The "b" mutated gene in heterozygous Belgrade anemic rat

The Belgrade b/b rat has an autosomal recessive mutation which in homozygous state induces severe anemia. So far, this mutation has been considered a recessive one and the heterozygous animals (+/b) as phenotypically normal. In this study, we showed that at the hematologic level, the heterozygous animals acquire some of the anemic characteristics as well. Namely, the young +/b animal displays reticulocytosis of 3.1 +/- 1.0%, identical to b/b rat, compared with 0.8 +/- 0.4% in young normal animals. This conclusion was further supported by examination of beta-globin expression. The level of beta-globin mRNA in anemic and heterozygous reticulocytes is decreased, as estimated by dot blot hybridization, to 25% and 50% of normal level, respectively. Although inapparent phenotypically, b mutated allele disturbs early erythropoiesis and markedly decreases globin mRNA level in the heterozygous rat.