Expression of Hemoglobin Related Proteins in Nucleated and Enucleated Red Blood Cells

Abstract

In vertebrates a total of eight different globins are known which are expressed in a highly species‐ and tissue‐specific manner. Globins are small molecules with a heme prosthetic group, by which they reversibly bind O2 and other gaseous ligands. They are all involved in cellular processes related to O2 transport (e.g. hemoglobin) and storage (e.g. myoglobin), detoxification of reactive oxygen and nitrogen species, sensing and signaling or may have yet unknown functions. The functions of hemoglobin and myoglobin are well understood and known since several years, but data on the other globins are fragmentary. In particular, the factors controlling globin mRNA stability, gene transcription and translation of these globins as well as their physiological functions are currently unknown. Here we examined the expression of globin genes in nucleated and enucleated erythrocytes of different vertebrate model species by quantitative real‐time reverse transcription PCR (qRT‐PCR). Furthermore we studied the transcription rate and mRNA levels of globin genes and other genes (e.g. hypoxia inducible factor 1α, sodium/proton exchanger) under hypoxia, temperature stress and adrenergic stimulation by the nuclear run‐off assay in rainbow trout red blood cells. We surprisingly detected transcripts of the whole gnathostome globin superfamily in mature circulating red blood cells of all vertebrate species but the mRNA expression levels varied among species. The transcription rate of the genes depended on the treatment. Our results add new and unexpected aspects to the current knowledge on the expression specificity of globins in vertebrate tissues and organs.