Sox21 is thought to function as a counteracting partner of SoxB1 (Sox1, 2, 3) genes and is involved in cell fate determination. In this study, we comparatively analyzed the expression patterns and conserved cis-regula...
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Sox21 is thought to function as a counteracting partner of SoxB1 (Sox1, 2, 3) genes and is involved in cell fate determination. In this study, we comparatively analyzed the expression patterns and conserved cis-regulatory elements of the duplicated sox21 genes in zebrafish. In embryogenesis, sox21b is predominantly expressed in the telencephalon, hypothalamus, mesencephalon and lens, and sox21a is solely expressed in the midbrain-hindbrain boundary, olfactory placode and lateral line, while both genes are expressed in the hindbrain, spinal cord and ear. In adult, sox21a is expressed in the brain, skin, ovary and intestine, while sox21b is expressed in the brain and testis. Interestingly, all 16 pan-vertebrate conserved non-coding elements (CNEs) are asymmetrically preserved in the sox21b locus, whereas two fish-specific elements are kept in the sox21a locus, and this is correlated with increased evolutionary rate of the sox21a protein sequence. Transient transgenic reporter analysis revealed that six sox21b CNEs and two sox21a CNEs drove green fluorescent protein (GFP) expression in tissues correlated with the partitioning of expression in two orthologues. These results indicate that sox21a and sox21b have reciprocally lost expression domains of the ancestral gene reflected by degeneration of certain CNEs in their genomic loci and provide clear evidence for evolution of the duplicated sox21 genes by subfunctionalization. In addition, our data suggest that some CNEs-based regulatory pathways have been predominantly preserved in the sox21b locus.
Uncovering the cis-regulatory logic of developmental enhancers is critical to understanding the role of non-coding DNA in development. However, it is cumbersome to identify functional motifs within enhancers, and thus...
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Uncovering the cis-regulatory logic of developmental enhancers is critical to understanding the role of non-coding DNA in development. However, it is cumbersome to identify functional motifs within enhancers, and thus few vertebrate enhancers have their core functional motifs revealed. Here we report a combined experimental and computational approach for discovering regulatory motifs in developmental enhancers. Making use of the zebrafish gene expression database, we computationally identified conserved non-coding elements (CNEs) likely to have a desired tissue-specificity based on the expression of nearby genes. Through a high throughput and robust enhancer assay, we tested the activity of similar to 100 such CNEs and efficiently uncovered developmental enhancers with desired spatial and temporal expression patterns in the zebrafish brain. Application of de novo motif prediction algorithms on a group of forebrain enhancers identified five top-ranked motifs, all of which were experimentally validated as critical for forebrain enhancer activity. These results demonstrate a systematic approach to discover important regulatory motifs in vertebrate developmental enhancers. Moreover, this dataset provides a useful resource for further dissection of vertebrate brain development and function. (C) 2009 Elsevier Inc. All rights reserved.
Natural populations of the Midas cichlid species in several different crater lakes in Nicaragua exhibit a conspicuous color polymorphism. Most individuals are dark and the remaining have a gold coloration. The color m...
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Natural populations of the Midas cichlid species in several different crater lakes in Nicaragua exhibit a conspicuous color polymorphism. Most individuals are dark and the remaining have a gold coloration. The color morphs mate assortatively and sympatric population differentiation has been shown based on neutral molecular data. We investigated the color polymorphism using segregation analysis and a candidate gene approach. The segregation patterns observed in a mapping cross between a gold and a dark individual were consistent with a single dominant gene as a cause of the gold phenotype. This suggests that a simple genetic architecture underlies some of the speciation events in the Midas cichlids. We compared the expression levels of several candidate color genes Mc1r, Ednrb1, Slc45a2, and Tfap1a between the color morphs. Mc1r was found to be up regulated in the gold morph. Given its widespread association in color evolution and role on melanin synthesis, the Mc1r locus was further investigated using sequences derived from a genomic library. Comparative analysis revealed conserved synteny in relation to the majority of teleosts and highlighted several previously unidentified conserved non-coding elements (CNEs) in the upstream and downstream regions in the vicinity of Mc1r. The identification of the CNEs regions allowed the comparison of sequences from gold and dark specimens of natural populations. No polymorphisms were found between in the population sample and Mc1r showed no linkage to the gold phenotype in the mapping cross, demonstrating that it is not causally related to the color polymorphism in the Midas cichlid.
Discovery of a large number of conserved non-coding elements (CNEs) in vertebrate genomes provides a cornerstone to elucidate molecular mechanisms of macroevolution. Extensive comparative genomics has proven that tran...
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Discovery of a large number of conserved non-coding elements (CNEs) in vertebrate genomes provides a cornerstone to elucidate molecular mechanisms of macroevolution. Extensive comparative genomics has proven that transposons such as short interspersed elements (SINEs) were an important source of CNEs. We recently characterized AmnSINE1, a SINE family in Amniota genomes, some of which are present in CNEs, and demonstrated that two AmnSINE1 loci play an important role in mammalian-specific brain development by functioning as an enhancer (Sasaki et al. Proc. Natl. Acad. Sci. USA 2008). To get more information about AmnSINE1s, we here performed a multi-species search for AmnSINE1, and revealed the distribution and evolutionary history of these SINEs in amniote genomes. The number of AmnSINE1 regions in amniotes ranged from 160 to 1200;the number in the eutherians were under 500 and the largest was that in chicken. Phylogenetic analysis established that each AmnSINE1 locus has evolved uniquely, primarily since the divergence of mammals from reptiles. These results support the notion that AmnSINE1s were amplified as an ancient retroposon in a common ancestor of Amniota and subsequently have survived for 300 Myr because of functions acquired by mutation-coupled exaptation prior mammalian radiation. On the basis of sequence homology and conserved synteny, we detected the orthologs of AmnSINE1 for candidates of further enhancer analysis, which are more conserved than two loci that were shown to have been involved in mammalian brain development. The present work provides a comprehensive data set to test the role of AmnSINE1s, many of which were exapted and contributed to mammalian macroevolution. (C) 2008 Elsevier B.V. All rights reserved.
Regulatory elements can affect specific genes from megabase distances, often from within or beyond unrelated neighbouring genes. The task of computational charting of regulatory inputs in the genome can be approached ...
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We recently identified approximately 1400 conserved non-coding elements (CNEs) shared by the genomes of fugu (Takifugu rubripes) and human that appear to be associated with developmental regulation in vertebrates [Woo...
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We recently identified approximately 1400 conserved non-coding elements (CNEs) shared by the genomes of fugu (Takifugu rubripes) and human that appear to be associated with developmental regulation in vertebrates [Woolfe, A., Goodson, M., Goode, D.K., Snell, P., McEwen, G.K., Vavouri, T., Smith, S.F., North, P., Callaway, H., Kelly, K., Walter, K., Abnizova, I., Gilks, W., Edwards, Y.J.K., Cooke, J.E., Elgar, G., 2005. Highly conservednon-coding sequences are associated with vertebrate development. PLoS Biol. 3 (1), e7]. This study encompassed a multi-disciplinary approach using bioinformatics, statistical methods and functional assays to identify and characterise the CNEs. Using an in vivo enhancer assay, over 90% of tested CNEs up-regulate tissue-specific GFP expression. Here we review our group's research in the field of characterising non-coding sequences conserved in vertebrates. We take this opportunity to discuss our research in progress and present some results of new and additional analyses. These include a phylogenomics analysis of CNEs, sequence conservation patterns in vertebrate CNEs and the distribution of human SNPs in the CNEs. We highlight the usefulness of the CNE dataset to help correlate genetic variation in health and disease. We also discuss the functional analysis using the enhancer assay and the enrichment of predicted transcription factor binding sites for two CNEs. Public access to the CNEs plus annotation is now possible and is described. The content of this review was presented by Dr. Y.J.K. Edwards at the TODAI International Symposium on Functional Genomics of the Pufferfish, Tokyo, Japan, 3 - 6 November 2004. (c) 2005 Elsevier Inc. All rights reserved.
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