Pomc knockout increases growth in zebrafish

Abstract

Genome editing is a promising tool to accelerate the genetic improvement of important traits if the causative genes are known. In aquaculture, only a few causative genes for traits are known and used in genome editing. The pro-opiomelanocortin (pomc) gene is important for regulation of feeding behaviour, sexual dimorphism, growth, and pigmentation. However, it is unknown whether the knockout of this gene will have any adverse effects on other aquaculture production traits. In this study, pomc knockout zebrafish were employed to study the effects of pomc-knockout on survival, growth, feed conversion ratio (FCR), histology of tissues, and liver, as well as expression of genes related to fatty acid and cholesterol synthesis. Pomc−/− zebrafish increased body weight and decreased FCR when compared to WT and pomc+/− zebrafish. The histological analysis revealed that more skeletal muscle was produced in pomc-knockout zebrafish without observable obesity. Knockout of pomc had no effect on the histology of the brain and liver, as well as the survival rate. Expression of genes related to fatty acid and cholesterol synthesis suggests that pomc mutants reduce cholesterol level. These results indicate that pomc knockout increases growth performance and reduces FCR without side effects on other important traits in aquaculture. Therefore, pomc is a valuable gene for genetic modification using the Crispr/Cas9 system to improve growth and reduce FCR in aquaculture species.