Identification and functional characterization of CD209 homologous genes in zebrafish

Innate immune responses play a crucial role in maintaining homeostasis, their initiation closely related to pattern recognition receptors or damage-associated molecules on the surface of innate immune cells. CD209, a pattern recognition receptor on the surface of macrophages or dendritic cells, plays an important role in immune functions. However, the impact of CD209 on innate immune cells such as macrophages or neutrophils in vivo remains unclear. In this study, through multiple sequence alignment and phylogenetic tree construction, three genes homologous to human CD209 were found in zebrafish. These are cd209(Ensembl ID:ENSDARG00000029461), zgc:174904(Ensembl ID:ENSDARG00000059049) and si:dkey-187I7.2(Ensembl ID: ENSDARG00000096624).Compared to the cd209 and si:dkey-187i8.2 genes in the Ensembl database, zgc:174904 is more similar to human CD209 in sequence. Using whole-mount in situ hybridization and fluorescence co-localization experiments, it was found that zgc:174904 is mainly expressed in macrophages. Further morpholino knockdown experiments showed that knocking down zgc:174904 leads to an upregulation of M1-type macrophage-related genes and a decrease in the number of mature neutrophils, indicating that zgc:174904 is functionally more similar to CD209. These findings not only reveal the potential role of CD209 in regulating macrophage function and neutrophil development but also provide significant insights for research into the mechanisms of innate immunity.