Cloning and characterization of zebrafish epidermal growth factor receptor (EGFR) family member, ErbB4

The EGFR family (ErbB1‐4) and their activating ligands regulate the development of numerous vertebrate cells and tissues. Previous studies in mammals suggest that redundant receptor signaling characterizes development of multipotent progenitor cells, while receptor‐specific signaling regulates subsequent lineage progression. These results are implied indirectly by mammalian studies in which technical difficulties limit manipulation of more than one gene at a time in vivo. The zebrafish model system allows more direct examination by down regulation of several genes simultaneously. To begin studies in zebrafish, we cloned zebrafish ErbB4 (zErbB4). We identified zErbB4 in zebrafish genomic contigs by similarity to rat ErbB4. We then cloned the zErbB4 cDNA from zebrafish kidney mRNA using RT‐PCR and 5′ RACE. A TATA box was located 25 bp upstream of the start ATG. zErbB4 was 70% identical to rat and human ErbB4. Amino acid identity in extracellular, tyrosine kinase, and intracellular domains were 91%, 92%, and 23%, respectively. The location and timing of ErbB4 expression in zebrafish embryos was determined by in situ hybridization. Specific labeling was apparent in the head and viscera 10 hours post fertilization (hpf) and 4 days (d)pf. Tissue distribution was similar to that in mammals with strong labeling of heart, brain, and GI tract by 4 dpf. These studies demonstrate the early embryonic expression of ErbB4, similar sequence and tissue distribution as in mammals, and are consistent with a role for zErbB4 in epithelial, heart, and CNS development. Wadsworth Foundation, Case Aces/NSF Advance, DK56218.