MOLECULAR CHARACTERIZATION OF HB-H-DISEASE BY POLYMERASE CHAIN-REACTION

We utilized the PCR method to amplify the alpha-thalassemia-1 breakpoi nt area of the Southeast Asia type and several regions of the alpha-gl obin gene cluster to diagnose rightward deletion (alpha(3.7)), leftwar d deletion (-alpha(4.2)) or nondeletion forms of the Hb H disease. For the nondeletion form, a natural restriction site of MseI was used to detect the Hb Constant Spring (Hb CS) or other termination codon mutat ions. Another naturally occurring restriction site of MspI was used to detect the Hb Quong-Sze. For the deletion form of the Hb H disease, t he differences among nonhomologous I, II and III of the rightward or l eftward deletion were used to distinguish the mutations. For further c haracterization of the subtype of -alpha(3.7) deletion, the same prime rs for detecting termination codon mutations were used to amplify part of the alpha-globin gene, then the PCR product was digested by the re striction enzyme ApaI. In the 57 cases which were studied, 19 were del etion forms while 38 were nondeletion forms. In the deletion form case s, 13 were rightward deletion (-alpha(3.7)) and the other 6 were leftw ard deletion (-alpha(4.2)). However, all of the nondeletion form cases were alpha-thalassemia-1 with Hb CS. After the subtyping of alpha(3.7 ) deletion, 11 out of 13 were type I deletions and the other 2 were ty pe II deletions.