Abnormal expression of miR-1388-5p and its target spindlin-1 in female triploid rainbow trout (Oncorhynchus mykiss)

Abstract

Triploid rainbow trout (Oncorhynchus mykiss) raised increasing concern on the commercial farming due to its prominent advantages, such as improved growth performance and efficiency of feed utilization. It typically shows impaired ovary development and is relatively sterile. Spindlin-1 (Spin-1) plays vital roles in hormone regulation, gametogenesis, and oocyte meiotic resumption in almost all vertebrates. miRNAs, small non-coding RNAs, have emerged as major regulators of gene expression in vertebrates by modulating target genes. In the present study, eight adult females of diploid and triploid rainbow trout maintained in the same conditions were included. miR-1388-5p was predicted to target the annotated 3′-UTR of Spin-1 specifically by online miRNA target prediction database: “MicroTrout”. Spin-1 mRNA was downregulated, and in contrast, miR-1388-5p was significantly elevated in the ovary of triploid rainbow trout by quantitative PCR (P < 0.01). Pearson's correlation indicated that the expression of Spin-1 was inversely correlated with that of miR-1388-5p both in diploid and triploid females. Then, Spin-1 was validated to be directly targeted and downregulated by miR-1388-5p by luciferase assay (P < 0.01). E2 injection elevated Spin-1 while suppressed miR-1388-5p expression, while the concentration of estradiol in diploid serum is relatively higher than that in triploid serum by ELISA (P < 0.05). The results showed that estrogen regulation can stimulate the expression of Spin-1 by inhibiting the expression of miR-1388-5p. The present evidence provide new insight into the mechanism underlying the impaired ovary development of triploid fish from a new perspective.