Characterization of emopamil binding protein (Cs-ebp) reveals its potential role in cholesterol biosynthesis and growth performance of Chinese tongue sole

Sexual size dimorphism (SSD) in Chinese tongue sole affects its annual yields and consequently hinders its sustainable aquaculture development. Females show faster growth rate than male from 6 month post hatch (m). Comparative transcriptome analysis suggested cholesterol biosynthesis as an important signaling pathway involved in Chinese tongue sole SSD. Emopamil-binding protein (EBP), identified as one of the differential expressed genes in females, is the key catalyzing enzyme in the final steps of cholesterol biosynthesis. In this study, Chinese tongue sole ebp (Cs-ebp) gene was characterized and its potential role in cholesterol biosynthesis and growth performance was assessed. Cs-ebp showed significant abundance in female ovaries and livers. Meanwhile, it was highly expressed in 6 m female ovaries compared to other developmental stages. Promoter analysis revealed that transcriptional factors JUNB (a subunit of the activating protein-1 transcription factor complex) and POU1F1 alpha (Pou-homeodomain transcription factor) could promote Cs-ebp transcription. Cs-ebp gene knockdown triggered the down-regulation of its downstream genes in cholesterol biosynthesis pathway (sc5d, dhcr7, and dhcr24), and genes related to estrogen biosynthesis (cyp19a1a) and body growth (akt1 and bmp2b). All the results revealed that there might be crosstalk among Cs-ebp, PI3K/Akt, TGF-beta/Bmp, and estrogen biosynthesis, eventually affected the growth performance of female Chinese tongue sole. Further investigation would provide us detailed information about the molecular mechanism beneath teleost SSD.