ABSTRACT
Mir-290 through mir-295 (mir-290-295) is a mammalian-specific microRNA (miRNA) cluster that, in mice, is expressed specifically in early embryos and embryonic germ cells. Here, we show that mir-290-295 plays important roles in embryonic development as indicated by the partially penetrant lethality of mutant embryos. In addition, we show that in surviving mir-290-295-deficient embryos, female but not male fertility is compromised. This impairment in fertility arises from a defect in migrating primordial germ cells and occurs equally in male and female mutant animals. Male mir-290-295(-/-) mice, due to the extended proliferative lifespan of their germ cells, are able to recover from this initial germ cell loss and are fertile. Female mir-290-295(-/-) mice are unable to recover and are sterile, due to premature ovarian failure.
Subject(s)
Embryo Loss/genetics , Embryo Loss/pathology , Germ Cells/metabolism , Germ Cells/pathology , MicroRNAs/metabolism , Penetrance , Aging/pathology , Animals , Animals, Newborn , Apoptosis , Cell Count , Cell Cycle , Embryo, Mammalian/metabolism , Embryo, Mammalian/pathology , Female , Fertility/genetics , Gene Expression Regulation, Developmental , Gonads/growth & development , Gonads/pathology , Infertility, Female/genetics , Infertility, Female/pathology , Male , Mice , Mice, Mutant Strains , MicroRNAs/geneticsABSTRACT
We have identified microRNAs (miRNAs) in undifferentiated and differentiated mouse embryonic stem (ES) cells. Some of these appear to be ES cell specific, have related sequences, and are encoded by genomic loci clustered within 2.2 kb of each other. Their expression is repressed as ES cells differentiate into embryoid bodies and is undetectable in adult mouse organs. In contrast, the levels of many previously described miRNAs remain constant or increase upon differentiation. Our results suggest that miRNAs may have a role in the maintenance of the pluripotent cell state and in the regulation of early mammalian development.
Subject(s)
MicroRNAs/metabolism , Stem Cells/physiology , Animals , Base Sequence , Biomarkers , Cell Differentiation/physiology , Databases, Nucleic Acid , Integrin alpha6/genetics , Integrin alpha6/metabolism , Mice , MicroRNAs/genetics , Molecular Sequence Data , Nucleic Acid Conformation , Sequence AlignmentABSTRACT
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.
Subject(s)
Evolution, Molecular , MicroRNAs/genetics , Multigene Family , RNA Precursors/genetics , Animals , Base Sequence , Embryo, Mammalian , Embryonic Stem Cells/cytology , Embryonic Stem Cells/metabolism , Germ Cells/cytology , Germ Cells/metabolism , Humans , Male , Mice , MicroRNAs/metabolism , Molecular Sequence Data , Nucleic Acid Conformation , Phylogeny , RNA Precursors/metabolism , Sequence Homology, Nucleic AcidABSTRACT
Mouse microRNAs (miRNAs) miR-290-miR295 are encoded by a cluster of partially homologous pre-miRNA hairpins and are likely to be functionally important in embryonic stem (ES) cells and preimplantation embryos. We present evidence that a spliced, capped, and polyadenylated primary transcript spans this entire Early Embryonic microRNA Cluster (EEmiRC). Partial Drosha processing yields additional large nuclear RNA intermediates. A conserved promoter element containing a TATA-box directs EEmiRC transcription. Sequence analysis shows that the EEmiRC transcription unit is remarkably variable and can only be identified bioinformatically in placental (eutherian) mammals. Consistent with eutherian-specific function, EEmiRC is expressed in trophoblastic stem (TS) cells. When analyzing evolutionary and functional relationships, the organization of the entire miRNA loci should be considered in addition to the mature miRNA sequences. Application of this concept suggests that EEmiRC is a recently acquired rapidly evolving gene important for eutherian development.