RNA processing errors in patients with beta-thalassemia.

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Abstract
A method was developed that permits rapid identification of the consequences of mutations that alter .beta.-globin RNA processing in erythroid cells. S1 nuclease mapping techniques were used to analyze total bone marrow RNA obtained from 15 patients who are clinically homozygous for .beta.-thalassemia and from 5 patients with erythroid hyperplasia from other causes. This analysis was facilitated by the use of single-stranded uniformly labeled DNA probes of high specific activity that were prepared by using recombinant phage M13-.beta.-globin DNA templates. Two abnormalities of RNA processing were found to occur with high frequency in these patients. Nine thalassemic patients were found to have increased levels of an RNA species that retains all sequences transcribed from intervening sequence 1, implying the presence of mutations that decrease the correct splicing of this intron. Of 15 thalassemic patients, 7 were found to have an abnormally processed RNA species that retains 19 nucleotides transcribed from the 3'' end of intron 1; this abnormality is caused by the G .fwdarw. A substitution in intron 1 that is known to create an alternative splice acceptor site.