A novel (g)gamma(a)gamma(deltabeta)O-thalassemia with a 27 kb deletion

A new (G)gamma(A)gamma(deltabeta)O-thalassemia (thal) was found in six unrelated Japanese individuals, and characterized by a method employing only polymerase chain reaction (PCR) and direct sequencing. This (G)gamma(A)gamma(deltabeta)O-thal mutation has removed a fragment of about 27 kb of DNA, that starts approximately 2.8 kb downstream of the Agamma-globin gene and ends in the L1 repeat sequence, 7.0 kb downstream of the beta-globin gene. The 5' breakpoint is similar to that of the previously reported Japanese (G)gamma(A)gamma(deltabeta)O-thal (called here Jpn type 1 for convenience). However, the 3' endpoint is quite different. This new Japanese deltabeta-thal, designated as Japanese type 2 (Jpn type 2), shows a deletion rather similar to Turkish type 3 deltabeta-thal but with 5' and 3' breakpoints located inside the deletion of Turkish type 3. A mutation-specific gap PCR was designed to diagnose patients with the Jpn type 2 (G)gamma(A)gamma(deltabeta)O-thal. The identified carriers exhibited a thalassemia minor.