A NEW APPROACH TO DIAGNOSIS OF HEMOGLOBIN OPATHY IN CHILDREN AND ADOLESCENTS

The present study provides information about the alpha/beta and alpha 2/alpha 1-mRNA ratios in reticulocytes of normal adults and individual s with different alpha- and beta-globin genes' deficiencies and abnorm alities. Normal ratios are 2.75+/-0.16 (alpha 2/alpha 1) and 4.40+/-0. 25 (alpha/beta). Higher alpha/beta ratios are found in beta-thal heter ozygotes with transcriptional mutants (similar to 6.7) and nonsense or frameshift mutants in the first or second exon (7.5-8.0). Exon 3 muta nts causing dominant beta-thal thrait have a lower alpha/beta ratio (s imilar to 6.0); the mutant mRNA can be detected and is present in decr eased quantities. RNA processing mutants are generally associated with high alpha/beta ratios (average 7.0 in heterozygotes) except for the IVS-I-110 (G-->A) mutation. Deletional mutants involving the entire be ta-globin gene have surprisingly low alpha/beta ratios (4.8-5.4). Abno rmal Hb heterozygotes have normal alpha/beta ratios (4.23+/-0.03 for t hose with stable Hb variants and 4.28+/-0.22 for those with unstable H b variants). These data suggest a normal stability for the Qbx-mRNA an d exclude the possibility that an unstable mRNA is a contributing fact or to the hematological abnormalities observed in the unstable Hb hemo lytic anemia. Thus, the instability of the abnormal globin chain or th e Hb type in which it is incorporated appears to be the major cause of hemolytic disease in these subjects. Loss of one a gene decreases alp ha 2/alpha 1 to similar to 1.6 and 0, and alpha/beta to similar to 3.8 and similar to 1.5 for -alpha/alpha alpha and -alpha/-alpha, respecti vely. Significant differences are observed between the deletional type s (--/-alpha; alpha 2/alpha 1 ratio of zero; alpha/beta ratio of simil ar to 1) and non-deletional types (--/alpha(T) alpha; alpha 2/alpha 1 ratio of 0.05-0.3 for those with T=the 5 nt deletion or the terminatin g codon mutant, and similar to 1.0 for those with T=a poly(A) mutation ; alpha/beta ratio in all types of similar to 0.7) of the Hb H disease . Comparable data are found for the non-deletional alpha-thal-2 homozy gotes. These data are in agreement with the variability of clinical pr esentation of the Hb H disease. The determination of the two ratios ma y be diagnostically of considerable value.