RELATIVE LEVELS OF ALPHA-MESSENGER-RNA, BETA-MESSENGER-RNA, AND GAMMA-MESSENGER-RNA FROM PATIENTS WITH SEVERE AND INTERMEDIATE BETA-THALASSEMIA MAJOR

We have determined the relative quantities of gamma- and beta-mRNAs an d the alpha/beta-mRNA ratios in 37 patients with beta-thalassemia majo r with specific genotypes, namely 8 with a homozygosity for codon (CD) 39 (C-->T), 7 with a homozygosity for IVS-I-110 (G-->A), 5 with a hom ozygosity for IVS-I-6 (T-->C), for 15 patients with compound heterozyg osities for 2 of these 3 mutations, and for 2 patients with the IVS-I- 110 (G-->A)/-87 (C-->G) mutations. None had an alpha-thalassemia. Twel ve patients had thalassemia intermedia and the remainder, transfusion- dependent severe conditions. Differences in phenotype were observed fo r compound heterozygotes involving the IVS-I-6 (T-->C) mutation in com bination with either the IVS-I-110 (G-->A) or the CD 39 (C-->T) mutati ons: patients with thalassemia intermedia had a lower alpha/beta-mRNA ratio, about half of that of the patients with severe beta-thalassemia major. This might suggest a higher beta-mRNA synthesis in some patien ts than in others with the same genotype; mutations in promoter, enhan cer, and/or locus control region sequences may be responsible for thes e differences. In vitro chain synthesis data were too incomplete to be helpful in this study. The RT-PCR procedure allowed the separation of abnormal (extended) mRNA from normal P-RNA in subjects carrying the I VS-I-110 (G-->T) mutation. The relative quantities of this beta(Th)-mR NA (% of beta(A)+beta(Th)) were determined by scanning of the appropri ate autoradiograms; they averaged 25% for homozygotes and about 4% for heterozygotes, indicating a considerable instability of the message.