| Summary: | Antarctic icefish (Channichthyidae) are the only vertebrate taxon with an erythrocyte-null phenotype, and present an interesting model for studying the evolution and regulation of erythropoiesis. The gene hemogen has been identified to encode a protein which plays a role in regulating erythropoietic processes in vertebrates. hemogen may have been potentially impacted by the loss of globin-expression. I investigated possible relaxed selection at the hemogen locus by looking for evolutionary change to the regulatory elements or segments encoding the Hemogen protein, and assessed the evolutionary processes that drove hemogen variation among Antarctic notothenioids. While regulatory mechanisms remain intact, icefish show a significant 90bp indel in exon 3 of hemogen that would disrupt conserved modules in the Hemogen protein that are critical for erythropoiesis. Despite this, hemogen still remains expressed at low levels in adult icefish and possesses a novel splice variant that encodes a truncated protein possibly serving as a dominant negative for wild-type Hemogen. I conclude that while hemogen has undergone relaxed selection and accumulated mutations that would impact erythropoietic function in non-Antarctic fish, the observed mutations may be tolerated due to erythrocyte and hematocrit modifications in notothenioid blood phenotypes. hemogen may have a decreased-but still important-role to play in icefish, possibly functioning as a dominant negative for hemogen's role in erythropoiesis.
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