Characterization of zebrafish gcsfr. (A) Analysis of the zebrafish gcsfr gene locus. Schematic representation of human (hs) GCSFR and zebrafish (dr) gcsfr genes: showing conserved transcription factor binding sites for HOXA5 (black ovals), SPI1 (black hexagons), and members of the C/EBP family (black rectangles) within the promoter region (dashed line) upstream of the 5′UTR (black line). The domain structure of the encoded protein is superimposed onto the respective splicing pattern: leader sequence (white triangle), Ig-like domain (oval), CHD (round rectangle), with thin lines indicating cysteines and thick lines indicating WSXWS motif, FBN-like domains (hexagons), transmembrane domain (black rectangle), and intracellular domain (white rectangle), containing boxes 1, 2, and 3 (gray rectangles). Splice sites are shown as vertical gray dashed lines, with exons numbered, whereas splice site–targeted morpholinos are indicated by striped black lines and labeled black triangles. (B) Alignment of human (hs), mouse (mm), and zebrafish (dr) GCSFR intracellular domains. Identical (*), strongly conserved (:), and weakly conserved (.) residues are displayed. Conserved motifs are indicated: Transmembrane (dotted line), Boxes 1, 2, and 3 (black lines), mammalian intracellular tyrosines (black squares labeled with human residue numbers), and zebrafish intracellular tyrosines (gray circles). (C-N) Expression of zebrafish gcsfr during development. Whole-mount in situ hybridization of staged wild-type embryos with sense (C) or antisense (D-N) gcsfr probes at the times indicated. (O-Q) Role of spi1 in regulation of gcsfr-expressing cells. Embryos injected with scramMo (O,R,T) or spi1Mo (P,S,U) were probed with antisense gcsfr (O,P) and positive cells enumerated (Q; dashed red line indicates mean; red lines, 95% confidence interval; **P < .01 level of statistical significance), or with antisense gata1 (R,S), or stained with O-dianisidine (T,U).