miR-430 microRNA Family in Fishes: Molecular Characterization and Evolution

SIMPLE SUMMARY: MicroRNAs regulate gene expression and, in particular, the miR-430 family plays an important role in the early development of fishes. In this study we have observed that this family appeared early in the evolution of fishes and all the studied species have multiple copies of miR-430. In some fishes that diverged early on, we have found three different versions of miR-430, yet as fishes evolved over time, some groups seem to have lost some of these versions. These findings could lead to more studies on the different functions of these versions, which could be preserved in farmed species. This knowledge could help improve aquaculture methods. ABSTRACT: The miR-430 microRNA family has been described in multiple fish species as one of the first microRNAs expressed by the zygote. It has been suggested that this family is implicated in maternal mRNA elimination, but may also play a role in steroidogenesis, sexual differentiation, and flatfish metamorphosis. The miR-430 sequences have been found in multiple-copy tandem clusters but evidence of their conservation outside of teleost fishes is scarce. In the present study, we have characterized the tandem repeats organization of these microRNAs in different fish species, both model and of interest in aquaculture. A phylogenetic analysis of this family has allowed us to identify that the miR-430 duplication, which took place before the Chondrostei and Neopterygii groups’ divergence, has resulted in three variants (“a”, “b”, and “c”). According to our data, variant “b” is the most closely related to the ancestral sequence. Furthermore, we have detected isolated instances of the miR-430 repeat subunit in some species, which suggests that this microRNA family may be affected by DNA rearrangements. This study provides new data about the abundance, variability, and organization of the miR-430 family in fishes.