MIR-9 OVEREXPRESSION ON TRANSCRIPTOME LEVEL IN FERTILIZED EGGS OF MONOPTERUS ALBUS

During fish sexual differentiation, microRNA (miRNA) plays an important regulatory role in the germ cells development. Previous studies showed that miR-9 might promote spermatogenesis during the natural sex reversal in the rice field eel (Monopterus albus). In this study, we cloned the precursor sequence of miR-9 and overexpressed miR-9 in the fertilized eggs of rice field eel. Finally, we screened 157 genes to be associated with miR-9 overexpression after RNA-seq. Relaxin signaling pathway (ko04926) was one of the significantly enriched KEGG term. The expression of tekt4, adcy2a, k1c13 and rdh5 was up-regulated after overexpressed miR-9; the expression of fgf13b and trhr2 was down-regulated after overexpressed miR-9 in the fertilized eggs of rice field eel. The retinol dehydrogenase 5 (rdh5) had the highest expression level in the eyes of rice field eel (P<0.01), whereas almost no expression in the brain, blood, testis and ovaries (P<0.01). The relaxin family genes, rln3a and rln3b, had similar tissue expression patterns in rice field eel, both with high expression levels in the brain and testis. We speculated that miR-9 might be associated with the development or maintenance of visual function in rice field eel; miR-9 may regulate the testis developmental of rice field eel through the relaxin signaling pathway. This study is helpful to further analyze regulation pathway of miR-9 on genes related to endocrine system, and provides theoretical evidence for sexual differentiation in the rice field eel.