Página 6 dos resultados de 157 itens digitais encontrados em 0.001 segundos

What Lies Beneath: Sub-Articular Long Bone Shape Scaling in Eutherian Mammals and Saurischian Dinosaurs Suggests Different Locomotor Adaptations for Gigantism

Bonnan, Matthew F.; Wilhite, D. Ray; Masters, Simon L.; Yates, Adam M.; Gardner, Christine K.; Aguiar, Adam
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 09/10/2013 EN
Relevância na Pesquisa
16.55%
Eutherian mammals and saurischian dinosaurs both evolved lineages of huge terrestrial herbivores. Although significantly more saurischian dinosaurs were giants than eutherians, the long bones of both taxa scale similarly and suggest that locomotion was dynamically similar. However, articular cartilage is thin in eutherian mammals but thick in saurischian dinosaurs, differences that could have contributed to, or limited, how frequently gigantism evolved. Therefore, we tested the hypothesis that sub-articular bone, which supports the articular cartilage, changes shape in different ways between terrestrial mammals and dinosaurs with increasing size. Our sample consisted of giant mammal and reptile taxa (i.e., elephants, rhinos, sauropods) plus erect and non-erect outgroups with thin and thick articular cartilage. Our results show that eutherian mammal sub-articular shape becomes narrow with well-defined surface features as size increases. In contrast, this region in saurischian dinosaurs expands and remains gently convex with increasing size. Similar trends were observed in non-erect outgroup taxa (monotremes, alligators), showing that the trends we report are posture-independent. These differences support our hypothesis that sub-articular shape scales differently between eutherian mammals and saurischian dinosaurs. Our results show that articular cartilage thickness and sub-articular shape are correlated. In mammals...

Echidna Venom Gland Transcriptome Provides Insights into the Evolution of Monotreme Venom

Wong, Emily S. W.; Nicol, Stewart; Warren, Wesley C.; Belov, Katherine
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 12/11/2013 EN
Relevância na Pesquisa
16.55%
Monotremes (echidna and platypus) are egg-laying mammals. One of their most unique characteristic is that males have venom/crural glands that are seasonally active. Male platypuses produce venom during the breeding season, delivered via spurs, to aid in competition against other males. Echidnas are not able to erect their spurs, but a milky secretion is produced by the gland during the breeding season. The function and molecular composition of echidna venom is as yet unknown. Hence, we compared the deeply sequenced transcriptome of an in-season echidna crural gland to that of a platypus and searched for putative venom genes to provide clues into the function of echidna venom and the evolutionary history of monotreme venom. We found that the echidna venom gland transcriptome was markedly different from the platypus with no correlation between the top 50 most highly expressed genes. Four peptides found in the venom of the platypus were detected in the echidna transcriptome. However, these genes were not highly expressed in echidna, suggesting that they are the remnants of the evolutionary history of the ancestral venom gland. Gene ontology terms associated with the top 100 most highly expressed genes in echidna, showed functional terms associated with steroidal and fatty acid production...

A connection to the past: Monodelphis domestica provides insight into the organization and connectivity of the brains of early mammals

Dooley, James C; Franca, João G.; Seelke, Adele M. H.; Cooke, Dylan F.; Krubitzer, Leah A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/2013 EN
Relevância na Pesquisa
16.55%
The current experiment is one of a series of comparative studies in our laboratory designed to determine the network of somatosensory areas that was present in the neocortex of the mammalian common ancestor. Such knowledge is critical for appreciating the basic functional circuitry that all mammals possess and how this circuitry was modified to generate species specific, sensory mediated behavior. Our animal model, the gray short-tailed opossum (Monodelphis domestica) is a marsupial that is proposed to represent this ancestral state more closely than most other marsupials and to some extent, even monotremes. We injected neuroanatomical tracers into the primary somatosensory area (S1), rostral and caudal somatosensory fields (SR and SC, respectively), and multimodal cortex (MM) and determined their connections with other architectonically defined cortical fields. Our results show that S1 has dense intrinsic connections, dense projections from the frontal myelinated area (FM), and moderate projections from S2 and SC. SR has strong projections from several areas, including S1, SR, FM and piriform cortex. SC has dense projections from S1, moderate to strong projections from other somatosensory areas, FM, along with connectivity from the primary (V1) and second visual areas. Finally...

Tracing Monotreme Venom Evolution in the Genomics Era

Whittington, Camilla M.; Belov, Katherine
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em 02/04/2014 EN
Relevância na Pesquisa
16.55%
The monotremes (platypuses and echidnas) represent one of only four extant venomous mammalian lineages. Until recently, monotreme venom was poorly understood. However, the availability of the platypus genome and increasingly sophisticated genomic tools has allowed us to characterize platypus toxins, and provides a means of reconstructing the evolutionary history of monotreme venom. Here we review the physiology of platypus and echidna crural (venom) systems as well as pharmacological and genomic studies of monotreme toxins. Further, we synthesize current ideas about the evolution of the venom system, which in the platypus is likely to have been retained from a venomous ancestor, whilst being lost in the echidnas. We also outline several research directions and outstanding questions that would be productive to address in future research. An improved characterization of mammalian venoms will not only yield new toxins with potential therapeutic uses, but will also aid in our understanding of the way that this unusual trait evolves.

Fc Receptors for Immunoglobulins and Their Appearance during Vertebrate Evolution

Akula, Srinivas; Mohammadamin, Sayran; Hellman, Lars
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 09/05/2014 EN
Relevância na Pesquisa
16.55%
Receptors interacting with the constant domain of immunoglobulins (Igs) have a number of important functions in vertebrates. They facilitate phagocytosis by opsonization, are key components in antibody-dependent cellular cytotoxicity as well as activating cells to release granules. In mammals, four major types of classical Fc receptors (FcRs) for IgG have been identified, one high-affinity receptor for IgE, one for both IgM and IgA, one for IgM and one for IgA. All of these receptors are related in structure and all of them, except the IgA receptor, are found in primates on chromosome 1, indicating that they originate from a common ancestor by successive gene duplications. The number of Ig isotypes has increased gradually during vertebrate evolution and this increase has likely been accompanied by a similar increase in isotype-specific receptors. To test this hypothesis we have performed a detailed bioinformatics analysis of a panel of vertebrate genomes. The first components to appear are the poly-Ig receptors (PIGRs), receptors similar to the classic FcRs in mammals, so called FcRL receptors, and the FcR γ chain. These molecules are not found in cartilagous fish and may first appear within bony fishes, indicating a major step in Fc receptor evolution at the appearance of bony fish. In contrast...

Trypanosomes of Australian mammals: A review

Thompson, Craig K.; Godfrey, Stephanie S.; Thompson, R.C. Andrew
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 15/03/2014 EN
Relevância na Pesquisa
16.55%
•Trypanosomes of Australian marsupials, rodents, bats and monotremes are reviewed.•22% of the indigenous terrestrial and arboreal mammals have been screened.•Trypanosomes have been identified from 28 mammal species.•Eight native trypanosome species have been described from Australian mammals•Potential pathogenic risks and threatening biosecurity concerns are discussed.

A Polychaete’s Powerful Punch: Venom Gland Transcriptomics of Glycera Reveals a Complex Cocktail of Toxin Homologs

von Reumont, Björn M.; Campbell, Lahcen I.; Richter, Sandy; Hering, Lars; Sykes, Dan; Hetmank, Jörg; Jenner, Ronald A.; Bleidorn, Christoph
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em 05/09/2014 EN
Relevância na Pesquisa
16.55%
Glycerids are marine annelids commonly known as bloodworms. Bloodworms have an eversible proboscis adorned with jaws connected to venom glands. Bloodworms prey on invertebrates, and it is known that the venom glands produce compounds that can induce toxic effects in animals. Yet, none of these putative toxins has been characterized on a molecular basis. Here we present the transcriptomic profiles of the venom glands of three species of bloodworm, Glycera dibranchiata, Glycera fallax and Glycera tridactyla, as well as the body tissue of G. tridactyla. The venom glands express a complex mixture of transcripts coding for putative toxin precursors. These transcripts represent 20 known toxin classes that have been convergently recruited into animal venoms, as well as transcripts potentially coding for Glycera-specific toxins. The toxins represent five functional categories: Pore-forming and membrane-disrupting toxins, neurotoxins, protease inhibitors, other enzymes, and CAP domain toxins. Many of the transcripts coding for putative Glycera toxins belong to classes that have been widely recruited into venoms, but some are homologs of toxins previously only known from the venoms of scorpaeniform fish and monotremes (stonustoxin-like toxin)...

Multiple Lineages of Ancient CR1 Retroposons Shaped the Early Genome Evolution of Amniotes

Suh, Alexander; Churakov, Gennady; Ramakodi, Meganathan P.; Platt, Roy N.; Jurka, Jerzy; Kojima, Kenji K.; Caballero, Juan; Smit, Arian F.; Vliet, Kent A.; Hoffmann, Federico G.; Brosius, Jürgen; Green, Richard E.; Braun, Edward L.; Ray, David A.; Schmit
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em 11/12/2014 EN
Relevância na Pesquisa
16.55%
Chicken repeat 1 (CR1) retroposons are long interspersed elements (LINEs) that are ubiquitous within amniote genomes and constitute the most abundant family of transposed elements in birds, crocodilians, turtles, and snakes. They are also present in mammalian genomes, where they reside as numerous relics of ancient retroposition events. Yet, despite their relevance for understanding amniote genome evolution, the diversity and evolution of CR1 elements has never been studied on an amniote-wide level. We reconstruct the temporal and quantitative activity of CR1 subfamilies via presence/absence analyses across crocodilian phylogeny and comparative analyses of 12 crocodilian genomes, revealing relative genomic stasis of retroposition during genome evolution of extant Crocodylia. Our large-scale phylogenetic analysis of amniote CR1 subfamilies suggests the presence of at least seven ancient CR1 lineages in the amniote ancestor; and amniote-wide analyses of CR1 successions and quantities reveal differential retention (presence of ancient relics or recent activity) of these CR1 lineages across amniote genome evolution. Interestingly, birds and lepidosaurs retained the fewest ancient CR1 lineages among amniotes and also exhibit smaller genome sizes. Our study is the first to analyze CR1 evolution in a genome-wide and amniote-wide context and the data strongly suggest that the ancestral amniote genome contained myriad CR1 elements from multiple ancient lineages...

Marsupials and monotremes possess a novel family of MHC class I genes that is lost from the eutherian lineage

Papenfuss, Anthony T; Feng, Zhi-Ping; Krasnec, Katina; Deakin, Janine E; Baker, Michelle L; Miller, Robert D
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 22/07/2015 EN
Relevância na Pesquisa
16.55%

Evolution of the Antisense Overlap between Genes for Thyroid Hormone Receptor and Rev-erbα and Characterization of an Exonic G-Rich Element That Regulates Splicing of TRα2 mRNA

Munroe, Stephen H.; Morales, Christopher H.; Duyck, Tessa H.; Waters, Paul D.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 14/09/2015 EN
Relevância na Pesquisa
16.55%
The α-thyroid hormone receptor gene (TRα) codes for two functionally distinct proteins: TRα1, the α-thyroid hormone receptor; and TRα2, a non-hormone-binding variant. The final exon of TRα2 mRNA overlaps the 3’ end of Rev-erbα mRNA, which encodes another nuclear receptor on the opposite strand of DNA. To understand the evolution of this antisense overlap, we sequenced these genes and mRNAs in the platypus Orthorhynchus anatinus. Despite its strong homology with other mammals, the platypus TRα/Rev-erbα locus lacks elements essential for expression of TRα2. Comparative analysis suggests that alternative splicing of TRα2 mRNA expression evolved in a stepwise fashion before the divergence of eutherian and marsupial mammals. A short G-rich element (G30) located downstream of the alternative 3’splice site of TRα2 mRNA and antisense to the 3’UTR of Rev-erbα plays an important role in regulating TRα2 splicing. G30 is tightly conserved in eutherian mammals, but is absent in marsupials and monotremes. Systematic deletions and substitutions within G30 have dramatically different effects on TRα2 splicing, leading to either its inhibition or its enhancement. Mutations that disrupt one or more clusters of G residues enhance splicing two- to three-fold. These results suggest the G30 sequence can adopt a highly structured conformation...

The status of dosage compensation in the multiple X chromosomes of the platypus

Deakin, Janine; Hore, Tim; Koina, Edda; Graves, Jennifer
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Journal article; Published Version Formato: 13 pages
Relevância na Pesquisa
16.55%
Dosage compensation has been thought to be a ubiquitous property of sex chromosomes that are represented differently in males and females. The expression of most X-borne genes is equalized between XX females and XY males in therian mammals (marsupials and “placentals”) by inactivating one X chromosome in female somatic cells. However, compensation seems not to be strictly required to equalize the expression of most Z-borne genes between ZZ male and ZW female birds. Whether dosage compensation operates in the third mammal lineage, the egg-laying monotremes, is of considerable interest, since the platypus has a complex sex chromosome system in which five X and five Y chromosomes share considerable genetic homology with the chicken ZW sex chromosome pair, but not with therian XY chromosomes. The assignment of genes to four platypus X chromosomes allowed us to examine X dosage compensation in this unique species. Quantitative PCR showed a range of compensation, but SNP analysis of several X-borne genes showed that both alleles are transcribed in a heterozygous female. Transcription of 14 BACs representing 19 X-borne genes was examined by RNA-FISH in female and male fibroblasts. An autosomal control gene was expressed from both alleles in nearly all nuclei...

The evolution of epigenetic regulators CTCF and BORIS/CTCFL in amniotes

Hore, Tim; Deakin, Janine; Graves, Jennifer
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Journal article; Published Version Formato: 11 pages
Relevância na Pesquisa
16.55%
CTCF is an essential, ubiquitously expressed DNA-binding protein responsible for insulator function, nuclear architecture, and transcriptional control within vertebrates. The gene CTCF was proposed to have duplicated in early mammals, giving rise to a paralogue called “brother of regulator of imprinted sites” (BORIS or CTCFL) with DNA binding capabilities similar to CTCF, but testis-specific expression in humans and mice. CTCF and BORIS have opposite regulatory effects on human cancer-testis genes, the anti-apoptotic BAG1 gene, the insulin-like growth factor 2/H19 imprint control region (IGF2/H19 ICR), and show mutually exclusive expression in humans and mice, suggesting that they are antagonistic epigenetic regulators. We discovered orthologues of BORIS in at least two reptilian species and found traces of its sequence in the chicken genome, implying that the duplication giving rise to BORIS occurred much earlier than previously thought. We analysed the expression of CTCF and BORIS in a range of amniotes by conventional and quantitative PCR. BORIS, as well as CTCF, was found widely expressed in monotremes (platypus) and reptiles (bearded dragon), suggesting redundancy or cooperation between these genes in a common amniote ancestor. However...

The Evolution of Genomic Imprinting and X Chromosome Inactivation in Mammals

Hore, Tim
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
EN
Relevância na Pesquisa
16.55%
Genomic imprinting is responsible for monoallelic gene expression that depends on the sex of the parent from which the alleles (one active, one silent) were inherited. X-chromosome inactivation is also a form of monoallelic gene expression. One of the two X chromosomes is transcriptionally silenced in the somatic cells of females, effectively equalising gene dosage with males who have only one X chromosome that is not complemented by a gene poor Y chromosome. X chromosome inactivation is random in eutherian mammals, but imprinted in marsupials, and in the extraembryonic membranes of some placentals. Imprinting and X inactivation have been studied in great detail in placental mammals (particularly humans and mice), and appear to occur also in marsupial mammals. However, both phenomena appear to have evolved specifically in mammals, since there is no evidence of imprinting or X inactivation in non-mammalian vertebrates, which do not show parent of origin effects and possess different sex chromosomes and dosage compensation mechanisms to mammals.¶ In order to understand how imprinting and X inactivation evolved, I have focused on the mammals most distantly related to human and mouse. I compared the sequence, location and expression of genes from major imprinted domains...

Parathyroids and Ultimobranchial Bodies in Monotremes

Haynes, J. I.
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Artigo de Revista Científica
Publicado em //1999 EN
Relevância na Pesquisa
16.55%

Reproduction, Mating Strategies and Sperm Competition in Marsupials and Monotremes

Taggert, D.; Breed, W.; Temple-Smith, P.; Purvis, A.; Shimmin, G.
Fonte: Academic Press, Harcourt Brace and Company, Publishers Publicador: Academic Press, Harcourt Brace and Company, Publishers
Tipo: Parte de Livro
Publicado em //1998 EN
Relevância na Pesquisa
16.55%

Response to comments on "Independent origins of middle ear bones in monotremes and therians"

Rich, Thomas H.; Hopson, James A.; Musser, Anne M.; Flannery, Tim Fridtjof; Vickers-Rich, Patricia
Fonte: American Association of Advancement Science Publicador: American Association of Advancement Science
Tipo: Artigo de Revista Científica
Publicado em //2005 EN
Relevância na Pesquisa
16.55%
T. H. Rich, J. A. Hopson, A. M. Musser, T. F. Flannery and P. Vickers-Rich

How did the platypus get its sex chromosome chain? A comparison of meiotic multiples and sex chromosomes in plants and animals

Grutzner, F.; Ashley, T.; Rowell, D.; Graves, J.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
16.55%
The duck-billed platypus is an extraordinary mammal. Its chromosome complement is no less extraordinary, for it includes a system in which ten sex chromosomes form an extensive meiotic chain in males. Such meiotic multiples are unprecedented in vertebrates but occur sporadically in plant and invertebrate species. In this paper, we review the evolution and formation of meiotic multiples in plants and invertebrates to try to gain insights into the origin of the platypus meiotic multiple. We describe the meiotic hurdles that translocated mammalian chromosomes face, which make longer chains disadvantageous in mammals, and we discuss how sex chromosomes and dosage compensation might have affected the evolution of sex-linked meiotic multiples. We conclude that the evolutionary conservation of the chain in monotremes, the structural properties of the translocated chromosomes and the highly accurate segregation at meiosis make the platypus system remarkably different from meiotic multiples in other species. We discuss alternative evolutionary models, which fall broadly into two categories: either the chain is the result of a sequence of translocation events from an ancestral pair of sex chromosomes (Model I) or the entire chain came into being at once by hybridization of two populations with different chromosomal rearrangements sharing monobrachial homology (Model II).; Frank Gruetzner...

DMRT gene cluster analysis in the platypus: New insights into genomic organization and regulatory regions

El-Mogharbel, N.; Wakefield, M.; Deakin, J.; Tsend-Ayush, E.; Grutzner, F.; Alsop, A.; Ezaz, T.; Graves, J.
Fonte: Academic Press Inc Elsevier Science Publicador: Academic Press Inc Elsevier Science
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
16.55%
We isolated and characterized a cluster of platypus DMRT genes and compared their arrangement, location, and sequence across vertebrates. The DMRT gene cluster on human 9p24.3 harbors, in order, DMRT1, DMRT3, and DMRT2, which share a DM domain. DMRT1 is highly conserved and involved in sexual development in vertebrates, and deletions in this region cause sex reversal in humans. Sequence comparisons of DMRT genes between species have been valuable in identifying exons, control regions, and conserved nongenic regions (CNGs). The addition of platypus sequences is expected to be particularly valuable, since monotremes fill a gap in the vertebrate genome coverage. We therefore isolated and fully sequenced platypus BAC clones containing DMRT3 and DMRT2 as well as DMRT1 and then generated multispecies alignments and ran prediction programs followed by experimental verification to annotate this gene cluster. We found that the three genes have 58-66% identity to their human orthologues, lie in the same order as in other vertebrates, and colocate on 1 of the 10 platypus sex chromosomes, X5. We also predict that optimal annotation of the newly sequenced platypus genome will be challenging. The analysis of platypus sequence revealed differences in structure and sequence of the DMRT gene cluster. Multispecies comparison was particularly effective for detecting CNGs...

Sex determination in platypus and echidna: autosomal location of SOX3 confirms the absence of SRY from monotremes

Wallis, M.; Waters, P.; Delbridge, M.; Kirby, P.; Pask, A.; Grutzner, F.; Rens, W.; Ferguson-Smith, M.; Graves, J.
Fonte: Kluwer Academic Publ Publicador: Kluwer Academic Publ
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
16.55%
In eutherian (‘placental’) mammals, sex is determined by the presence or absence of the Y chromosome-borne gene SRY, which triggers testis determination. Marsupials also have a Y-borne SRY gene, implying that this mechanism is ancestral to therians, the SRY gene having diverged from its X-borne homologue SOX3 at least 180 million years ago. The rare exceptions have clearly lost and replaced the SRY mechanism recently. Other vertebrate classes have a variety of sex-determining mechanisms, but none shares the therian SRY-driven XX female:XY male system. In monotreme mammals (platypus and echidna), which branched from the therian lineage 210 million years ago, no orthologue of SRY has been found. In this study we show that its partner SOX3 is autosomal in platypus and echidna, mapping among human X chromosome orthologues to platypus chromosome 6, and to the homologous chromosome 16 in echidna. The autosomal localization of SOX3 in monotreme mammals, as well as non-mammal vertebrates, implies that SRY is absent in Prototheria and evolved later in the therian lineage 210–180 million years ago. Sex determination in platypus and echidna must therefore depend on another male-determining gene(s) on the Y chromosomes, or on the different dosage of a gene(s) on the X chromosomes.; M. C. Wallis...

Retroposed SNOfall - A mammalian-wide comparison of platypus snoRNAs

Schmitz, J.; Zemann, A.; Churakov, G.; Kuhl, H.; Grutzner, F.; Reinhardt, R.; Brosius, J.
Fonte: Cold Spring Harbor Lab Press Publicador: Cold Spring Harbor Lab Press
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
16.55%
Diversification of mammalian species began more than 160 million years ago when the egg-laying monotremes diverged from live bearing mammals. The duck-billed platypus (Ornithorhynchus anatinus) and echidnas are the only potential contemporary witnesses of this period and, thereby, provide a unique insight into mammalian genome evolution. It has become clear that small RNAs are major regulatory agents in eukaryotic cells, and the significant role of non-protein-coding (npc) RNAs in transcription, processing, and translation is now well accepted. Here we show that the platypus genome contains more than 200 small nucleolar (sno) RNAs among hundreds of other diverse npcRNAs. Their comparison among key mammalian groups and other vertebrates enabled us to reconstruct a complete temporal pathway of acquisition and loss of these snoRNAs. In platypus we found cis- and trans-duplication distribution patterns for snoRNAs, which have not been described in any other vertebrates but are known to occur in nematodes. An exciting novelty in platypus is a snoRNA-derived retroposon (termed snoRTE) that facilitates a very effective dispersal of an H/ACA snoRNA via RTE-mediated retroposition. From more than 40,000 detected full-length and truncated genomic copies of this snoRTE...