Evolution of the miR-290-295/miR-371-373 cluster family seed repertoire

Expression of the mouse miR-290-295 cluster and its miR-371-373 homolog in human is restricted to early embryos, primordial germ cells, the germ line stem cell compartment of the adult testis and to stem cell lines derived from the early embryonic lineages. Sequencing data suggest considerable seed diversification between the seven homologous pre-miRNAs of miR-290-295 but it is not clear if all of the implied miR-290-295 seeds are also conserved in the human miR-371-373 cluster, which consists of only three homologous pre-miRNAs. By employing miRNA target reporters we show that most, if not all, seeds in miR-290-295 are represented in miR-371-373. In the mouse, pre-miR-290, pre-miR-292 and pre-miR-293 express subsets of the miRNA isoforms processed from the single human pre-miR-371. Comparison of the possible miR-290-295/miR-371-373 seed repertoires in placental mammals suggests a model for the evolution of this miRNA cluster family, which would be otherwise difficult to deduce based solely on pre-miRNA sequence comparisons. The conservation of co-expressed seeds that is characteristic of miR-290-295/miR-371-373 should be taken into account in models of the corresponding miRNA-target interaction networks.