Página 3 dos resultados de 157 itens digitais encontrados em 0.001 segundos

The complete mitochondrial genome of the wallaroo (Macropus robustus) and the phylogenetic relationship among Monotremata, Marsupialia, and Eutheria

Janke, Axel; Xu, Xiufeng; Arnason, Ulfur
Fonte: The National Academy of Sciences of the USA Publicador: The National Academy of Sciences of the USA
Tipo: Artigo de Revista Científica
Publicado em 18/02/1997 EN
Relevância na Pesquisa
16.55%
The complete mitochondrial DNA (mtDNA) (16,896 nt) of the wallaroo (Macropus robustus) was sequenced. The concatenated amino acid sequences of 12 mitochondrial protein-coding genes of the wallaroo plus those of a number of other mammals were included in a phylogenetic study of early mammalian divergences. The analysis joined monotremes and marsupials (the Marsupionta hypothesis) to the exclusion of eutherians. The analysis rejected significantly the commonly acknowledged Theria hypothesis, according to which Marsupialia and Eutheria are grouped together to the exclusion of Monotremata. The region harboring the gene for lysine tRNA (tRNA-Lys) in the mtDNA of other vertebrates is in the wallaroo occupied by a sequence (tRNA-Lys) that lacks both an anticodon loop as well as the anticodon for the amino acid lysine. An alternative tRNA-Lys gene was not identified in any other region of the mtDNA of the wallaroo, suggesting that a tRNA-Lys of nuclear origin is imported into marsupial mitochondria. Previously described RNA editing of tRNA-Asp and rearrangement of some tRNA genes were reconfirmed in the mtDNA of the wallaroo. The divergence between Monotremata/Marsupialia and Eutheria was timed to ≈130 million years before present (MYBP). The same calculations suggested that Monotremata and Marsupialia diverged ≈115 MYBP and that Australian and American marsupials separated ≈75 MYBP. The findings also show that many...

Molecular evidence for multiple origins of Insectivora and for a new order of endemic African insectivore mammals

Stanhope, Michael J.; Waddell, Victor G.; Madsen, Ole; de Jong, Wilfried; Hedges, S. Blair; Cleven, Gregory C.; Kao, Diana; Springer, Mark S.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 18/08/1998 EN
Relevância na Pesquisa
16.55%
The traditional views regarding the mammalian order Insectivora are that the group descended from a single common ancestor and that it is comprised of the following families: Soricidae (shrews), Tenrecidae (tenrecs), Solenodontidae (solenodons), Talpidae (moles), Erinaceidae (hedgehogs and gymnures), and Chrysochloridae (golden moles). Here we present a molecular analysis that includes representatives of all six families of insectivores, as well as 37 other taxa representing marsupials, monotremes, and all but two orders of placental mammals. These data come from complete sequences of the mitochondrial 12S rRNA, tRNA-Valine, and 16S rRNA genes (2.6 kb). A wide range of different methods of phylogenetic analysis groups the tenrecs and golden moles (both endemic to Africa) in an all-African superordinal clade comprised of elephants, sirenians, hyracoids, aardvark, and elephant shrews, to the exclusion of the other four remaining families of insectivores. Statistical analyses reject the idea of a monophyletic Insectivora as well as traditional concepts of the insectivore suborder Soricomorpha. These findings are supported by sequence analyses of several nuclear genes presented here: vWF, A2AB, and α-β hemoglobin. These results require that the order Insectivora be partitioned and that the two African families (golden moles and tenrecs) be placed in a new order. The African superordinal clade now includes six orders of placental mammals.

Electroreception in the Guiana dolphin (Sotalia guianensis)

Czech-Damal, Nicole U.; Liebschner, Alexander; Miersch, Lars; Klauer, Gertrud; Hanke, Frederike D.; Marshall, Christopher; Dehnhardt, Guido; Hanke, Wolf
Fonte: The Royal Society Publicador: The Royal Society
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
17.13%
Passive electroreception is a widespread sense in fishes and amphibians, but in mammals this sensory ability has previously only been shown in monotremes. While the electroreceptors in fish and amphibians evolved from mechanosensory lateral line organs, those of monotremes are based on cutaneous glands innervated by trigeminal nerves. Electroreceptors evolved from other structures or in other taxa were unknown to date. Here we show that the hairless vibrissal crypts on the rostrum of the Guiana dolphin (Sotalia guianensis), structures originally associated with the mammalian whiskers, serve as electroreceptors. Histological investigations revealed that the vibrissal crypts possess a well-innervated ampullary structure reminiscent of ampullary electroreceptors in other species. Psychophysical experiments with a male Guiana dolphin determined a sensory detection threshold for weak electric fields of 4.6 µV cm−1, which is comparable to the sensitivity of electroreceptors in platypuses. Our results show that electroreceptors can evolve from a mechanosensory organ that nearly all mammals possess and suggest the discovery of this kind of electroreception in more species, especially those with an aquatic or semi-aquatic lifestyle.

Identification and Functional Characterization of a Novel Monotreme- Specific Antibacterial Protein Expressed during Lactation

Bisana, Swathi; Kumar, Satish; Rismiller, Peggy; Nicol, Stewart C.; Lefèvre, Christophe; Nicholas, Kevin R.; Sharp, Julie A.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 09/01/2013 EN
Relevância na Pesquisa
17.13%
Monotremes are the only oviparous mammals and exhibit a fascinating combination of reptilian and mammalian characters. They represent a component of synapsidal reproduction by laying shelled eggs which are incubated outside the mother’s body. This is accompanied by a prototherian lactation process, marking them as representatives of early mammals. The only extant monotremes are the platypus, and the short- and long- beaked echidnas, and their distributions are limited to Australia and New Guinea. Apart for a short weaning period, milk is the sole source of nutrition and protection for the hatchlings which are altricial and immunologically naive. The duration of lactation in these mammals is prolonged relative to the gestational length and period of incubation of eggs. Much of the development of monotreme young occurs in the non-sterile ex-utero environment. Therefore the role of milk in the growth, development and disease protection of the young is of significant interest. By sequencing the cDNA of cells harvested from monotreme milk, we have identified a novel monotreme- specific transcript, and the corresponding gene was designated as the EchAMP. The expression profile of this gene in various tissues revealed that it is highly expressed in milk cells. The peptides corresponding to the EchAMP protein have been identified in a sample of echidna milk In silico analysis indicated putative antimicrobial potential for the cognate protein of EchAMP. This was further confirmed by in vitro assays using a host of bacteria. Interestingly...

Bird-like sex chromosomes of platypus imply recent origin of mammal sex chromosomes

Veyrunes, F.; Waters, P.; Miethke, P.; Rens, W.; McMillan, D.; Alsop, A.; Grutzner, F.; Deakin, J.; Whittington, C.; Schatzkamer, K.; Kremitzki, C.; Graves, T.; Ferguson-Smith, M.; Warren, W.; Graves, 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
17.13%
In therian mammals (placentals and marsupials), sex is determined by an XX female: XY male system, in which a gene (SRY) on the Y affects male determination. There is no equivalent in other amniotes, although some taxa (notably birds and snakes) have differentiated sex chromosomes. Birds have a ZW female: ZZ male system with no homology with mammal sex chromosomes, in which dosage of a Z-borne gene (possibly DMRT1) affects male determination. As the most basal mammal group, the egg-laying monotremes are ideal for determining how the therian XY system evolved. The platypus has an extraordinary sex chromosome complex, in which five X and five Y chromosomes pair in a translocation chain of alternating X and Y chromosomes. We used physical mapping to identify genes on the pairing regions between adjacent X and Y chromosomes. Most significantly, comparative mapping shows that, contrary to earlier reports, there is no homology between the platypus and therian X chromosomes. Orthologs of genes in the conserved region of the human X (including SOX3, the gene from which SRY evolved) all map to platypus chromosome 6, which therefore represents the ancestral autosome from which the therian X and Y pair derived. Rather, the platypus X chromosomes have substantial homology with the bird Z chromosome (including DMRT1) and to segments syntenic with this region in the human genome. Thus...

Loss of genes implicated in gastric function during platypus evolution

Ordonez, G.; Hillier, L.; Warren, W.; Grutzner, F.; Lopez-Otin, C.; Puente, X.
Fonte: BioMed Central Ltd. Publicador: BioMed Central Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
17.13%
Background The duck-billed platypus (Ornithorhynchus anatinus) belongs to the mammalian subclass Prototheria, which diverged from the Theria line early in mammalian evolution. The platypus genome sequence provides a unique opportunity to illuminate some aspects of the biology and evolution of these animals. Results We show that several genes implicated in food digestion in the stomach have been deleted or inactivated in platypus. Comparison with other vertebrate genomes revealed that the main genes implicated in the formation and activity of gastric juice have been lost in platypus. These include the aspartyl proteases pepsinogen A and pepsinogens B/C, the hydrochloric acid secretion stimulatory hormone gastrin, and the α subunit of the gastric H+/K+-ATPase. Other genes implicated in gastric functions, such as the β subunit of the H+/K+-ATPase and the aspartyl protease cathepsin E, have been inactivated because of the acquisition of loss-of-function mutations. All of these genes are highly conserved in vertebrates, reflecting a unique pattern of evolution in the platypus genome not previously seen in other mammalian genomes. Conclusion The observed loss of genes involved in gastric functions might be responsible for the anatomical and physiological differences in gastrointestinal tract between monotremes and other vertebrates...

Reproductive biology in egg-laying mammals

Grutzner, F.; Nixon, B.; Jones, R.
Fonte: S. Karger AG Publicador: S. Karger AG
Tipo: Artigo de Revista Científica
Publicado em //2008 EN
Relevância na Pesquisa
17.13%
The duck-billed platypus and short-beaked echidna are iconic species in Australia. Their morphology and physiology have puzzled scientists all over the world for more than 200 years. Recent genetic studies, particularly the platypus whole-genome sequencing project, have revealed the molecular basis of some of the extraordinary characteristics of monotremes. This and other works demonstrate the great value of research on our most distantly related mammalian relatives for comparative genomics and developmental biology. In this review we focus on the reproductive biology of monotremes and discuss works that unravel genes involved in lactation, testicular descent, gamete biology and fertilization, and early development. In addition we discuss works on the evolution of the complex sex chromosome system in platypus and echidna, which has also significant impact on our general understanding of mammalian sex chromosomes and sex determination.; F. Grützner, B. Nixon, R.C. Jones

The evolution of gene expression levels in mammalian organs

Brawand, D.; Soumillon, M.; Necsulea, A.; Julien, P.; Csardi, G.; Harrigan, P.; Weier, M.; Liechti, A.; Aximu-Petri, A.; Kircher, M.; Albert, F.; Zeller, U.; Khaitovich, P.; Grutzner, F.; Bergmann, S.; Nielsen, R.; Paabo, S.; Kaessmann, H.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //2011 EN
Relevância na Pesquisa
17.13%
Changes in gene expression are thought to underlie many of the phenotypic differences between species. However, large-scale analyses of gene expression evolution were until recently prevented by technological limitations. Here we report the sequencing of polyadenylated RNA from six organs across ten species that represent all major mammalian lineages (placentals, marsupials and monotremes) and birds (the evolutionary outgroup), with the goal of understanding the dynamics of mammalian transcriptome evolution. We show that the rate of gene expression evolution varies among organs, lineages and chromosomes, owing to differences in selective pressures: transcriptome change was slow in nervous tissues and rapid in testes, slower in rodents than in apes and monotremes, and rapid for the X chromosome right after its formation. Although gene expression evolution in mammals was strongly shaped by purifying selection,we identify numerous potentially selectively driven expression switches, which occurred at different rates across lineages and tissues and which probably contributed to the specific organ biology of various mammals.; David Brawand, Magali Soumillon, Anamaria Necsulea, Philippe Julien, Gábor Csárdi, Patrick Harriga, Manuela Weier...

An exon splice enhancer primes IGF2:IGF2R binding site structure and function evolution

Williams, C.; Hoppe, H.J.; Rezgui, D.; Strickland, M.; Forbes, B.; Grutzner, F.; Frago, S.; Ellis, R.; Wattana-Amorn, P.; Prince, S.; Zaccheo, O.; Nolan, C.; Mungall, A.; Jones, E.; Crump, M.; Hassan, A.
Fonte: Amer Assoc Advancement Science Publicador: Amer Assoc Advancement Science
Tipo: Artigo de Revista Científica
Publicado em //2012 EN
Relevância na Pesquisa
17.13%
Placental development and genomic imprinting coevolved with parental conflict over resource distribution to mammalian offspring. The imprinted genes IGF2 and IGF2R code for the growth promoter insulin-like growth factor 2 (IGF2) and its inhibitor, mannose 6-phosphate (M6P)/IGF2 receptor (IGF2R), respectively. M6P/IGF2R of birds and fish do not recognize IGF2. In monotremes, which lack imprinting, IGF2 specifically bound M6P/IGF2R via a hydrophobic CD loop. We show that the DNA coding the CD loop in monotremes functions as an exon splice enhancer (ESE) and that structural evolution of binding site loops (AB, HI, FG) improved therian IGF2 affinity. We propose that ESE evolution led to the fortuitous acquisition of IGF2 binding by M6P/IGF2R that drew IGF2R into parental conflict; subsequent imprinting may then have accelerated affinity maturation.; Christopher Williams, Hans-Jürgen Hoppe, Dellel Rezgui, Madeleine Strickland, Briony E. Forbes, Frank Grutzner, Susana Frago, Rosamund Z. Ellis, Pakorn Wattana-Amorn, Stuart N. Prince, Oliver J. Zaccheo, Catherine M. Nolan, Andrew J. Mungall, E. Yvonne Jones, Matthew P. Crump, A. Bassim Hassan

Identification and functional characterization of a novel monotreme-specific antibacterial protein expressed during lactation

Bisana, S.; Kumar, S.; Rismiller, P.; Nicol, S.; Lefevre, C.; Nicholas, K.; Sharp, J.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
17.13%
Monotremes are the only oviparous mammals and exhibit a fascinating combination of reptilian and mammalian characters. They represent a component of synapsidal reproduction by laying shelled eggs which are incubated outside the mother’s body. This is accompanied by a prototherian lactation process, marking them as representatives of early mammals. The only extant monotremes are the platypus, and the short- and long- beaked echidnas, and their distributions are limited to Australia and New Guinea. Apart for a short weaning period, milk is the sole source of nutrition and protection for the hatchlings which are altricial and immunologically naive. The duration of lactation in these mammals is prolonged relative to the gestational length and period of incubation of eggs. Much of the development of monotreme young occurs in the non-sterile ex-utero environment. Therefore the role of milk in the growth, development and disease protection of the young is of significant interest. By sequencing the cDNA of cells harvested from monotreme milk, we have identified a novel monotreme- specific transcript, and the corresponding gene was designated as the EchAMP. The expression profile of this gene in various tissues revealed that it is highly expressed in milk cells. The peptides corresponding to the EchAMP protein have been identified in a sample of echidna milk In silico analysis indicated putative antimicrobial potential for the cognate protein of EchAMP. This was further confirmed by in vitro assays using a host of bacteria. Interestingly...

Role of the epididymis in sperm competition

Jones, R.; Dacheux, J.L.; Nixon, B.; Ecroyd, H.
Fonte: Blackwell Publishing Publicador: Blackwell Publishing
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
17.13%
Although it is generally understood that the testes recruited kidney ducts for reproductive function during the evolution of vertebrates, little is understood of the biological significance of the adaptation. In the context of the evolution of the mammalian epididymis, this report provides evidence that a major role of the epididymis is to enhance a male's chance of achieving paternity in a competitive mating system. A unique example of sperm cooperation in monotremes is used as evidence that the epididymis produces sperm competition proteins to form groups of 100 sperm into bundles that have a forward motility nearly thrice that of individual spermatozoa. As it required 3-h incubation in vitro under capacitation conditions to release motile sperm from the bundles, it is suggested that the monotremes provide an example of capacitation that is quite different from capacitation in higher mammals. It is suggested that variation between species in the intensity of sperm competition could explain the variation that occurs between species in the amount of post-testicular sperm maturation and storage in the epididymis, an explanation of why the human epididymis does not play as important a role in reproduction as the epididymis of most mammals.; Russell C. Jones...

The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

Rens, W.; O'Brien, P.; Grutzner, F.; Clarke, O.; Graphodatskaya, D.; Tsend-Ayush, E.; Trifonov, V.; Skelton, H.; Wallis, M.; Johnston, S.; Veyrunes, F.; Graves, J.; Ferguson-Smith, M.
Fonte: BioMed Central Ltd. Publicador: BioMed Central Ltd.
Tipo: Artigo de Revista Científica
Publicado em //2007 EN
Relevância na Pesquisa
17.13%
Background: Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping. Results: Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X1, X2, X3, X5, and in chromosome Y1. Conclusion: Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain...

The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

Rens, Willem; O'Brien, Patricia CM; Grutzner, Frank; Clarke, Oliver; Graphodatskaya, Daria; Tsend-Ayush, Enkhjargal; Trifonov, Vladimir A; Skelton, Helen; Wallis, Mary C; Johnston, Steve; Veyrunes, Frederic; Graves, Jennifer AM; Ferguson-Smith, Malcolm A
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
17.13%
BACKGROUND Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping. RESULTS Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus, three of the platypus sex chromosomes differ from those of the echidna and the order of several chromosomes is rearranged. Comparative gene mapping shows that, in addition to bird autosome regions, regions of bird Z chromosomes are homologous to regions in four platypus X chromosomes, that is, X1, X2, X3, X5, and in chromosome Y1. CONCLUSION Monotreme sex chromosomes are easiest to explain on the hypothesis that autosomes were added sequentially to the translocation chain...

The evolutionary emergence and refinement of the mammalian pattern of foot architecture.

Lewis, O J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/1983 EN
Relevância na Pesquisa
17.13%
It is shown that in form and function the articular complexes of the monotreme foot are pre-adaptive to the therian condition, but the echidna differs by having a tuber calcaneus which is directed downward and distally. The cynodont foot (TR. 8) and that of the Triassic mammal Eozostrodon seem to possess the essential articular features present in monotremes, but they are assembled rather differently. In both, tuber calcaneus was apparently directed downwards. It follows that monotremes were probably derived from some way along the lineage usually, but inappropriately, termed "Theria'. A calcaneofibular articulation is present in kangaroos, certain shrews, elephant shrews, rabbits and artiodactyls. In all of them it is an apomorphic condition involving annexation of part of the posterior talar facet on the calcaneus by the fibula, which invariably shows some degree of amalgamation with the tibia. It is shown that the trochlear process of the mammalian calcaneus has the dual function of providing origin for the m. flexor accessorius and acting as a supporting shelf for the bundle of peroneal tendons. It is almost certainly a derivative of the lateral flange on the cynodont calcaneus, which presumably had a comparable function. In man...

Epigenetic modifications on X chromosomes in marsupial and monotreme mammals and implications for evolution of dosage compensation

Rens, Willem; Wallduck, Margaret S.; Lovell, Frances L.; Ferguson-Smith, Malcolm A.; Ferguson-Smith, Anne C.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
17.13%
X chromosome dosage compensation in female eutherian mammals is regulated by the noncoding Xist RNA and is associated with the differential acquisition of active and repressive histone modifications, resulting in repression of most genes on one of the two X chromosome homologs. Marsupial mammals exhibit dosage compensation; however, they lack Xist, and the mechanisms conferring epigenetic control of X chromosome dosage compensation remain elusive. Oviparous mammals, the monotremes, have multiple X chromosomes, and it is not clear whether they undergo dosage compensation and whether there is epigenetic dimorphism between homologous pairs in female monotremes. Here, using antibodies against DNA methylation, eight different histone modifications, and HP1, we conduct immunofluorescence on somatic cells of the female Australian marsupial possum Trichosurus vulpecula, the female platypus Ornithorhynchus anatinus, and control mouse cells. The two marsupial X's were different for all epigenetic features tested. In particular, unlike in the mouse, both repressive modifications, H3K9me3 and H4K20Me3, are enriched on one of the X chromosomes, and this is associated with the presence of HP1 and hypomethylation of DNA. Using sequential labeling...

Ostriches Sleep like Platypuses

Lesku, John A.; Meyer, Leith C. R.; Fuller, Andrea; Maloney, Shane K.; Dell'Omo, Giacomo; Vyssotski, Alexei L.; Rattenborg, Niels C.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 24/08/2011 EN
Relevância na Pesquisa
17.13%
Mammals and birds engage in two distinct states of sleep, slow wave sleep (SWS) and rapid eye movement (REM) sleep. SWS is characterized by slow, high amplitude brain waves, while REM sleep is characterized by fast, low amplitude waves, known as activation, occurring with rapid eye movements and reduced muscle tone. However, monotremes (platypuses and echidnas), the most basal (or ‘ancient’) group of living mammals, show only a single sleep state that combines elements of SWS and REM sleep, suggesting that these states became temporally segregated in the common ancestor to marsupial and eutherian mammals. Whether sleep in basal birds resembles that of monotremes or other mammals and birds is unknown. Here, we provide the first description of brain activity during sleep in ostriches (Struthio camelus), a member of the most basal group of living birds. We found that the brain activity of sleeping ostriches is unique. Episodes of REM sleep were delineated by rapid eye movements, reduced muscle tone, and head movements, similar to those observed in other birds and mammals engaged in REM sleep; however, during REM sleep in ostriches, forebrain activity would flip between REM sleep-like activation and SWS-like slow waves, the latter reminiscent of sleep in the platypus. Moreover...

Marsupial and Monotreme Genomes

Koina, Edda; Fong, James; Graves, Jennifer
Fonte: S Karger AG Publicador: S Karger AG
Tipo: Parte de Livro
Relevância na Pesquisa
17.13%
Marsupials and monotremes are 'alternative mammals', independent experiments of mammalian evolution that diverged from placental mammals 180 and 210 million years ago (MYA), respectively. Marsupials (e.g. kangaroo, opossum) and monotremes (e.g. platypus)

An exon splice enhancer primes IGF2:IGF2R binding site structure and function evolution

Williams, Christopher; Hoppe, Hans-Jürgen; Rezgui, Dellel; Strickland, Madeleine; Forbes, Briony E.; Grutzner, Frank; Frago, Susana; Ellis, Rosamund Z.; Wattana-Amorn, Pakorn; Prince, Stuart N.; Zaccheo, Oliver J.; Nolan, Catherine M.; Mungall, Andrew J.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 30/11/2012 EN
Relevância na Pesquisa
17.13%
Placental development and imprinting co-evolved with parental conflict over resource distribution to mammalian offspring. The imprinted genes, IGF2 and IGF2R, code for the growth promoter insulin-like growth factor 2 and its binding inhibitor, mannose 6-phosphate/IGF2 receptor, respectively. M6P/IGF2R of birds and fish do not recognize IGF2. In monotremes that lack imprinting, IGF2 specifically bound M6P/IGF2R via a hydrophobic CD loop. We show that the DNA coding the CD loop in monotremes functions as an exon splice enhancer (ESE) and that structural evolution of binding site loops (AB, HI, FG) improved therian IGF2 affinity. We propose that evolution of this ESE led to the fortuitous acquisition of M6P/IGF2R IGF2 binding that drew IGF2R into parental conflict prior to imprinting, that may have accelerated subsequent affinity maturation.

The multiple sex chromosomes of platypus and echidna are not completely identical and several share homology with the avian Z

Rens, Willem; O'Brien, Patricia C. M.; Grutzner, Frank; Clarke, Oliver; Graphodatskaya, Daria; Tsend-Ayush, Enkhjargal; Trifonov, Vladimir A.; Skelton, Helen; Wallis, Mary C.; Johnston, Steve; Veyrunes, Frederic; Graves, Jennifer A. M.; Ferguson-Smith, Ma
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Article; Published Version
EN
Relevância na Pesquisa
17.13%
RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.; Abstract Background Sex-determining systems have evolved independently in vertebrates. Placental mammals and marsupials have an XY system, birds have a ZW system. Reptiles and amphibians have different systems, including temperature-dependent sex determination, and XY and ZW systems that differ in origin from birds and placental mammals. Monotremes diverged early in mammalian evolution, just after the mammalian clade diverged from the sauropsid clade. Our previous studies showed that male platypus has five X and five Y chromosomes, no SRY, and DMRT1 on an X chromosome. In order to investigate monotreme sex chromosome evolution, we performed a comparative study of platypus and echidna by chromosome painting and comparative gene mapping. Results Chromosome painting reveals a meiotic chain of nine sex chromosomes in the male echidna and establishes their order in the chain. Two of those differ from those in the platypus...

A platypus eye view of the mammalian genome

Gruetzner, Frank; Graves, Jennifer
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
17.13%
The genome of monotremes, like the animals themselves, is unique and strange. The importance of monotremes to genomics depends on their position as the earliest offshoot of the mammalian lineage. Although there has been controversy in the literature over