Further evidence for a post-translational phenomenon in the interaction of alpha-thalassemia with sickle cell trait

High performance liquid chromatography (HPLC): a simple method to quantify Hb C, O-Arab, Agenogi and F

Differentiation of some abnormal haemoglobins, such as Hb C, O-Arab, Agenogi, E, O-Indonesia, C-Harlem, and Siriraj, is difficult and quantitation of the various fractions is impossible with cellulose acetate electrophoresis. The authors report 13 cases of Hb C, 10 of Hb O-Arab and 5 of Hb Agenogi whose haemoglobin fractions were quantitated by HPLC during a thalassaemia screening programme. Hb F was determined by both Betke's method and HPLC. Analysis of data by linear regression demonstrates that the methods furnish overlapping results. Our findings show that HPLC is a rapid and easily reproduced method which allows quantitative and qualitative discrimination of the various haemoglobin fractions, making it a valid tool in screening programmes for haemoglobinopathies.

A novel intrachromosomal rearrangement in the beta-globin gene found in an African-American family

We describe here a deletion of 34 nucleotides from the 3' end of the first intervening sequence of the beta-globin gene covering the AGGC splice junction, and the insertion of 32 nucleotides of the delta-globin gene at the same location. This gene rearrangement was detected in three members of an African-American family. The proband, a 28-year-old female, and her mother had a history of chronic anemia. One of her two brothers, who inherited the same gene defect, was apparently healthy with no symptoms of hemolytic anemia. The proband, her father, and her two brothers, including the one who carried the beta-globin gene rearrangement, were found to be heterozygous for alpha-thalassemia-2 (-alpha 3.7). Although the AGGC splice junction is disrupted (AGGC-->AGAT), the invariant AG has remained intact after this gene rearrangement. Our investigations could not detect any defect in RNA processing in the affected beta-globin genes. The discrepancies between the phenotypes and the globin chain synthesis ratios of the mother, her daughter, and her son who inherited the same gene defect at their beta-globin genes, remain unexplained.

Direct analysis of single nucleotide variation in human DNA and RNA using in situ dot hybridization

Using oligonucleotide hybridization, single and multiple nucleotide differences between alleles were detected directly in genomic DNA without electrophoretic separation. The DNA was immobilized in depressions in an agarose gel (in situ dots) and hybridized with radiolabeled, allele-specific oligonucleotide probes. An oligonucleotide complementary to a unique sequence region of the human major histocompatibility complex gene HLA-B27 only hybridized with genomic DNA from an HLA-B27-positive individual. Two other oligonucleotides complementary to the normal human beta-globin gene (beta A) and to the sickle cell globin gene (beta S) were synthesized. Using competition hybridization conditions which included the presence of a 10-fold molar excess of unlabeled oligonucleotide complementary to the other beta-globin allele, DNA from individuals homozygous for the normal beta-globin gene (beta A beta A) hybridized to the beta A probe exclusively, whereas DNA from individuals homozygous for the sickle cell globin gene (beta S beta S) hybridized only with the probe for the sickle cell gene. As expected, DNA from heterozygous individuals bound to both probes. Similar results were obtained with total human RNA immobilized in in situ dots. Possible applications of this methodology include genetic disease diagnosis, population carrier screening, HLA "DNA" typing, and DNA and RNA sequence polymorphism analysis.

Rapid HPLC techniques for globin chain synthesis studies

Globin chain synthesis and alpha/beta ratios were determined in a number of normal subjects, alpha-thalassemia-2 homozygotes, and beta-thalassemia trait using three different techniques. Cation exchange high performance liquid chromatography on a Pharmacia Mono-S, HR 5/5 and reversed phase high performance liquid chromatography on a semi-preparative Vydac C4 column were compared with the traditional carboxymethylcellulose chromatography. Both high performance liquid chromatography columns give excellent results when 2 mg of hemoglobin was chromatographed in each analysis. By modifying the protocols for column equilibration and gradient shape for preparative Vydac C4 columns, conditions were found yielding excellent resolutions of the labeled globin chains in less than an hour without the need for substantial increase of the flowrate. This method was found to be superior to other methods and may be a suitable alternative for the classical carboxymethylcellulose chromatography. Up to five specimens could easily be analyzed in a single day with this system.