Evolution of mammalian miRNA genes
Ontology highlight
ABSTRACT:
ORGANISM(S): Didelphis virginiana Mus musculus Gallus gallus Homo sapiens Macaca mulatta Monodelphis domestica Ornithorhynchus anatinus
PROVIDER: GSE40499 | GEO | 2012/10/01
SECONDARY ACCESSION(S): PRJNA174234
REPOSITORIES: GEO
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Project description:MicroRNAs (miRNAs) are major post-transcriptional regulators of gene expression, yet their origins and functional evolution in mammals remain little understood due to the lack of appropriate comparative data. Using RNA sequencing, we have generated extensive and comparable miRNA data for five organs in six species that represent all main mammalian lineages and birds (the evolutionary outgroup), with the aim to unravel the evolution of mammalian miRNAs. Our analyses reveal an overall expansion of miRNA repertoires in mammals, with three-fold accelerated birth rates of miRNA families in placentals and marsupials, facilitated by the de novo emergence of miRNAs in host gene introns. Generally, our analyses suggest a high rate of miRNA family turnover in mammals, with many newly emerged miRNA families being lost soon after their formation. Selectively preserved mammalian miRNA families gradually evolved higher expression levels as well as altered mature sequences and target gene repertoires, and were apparently mainly recruited to exert regulatory functions in nervous tissues. However, miRNAs that originated on the X chromosome evolved high expression levels and potentially diverse functions during spermatogenesis, including meiosis, through selectively driven duplication-divergence processes. Overall, our study thus provides detailed insights into the birth and evolution of mammalian miRNA genes and the associated selective forces. 30 main samples from five adult tissues (brain, cerebellum, heart, kidney and testis) collected in six species (human, macaque, mouse, opossum, platypus and chicken) + 5 biological replicates + 3 samples from spermatogenic cells in adult mouse testis (Sertoli cells, spermatocytes and spermatids)
2012-10-01 | E-GEOD-40499 | biostudies-arrayexpress
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Project description:A major challenge in biology is to determine how evolutionarily novel characters originate, however, mechanistic explanations for the origin of novelties are almost completely unknown. The evolution of mammalian pregnancy is an excellent system in which to study the origin of novelties because extant mammals preserve major stages in the transition from egg-laying to live-birth. To determine the molecular bases of this transition, we characterized the pregnant/gravid uterine transcriptome from tetrapods, including species in the three major mammalian lineages, and used ancestral transcriptome reconstruction to trace the evolutionary history of uterine gene expression. We show that thousands of genes evolved or lost uterine expression during the origins of mammalian pregnancy, including the loss of genes responsible for the mineralization of the eggshell in the Mammalian and Therian stem-lineages, and the recruitment of genes into uterine expression that mediate maternal-fetal communication and maternal immunotolerance of the fetal allograft in the Therian and Eutherian stem-lineages. Our results indicate that one of the defining mammalian novelties evolved through a step-wise process that dramatically changed uterine gene expression, generating a suite of evolutionary innovations that support prolonged gestations. We report genome-wide gene expression generated by mRNA-Seq from the pregnant endometrium of dog, armadillo, and the platypus.
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Project description:New genes contribute substantially to adaptive evolutionary innovation, but the functional evolution of new mammalian genes has been little explored at a broad scale. Previous work established mRNA-derived gene duplicates, known as retrocopies, as useful models for the study of new gene origination. Here we combine extensive mammalian transcriptomic and epigenomic data to unveil the processes underlying the evolution of stripped-down retrocopies into complex new genes. We show that although some robustly expressed retrocopies are transcribed from preexisting promoters, the majority evolved new promoters from scratch or recruited proto-promoters in their genomic vicinity. In particular, many retrocopy promoters emerged from ancestral enhancers or bivalent regulatory elements, as well as from CpG islands not associated to other genes. Altogether, these mechanisms facilitated the birth of up to 280 retrogenes in each therian species. Furthermore, the regulatory evolution of the originally monoexonic retrocopies was frequently accompanied by exon gain, which facilitated the cooption of distant promoters and in many cases allowed the expression of alternative isoforms. While young retrogenes are often initially expressed in the testis, increased regulatory and structural complexities allowed retrogenes to functionally diversify and evolve somatic organ functions, sometimes as complex as those of their parents. Thus, some retrogenes evolved the capacity to temporarily substitute their parents during the process of male (meiotic) X inactivation, while others even rendered parental functions completely superfluous, allowing for parental gene loss. Overall, our reconstruction of the complete â??life historyâ?? of mammalian retrogenes highlights the usefulness of retroposition as a general model for understanding new gene birth and functional evolution. Assembly and expression of vertebrate retrogene transcripts
2015-12-16 | E-GEOD-72236 | biostudies-arrayexpress
Project description:A major challenge in biology is to determine how evolutionarily novel characters originate, however, mechanistic explanations for the origin of novelties are almost completely unknown. The evolution of mammalian pregnancy is an excellent system in which to study the origin of novelties because extant mammals preserve major stages in the transition from egg-laying to live-birth. To determine the molecular bases of this transition, we characterized the pregnant/gravid uterine transcriptome from tetrapods, including species in the three major mammalian lineages, and used ancestral transcriptome reconstruction to trace the evolutionary history of uterine gene expression. We show that thousands of genes evolved or lost uterine expression during the origins of mammalian pregnancy, including the loss of genes responsible for the mineralization of the eggshell in the Mammalian and Therian stem-lineages, and the recruitment of genes into uterine expression that mediate maternal-fetal communication and maternal immunotolerance of the fetal allograft in the Therian and Eutherian stem-lineages. Our results indicate that one of the defining mammalian novelties evolved through a step-wise process that dramatically changed uterine gene expression, generating a suite of evolutionary innovations that support prolonged gestations.
2015-01-30 | GSE57714 | GEO
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