In many multicellular organisms, oxygen is transported by respiratory proteins,

which are globins in vertebrates, between respiratory organs and tissues.

In jawed vertebrates, eight globins are known which are expressed in a highly

tissue-specific manner. Until now, hemoglobin (Hb) had been agreed to be

the only globin expressed in vertebrate erythrocytes. Here, we investigate for

the first time the mRNA expression of globin genes in nucleated and anucleated

erythrocytes of model vertebrate species by quantitative real-time reverse

transcription PCR (qRT-PCR). Surprisingly, we found transcripts of the whole

gnathostome globin superfamily in RBCs. The mRNA expression levels varied

among species, with Hb being by far the dominant globin. Only in stickleback,

a globin previously thought to be neuron-specific, neuroglobin, had higher

mRNA expression. We furthermore show that in birds transcripts of globin E,

which was earlier reported to be transcribed only in the eye, are also present

in RBCs. Even in anucleated RBCs of mammals, we found transcripts of myoglobin,

neuroglobin, and cytoglobin. Our findings add new aspects to the current

knowledge on the expression of globins in vertebrate tissues. However,

whether or not the mRNA expression of these globin genes has any functional

significance in RBCs has to be investigated in future studies.