School of BioSciences - Research Publications

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    Letting the 'cat' out of the bag: pouch young development of the extinct Tasmanian tiger revealed by X-ray computed tomography
    Newton, AH ; Spoutil, F ; Prochazka, J ; Black, JR ; Medlock, K ; Paddle, RN ; Knitlova, M ; Hipsley, CA ; Pask, AJ (ROYAL SOC, 2018-02-01)
    The Tasmanian tiger or thylacine (Thylacinus cynocephalus) was an iconic Australian marsupial predator that was hunted to extinction in the early 1900s. Despite sharing striking similarities with canids, they failed to evolve many of the specialized anatomical features that characterize carnivorous placental mammals. These evolutionary limitations are thought to arise from functional constraints associated with the marsupial mode of reproduction, in which otherwise highly altricial young use their well-developed forelimbs to climb to the pouch and mouth to suckle. Here we present the first three-dimensional digital developmental series of the thylacine throughout its pouch life using X-ray computed tomography on all known ethanol-preserved specimens. Based on detailed skeletal measurements, we refine the species growth curve to improve age estimates for the individuals. Comparison of allometric growth trends in the appendicular skeleton (fore- and hindlimbs) with that of other placental and marsupial mammals revealed that despite their unique adult morphologies, thylacines retained a generalized early marsupial ontogeny. Our approach also revealed mislabelled specimens that possessed large epipubic bones (vestigial in thylacine) and differing vertebral numbers. All of our generated CT models are publicly available, preserving their developmental morphology and providing a novel digital resource for future studies of this unique marsupial.
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    Transcriptomic analysis of MAP3K1 and MAP3K4 in the developing marsupial gonad
    Paranjpe, Monika ; Yu, Hongshi ; Pask, Andrew J. ; Shaw, Geoff ; Renfree, Marilyn B. ( 2018)
    MAPKs affect gonadal differentiation in mice and humans, but whether this applies to all mammals is as yet unknown. We investigated MAPK expression during gonadal differentiation in a distantly related mammal, the marsupial tammar wallaby, using our model of oestrogen-induced gonadal sex reversal. MAPK pathway genes in the tammar were highly conserved at the sequence and amino acid level with those of mice and humans. Marsupial MAP3K1 and MAP3K4 clustered together in a separate branch from eutherian mammals. We characterised the transcriptome of the key sex differentiation genes and those of the MAPK pathway in developing testes and also after testis culture with exogenous oestrogen. There was a marked decrease in levels of mRNA of both male-determining genes SOX9 and AMH, while levels of the female marker FOXL2 increased in male tammar gonads exposed to exogenous oestrogen. Only MAP3K1 expression increased after male gonads were cultured in media to which oestrogen was added, but the other MAPK genes were not affected by oestrogen. This study suggests that MAP3K1 can be influenced by exogenous oestrogens during gonadal differentiation in this marsupial.