Sex-inclined microRNAs in serum exosomes for sex determination in the greater amberjack (Seriola dumerili)

The greater amberjack (Seriola dumerili) does not exhibit apparent sexual dimorphism in appearance, which makes it difficult to determinate its sex. MicroRNAs (miRNAs) can modulate the expression levels of targets through RNA silencing and post-transcriptional regulation and participate in various reproduction processes. Exosomal miRNAs can be signatures for the sex determination in fish. This study identified three miRNAs (abu-miR-30b, dre-miR-223, and dre-miR-133b-3p) that were significantly highly expressed in four tissues (serum exosomes, hypothalamus, pituitary, and gonad) in males compared to females, in line with the sequencing results of serum exosomes. Three miRNAs (abu-miR-30b, dre-miR-223, and dre-miR-133b-3p) could be used as signatures to detect the sex of greater amberjack with their expression levels in serum exosomes, providing an accurate and effective method. Furthermore, dre-miR-133b-3p could regulate the expression of its target gene (WW domain binding protein 2, wbp2). The negative regulation of dre-miR-133b-3p on wbp2 may modulate the gonadal development of greater amberjack. This study not only offers an effective method of sex determination in greater amberjack but also helps to understand the effect of sex-inclined miRNAs and their sex-related targets on gonad development within this species.