caused by a deletion of (G)TGGCTGGTGT(G) and an insertion of (G)GCAG(G) in codons 134, 135, 136 and 137 of the beta-globin gene

We have studied a Portuguese family with a dominant beta-thalassaemia trait that was present in one member of each of three generations. It was characterized by a moderate anaemia, microcytosis and hypochromia, anisopoikilocytosis, Heinz body formation in peripheral red cells, splenomegaly, and a blood transfusion requirement during pregnancy. Sequence analyses of amplified DNA detected a deletion of (G) TG.GCT.GGT.GT(G) at codons 134-137 (Val.Ala.Gly.Val) and the insertion of (G)GC.AG(G) (Gly.Arg) at the same location. Thus, the resulting beta chain has an abnormal structure only at codons 134-137 and is two residues shorter than the normal 146 residues. This chain could not be detected in circulating red cells and must be degraded rapidly by proteolysis because the Heinz bodies consisted mainly of alpha chains.

The linkage of Hb Valletta [alpha 2 beta 287(f3)Thr----Pro] and Hb F-Malta-I [alpha 2G gamma 2117(G19)His----Arg] in the Maltese population

We have identified a new stable abnormal hemoglobin called Hb Valletta, which is characterized by a Thr----Pro substitution at position 87 of the beta chain. This mutation was found to be linked to that of the gamma chain variant Hb F-Malta-I with a His----Arg mutation at position 117 of the G gamma chain. Both variants were detected in the blood samples of 34 Maltese and two Italian newborn babies with isoelectrofocusing and reversed phase high performance liquid chromatography. Similar analyses of cord blood from 388 additional Maltese newborns failed to identify either one of these two variants. Additional analyses of 353 Maltese adults (including 39 beta-thalassemia heterozygotes) resulted in the detection of two adult Hb Valletta heterozygotes. Dot-blot hybridization analyses of amplified DNA with a probe specific for the G gamma-F-Malta-I variant showed that both also carried that mutation. These results show close linkage of the mutant forms of the G gamma- and beta-globin genes, 27-28 kb apart, and a failure to identify chromosomes with either the Hb F-Malta-I mutation alone or with the Hb Valletta mutation alone, indicating a low recombination frequency.

Hb Coimbra or alpha 2 beta (2)99(G1)Asp----Glu, a newly discovered highoxygen affinity variant

We have identified a new high oxygen affinity hemoglobin variant in members of a Portuguese family; it is characterized by an Asp----Glu replacement at codon 99 of the beta chain which is in the alpha 1 beta 2 interface. The altered functional properties of Hb Coimbra likely result from the inability to form a hydrogen bond between beta 99Glu and alpha 42Tyr; such a bond is formed in deoxy Hb A between the normally occurring beta 99Asp and alpha 42Tyr. The two affected members of the family have a distinct erythrocytosis with hemoglobin levels of 18 to 20 g/dl. The mutation in the beta-globin gene (GAT----GAA at codon 99) resulting in the Asp----Glu replacement is the seventh type at this specific location. A review of the many variants of the alpha and beta chains identifies primarily aspartic acid and glutamic acid residues as being most frequently replaced; it is speculated that codons GAC and GAT (for Asp), and GAG and GAA (for Glu) are most susceptible to mutational events.

Hb Cleveland or alpha 2 beta 2(93)(F9)Cys----Arg;121(GH4)Glu----Gln

Hb Cleveland is characterized by two amino acid substitutions, namely beta 121(GH4)Glu----Gln as in Hb D-Los Angeles and beta 93(F9)Cys----Arg as in Hb Okazaki, and shares with Hb Okazaki a decreased stability, an increase in oxygen affinity, and decreases in Bohr effect and heme-heme interaction. It is the 13th beta chain variant with two substitutions that has been described thus far.

Hb Mizuho or alpha 2 beta (2)68(E12)Leu----Pro in a Caucasian boy with high levels of Hb F; identification by sequencing of amplified DNA

Hb Mizuho, an unstable beta chain variant with a Leu----Pro substitution at position beta 68, was observed in a young Caucasian boy from Kentucky. Identification was made by sequence analyses of amplified DNA and by hybridization of amplified DNA with specific probes. The patient had high Hb F levels up to the present age of nearly 5 years; this high Hb F might in part be responsible for his condition which was considerably milder than that seen in the two patients described in earlier reports. The increased gamma chain synthesis may be due to special characteristics of the beta-globin gene cistron which are comparable to those observed in sickle cell anemia patients with a relatively mild disease.

Hemoglobin Montreal: a new variant with an extended beta chain due to a deletion of Asp, Gly, Leu at positions 73, 74, and 75, and an insertion of Ala, Arg, Cys, Gln at the same location

The unstable hemoglobin Montreal with a deletion of three amino acid residues (Asp, Gly, Leu) at positions 73, 74, and 75 of the beta chain and an insertion of four residues (Ala, Arg, Cys, Gln) at the same location was observed in a 7-year-old Canadian boy suffering from a moderate hemolytic anemia. The introduction of an extra amino acid residue and of other changes in the crevice where the heme group is located is the likely cause of the instability of this hemoglobin variant. The above listed changes were detected through analyses of tryptic peptides of the beta-Montreal chain, sequencing of amplified DNA, and hybridization of amplified DNA with appropriate, 32P-labeled, oligonucleotide probes. It is suggested that a mispairing involving the AGTG sequences at codons 66 and 67 and at codons 72 and 73 of the normal beta gene caused a repetition of a 16-bp segment, while a deletion of 10 nucleotides due to recombination or slippage followed by a second short deletion during DNA repair resulted in the modified sequence of the beta-Montreal gene.

Chinese in west Malaysia: the geography of beta thalassaemia mutations

The overseas Chinese in West Malaysia are almost exclusively from the south-eastern provinces of China-Kwangtung, Fukien, and Kwangsi. To institute a comprehensive thalassaemia control programme for this region we have characterised the beta thalassaemia mutations in 16 Chinese patients from West Malaysia: 4 beta thalassaemia mutations were seen: a) an A----G substitution in the TATA box [-28 base pairs (bp)], an A----T substitution in codon 17 [17 A----T], c) a 4 base pairs - TCTT deletion in codon 41-42 [frameshift mutation (FSC 41-42)], and d) a C----T substitution at the second intervening sequence (IVS 11) position 654. Similar mutations have been described in patients from the south-eastern provinces of China. The delineation of the specific mutations present will enable effective prenatal diagnosis for beta thalassaemia of ethnic Chinese in West Malaysia to be instituted.

Expression of the BNLF-1 oncogene of Epstein-Barr virus in the skin of transgenic mice induces hyperplasia and aberrant expression of keratin 6

The BNLF-1 gene of Epstein-Barr virus (EBV) encodes the latent membrane protein (LMP), one of the putative oncogene products of the virus. This gene has been expressed from two different enhancer-promoter constructs in transgenic mice, to determine its biological activity and possible contribution to oncogenesis. While transgenic mice expressing LMP in many tissues demonstrated poor viability, expression of LMP specifically in the epidermis induces a phenotype of hyperplastic dermatosis. Concomitant with the expression of LMP in this tissue (and in the esophagus) is an induction of the expression of a hyperproliferative keratin, K6, at aberrant locations within the epidermis. The epithelial hyperplastic phenotype caused by the LMP-encoding transgenes implies that the LMP plays a role in the acanthotic condition of the tongue epithelium in the human EBV- and HIV-associated syndrome oral hairy leukoplakia, as well as possibly predisposing the nasopharyngeal epithelium to carcinogenesis.

Hemoglobin Birmingham and hemoglobin Galicia: two unstable beta chain variants characterized by small deletions and insertions

Two unstable hemoglobins (Hbs) causing rather severe hemolytic anemia have been characterized. The beta chain of Hb Birmingham, found in an adult black man, is characterized by the loss of -Leu-Ala-His-Lys- at positions 141, 142, 143, and 144 and their replacement by one Gln residue. These changes are the result of a deletion of nine nucleotides, namely two base pairs (bp) of codon 141, all of codons 142 and 143, and one bp of codon 144; the remaining CAG triplet (C from codon 141 and AG from codon 144) codes for the inserted glutamine. In the beta chain of Hb Galicia from a Spanish patient, His and Val at positions 97 and 98 are replaced by one Leu residue. This is due to an ACG deletion in codons 97 and 98, which causes the removal of one His and one Val residue, while the remaining CTG triplet (C from codon 97 and TG from codon 98) codes for the inserted leucine residue. Two mechanisms, namely slipped mispairing in the presence of short repeats, and misreading by DNA polymerase due to a local distortion of the DNA helix, are considered in explaining the origin of the small deletions.