Project description:Neurons and endothelial cells were identified by immunohistochemistry in human brains, isolated by laser-capture-microdissection and used to find genes preferentially expressed in the two cell types. Keywords: cell type comparison Laser capture microdissection was used to isolate approximately 1000 neurons and endothelial cells from 6 (for neurons) and 7 (for endothelial cells) human post mortem brain samples. RNA was isolated and amplified (3 linear amplifications) and genome wide expression was measured. This allowed the identification of genes that are differentially expressed between neurons and endothelial cells in the human brain.
Project description:Neurons and endothelial cells were identified by immunohistochemistry in human brains, isolated by laser-capture-microdissection and used to find genes preferentially expressed in the two cell types. Keywords: cell type comparison
Project description:LEUTX is a homeodomain transcription factor expressed in the very early embryo with a function around embryonic genome activation. The LEUTX gene is found only in eutherian mammals, including humans, but unlike the majority of homeobox genes, the encoded amino acid sequence is very different between divergent mammalian species. However, whether dynamic evolution has also occurred between closely related mammalian species remains unclear. In this work, we perform a comparative genomics study of LEUTX within the primates, revealing dramatic evolutionary sequence change between closely related species. Positive selection has acted on sites in the LEUTX protein, including six sites within the homeodomain; this suggests that selection may have driven changes in the set of downstream targets. Transfection into cell culture followed by transcriptomic analysis reveals small functional differences between human and marmoset LEUTX, suggesting rapid sequence evolution has fine-tuned the role of this homeodomain protein within the primates.
Project description:Complex multicellular organisms have evolved numerous cell types with many different functions. Comparative transcriptomic data yields valuable insights into cell type, tissue, and organ evolution. However, interpreting this data requires understanding how transcriptomes evolve. A particularly difficult problem is that cell type transcriptomes may not evolve independently, a key assumption of most evolutionary analyses. Non-independence of cell types can occur when cell types share regulatory mechanisms. This leads to concerted evolution in gene expression across different cell types, confounding efforts to unravel the history of cell type evolution, and identify cell type-specific patterns of expression. Here we present a statistical model to estimate the level of concerted transcriptome evolution and apply it to published and new data. The results indicate that tissues undergo pervasive concerted evolution in gene expression. Tissues related by morphology or developmental lineage exhibit higher levels of concerted evolution. Concerted evolution also causes tissues from the same species to be more similar in gene expression to each other than to homologous tissues in another species. This result may explain why some tissue transcriptomes cluster by species rather than homology. Our analysis of bird skin appendages data suggests levels of concerted evolution also varies with phylogenetic age of the tissue. Our study illustrates the importance of accounting for concerted evolution when interpreting comparative transcriptome data, and should serve as a foundation for future investigations of cell type evolution.
Project description:Phenotypic differences within populations and between closely related species are often driven by variation and evolution of gene expression. However, most analyses have focused on the effects of genomic variation at cis-regulatory elements such as promoters and enhancers that control transcriptional activity, and little is understood about the influence of post-transcriptional processes on transcript evolution. Post-transcriptional modification of RNA by N6-methyladenosine (m6A) has been shown to be widespread throughout the transcriptome, and this reversible mark can affect transcript stability and translation dynamics. Here we analyze m6A mRNA modifications in lymphoblastoid cell lines (LCLs) from human, chimpanzee and rhesus, and we identify patterns of m6A evolution among species. We find that m6A evolution occurs in parallel with evolution of consensus RNA sequence motifs known to be associated with the enzymatic complexes that regulate m6A dynamics, and expression evolution of m6A-modified genes occurs in a parallel evolutionary pattern with m6A evolution. Further, genes modified by evolved m6A in humans are significantly enriched in transcriptional regulatory processes and disease related pathways, suggesting an important role in human biology for the evolution of m6A modification.