Sammendrag
In aquaculture conditions, Atlantic cod (Gadus morhua L.) mature a few months before reaching the desired market size. This results in serious economic losses that make the industry unsustainable at present. In order to minimize the negative impact of precocious sexual maturation on growth performance, there is a need to improve our fundamental knowledge about the molecular mechanisms involved in gonadal development. MicroRNAs (miRNAs) are short non-coding RNA molecules that down-regulate expression of target mRNAs at the post-transcriptional level by binding to their 3′ untranslated regions. In spite of their importance in numerous biological processes in vertebrates, the role of miRNAs in gonadal maturation has not been investigated in fish.
Using massively parallel next-generation SOLiD sequencing, we have examined the miRNA profiles between oocytes at a perinuclear developmental stage in immature female gonads and oocytes during vitellogenesis in mature ovaries. After trimming and filtering the raw sequencing data, a total of 229,359 reads were mapped to the zebrafish genome. In a preliminary screen for known miRNAs on miRBase, we have identified 60 (16,747 reads) and 47 (2,386 reads) miRNAs from mature and immature ovaries, respectively. It was apparent that miRNAs are more abundant in mature gonads and several known miRNAs and corresponding miRNA* were found to be differentially expressed between the two samples. In particular, the cod homologue of zebrafish mir203b*, whose function is currently unknown, was found only in mature ovaries and corresponded to a large proportion of the total number of mapped reads (Fig. 1).
Our data shows that miRNA profiles depend markedly on the maturation status of the ovaries. Knowledge of miRNAs involved in gonadal maturation will help us understanding the genetic networks underlying this process and will be most useful to control precocious sexual maturation, which is one of the major bottlenecks affecting the cod farming industry.
Acknowledgement: This work was financed by a Research Council of Norway grant to J.M.O. Fernandes (ref. 190350).
Vis fullstendig beskrivelse