Zebrafish nephrosin helps host defence against infection.

Neutrophils play important roles in innate immunity and are mainly dependent on various enzyme-containing granules to kill engulfed microorganisms. Zebrafish () is specifically expressed in neutrophils; however, its function is largely unknown. Here, we generated an mutant ( ) via CRISPR/Cas9 to investigate the function of Npsn. The overall development and number of neutrophils remained unchanged in -deficient mutants, whereas neutrophil antibacterial function was defective. Upon infection with , the mutants exhibited a lower survival rate and more severe bacterial burden, as well as augmented inflammatory response to challenge with infection when compared with wild-type embryos, whereas -overexpressing zebrafish exhibited enhanced host defence against infection. These findings demonstrated that zebrafish Npsn promotes host defence against bacterial infection. Furthermore, our findings suggested that -deficient and -overexpressing zebrafish might serve as effective models of innate immunity.