Browsing by Subject "Gene Duplication"

Now showing 1 - 7 of 7
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    Conservation, duplication, and loss of the Tor signaling pathway in the fungal kingdom.
    (BMC Genomics, 2010-09-23) Shertz, Cecelia A; Bastidas, Robert J; Li, Wenjun; Heitman, Joseph; Cardenas, Maria E
    BACKGROUND: The nutrient-sensing Tor pathway governs cell growth and is conserved in nearly all eukaryotic organisms from unicellular yeasts to multicellular organisms, including humans. Tor is the target of the immunosuppressive drug rapamycin, which in complex with the prolyl isomerase FKBP12 inhibits Tor functions. Rapamycin is a gold standard drug for organ transplant recipients that was approved by the FDA in 1999 and is finding additional clinical indications as a chemotherapeutic and antiproliferative agent. Capitalizing on the plethora of recently sequenced genomes we have conducted comparative genomic studies to annotate the Tor pathway throughout the fungal kingdom and related unicellular opisthokonts, including Monosiga brevicollis, Salpingoeca rosetta, and Capsaspora owczarzaki. RESULTS: Interestingly, the Tor signaling cascade is absent in three microsporidian species with available genome sequences, the only known instance of a eukaryotic group lacking this conserved pathway. The microsporidia are obligate intracellular pathogens with highly reduced genomes, and we hypothesize that they lost the Tor pathway as they adapted and streamlined their genomes for intracellular growth in a nutrient-rich environment. Two TOR paralogs are present in several fungal species as a result of either a whole genome duplication or independent gene/segmental duplication events. One such event was identified in the amphibian pathogen Batrachochytrium dendrobatidis, a chytrid responsible for worldwide global amphibian declines and extinctions. CONCLUSIONS: The repeated independent duplications of the TOR gene in the fungal kingdom might reflect selective pressure acting upon this kinase that populates two proteinaceous complexes with different cellular roles. These comparative genomic analyses illustrate the evolutionary trajectory of a central nutrient-sensing cascade that enables diverse eukaryotic organisms to respond to their natural environments.
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    Evolutionary genomics and adaptive evolution of the Hedgehog gene family (Shh, Ihh and Dhh) in vertebrates.
    (PLoS One, 2014) Pereira, Joana; Johnson, Warren E; O'Brien, Stephen J; Jarvis, Erich D; Zhang, Guojie; Gilbert, M Thomas P; Vasconcelos, Vitor; Antunes, Agostinho
    The Hedgehog (Hh) gene family codes for a class of secreted proteins composed of two active domains that act as signalling molecules during embryo development, namely for the development of the nervous and skeletal systems and the formation of the testis cord. While only one Hh gene is found typically in invertebrate genomes, most vertebrates species have three (Sonic hedgehog--Shh; Indian hedgehog--Ihh; and Desert hedgehog--Dhh), each with different expression patterns and functions, which likely helped promote the increasing complexity of vertebrates and their successful diversification. In this study, we used comparative genomic and adaptive evolutionary analyses to characterize the evolution of the Hh genes in vertebrates following the two major whole genome duplication (WGD) events. To overcome the lack of Hh-coding sequences on avian publicly available databases, we used an extensive dataset of 45 avian and three non-avian reptilian genomes to show that birds have all three Hh paralogs. We find suggestions that following the WGD events, vertebrate Hh paralogous genes evolved independently within similar linkage groups and under different evolutionary rates, especially within the catalytic domain. The structural regions around the ion-binding site were identified to be under positive selection in the signaling domain. These findings contrast with those observed in invertebrates, where different lineages that experienced gene duplication retained similar selective constraints in the Hh orthologs. Our results provide new insights on the evolutionary history of the Hh gene family, the functional roles of these paralogs in vertebrate species, and on the location of mutational hotspots.
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    Fern genomes elucidate land plant evolution and cyanobacterial symbioses.
    (Nature plants, 2018-07-02) Li, F; Brouwer, P; Carretero-Paulet, L; Cheng, S; De Vries, J; Delaux, P; Eily, A; Koppers, N; Kuo, L; Li, Z
    Ferns are the closest sister group to all seed plants, yet little is known about their genomes other than that they are generally colossal. Here, we report on the genomes of Azolla filiculoides and Salvinia cucullata (Salviniales) and present evidence for episodic whole-genome duplication in ferns-one at the base of 'core leptosporangiates' and one specific to Azolla. One fern-specific gene that we identified, recently shown to confer high insect resistance, seems to have been derived from bacteria through horizontal gene transfer. Azolla coexists in a unique symbiosis with N2-fixing cyanobacteria, and we demonstrate a clear pattern of cospeciation between the two partners. Furthermore, the Azolla genome lacks genes that are common to arbuscular mycorrhizal and root nodule symbioses, and we identify several putative transporter genes specific to Azolla-cyanobacterial symbiosis. These genomic resources will help in exploring the biotechnological potential of Azolla and address fundamental questions in the evolution of plant life.
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    Genome-wide analyses of exonic copy number variants in a family-based study point to novel autism susceptibility genes.
    (PLoS Genet, 2009-06) Bucan, Maja; Abrahams, Brett S; Wang, Kai; Glessner, Joseph T; Herman, Edward I; Sonnenblick, Lisa I; Alvarez Retuerto, Ana I; Imielinski, Marcin; Hadley, Dexter; Bradfield, Jonathan P; Kim, Cecilia; Gidaya, Nicole B; Lindquist, Ingrid; Hutman, Ted; Sigman, Marian; Kustanovich, Vlad; Lajonchere, Clara M; Singleton, Andrew; Kim, Junhyong; Wassink, Thomas H; McMahon, William M; Owley, Thomas; Sweeney, John A; Coon, Hilary; Nurnberger, John I; Li, Mingyao; Cantor, Rita M; Minshew, Nancy J; Sutcliffe, James S; Cook, Edwin H; Dawson, Geraldine; Buxbaum, Joseph D; Grant, Struan FA; Schellenberg, Gerard D; Geschwind, Daniel H; Hakonarson, Hakon
    The genetics underlying the autism spectrum disorders (ASDs) is complex and remains poorly understood. Previous work has demonstrated an important role for structural variation in a subset of cases, but has lacked the resolution necessary to move beyond detection of large regions of potential interest to identification of individual genes. To pinpoint genes likely to contribute to ASD etiology, we performed high density genotyping in 912 multiplex families from the Autism Genetics Resource Exchange (AGRE) collection and contrasted results to those obtained for 1,488 healthy controls. Through prioritization of exonic deletions (eDels), exonic duplications (eDups), and whole gene duplication events (gDups), we identified more than 150 loci harboring rare variants in multiple unrelated probands, but no controls. Importantly, 27 of these were confirmed on examination of an independent replication cohort comprised of 859 cases and an additional 1,051 controls. Rare variants at known loci, including exonic deletions at NRXN1 and whole gene duplications encompassing UBE3A and several other genes in the 15q11-q13 region, were observed in the course of these analyses. Strong support was likewise observed for previously unreported genes such as BZRAP1, an adaptor molecule known to regulate synaptic transmission, with eDels or eDups observed in twelve unrelated cases but no controls (p = 2.3x10(-5)). Less is known about MDGA2, likewise observed to be case-specific (p = 1.3x10(-4)). But, it is notable that the encoded protein shows an unexpectedly high similarity to Contactin 4 (BLAST E-value = 3x10(-39)), which has also been linked to disease. That hundreds of distinct rare variants were each seen only once further highlights complexity in the ASDs and points to the continued need for larger cohorts.
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    The characterization of twenty sequenced human genomes.
    (PLoS Genet, 2010-09-09) Pelak, Kimberly; Shianna, Kevin V; Ge, Dongliang; Maia, Jessica M; Zhu, Mingfu; Smith, Jason P; Cirulli, Elizabeth T; Fellay, Jacques; Dickson, Samuel P; Gumbs, Curtis E; Heinzen, Erin L; Need, Anna C; Ruzzo, Elizabeth K; Singh, Abanish; Campbell, C Ryan; Hong, Linda K; Lornsen, Katharina A; McKenzie, Alexander M; Sobreira, Nara LM; Hoover-Fong, Julie E; Milner, Joshua D; Ottman, Ruth; Haynes, Barton F; Goedert, James J; Goldstein, David B
    We present the analysis of twenty human genomes to evaluate the prospects for identifying rare functional variants that contribute to a phenotype of interest. We sequenced at high coverage ten "case" genomes from individuals with severe hemophilia A and ten "control" genomes. We summarize the number of genetic variants emerging from a study of this magnitude, and provide a proof of concept for the identification of rare and highly-penetrant functional variants by confirming that the cause of hemophilia A is easily recognizable in this data set. We also show that the number of novel single nucleotide variants (SNVs) discovered per genome seems to stabilize at about 144,000 new variants per genome, after the first 15 individuals have been sequenced. Finally, we find that, on average, each genome carries 165 homozygous protein-truncating or stop loss variants in genes representing a diverse set of pathways.
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    The genome of a songbird.
    (Nature, 2010-04-01) Warren, Wesley C; Clayton, David F; Ellegren, Hans; Arnold, Arthur P; Hillier, Ladeana W; Künstner, Axel; Searle, Steve; White, Simon; Vilella, Albert J; Fairley, Susan; Heger, Andreas; Kong, Lesheng; Ponting, Chris P; Jarvis, Erich D; Mello, Claudio V; Minx, Pat; Lovell, Peter; Velho, Tarciso AF; Ferris, Margaret; Balakrishnan, Christopher N; Sinha, Saurabh; Blatti, Charles; London, Sarah E; Li, Yun; Lin, Ya-Chi; George, Julia; Sweedler, Jonathan; Southey, Bruce; Gunaratne, Preethi; Watson, Michael; Nam, Kiwoong; Backström, Niclas; Smeds, Linnea; Nabholz, Benoit; Itoh, Yuichiro; Whitney, Osceola; Pfenning, Andreas R; Howard, Jason; Völker, Martin; Skinner, Bejamin M; Griffin, Darren K; Ye, Liang; McLaren, William M; Flicek, Paul; Quesada, Victor; Velasco, Gloria; Lopez-Otin, Carlos; Puente, Xose S; Olender, Tsviya; Lancet, Doron; Smit, Arian FA; Hubley, Robert; Konkel, Miriam K; Walker, Jerilyn A; Batzer, Mark A; Gu, Wanjun; Pollock, David D; Chen, Lin; Cheng, Ze; Eichler, Evan E; Stapley, Jessica; Slate, Jon; Ekblom, Robert; Birkhead, Tim; Burke, Terry; Burt, David; Scharff, Constance; Adam, Iris; Richard, Hugues; Sultan, Marc; Soldatov, Alexey; Lehrach, Hans; Edwards, Scott V; Yang, Shiaw-Pyng; Li, Xiaoching; Graves, Tina; Fulton, Lucinda; Nelson, Joanne; Chinwalla, Asif; Hou, Shunfeng; Mardis, Elaine R; Wilson, Richard K
    The zebra finch is an important model organism in several fields with unique relevance to human neuroscience. Like other songbirds, the zebra finch communicates through learned vocalizations, an ability otherwise documented only in humans and a few other animals and lacking in the chicken-the only bird with a sequenced genome until now. Here we present a structural, functional and comparative analysis of the genome sequence of the zebra finch (Taeniopygia guttata), which is a songbird belonging to the large avian order Passeriformes. We find that the overall structures of the genomes are similar in zebra finch and chicken, but they differ in many intrachromosomal rearrangements, lineage-specific gene family expansions, the number of long-terminal-repeat-based retrotransposons, and mechanisms of sex chromosome dosage compensation. We show that song behaviour engages gene regulatory networks in the zebra finch brain, altering the expression of long non-coding RNAs, microRNAs, transcription factors and their targets. We also show evidence for rapid molecular evolution in the songbird lineage of genes that are regulated during song experience. These results indicate an active involvement of the genome in neural processes underlying vocal communication and identify potential genetic substrates for the evolution and regulation of this behaviour.
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    Trapped topoisomerase II initiates formation of de novo duplications via the nonhomologous end-joining pathway in yeast.
    (Proceedings of the National Academy of Sciences of the United States of America, 2020-10) Stantial, Nicole; Rogojina, Anna; Gilbertson, Matthew; Sun, Yilun; Miles, Hannah; Shaltz, Samantha; Berger, James; Nitiss, Karin C; Jinks-Robertson, Sue; Nitiss, John L
    Topoisomerase II (Top2) is an essential enzyme that resolves catenanes between sister chromatids as well as supercoils associated with the over- or under-winding of duplex DNA. Top2 alters DNA topology by making a double-strand break (DSB) in DNA and passing an intact duplex through the break. Each component monomer of the Top2 homodimer nicks one of the DNA strands and forms a covalent phosphotyrosyl bond with the 5' end. Stabilization of this intermediate by chemotherapeutic drugs such as etoposide leads to persistent and potentially toxic DSBs. We describe the isolation of a yeast top2 mutant (top2-F1025Y,R1128G) the product of which generates a stabilized cleavage intermediate in vitro. In yeast cells, overexpression of the top2-F1025Y,R1128G allele is associated with a mutation signature that is characterized by de novo duplications of DNA sequence that depend on the nonhomologous end-joining pathway of DSB repair. Top2-associated duplications are promoted by the clean removal of the enzyme from DNA ends and are suppressed when the protein is removed as part of an oligonucleotide. TOP2 cells treated with etoposide exhibit the same mutation signature, as do cells that overexpress the wild-type protein. These results have implications for genome evolution and are relevant to the clinical use of chemotherapeutic drugs that target Top2.