Characterization of Maskin Isoforms in Atlantic Salmon, a Candidate Gene Associated to Sexual Maturation

In most metazoan, oocytes differentiate from primordial germ cells (PGCs) that arise at a distant site and migrate to the somatic gonad. Oocytes enter meiosis; but become arrested at the prophase of the first meiotic division. During this stage, oocyte maturation is regulated by suppression of transcription and by a complex network of translational activation and repression that regulate gene expression of maternally derived mRNA. In Xenopus, maskin plays a crucial rol preventing oocyte maturation and the translation of the CPE-containing cyclin B1 mRNA by blocking the association of eIF4G with eIF4E. In a recent GWA study we identified many SNPs in significant association with late maturation in Atlantic salmon. One of them was located on a maskin gene, specifically on the 3’UTR region which is shared between many Atlantic salmon isoforms. Further investigating the importance of this gene, we identified 2 new maskin isoforms by RACE, present in Atlantic salmon gonads. One of these isoforms showed a higher expression in ovaries compared to other tissues. In addition, numerous SNPs were identified from sequencing of the genomic regions harbouring the newly identified maskin isoform. These newly identified SNPs still need intensive testing on fish maturing at different ages; nevertheless, they provide evidence of polymorphism in the genomic region encoding maskin in Atlantic salmon.