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1.
Sci Rep ; 14(1): 2854, 2024 02 03.
Artigo em Inglês | MEDLINE | ID: mdl-38310138

RESUMO

Theria represent an extant clade that comprises placental and marsupial mammals. Here we report on the discovery of a new Late Cretaceous mammal from southern Patagonia, Patagomaia chainko gen. et sp. nov., represented by hindlimb and pelvic elements with unambiguous therian features. We estimate Patagomaia chainko attained a body mass of 14 kg, which is considerably greater than the 5 kg maximum body mass of coeval Laurasian therians. This new discovery demonstrates that Gondwanan therian mammals acquired large body size by the Late Cretaceous, preceding their Laurasian relatives, which remained small-bodied until the beginning of the Cenozoic. Patagomaia supports the view that the Southern Hemisphere was a cradle for the evolution of modern mammalian clades, alongside non-therian extinct groups such as meridiolestidans, gondwanatherians and monotremes.


Assuntos
Marsupiais , Monotremados , Feminino , Gravidez , Animais , Evolução Biológica , Filogenia , Fósseis , Placenta , Mamíferos , América do Sul
2.
Sci Rep ; 14(1): 1437, 2024 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-38228724

RESUMO

The function of the skin as a barrier against the environment depends on the differentiation of epidermal keratinocytes into highly resilient corneocytes that form the outermost skin layer. Many genes encoding structural components of corneocytes are clustered in the epidermal differentiation complex (EDC), which has been described in placental and marsupial mammals as well as non-mammalian tetrapods. Here, we analyzed the genomes of the platypus (Ornithorhynchus anatinus) and the echidna (Tachyglossus aculeatus) to determine the gene composition of the EDC in the basal clade of mammals, the monotremes. We report that mammal-specific subfamilies of EDC genes encoding small proline-rich proteins (SPRRs) and late cornified envelope proteins as well as single-copy EDC genes such as involucrin are conserved in monotremes, suggesting that they have originated in stem mammals. Monotremes have at least one gene homologous to the group of filaggrin (FLG), FLG2 and hornerin (HRNR) in placental mammals, but no clear one-to-one pairwise ortholog of either FLG, FLG2 or HRNR. Caspase-14, a keratinocyte differentiation-associated protease implicated in the processing of filaggrin, is encoded by at least 3 gene copies in the echidna. Our results reveal evolutionarily conserved and clade-specific features of the genetic regulation of epidermal differentiation in monotremes.


Assuntos
Monotremados , Ornitorrinco , Tachyglossidae , Gravidez , Animais , Feminino , Tachyglossidae/fisiologia , Proteínas Filagrinas , Placenta , Ornitorrinco/genética , Mamíferos/genética , Genômica
3.
Proteins ; 91(8): 1054-1064, 2023 08.
Artigo em Inglês | MEDLINE | ID: mdl-36964925

RESUMO

Forkhead box protein P3 (FOXP3) is known to orchestrate the development and maintenance of T regulatory cells, a cell population specialized in immune suppression and peripheral immune tolerance. FOXP3 activity is fine-tuned through its interaction with several protein-binding partners. By using IntAct database, we retrieved three physical binary interactors: E3 ubiquitin-protein ligase CHIP, Zfp-90, and nuclear receptor ROR-α. Coevolution clusters between FOXP3 and its interactors were identified with the use of iBIS2 algorithm, the iterative version of BIS/BIS2. Most of the coevolving pairs came from some species of monotremes and marsupials, as well as from a group of bats, thus suggesting that protein interactions of FOXP3 with its partners may be changed and/or modulated during mammalian speciation. Furthermore, our analysis would suggest the occurrence of a determinant role of FOXP3 in suppressing pregnancy alloreactions in placental mammals. Similarly, FOXP3, through its interaction with different protein interaction mechanisms, would explain the unique control of inflammatory response to infections in bats. By identifying several inter-protein clusters between the different protein pairs, our findings may provide a guide for new therapeutic approaches to modulate T regulatory suppression and/or enhance immune tolerance.


Assuntos
Quirópteros , Marsupiais , Monotremados , Membro 1 do Grupo F da Subfamília 1 de Receptores Nucleares , Animais , Feminino , Gravidez , Quirópteros/genética , Fatores de Transcrição Forkhead/genética , Fatores de Transcrição Forkhead/metabolismo , Placenta/metabolismo , Ubiquitina-Proteína Ligases/genética
4.
Commun Biol ; 6(1): 146, 2023 02 16.
Artigo em Inglês | MEDLINE | ID: mdl-36797304

RESUMO

Monotremata is a clade of egg-lying mammals, represented by the living platypus and echidnas, which is endemic to Australia, and adjacent islands. Occurrence of basal monotremes in the Early Cretaceous of Australia has led to the consensus that this clade originated on that continent, arriving later to South America. Here we report on the discovery of a Late Cretaceous monotreme from southern Argentina, demonstrating that monotremes were present in circumpolar regions by the end of the Mesozoic, and that their distinctive anatomical features were probably present in these ancient forms as well.


Assuntos
Monotremados , Ornitorrinco , Tachyglossidae , Animais , Mamíferos , América do Sul
5.
Anat Rec (Hoboken) ; 306(5): 972-982, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-35363436

RESUMO

Since its initial discovery in the 1500s, the cecal appendix has been an anatomical structure of great intrigue, notorious for its inconvenient tendency to become inflamed and often require surgical intervention. Appendicitis is one of the most common indications for emergency abdominal surgery, costing healthcare systems billions of dollars globally and causing tens of thousands of deaths annually. Yet, recent studies have indicated that the appendix may serve important protective functions in fortifying the body's immune response against invading pathogens and re-inoculating the gut with commensal bacteria after periods of gastrointestinal illness. While the cecal appendix was once believed to be a synapomorphy of hominoids (humans and other great apes), recent studies suggested that it is a recurrent trait found in several other species of primates, rodents, lagomorphs, marsupials, and monotremes. Mapping appendiceal and other gastrointestinal traits across a mammalian consensus phylogeny revealed that the cecal appendix has evolved independently numerous times throughout mammalian evolution, significantly more than would be expected due to chance alone, suggesting that the appendix is adaptively advantageous. However, attempts to identify an overarching ecological, behavioral, dietary, or environmental factor driving some species to evolve an appendix have been largely unsuccessful, indicating that the cecal appendix has a complex and diverse evolutionary history. This review discusses the current understanding of the pathophysiology, evolution, and possible functions of the appendix, both within humans and broadly across the class Mammalia.


Assuntos
Apendicite , Apêndice , Marsupiais , Monotremados , Humanos , Animais , Apendicite/cirurgia , Filogenia , Mamíferos
6.
Gen Comp Endocrinol ; 330: 114142, 2023 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-36243057

RESUMO

This study demonstrates the utility of the analysis of fecal hormone metabolites as a reproductive management tool for captive short-beaked echidnas. Over three breeding seasons daily fecal samples were collected from female echidnas (n = 8) that were monitored continuously by video surveillance to confirm key reproductive events. Fecal progesterone metabolite concentrations were elevated above baseline values (448.0 ± 156.3 ng/g) during pregnancy and the luteal phase. However, compared to plasma progesterone the rise in fecal progesterone metabolite concentrations after copulation was delayed (3.3 ± 0.4 versus 8.3 ± 0.6 days, respectively), such that pregnancy was more reliably detected in its latter half when using fecal samples. Mating and oviposition were observed for 14 of the 19 pregnancies resulting in an estimated gestation of 16.7 ± 0.2 days (range 16.0-18.1 d). The estrogen enzyme-immunoassays tested (n = 3) in this study were not suitable for the fecal samples of the echidna. Fecal progesterone metabolites are an effective tool for confirming the timing and occurrence of estrous cycles in captive echidna colonies and can assist zookeepers in identifying possible causes of sub-optimal reproductive success without the unnecessary stress of repeated capture and anaesthesia for blood collection.


Assuntos
Monotremados , Tachyglossidae , Gravidez , Animais , Feminino , Progesterona/metabolismo , Reprodução , Fezes , Estrogênios/metabolismo
7.
Sci Rep ; 12(1): 12293, 2022 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-35853976

RESUMO

Mammals are generally brown in colour, but recent publications are showing that they may not be as uniform as once assumed. Monotremes, marsupials, and a handful of eutherians reflect various colours when lit with UV light, mostly purple. Because of these still scarce records, we aimed to explore UV reflectance among rodent genera, the most diverse mammalian group, and the group of eutherians with the most common records of biofluorescence. Here we report structures like nails and quills reflected green, but for most genera, it was faded. However, Hystrix, Erethizon, and Ctenomys showed intense and contrasting green glow, while Chaetomys presented a vivid orange anogenital. The main available explanation of fluorescence in mammals relies on porphyrin. This explanation applies to the cases like Chaetomys, where specimens showed anogenital orange biofluorescence, but does not apply to the green biofluorescence we observed. In our sample, because the structures that reflected green were all keratinized, we have reasons to believe that biofluorescence results from keratinization and is a structurally-based colouration. However, not all spines/quills equally biofluoresced, so we cannot rule out other explanations. Since Rodentia is the most common mammalian group with reports on biofluorescence, this trait likely serves various functions that match the species diversity of this group.


Assuntos
Marsupiais , Monotremados , Porcos-Espinhos , Animais , Fluorescência , Mamíferos , Roedores
8.
Gen Comp Endocrinol ; 327: 114092, 2022 10 01.
Artigo em Inglês | MEDLINE | ID: mdl-35792163

RESUMO

The monotreme adrenocortical response to stress may not rely as heavily on the hypothalamic-pituitaryadrenal (HPA) axis compared to other mammals. This study aimed to validate a technique in which glucocorticoid metabolites could be quantified non-invasively in short-beaked echidna faeces by examining the secretion of glucocorticoids (GC) using an adrenocorticotrophic hormone (ACTH) challenge on sexually mature captive echidnas. Echidnas were housed individually for 15 days, with the ACTH challenge occurring on day five. Blood samples were collected on day five during the challenge and faecal samples were collected each morning for the 15 days. Both sample types were analysed for glucocorticoids (GC) or its metabolites. Plasma corticosterone concentrations increased significantly after 30 min and 60 min relative to time 0, whilst plasma cortisol concentrations increased significantly after 60 min. The ACTH challenge also resulted in an increase in glucocorticoid metabolite concentration in faecal samples from four of the six echidnas detected one to two days post ACTH injection, thereby validating a non-invasive method to assess adrenal response in the echidna. These results confirm that echidnas respond to a synthetic ACTH challenge in a similar manner to that of eutherian species indicating that echidnas appear to use the HPA axis in their stress response.


Assuntos
Monotremados , Tachyglossidae , Hormônio Adrenocorticotrópico/metabolismo , Animais , Fezes , Glucocorticoides/metabolismo , Sistema Hipotálamo-Hipofisário/metabolismo , Monotremados/fisiologia , Sistema Hipófise-Suprarrenal/metabolismo
9.
Genome Biol Evol ; 14(7)2022 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-35749276

RESUMO

Genomic imprinting is found in marsupial and eutherian mammals, but not in monotremes. While the primary regulator of genomic imprinting in eutherians is differential DNA methylation between parental alleles, conserved imprinted genes in marsupials tend to lack DNA methylation at their promoters. DNA methylation at eutherian imprinted genes is mainly catalyzed by a DNA methyltransferase (DNMT) enzyme, DNMT3A. There are two isoforms of eutherian DNMT3A: DNMT3A and DNMT3A2. DNMT3A2 is the primary isoform for establishing DNA methylation at eutherian imprinted genes and is essential for eutherian genomic imprinting. In this study, we investigated whether DNMT3A2 is also present in the two other mammalian lineages, marsupials and monotremes. We identified DNMT3A2 in both marsupials and monotremes, although imprinting has not been identified in monotremes. By analyzing genomic sequences and transcriptome data across vertebrates, we concluded that the evolution of DNMT3A2 occurred in the common ancestor of mammals. In addition, DNMT3A/3A2 gene and protein expression during gametogenesis showed distinct sexual dimorphisms in a marsupial, the tammar wallaby, and this pattern coincided with the sex-specific DNA methylation reprogramming in this species as it does in mice. Our results show that DNMT3A2 is present in all mammalian groups and suggests that the basic DNMT3A/3A2-based DNA methylation mechanism is conserved at least in therian mammals.


Assuntos
Metilação de DNA , DNA Metiltransferase 3A , Evolução Molecular , Monotremados , Animais , Metilação de DNA/genética , DNA Metiltransferase 3A/genética , Impressão Genômica/genética , Macropodidae/genética , Mamíferos/genética , Marsupiais/genética , Camundongos , Monotremados/genética
10.
J Anat ; 239(5): 1096-1103, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34195985

RESUMO

Despite the well-established anatomy nomenclature for the marsupial skeleton, there are no names for the epipubic bone structures. Epipubic bones are paired bones articulating with the pubis and projecting cranially in the ventral body wall, present on the pelvic girdle of cynodonts, monotremes and marsupials. These bones were commonly thought to be related to pouch support in marsupials and more recently associated with locomotion. The parts of the epipubic bones have not been named and this has impeded proper morphological analysis. We analyzed the epipubic bones of 302 skeletons comprising American and Australian marsupials, as well as 27 monotreme skeletons, and dissected 10 marsupials for myological attachments analysis. We suggest the following nomenclature for the epipubic bone structures: crest for the cranial end, shaft for the body of the bone, lateral tubercle and the medial articular process. Some markings on the epipubic bone include the oblique line, pertaining to the attachment of external abdominal oblique muscle from the opposite side. The pyramidalis line is the suggested nomenclature for the pyramidalis muscle attachment and the inguinal ligament line for the inguinal ligament attachment. Regarding myology and attachments, based on dissections and review of the literature, the muscles pyramidalis, pectineus, external and internal abdominal oblique, transversus abdominis and rectus abdominis and the structures linea alba, linea semilunaris and the inguinal ligament are connected to the epipubic bone. As has been previously noted, anatomically, epipubic bones are so named due to their position (epi-above, pubic-pubis), and the same applies to structures such as the "epipubic process" or "epipubic cartilage" in amphibians and reptiles. While testing epipubic bone homology in vertebrates is beyond the scope of this work, we believe that using "epipubic bones" or epipubic cartilage/process as standardized terms for the structures found in the most cranial part of the superior ramus of the pubis would facilitate better anatomical communication. This should be valid for other similar terms, such as "epipubes" or "prepubis", that might occur in the literature in relation to this same physiographic position, and it should also be named as epipubic. We believe that this nomenclature will help in future morphologic studies.


Assuntos
Marsupiais , Monotremados , Músculos Abdominais , Animais , Austrália , Mamíferos
11.
J Morphol ; 282(7): 1015-1023, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33393100

RESUMO

Knowledge of oocyte development and the early differentiation of the germ layers in monotremes stems largely from two articles by J. P. Hill and T. Thomson Flynn. The completeness of their account was due to the large series of echidna ovaries and eggs collected on Tasmania by Flynn, an Australian biologist of whom a brief account is given. A striking finding in the oocyte and early embryo of monotremes was the presence of a latebra connected to the yolk bed beneath the germinal disc as described in birds and several reptiles. A further resemblance was the presence early in vitellogenesis of a striate zone beneath the zona pellucida. Cleavage resulted first in a lens-shaped blastodisc encircled by cells called vitellocytes that later fused to form a germ-ring. The blastodisc gave rise to a blastoderm that eventually became unilaminar but comprised two cell types identified as ectoderm and primitive endoderm. Eventually these segregated into two layers and formed a blastula. This sequence resembled that in marsupials except there was no obvious distinction between future embryonic and extra-embryonic regions. As the blastoderm extended over the surface of the yolk, it was preceded by the germ-ring that eventually played a role in forming the yolk navel. This was a unique feature of monotreme development. It is shown that Flynn played an important role in analysis of the material as well as in its collection.


Assuntos
Monotremados , Tachyglossidae , Animais , Austrália , Camadas Germinativas , Oócitos
12.
Acta Parasitol ; 66(1): 228-235, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32951158

RESUMO

INTRODUCTION: Nematodes were found in the digestive tracts of 15 short-beaked echidnas Tachyglossus aculeatus (Shaw, 1792) collected from southwestern Australia between August 1964 and March 2020. METHODS: Specimens were prepared for microscopic examination as temporary wet mounts, measurements were made, figures prepared using a drawing tube and light micrographs taken. All nematodes were identified to at least genus level and a bootstrap analysis of the helminth community was carried out. RESULTS: Two previously described species, one species identified to genus and one new nematode species were recovered, including Nicollina ridei (Nicollinidae), Parapharyngodon anomalus (Pharyngodonidae), Parastrongyloides sp. (Strongyloididae) and Echidnonema coronorum n. g., n. sp. (Subuluridae, Echidnonematinae n. sf.). Echidnonema coronorum n. sp. can be distinguished from all other subulurids in having a mouth encircled by six leaf-like elements separated by six small pointed elements. The buccal complex is also unique to this species and is composed of three parts, including an anterior buccal capsule and a posterior pharyngeal portion divided into two; the proximal part contains lobes which are ornamented with numerous irregular teeth. A bootstrap estimate of species richness of 99.9% indicated that there were few, if any, additional species to be discovered in the southwestern Australian population of short-beaked echidnas. CONCLUSION: Morphological analysis supports the status of E. coronorum as a new species and the erection of the Echidnonematinae as a new subfamily to accommodate it. The helminth community of the population of short-beaked echidnas studied appears to be depauperate and contains species unique to the region.


Assuntos
Ascaridídios , Monotremados , Parasitos , Tachyglossidae , Animais , Austrália/epidemiologia , Austrália Ocidental
13.
Zoology (Jena) ; 139: 125753, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-32086142

RESUMO

To superficial inspection, the mammalian cerebellum appears to be a stereotypical structure that varies little in morphology across mammals. In the present study, the volumes of components of the corpus cerebelli, foliation of the cerebellar cortex and the volumes of the pontine and deep cerebellar nuclei have been measured and compared in three species of monotreme, 90 species of marsupial and 57 species of eutherian mammal. In all three mammalian groups, the volume of the corpus cerebelli scales isometrically with brain volume, and pontine nuclear volume also scales isometrically with cerebellar volume. The ratio of hemisphere to vermal cerebellar cortex is comparable in all mammals at small cerebellar volume, but elaboration of cerebellar hemispheres is largely confined to large cerebella of eutherian mammals. At small cerebellar volumes, diprotodontid metatherians have proportionally large cerebellar hemispheres compared to non-diprotodontid metatherians, and metatherian cerebella in general have a high volume of central white matter for a given cerebellar cortex volume compared to eutherians. The degree of foliation of the cerebellum scales similarly in therian mammals, but is relatively low in the monotremes for the volume of their corpus cerebelli. Among metatherians, cerebellar foliation is stronger among diprotodontid as compared to non-diprotodontids. Although the cerebellum has a similar structure in all mammals, there are subtle differences in structure between different mammal groups with possible functional implications.


Assuntos
Cerebelo/anatomia & histologia , Eutérios/anatomia & histologia , Marsupiais/anatomia & histologia , Monotremados/anatomia & histologia , Animais , Evolução Biológica , Especificidade da Espécie
14.
Anat Rec (Hoboken) ; 303(7): 1998-2013, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-31633884

RESUMO

We have used a quantitative statistical approach to compare the pace of development in the cerebellum and precerebellar systems relative to body size in monotremes and metatherians with that in eutherians (rodents and humans). Embryos, fetuses, and early postnatal mammals were scored on whether key structural events had been reached in the development of the cerebellum itself (CC-corpus cerebelli; 10 milestones), or the pontine and inferior olivary precerebellar nuclear groups (PC; 4 milestones). We found that many early cerebellar and precerebellar milestones (e.g., formation of Purkinje cell layer and deep cerebellar nuclei) were reached at a smaller absolute body length in both metatherians and eutherians together, compared to monotremes. Some later milestones (e.g., formation of the external granular layer and primary fissuration) were reached at a smaller body length in metatherians than eutherians. When the analysis was performed with proportional body length expressed as a natural log-transformed ratio of length at birth, milestones were reached at a much smaller proportional body length in rodents and humans than in the metatherians or monotremes. The findings are consistent with the slower pace of metabolic activity and embryonic development in monotremes. They also indicate slightly advanced maturation of some early features of the cerebellum in some metatherians (i.e., early cerebellar development in dasyurids relative to body size), but do not support the notion of an accelerated development of the cerebellum to cope with the demands of early birth. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:1998-2013, 2020. © 2019 American Association for Anatomy.


Assuntos
Cerebelo/crescimento & desenvolvimento , Marsupiais/crescimento & desenvolvimento , Monotremados/crescimento & desenvolvimento , Roedores/crescimento & desenvolvimento , Animais , Humanos , Especificidade da Espécie
15.
Genome Biol Evol ; 11(11): 3054-3067, 2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31605487

RESUMO

The age of sex chromosomes is commonly obtained by comparing the substitution rates of XY gametologs. Coupled with phylogenetic reconstructions, one can refine the origin of a sex chromosome system relative to specific speciation events. However, these approaches are insufficient to determine the presence and duration of ancestral sex chromosome systems that were lost in some species. In this study, we worked with genomic and transcriptomic data from mammals and squamates and analyzed the effect of male mutation bias on X-linked sequences in these groups. We searched for signatures indicating whether monotremes shared the same sex chromosomes with placental mammals or whether pleurodonts and acrodonts had a common ancestral sex chromosome system. Our analyses indicate that platypus did not share the XY chromosomes with placental mammals, in agreement with previous work. In contrast, analyses of agamids showed that this lineage maintained the pleurodont XY chromosomes for several million years. We performed multiple simulations using different strengths of male mutation bias to confirm the results. Overall, our work shows that variations in substitution rates due to male mutation bias could be applied to uncover signatures of ancestral sex chromosome systems.


Assuntos
Filogenia , Cromossomos Sexuais , Animais , Cromossomos de Mamíferos , Eutérios/genética , Evolução Molecular , Feminino , Genoma , Lagartos/genética , Masculino , Monotremados/genética , Mutação , Cromossomos Sexuais/genética , Cromossomo X , Cromossomo Y
16.
Zoology (Jena) ; 134: 38-57, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-31146906

RESUMO

We have made quantitative volumetric analyses of cerebral cortical (pallial) structures in the brains of three species of monotreme (Ornithorhynchus anatinus, Tachyglossus aculeatus, Zaglossus bruijni) and compared the findings with similar measurements in a range of therian mammals (6 marsupials and 50 placentals). We have found that although the iso- and periallocortical grey matter volume of the monotremes is about what would be expected for their brain size, the proportion of iso- and periallocortical white matter in monotremes is substantially lower than that in the forebrains of therians. This suggests that the forebrains of the three monotremes have fewer association, commissural and/or projection connections than those of similarly sized forebrains of therian mammals. We also found that the iso- and periallocortex of the platypus is relatively smooth-surfaced compared to similarly sized brains of therian mammals, with a distinct caudal shift in the positioning of cortical white matter in the forebrain, consistent with expansion of the posterior thalamic radiation. Central laminated olfactory structures (anterior olfactory nucleus and piriform cortex) are large in the tachyglossid monotremes (Tachyglossus aculeatus and Zaglossus bruijni) and large in xenarthran placental mammals, suggesting convergence of the forebrain structure of monotreme formivores with that of similarly specialized therians like the xenarthrans Myrmecophaga tridactyla and Dasypus novemcinctus.


Assuntos
Eutérios/anatomia & histologia , Marsupiais/anatomia & histologia , Monotremados/anatomia & histologia , Prosencéfalo/anatomia & histologia , Animais
17.
Artigo em Inglês | MEDLINE | ID: mdl-30181353

RESUMO

This review summarizes paleontological data as well as studies on the morphology, function, and molecular evolution of the cochlea of living mammals (monotremes, marsupials, and placentals). The most parsimonious scenario is an early evolution of the characteristic organ of Corti, with inner and outer hair cells and nascent electromotility. Most remaining unique features, such as loss of the lagenar macula, coiling of the cochlea, and bony laminae supporting the basilar membrane, arose later, after the separation of the monotreme lineage, but before marsupial and placental mammals diverged. The question of when hearing sensitivity first extended into the ultrasonic range (defined here as >20 kHz) remains speculative, not least because of the late appearance of the definitive mammalian middle ear. The last significant change was optimizing the operating voltage range of prestin, and thus the efficiency of the outer hair cells' amplifying action, in the placental lineage only.


Assuntos
Evolução Biológica , Cóclea/anatomia & histologia , Monotremados/anatomia & histologia , Animais , Cóclea/fisiologia , Células Ciliadas Auditivas Externas/ultraestrutura , Humanos , Mamíferos , Microscopia Eletrônica de Varredura
18.
Curr Top Dev Biol ; 130: 357-377, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29853183

RESUMO

Mammals evolved from oviparous reptiles that laid eggs in a dry, terrestrial environment, thus requiring large amounts of yolk to support development and tough, outer coats to protect them. Eutherian mammals such as humans and mice exhibit an "extreme" form of viviparity in which yolk and conceptus coats have become largely redundant. However, the "other" mammals-monotremes and marsupials-have retained and modified some features of reptilian development that provide valuable insights into the evolution of viviparity in mammals. Most striking of these are the conceptus coats, which include the zona pellucida, the mucoid coat, and the shell coat. We discuss current knowledge of these coats in monotremes and marsupials, their possible roles, and recently identified components such as the zona pellucida protein ZPAX, conceptus coat mucin (CCM), and nephronectin (NPNT).


Assuntos
Embrião de Mamíferos/química , Marsupiais/embriologia , Monotremados/embriologia , Glicoproteínas da Zona Pelúcida/fisiologia , Zigoto/metabolismo , Animais , Proteínas do Ovo/química , Proteínas do Ovo/fisiologia , Embrião de Mamíferos/metabolismo , Óvulo/química , Óvulo/metabolismo , Zona Pelúcida/química , Zona Pelúcida/fisiologia , Glicoproteínas da Zona Pelúcida/química , Zigoto/química
19.
Genome Res ; 28(4): 460-473, 2018 04.
Artigo em Inglês | MEDLINE | ID: mdl-29549088

RESUMO

Eukaryotic genomes must accomplish both compact packaging for genome stability and inheritance, as well as accessibility for gene expression. They do so using post-translational modifications of four ancient canonical histone proteins (H2A, H2B, H3, and H4) and by deploying histone variants with specialized chromatin functions. Some histone variants are conserved across all eukaryotes, whereas others are lineage-specific. Here, we performed detailed phylogenomic analyses of "short H2A histone" variants found in mammalian genomes. We discovered a previously undescribed typically-sized H2A variant in monotremes and marsupials, H2A.R, which may represent the common ancestor of the short H2As. We also discovered a novel class of short H2A histone variants in eutherian mammals, H2A.Q We show that short H2A variants arose on the X Chromosome in the common ancestor of all eutherian mammals and diverged into four evolutionarily distinct clades: H2A.B, H2A.L, H2A.P, and H2A.Q However, the repertoires of short histone H2A variants vary extensively among eutherian mammals due to lineage-specific gains and losses. Finally, we show that all four short H2As are subject to accelerated rates of protein evolution relative to both canonical and other variant H2A proteins including H2A.R. Our analyses reveal that short H2As are a unique class of testis-restricted histone variants displaying an unprecedented evolutionary dynamism. Based on their X-Chromosomal localization, genetic turnover, and testis-specific expression, we hypothesize that short H2A variants may participate in genetic conflicts involving sex chromosomes during reproduction.


Assuntos
Evolução Molecular , Genoma/genética , Histonas/genética , Mamíferos/genética , Animais , Cromatina/genética , Regulação da Expressão Gênica , Variação Genética , Instabilidade Genômica , Masculino , Marsupiais/genética , Monotremados/genética , Filogenia , Isoformas de Proteínas/genética , Testículo/metabolismo
20.
Annu Rev Anim Biosci ; 6: 1-22, 2018 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-29215911

RESUMO

Making my career in Australia exposed me to the tyranny of distance, but it gave me opportunities to study our unique native fauna. Distantly related animal species present genetic variation that we can use to explore the most fundamental biological structures and processes. I have compared chromosomes and genomes of kangaroos and platypus, tiger snakes and emus, devils (Tasmanian) and dragons (lizards). I particularly love the challenges posed by sex chromosomes, which, apart from determining sex, provide stunning examples of epigenetic control and break all the evolutionary rules that we currently understand. Here I describe some of those amazing animals and the insights on genome structure, function, and evolution they have afforded us. I also describe my sometimes-random walk in science and the factors and people who influenced my direction. Being a woman in science is still not easy, and I hope others will find encouragement and empathy in my story.


Assuntos
Evolução Biológica , Genômica , Cromossomos Sexuais/genética , Animais , Austrália , Aves/genética , Epigenômica , Feminino , História do Século XX , História do Século XXI , Masculino , Marsupiais/genética , Monotremados/genética , Répteis/genética
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