Knockout of hsd3b1 leads to disrupted steroid hormone homeostasis and compromised gonadal development in zebrafish

Steroid hormones play crucial roles in gonadal development, and defects in steroid synthesis can lead to various metabolic diseases and reproductive disorders. Among these, 3β-hydroxysteroid dehydrogenase (3β-HSD), encoded by <i>HSD3B</i> gene, catalyzes the conversion of inactive Δ⁵-3β-hydroxysteroid precursors to active Δ⁴-ketosteroids, representing a critical step in steroidogenesis. In this study, we successfully generated the <i>hsd3b1</i> mutant zebrafish using CRISPR/Cas9, and the mutant zebrafish display abnormal gonadal development, interrenal hyperplasia, hyperpigmentation and reduced reproductive capacity. RNA sequencing and targeted metabolomic analysis of steroid hormones revealed that steroid hormone homeostasis was disrupted in <i>hsd3b1</i> mutants, characterized by reduced metabolic differences between males and females. These findings indicate that <i>hsd3b1</i> is essential for gonadal development and steroid hormone regulation in zebrafish. The <i>hsd3b1</i> mutant provides a robust model for investigating the mechanisms linking steroidogenesis to reproductive development in vertebrates.