Gcsfa and Gcsfb are paralogous genes that arose from a gene duplication event early in teleost evolution. (A) Synteny analysis of Gcsf ligands across species. Data from chicken, green spotted pufferfish, and fugu are adapted from Santos et al.¹²  (B) Alignment of human, mouse, and zebrafish Gcsfa and Gcsfb with Clustal Omega (EMBL-European Bioinformatics Institute). Predicted α-helical regions are underlined, modeled on the structure of human GCSF. (C) Proposed structure of Gcsfa and Gcsfb, modeled on the structure of human GCSF; α-helical regions of Gcsfa and Gcsfb are underlined in panel B.