Project description:As the evolution of miRNA genes has been found to be one of the important factors in formation of the modern type of man, we performed a comparative analysis of the evolution of miRNA genes in two archaic hominines, Homo sapiens neanderthalensis and Homo sapiens denisova, and elucidated the expression of their target mRNAs in bain.A comparative analysis of the genomes of primates, including species in the genus Homo, identified a group of miRNA genes having fixed substitutions with important implications for the evolution of Homo sapiens neanderthalensis and Homo sapiens denisova. The mRNAs targeted by miRNAs with mutations specific for Homo sapiens denisova exhibited enhanced expression during postnatal brain development in modern humans. By contrast, the expression of mRNAs targeted by miRNAs bearing variations specific for Homo sapiens neanderthalensis was shown to be enhanced in prenatal brain development.Our results highlight the importance of changes in miRNA gene sequences in the course of Homo sapiens denisova and Homo sapiens neanderthalensis evolution. The genetic alterations of miRNAs regulating the spatiotemporal expression of multiple genes in the prenatal and postnatal brain may contribute to the progressive evolution of brain function, which is consistent with the observations of fine technical and typological properties of tools and decorative items reported from archaeological Denisovan sites. The data also suggest that differential spatial-temporal regulation of gene products promoted by the subspecies-specific mutations in the miRNA genes might have occurred in the brains of Homo sapiens denisova and Homo sapiens neanderthalensis, potentially contributing to the cultural differences between these two archaic hominines.
Project description:After a brief review of the most recent findings in the study of human evolution, an extensive comparison of the complete genomes of our nearest relative, the chimpanzee (Pan troglodytes), of extant Homo sapiens, archaic Homo neanderthalensis and the Denisova specimen were made. The focus was on non-synonymous mutations, which consequently had an impact on protein levels and these changes were classified according to degree of effect. A total of 10,447 non-synonymous substitutions were found in which the derived allele is fixed or nearly fixed in humans as compared to chimpanzee. Their most frequent location was on chromosome 21. Their presence was then searched in the two archaic genomes. Mutations in 381 genes would imply radical amino acid changes, with a fraction of these related to olfaction and other important physiological processes. Eight new alleles were identified in the Neanderthal and/or Denisova genetic pools. Four others, possibly affecting cognition, occured both in the sapiens and two other archaic genomes. The selective sweep that gave rise to Homo sapiens could, therefore, have initiated before the modern/archaic human divergence.
Project description:We have sequenced miRNA libraries from human embryonic, neural and foetal mesenchymal stem cells. We report that the majority of miRNA genes encode mature isomers that vary in size by one or more bases at the 3’ and/or 5’ end of the miRNA. Northern blotting for individual miRNAs showed that the proportions of isomiRs expressed by a single miRNA gene often differ between cell and tissue types. IsomiRs were readily co-immunoprecipitated with Argonaute proteins in vivo and were active in luciferase assays, indicating that they are functional. Bioinformatics analysis predicts substantial differences in targeting between miRNAs with minor 5’ differences and in support of this we report that a 5’ isomiR-9-1 gained the ability to inhibit the expression of DNMT3B and NCAM2 but lost the ability to inhibit CDH1 in vitro. This result was confirmed by the use of isomiR-specific sponges. Our analysis of the miRGator database indicates that a small percentage of human miRNA genes express isomiRs as the dominant transcript in certain cell types and analysis of miRBase shows that 5’ isomiRs have replaced canonical miRNAs many times during evolution. This strongly indicates that isomiRs are of functional importance and have contributed to the evolution of miRNA genes Sequence library of miRNAs from a single sample of human foetal mesenchymal stem cells. Results tested and confirmed by northern blotting. Please note that only raw data files are available for the embryonic and neual samples and thus, directly submitted to SRA (SRX547311, SRX548700, respectively under SRP042115/PRJNA247767)