Hemoglobin K#{246}ln:Direct Analysis of the Gene Mutation by Synthetic DNA Probes

H EMOGLOBIN (Hb) K#{246}ln disease belongs to the group of nonspherocytic hemolytic anemias with a dominant inheritance pattern in which anemia is attributable to instability of the Hb molecule. The molecular pathology of this most common of the unstable Hbs was found to be the result of replacement of valine with methionine at f. 98 (FG 5), causing increased oxygen affinity and instability, possibly because of hemedepletion.”2 The clinical features of patients with Hb K#{246}ln are those associated with hemolytic anemia. They may vary individually from mild to severe, and transfusion therapy might have to be started in childhood. The underlying molecular defect in the chromosomal DNA leading to the amino acid substitution in Hb K#{246}ln has not directly been analyzed thus far, but it can be explained by a G-to-A transition caused by a point mutation. A direct detection of the mutation by virtue of the specificity of restriction enzymes was not possible because of the lack of suitable endonucleases. However, identification of the chromosomes that have passed the mutant gene on for three generations was possible by analyzing linked polymorphisms for DNA restriction sites within the /3-globin gene cluster.’ Although the results indicated the possible use of this method for prenatal diagnosis from DNA to amniotic fluid cells or chorion biopsy material, a diagnosis could only be expected in those cases where the haplotype constellations were informative. In all other cases prenatal diagnosis of the Hb K#{246}ln mutation has thus far been precluded because current Hb analysis is not available for identification of the fl-anomaly from fetal blood with absolute certainty. Here we report the detection of the Hb K#{246}ln hemoglobinopathy by direct analysis of the G-to-A transition mutation on the chromosomal DNA via synthetic oligonucleotide probes, thus establishing a method available for prenatal diagnosis of the disease.