Borrowing from the Platypus: Proline Substitution in Cardiac Troponin I
0
Citation
0
Reference
10
Related Paper
Keywords:
Platypus
Troponin C
Monotreme
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) differ from placental mammals in many characteristics, particularly reproduction. With their early divergence from placentals, they fill the phylogenetic gap between the mammal-reptile divergence 310MYA and the placental radiation 100MYA. Their genomes are similar in size to those of placentals, but their chromosomes are quite distinctive. Marsupials have a few very large and very conserved chromosomes, while monotremes show a reptile-like size dichotomy and have a unique chain of ten sex chromosomes. Studies of gene arrangement in marsupials and monotremes have delivered many surprises that necessitate re-evaluation of the function and control of several genes in all mammals including humans, and provide new insights into the evolution of the mammalian genome, particularly the sex chromosomes. With the imminent sequencing of the genomes of two marsupials (the short-tailed grey Brazilian opossum and an Australian model kangaroo) and the platypus, much more detailed comparisons become possible. Even the first few analyses of marsupial and platypus sequences confirm the value of sequence comparisons for f inding new genes and regulatory regions and exploring their function, as well as deducing how they evolved.
Monotreme
Platypus
Cite
Citations (9)
A mammal that lays eggs. Monotreme mammals—spiny anteaters and this Australian platypus (Ornithorhynchus anatinus )—are one of the two oldest branches of the phylogeny of mammals. Monotremes lay eggs, while all other mammals have live birth.
Platypus
Monotreme
Mammal
Theria
Cite
Citations (0)
Platypus
Monotreme
Mammal
Theria
Lineage (genetic)
Cite
Citations (81)
cx-Lactalbumins were isolated from milk of the platypus (Ornithorhynchus anatinus) and the echidna (Tachyglossus aculeatus). Their amino acid sequences were determined and compared with those of the cx- lactalbumins often eutherian and two marsupial species, using the computer programme ("Distances") to calculate the number of differences (substitutions) between a total of 36 pairs of cx-lactalbumins. As expected, the amino acid sequences of the monotreme cx-lactalbumins were more similar to each other than to those of other mammals, as were the sequences of the marsupial and the eutherian cx-lactalbumins. If one makes the common assumption that marsupials and eutherians diverged from each other 135 Myr ago then simple calculations from the data would suggest that the platypus and echidna lineages diverged 56 ± 8 (SD) Myr ago and that monotremes diverged from the other mammals 152 ± 29 Myr ago. These values are not inconsistent with the little that is known about the palaeontology of the monotremes and are very similar to those derived from previous studies on globin sequences. If, however, monotreme cx-lactalbumins evolved more slowly than the cx-lactalbumins of eutherians and marsupials, these dates could be underestimates.
Monotreme
Platypus
Theria
Evolution of mammals
Mammal
myr
Cite
Citations (0)
We present a draft genome sequence of the platypus, Ornithorhynchus anatinus. This monotreme exhibits a fascinating combination of reptilian and mammalian characters. For example, platypuses have a coat of fur adapted to an aquatic lifestyle; platypus females lactate, yet lay eggs; and males are equipped with venom similar to that of reptiles. Analysis of the first monotreme genome aligned these features with genetic innovations. We find that reptile and platypus venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved despite platypuses laying eggs; and immune gene family expansions are directly related to platypus biology. Expansions of protein, non-protein-coding RNA and microRNA families, as well as repeat elements, are identified. Sequencing of this genome now provides a valuable resource for deep mammalian comparative analyses, as well as for monotreme biology and conservation. The duck-billed platypus (Ornithorhynchus anatinus) is a unique egg-laying mammal, with lactation, venom and a bill. It even has an electrosensory system for foraging underwater. Platypuses are monotremes descended from the most basal branch of the mammalian lineage and combine aspects of both reptilian and mammalian biology. Now an international consortium reports the sequence and analysis of the platypus genome. It is an amalgam of reptilian, mammalian and its own unique characteristics that provides clues to the function and evolution of all mammalian genomes. As well as helping uncover the origins of genomic imprinting, analyses show that platypus and reptile venom proteins have been co-opted independently from the same gene families; milk protein genes are conserved; and immune gene family expansions are directly related to platypus biology. The sequence provides an invaluable resource for comparative genomics, and it will be important for monotreme conservation. The cover image shows the bill with electrosensory pits, eye and ear opening behind the eye. Platypuses are monotremes and combine aspects of both reptilian and mammalian behaviour. An international consortium reports the genome sequence and analysis of Ornithorhynchus anatinus and as expected, parts of the genome look more like mammals, whereas other parts more like reptiles or even chickens.
Platypus
Monotreme
Cite
Citations (708)
Abstract The sequencing of the platypus genome represents a significant milestone in the study of mammalian evolution. The platypus is an egg‐laying mammal, a member of the order Monotremata, the most divergent mammalian clade. It is the first monotreme to have its genome sequenced. Its unique evolutionary position, as an offshoot between the early divergence of birds and the later emergence of therian (eutherian and marsupials) mammals, provides an unrivalled opportunity to understand the evolution of all mammals. Much like the physical characteristics of the platypus, the platypus genome shows traces of an amalgamation of mammalian and reptilian traits. Key findings to emerge from the genome project include the complex evolution of mammalian sex chromosomes, the transition from egg‐laying to live birth in mammals, and the evolution of immune genes and venom molecules in this unique species. Key concepts: The platypus genome is the first monotreme genome to be sequenced. The platypus's unique evolutionary position, as an offshoot between the early divergence of birds and the later emergence of therian (eutherian and marsupials) mammals, provides an opportunity to increase our understanding of the evolution of all mammals. The platypus genome shows features of mammalian and reptilian traits. The platypus has 10 sex chromosomes, some of which have homology to chicken Z. The mechanism used by platypuses to determine sex is not known. The density of interspersed repeat elements in the platypus genome is greater than that seen in any other vertebrate genome. The platypus genome contains a high G+C content (45.4%). The platypus possesses a unique class of over 40 000 noncoding RNA known as snoRTE. The platypus contains the largest repertoire of V1R vomeronasal receptors seen in any vertebrate. The platypus genome contains the major egg yolk protein, vitellogenin. Key mammalian milk genes, caseins, are present in the platypus. The platypus genome contains an expansion of antimicrobial peptide genes. Platypus venom molecules evolved independently to snake venom molecules.
Platypus
Monotreme
Evolution of mammals
Mammal
Cite
Citations (2)
Abstract Milk triglycerides from the platypus were subjected to fatty acid and stereospecific analysis to determine the positional distribution of fatty acids in the triglycerides. Of the major fatty acids, 12∶0 was preferentially esterified at the sn ‐3 position, 14∶0 and 16∶0 were selectively associated with the sn ‐2 position, and 18∶0 was located predominantly at the sn ‐1 position. The unsaturated fatty acids, 14∶1, 16∶1, 18∶1, 18∶2 and 18∶3, were preferentially esterified at the sn ‐3 position. The fatty acid distribution pattern of the platypus, a monotreme, is similar to that of marsupials and eutherians but is in contrast to the only other extant monotreme, the echidna.
Platypus
Monotreme
Lipidology
Theria
Cite
Citations (4)
NA
Platypus
Monotreme
Mammal
Cite
Citations (17)
Over two centuries after the first platypus specimen stirred the scientific community in Europe, the whole-genome sequence of the duck-billed platypus has been completed and is publicly available. After publication of eutherian and marsupial genomes, this is the first genome of a monotreme filling an important evolutionary gap between the divergence of birds more that 300 million years ago and marsupials more than 140 million years ago. Monotremes represent the most basal surviving branch of mammals and the platypus genome sequence allows unprecedented insights into the evolution of mammals and the fascinating biology of the egg-laying mammals. Here, we discuss some of the key findings of the analysis of the platypus genome and point to new findings and future research directions, which illustrate the broad impact of the platypus genome project for understanding monotreme biology and mammalian genome evolution.
Platypus
Monotreme
Genome size
Convergent evolution
Cite
Citations (6)
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.
Platypus
Monotreme
Cite
Citations (16)