Evolutionary suppression of erythropoiesis via the modulation of TGF-ß signaling in an Antarctic icefish

The Antarctic icefish, a family (Channichthyidae) of teleosts within the perciform suborder Notothenioidei, are the only known vertebrates without oxygen-transporting hemoglobins and that are largely devoid of circulating erythrocytes. To elucidate the evo-devo mechanisms underpinning the suppressed erythropoiesis in the icefish, we conducted comparative studies on the transcriptomes and microRNAomes of the primary hematopoietic tissues between an icefish (Chionodraco hamatus) and two red-blooded notothenioids (Trematomus bernacchii and Gymnodraco acuticeps). We identified substantial remodeling of the hematopoietic programs in the icefish through which erythropoiesis is selectively suppressed. Experimental verification showed that erythropoietic suppression in the icefish may be attributable to the upregulation of TGF-ß signaling, which coincides with reductions in multiple transcription factors essential for erythropoiesis and the upregulation of hundreds of microRNAs, the majority (> 80%) of which potentially target erythropoiesis regulating factors. Overall design: Comparative transcriptome studies on 9 samples (hematopoietic tissues of three notothenioids fish)