Deficiency of promotes somatic growth in zebrafish: Involvement of the growth hormone system.

Purpose: Liver-expressed antimicrobial peptide-2 (LEAP2) is identified as an endogenous antagonist and inverse agonist of the growth hormone secretagogue receptor type 1a (GHSR1a), its effect on the GHSR1a is contrary to the role of GHRELIN. Growth hormone (GH) is a crucial hormone for early development. Previous studies report that LEAP2 dose-dependently attenuates ghrelin-induced GH secretion, and Leap2-knockout mice exhibit increased plasma GH levels after GHRELIN administration. Clinical data revealed a possible correlation between LEAP2 and height development. However, the role of LEAP2 in early development remains unclear. This study aimed to investigate the role of LEAP2 in early development using mutant zebrafish larvae as a model.

Method: We analyzed the conservation of LEAP2 peptide across multiple species and generated 2 mutants in zebrafish by CRISPR-Cas9, dynamically observed and measured the growth and development of zebrafish larvae from fertilization to 5 day post fertilization (dpf). In situ hybridization, transcriptome sequencing, quantitative real-time PCR and Western blot were used to detect the expression levels of GH and its signaling in early stage of embryonic development.

Result: Our data demonstrate that zebrafish with a knockout of the gene display a significant increase in hatching rate, body length, and the distance between their eyes, all without visible developmental defects in the early stages of development. In addition, both RNA and protein analyses revealed a significant increase in GH expression in mutant.

Conclusion: In general, this study demonstrates that LEAP2 regulates the expression of GH during early development, particularly influencing body length.