School of BioSciences - Research Publications
Permanent URI for this collection
Search Results
1 - 10 of 36
-
ItemProteomics and Deep Sequencing Comparison of Seasonally Active Venom Glands in the Platypus Reveals Novel Venom Peptides and Distinct Expression Profiles(AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC, 2012-11)The platypus is a venomous monotreme. Male platypuses possess a spur on their hind legs that is connected to glands in the pelvic region. They produce venom only during the breeding season, presumably to fight off conspecifics. We have taken advantage of this unique seasonal production of venom to compare the transcriptomes of in- and out-of-season venom glands, in conjunction with proteomic analysis, to identify previously undiscovered venom genes. Comparison of the venom glands revealed distinct gene expression profiles that are consistent with changes in venom gland morphology and venom volumes in and out of the breeding season. Venom proteins were identified through shot-gun sequenced venom proteomes of three animals using RNA-seq-derived transcripts for peptide-spectral matching. 5,157 genes were expressed in the venom glands, 1,821 genes were up-regulated in the in-season gland, and 10 proteins were identified in the venom. New classes of platypus-venom proteins identified included antimicrobials, amide oxidase, serpin protease inhibitor, proteins associated with the mammalian stress response pathway, cytokines, and other immune molecules. Five putative toxins have only been identified in platypus venom: growth differentiation factor 15, nucleobindin-2, CD55, a CXC-chemokine, and corticotropin-releasing factor-binding protein. These novel venom proteins have potential biomedical and therapeutic applications and provide insights into venom evolution.
-
ItemUterine molecular changes for non-invasive embryonic attachment in the marsupials Macropus eugenii (Macropodidae) and Trichosurus vulpecula (Phalangeridae)(WILEY, 2017-10)Pregnancy in mammals requires remodeling of the uterus to become receptive to the implanting embryo. Remarkably similar morphological changes to the uterine epithelium occur in both eutherian and marsupial mammals, irrespective of placental type. Nevertheless, molecular differences in uterine remodeling indicate that the marsupial uterus employs maternal defences, including molecular reinforcement of the uterine epithelium, to regulate embryonic invasion. Non-invasive (epitheliochorial) embryonic attachment in marsupials likely evolved secondarily from invasive attachment, so uterine defences in these species may prevent embryonic invasion. We tested this hypothesis by identifying localization patterns of Talin, a key basal anchoring molecule, in the uterine epithelium during pregnancy in the tammar wallaby (Macropus eugenii; Macropodidae) and the brush tail possum (Trichosurus vulpecula; Phalangeridae). Embryonic attachment is non-invasive in both species, yet Talin undergoes a clear distributional change during pregnancy in M. eugenii, including recruitment to the base of the uterine epithelium just before attachment, that closely resembles that of invasive implantation in the marsupial species Sminthopsis crassicaudata. Basal localization occurs throughout pregnancy in T. vulpecula, although, as for M. eugenii, this pattern is most specific prior to attachment. Such molecular reinforcement of the uterine epithelium for non-invasive embryonic attachment in marsupials supports the hypothesis that less-invasive and non-invasive embryonic attachment in marsupials may have evolved via accrual of maternal defences. Recruitment of basal molecules, including Talin, to the uterine epithelium may have played a key role in this transition.
-
ItemUterine morphology during diapause and early pregnancy in the tammar wallaby (Macropus eugenii)(WILEY-BLACKWELL, 2016-09)In mammals, embryonic diapause, or suspension of embryonic development, occurs when embryos at the blastocyst stage are arrested in growth and metabolism. In the tammar wallaby (Macropus eugenii), there are two separate uteri, only one of which becomes gravid with the single conceptus at a post-partum oestrus, so changes during pregnancy can be compared between the gravid and non-gravid uterus within the same individual. Maintenance of the viable blastocyst and inhibition of further conceptus growth during diapause in the tammar is completely dependent on the uterine environment. Although the specific endocrine and seasonal signals are well established, much less is known about the cellular changes required to create this environment. Here we present the first detailed study of uterine morphology during diapause and early pregnancy of the tammar wallaby. We combined transmission electron microscopy and light microscopy to describe the histological and ultrastructural changes to luminal and glandular epithelial cells. At entry into diapause after the post-partum oestrus and formation of the new conceptus, there was an increase in abundance of organelles associated with respiration in the endometrial cells of the newly gravid uterus, particularly in the endoplasmic reticulum and mitochondria, as well as an increase in secretory activity. Organelle changes and active secretion then ceased in these cells as they became quiescent and remained so for the duration of diapause. In contrast, cells of the non-gravid, post-partum, contralateral uterus underwent sloughing and remodelling during this time and some organelle changes in glandular epithelial cells continued throughout diapause, suggesting these cells are not completely quiescent during diapause, although no active secretion occurred. These findings demonstrate that diapause, like pregnancy, is under unilateral endocrine control in the tammar, and that preparation for and maintenance of diapause requires substantial changes to uterine endometrial cell ultrastructure and activity.
-
ItemNon-invasive placentation in the marsupials Macropus eugenii (Macropodidae) and Trichosurus vulpecula (Phalangeridae) involves redistribution of uterine Desmoglein-2(WILEY, 2018-01-01)In mammalian pregnancy, the uterus is remodeled to become receptive to embryonic implantation. Since non-invasive placentation in marsupials is likely derived from invasive placentation, and is underpinned by intra-uterine conflict between mother and embryo, species with non-invasive placentation may employ a variety of molecular mechanisms to maintain an intact uterine epithelium and to prevent embryonic invasion. Identifying such modifications to the uterine epithelium of marsupial species with non-invasive placentation is key to understanding how conflict is mediated during pregnancy in different mammalian groups. Desmoglein-2, involved in maintaining lateral cell–cell adhesion of the uterine epithelium, is redistributed before implantation to facilitate embryo invasion in mammals with invasive placentation. We identified localization patterns of this cell adhesion molecule throughout pregnancy in two marsupial species with non-invasive placentation, the tammar wallaby (Macropus eugenii; Macropodidae), and the brushtail possum (Trichosurus vulpecula; Phalangeridae). Interestingly, Desmoglein-2 redistribution also occurs in both M. eugenii and T. vulpecula, suggesting that cell adhesion, and thus integrity of the uterine epithelium, is reduced during implantation regardless of placental type, and may be an important component of uterine remodeling. Desmoglein-2 also localizes to the mesenchymal stromal cells of M. eugenii and to epithelial cell nuclei in T. vulpecula, suggesting its involvement in cellular processes that are independent of adhesion and may compensate for reduced lateral adhesion in the uterine epithelium. We conclude that non-invasive placentation in marsupials involves diverse and complementary strategies to maintain an intact epithelial barrier.
-
ItemCharacterisation of major histocompatibility complex class I genes at the fetal-maternal interface of marsupials(SPRINGER, 2015-07)Major histocompatibility complex class I molecules (MHC-I) are expressed at the cell surface and are responsible for the presentation of self and non-self antigen repertoires to the immune system. Eutherian mammals express both classical and non-classical MHC-I molecules in the placenta, the latter of which are thought to modulate the maternal immune response during pregnancy. Marsupials last shared a common ancestor with eutherian mammals such as humans and mice over 160 million years ago. Since, like eutherians, they have an intra-uterine development dependent on a placenta, albeit a short-lived and less invasive one, they provide an opportunity to investigate the evolution of MHC-I expression at the fetal-maternal interface. We have characterised MHC-I mRNA expression in reproductive tissues of the tammar wallaby (Macropus eugenii) from the time of placental attachment to day 25 of the 26.5 day pregnancy. Putative classical MHC-I genes were expressed in the choriovitelline placenta, fetus, and gravid endometrium throughout the whole of this period. The MHC-I classical sequences were phylogenetically most similar to the Maeu-UC (50/100 clones) and Maeu-UA genes (7/100 clones). Expression of three non-classical MHC-I genes (Maeu-UD, Maeu-UK and Maeu-UM) were also present in placental samples. The results suggest that expression of classical and non-classical MHC-I genes in extant marsupial and eutherian mammals may have been necessary for the evolution of the ancestral therian placenta and survival of the mammalian fetus at the maternal-fetal interface.
-
ItemEverything About Kangaroos(Springer Science and Business Media LLC, 2014-09)
-
ItemEmbryos and embryonic stem cells from the white rhinoceros(NATURE PUBLISHING GROUP, 2018-07-04)The northern white rhinoceros (NWR, Ceratotherium simum cottoni) is the most endangered mammal in the world with only two females surviving. Here we adapt existing assisted reproduction techniques (ART) to fertilize Southern White Rhinoceros (SWR) oocytes with NWR spermatozoa. We show that rhinoceros oocytes can be repeatedly recovered from live SWR females by transrectal ovum pick-up, matured, fertilized by intracytoplasmic sperm injection and developed to the blastocyst stage in vitro. Next, we generate hybrid rhinoceros embryos in vitro using gametes of NWR and SWR. We also establish embryonic stem cell lines from the SWR blastocysts. Blastocysts are cryopreserved for later embryo transfer. Our results indicate that ART could be a viable strategy to rescue genes from the iconic, almost extinct, northern white rhinoceros and may also have broader impact if applied with similar success to other endangered large mammalian species.
-
ItemIdentification of a Novel PNMA-MS1 Gene inMarsupials Suggests the LTR Retrotransposon-Derived PNMA leGenes Evolved Differently inMarsupials and Eutherians(OXFORD UNIV PRESS, 2013-10)Two major gene families derived from Ty3/Gypsy long terminal repeat (LTR) retrotransposons were recently identified in mammals. The sushi-ichi retrotransposon homologue (SIRH) family comprises 12 genes: 11 in eutherians including Peg10 and Peg11/Rtl1 that have essential roles in the eutherian placenta and 1 that is marsupial specific. Fifteen and 12 genes were reported in the second gene family, para-neoplastic antigen MA (PNMA), in humans and mice, respectively, although their biological functions and evolutionary history remain largely unknown. Here, we identified two novel candidate PNMA genes, PNMA-MS1 and -MS2 in marsupials. Like all eutherian-specific PNMA genes, they exhibit the highest homology to a Gypsy12_DR (DR, Danio rerio) Gag protein. PNMA-MS1 is conserved in both Australian and South American marsupial species, the tammar wallaby and grey short-tailed opossum. However, no PNMA-MS1 orthologue was found in eutherians, monotremes or non-mammalian vertebrates. PNMA-MS1 was expressed in the ovary, mammary gland and brain during development and growth in the tammar, suggesting that PNMA-MS1 may have acquired a marsupial-specific function. However, PNMA-MS2 seems to be a pseudogene. The absence of marsupial orthologues of eutherian PNMA genes suggests that the retrotransposition events of the Gypsy12_DR-related retrotransposons that gave rise to the PNMA family occurred after the divergence of marsupials and eutherians.
-
ItemA new role for muscle segment homeobox genes in mammalian embryonic diapause(ROYAL SOC, 2013-04)Mammalian embryonic diapause is a phenomenon defined by the temporary arrest in blastocyst growth and metabolic activity within the uterus which synchronously becomes quiescent to blastocyst activation and implantation. This reproductive strategy temporally uncouples conception from parturition until environmental or maternal conditions are favourable for the survival of the mother and newborn. The underlying molecular mechanism by which the uterus and embryo temporarily achieve quiescence, maintain blastocyst survival and then resume blastocyst activation with subsequent implantation remains unknown. Here, we show that uterine expression of Msx1 or Msx2, members of an ancient, highly conserved homeobox gene family, persists in three unrelated mammalian species during diapause, followed by rapid downregulation with blastocyst activation and implantation. Mice with uterine inactivation of Msx1 and Msx2 fail to achieve diapause and reactivation. Remarkably, the North American mink and Australian tammar wallaby share similar expression patterns of MSX1 or MSX2 as in mice-it persists during diapause and is rapidly downregulated upon blastocyst activation and implantation. Evidence from mouse studies suggests that the effects of Msx genes in diapause are mediated through Wnt5a, a known transcriptional target of uterine Msx. These studies provide strong evidence that the Msx gene family constitutes a common conserved molecular mediator in the uterus during embryonic diapause to improve female reproductive fitness.
-
ItemPostnatal epigenetic reprogramming in the germline of a marsupial, the tammar wallaby(BMC, 2013-06-03)BACKGROUND: Epigenetic reprogramming is essential to restore totipotency and to reset genomic imprints during mammalian germ cell development and gamete formation. The dynamic DNA methylation change at DMRs (differentially methylated regions) within imprinted domains and of retrotransposons is characteristic of this process. Both marsupials and eutherian mammals have genomic imprinting but these two subgroups have been evolving separately for up to 160 million years. Marsupials have a unique reproductive strategy and deliver tiny, altricial young that complete their development within their mother's pouch. Germ cell proliferation in the genital ridge continues after birth in the tammar wallaby (Macropus eugenii), and it is only after 25 days postpartum that female germ cells begin to enter meiosis and male germ cells begin to enter mitotic arrest. At least two marsupial imprinted loci (PEG10 and H19) also have DMRs. To investigate the evolution of epigenetic reprogramming in the marsupial germline, here we collected germ cells from male pouch young of the tammar wallaby and analysed the methylation status of PEG10 and H19 DMR, an LTR (long terminal repeat) and a non-LTR retrotransposons. RESULTS: Demethylation of the H19 DMR was almost completed by 14 days postpartum and de-novo methylation started from 34 days postpartum. These stages correspond to 14 days after the completion of primordial germ cell migration into genital ridge (demethylation) and 9 days after the first detection of mitotic arrest (re-methylation) in the male germ cells. Interestingly, the PEG10 DMR was already unmethylated at 7 days postpartum, suggesting that the timing of epigenetic reprogramming is not the same at all genomic loci. Retrotransposon methylation was not completely removed after the demethylation event in the germ cells, similar to the situation in the mouse. CONCLUSIONS: Thus, despite the postnatal occurrence of epigenetic reprogramming and the persistence of genome-wide undermethylation for 20 days in the postnatal tammar, the relative timing and mechanism of germ cell reprogramming are conserved between marsupials and eutherians. We suggest that the basic mechanism of epigenetic reprogramming had already been established before the marsupial-eutherian split and has been faithfully maintained for at least 160 million years and may reflect the timing of the onset of mitotic arrest in the male germline.