Zebrafish bloodthirsty: Developmental expression and identification of the mammalian ortholog.

摘要

Blood disorders, such as anemias, are serious diseases in humans. Because the hematopoietic program is highly conserved among vertebrates, we are using fish models to isolate novel erythropoietic genes and to elucidate the functions of the encoded proteins. In this thesis, I describe experiments to examine the developmental expression patterns of the novel zebrafish gene, bloodthirsty (bty), and to identify its probable mammalian ortholog.;The novel gene bloodthirsty (bty) was discovered in a subtractive screen that isolated hematopoietic genes that were differentially expressed by the pronephric kidneys of the red-blood Antarctic rockcod, Notothenia coriiceps, and its white-blood relative, the icefish Chaenocephalus aceratus. Zebrafish bty encodes a 532 residue protein (Bloodthirsty, Bty) that belongs to the TRIM (TRIpartite Motif) protein family. Bty contains an N-terminal RING finger, two B-boxes, a coiled-coil region and a C-terminal B30.2 domain. Suppression of translation of the bty mRNA by morpholino oligonucleotide (MO) treatment suggests that Bty is involved in regulation of the terminal steps of the erythropoietic program.;Although bty plays a role in erythropoiesis, it is widely expressed during zebrafish embryogenesis. bty mRNA is expressed in multiple tissues including gut, brain, spinal cord, etc. In contrast, it is not expressed in somites, white matter or matured erythrocytes.;Bioinformatic analysis suggested two candidates for the mammalian ortholog of zebrafish Bty: TRIM27/ret finger protein (33% identity) and TRIM39 (32% identity). To identify the probable ortholog, TRIM27 and TRIM39 mRNAs were tested for their ability to rescue erythropoiesis in zebrafish bty morphant embryos. My results demonstrate that TRIM27 mRNA is able to restore erythropoiesis, whereas TRIM39 mRNA does not, thereby providing strong evidence that the former corresponds to zebrafish bty.;My research advances our understanding of vertebrate erythropoiesis, and therefore may provide new avenues for therapeutic intervention in human diseases of the red blood cell.