A pool of nonpolysomal globin mRNAs in globin deficient reticulocytes of the anemic Belgrade rat

Alpha- and beta-globins of the anemic Belgrade laboratory rat. I. Status of alpha- and beta-globins in bone marrow and spleen

In this study we have demonstrated that the bone marrow of the anemic Belgrade laboratory (b/b) rat, as the primary site of erythropoiesis, has a decreased globin polypeptide synthesis in total protein cell extracts. Therefore, it is the source of red blood cells containing decreased amounts of globin mRNAs and polypeptides. In spite of the fact that the b/b rat shows a splenomegaly, the spleen is not capable of compensating for the anemic state. Spleen erythroid cells are defective in differentiation and contain a decreased share of globin polypeptides in total protein cell extracts compared to the control. Spleen cells are also characterized by a drastic imbalance of alpha- to beta-globin resulting in the beta-globin chains surplus.

Molecular evidence for increased hematopoietic proliferation in the spleen of the b/b laboratory rat

The splenomegaly and the appearance of a significant number of CFU-E (erythroid colony-forming units) and BFU-E1 (erythroid burst-forming units) in the Belgrade laboratory rat (b/b) spleen prompted us to analyse further the molecular evidence for increased hematopoietic proliferation in the b/b spleen. Messenger RNAs (mRNAs) specific for globins, proteins for iron transport and deposition and the band 3 protein were used in rat erythropoietic tissues as markers for proliferation and erythroid differentiation. In the b/b spleen, all mRNAs analysed display an erythroid-specific pattern of expression. This analysis also revealed an enhanced level of mRNA for ferritin in the +/b spleen, whereas erythrocyte-specific mRNA production was normal.

Variant chromosomal arrangement of adult beta-globin genes in rat

The genomic organization of three haplotypes of beta-globin genes was determined to resolve the question of the number of those genes in rat. Haplotype a, found in inbred strain DA, has three genes or pseudogenes, while haplotypes b, found in AO, Y5 and Wistar strains, and c, found in Wistar strain, have five genes or pseudogenes each. In haplotypes b and c, the first gene is of beta major type and the remaining four are of beta minor type. Partial sequencing of six out of 13 genes shows that duplications of beta minor genes are causing polymorphism in a number of genes. Also, in haplotype b two beta minor genes have a 6.5-kb intron 2, while in haplotype c only one beta minor gene contains such a large intron 2. The three structurally different haplotypes described are not interconvertible by single recombination events. The results indicate that the rat has the highest number of adult beta-globin genes found in mammals so far.

Level of translatable messenger RNA coding for argininosuccinate synthetase in the liver of the patients with quantitative-type citrullinemia

The translation activity of mRNA coding for argininosuccinate synthetase in total RNA extracted from the liver of three patients with quantitative-type citrullinemia was determined using a cell-free translation system. In two patients, the hepatic content of the enzyme was about 20% of the control value, whereas translatable mRNA level for the enzyme was similar to or slightly lower than those of control livers. In the third patient, the enzyme content was about 50% of the control value, and mRNA activity for the enzyme was low normal. These results indicate that at least in the first two patients, the decrease in the enzyme protein is due either to increased degradation of the enzyme or to decreased translation in the patient's liver.

Characterization of two rat globin cDNA clones

The rat globin gene system is suitable for studying a coordinated regulation of seven genes from two gene families. A rat reticulocyte cDNA globin library has been constructed and two clones analyzed in detail. pBRrg 5 contains alpha while pBRrg X contains beta type sequence. These cloned cDNAs will be useful probes of structure and function of rat globin genes. The deduced amino acid sequences extend the information about the variability of rat globin chains.