Characterization of beta-globin mRNA in the beta0 thalassemias.

A number of cases of beta0 thalassemia have been examined for the presence or absence of beta-globin mRNA. Total RNA extracted from peripheral blood was hybridized to purified complementary DNA specific for beta-globin mRNA, and to beta-cDNA probes specific for the 5' and 3' noncoding regions of beta-globin mRNA. Three clear-cut categories of beta0 thalassemia were identified. The first type had no detectable beta-globin mRNA. A second typed had beta-globin mRNA sequences which hybridized incompletely to the cDNA probes and probably represented mRNAs with grossly altered structures. A third type appeared to have essentially intact, though untranslatable, beta-globin mRNA. Depurination products from 5' and 3' beta-cDNAs synthesized from this latter mRNA were identical to those from normal beta-globin mRNA, but the relative yields were different, suggesting a possible defect near the initiation codon.