Search

Information on the extent of genetic differentiation among seabird populations is essential for conservation planning. Here we used, for the first time in little penguins (Eudyptula minor), a next generation sequencing approach to investigate population genetic structure, gene flow and inbreeding among eight colonies in South Australia. We found that Troubridge Island individuals were genetically distinct from the other sampled colonies, and that colonies on all islands were connected by moderate levels of gene flow possibly due to migration from the Kangaroo Island colonies. While further genetic sampling is needed, these data support the idea that South Australia may be a zone of subtle and rapid genetic change for little penguins.

ContextIn the era of the Anthropocene, habitat loss and environmental change threaten the persistence of many species. Genotyping-By-Sequencing (GBS) is a useful molecular tool for understanding how patterns of gene flow are associated with contemporary habitat distributions that may be affected by environmental change. Two parapatric subspecies of the threatened thick-billed grasswren (TBGW; Amytornis modestus) more frequently occur in different plant communities. As such, a preference for plant community type could reduce subspecific introgression and increase genetic diversity at the parapatric boundary.AimsWe aimed to measure gene flow within and among two TBGW subspecies and tested whether divergent genomic markers were associated with plant community type.MethodsWe sequenced 118 individuals from either of the two TBGW subspecies or in the region of parapatry and identified 7583 SNPs through ddRADseq.Key resultsWe found evidence of asymmetric gene flow and a genomic pattern of isolation-by-distance. There were sixteen genomic outliers correlated with plant community type (regardless of location).ConclusionsThese findings show that plant community type does not prevent introgression in one subspecies (A. m. raglessi), but low dispersal and habitat heterogeneity could contribute to the maintenance of distinct subspecific morphotypes. Local adaptation in different plant community types could also provide a mechanism for future divergence.ImplicationsWe suggest subspecific introgression could increase genetic variation and the adaptive potential of the species, facilitating species persistence under conditions of climate change.Introgression between grasswren subspeciesCharacterising gene flow facilitates conservation management. This study used genomic markers to measure gene flow between thick-billed grasswren subspecies and found results that support taxonomic identification of the two subspecies and suggests grasswrens have low dispersal and may benefit from increased genetic diversity. Recognition of models of divergence with gene flow will be necessary for future conservation management.

Passerine song has many functions including mate attraction and territory defence. When songs across populations diverge, this can lead to changes in conspecific recognition and barriers to gene flow, which affect evolutionary processes that could lead to speciation. Two subspecies of thick-billed grasswren (Amytornis modestus) have a parapatric distribution characterised as a narrow region of high genetic admixture where the two subspecies meet. Outside the region of parapatry, the subspecies are genetically and morphologically diverged and weak inter-subspecific gene flow is asymmetric from A. m. indulkanna to A. m. raglessi. We examined the differences between song of A. m. indulkanna and A. m. raglessi and experimentally broadcast each subspecies song to compare territory-holder response in relation to intruder subspecies type. Our aim was to determine if territory owners have a different response to intruders based on the subspecific song type. The song of each subspecies contained unique vocal elements that were absent in the other subspecies. A. m. raglessi responded similarly to con-subspecific and hetero-subspecific intruder song, and A. m. indulkanna responded more often and with greater intensity to hetero- compared to con-subspecific intruder song. The stronger response by A. m. indulkanna towards hetero-subspecific intruders provides a plausible behavioural explanation for the observed patterns of asymmetrical gene flow.

RATIONALE: The prevalence of Alzheimer's disease is increased in people with Down syndrome. The pathology appears much earlier than in the general population, suggesting a predisposition to develop Alzheimer's disease. Down syndrome results from trisomy of human chromosome 21, leading to overexpression of possible Alzheimer's disease candidate genes, such as amyloid precursor protein gene. To better understand how the Down syndrome context results in increased vulnerability to Alzheimer's disease, we analysed amyloid-β [25-35] peptide toxicity in the Tc1 mouse model of Down syndrome, in which ~75% of protein coding genes are functionally trisomic but, importantly, not amyloid precursor protein. RESULTS: Intracerebroventricular injection of oligomeric amyloid-β [25-35] peptide in three-month-old wildtype mice induced learning deficits, oxidative stress, synaptic marker alterations, activation of glycogen synthase kinase-3β, inhibition of protein kinase B (AKT), and apoptotic pathways as compared to scrambled peptide-treated wildtype mice. Scrambled peptide-treated Tc1 mice presented high levels of toxicity markers as compared to wildtype mice. Amyloid-β [25-35] peptide injection in Tc1 mice induced significant learning deficits and enhanced glycogen synthase kinase-3β activity in the cortex and expression of apoptotic markers in the hippocampus and cortex. Interestingly, several markers, including oxidative stress, synaptic markers, glycogen synthase kinase-3β activity in the hippocampus and AKT activity in the hippocampus and cortex, were unaffected by amyloid-β [25-35] peptide injection in Tc1 mice. CONCLUSIONS: Tc1 mice present several toxicity markers similar to those observed in amyloid-β [25-35] peptide-treated wildtype mice, suggesting that developmental modifications in these mice modify their response to amyloid peptide. However, amyloid toxicity led to severe memory deficits in this Down syndrome mouse model.

Divergence is the first phase of speciation and is commonly thought to occur more readily in allopatric populations. Subspecies are populations that are divergent but generally retain the capacity to interbreed should they come into contact. Two subspecies of the Thick-billed Grasswren (Amytornis modestus) are divergent by 1.7% at the mitochondrial ND2 gene and were previously considered to be allopatric. In this study, we discovered that the subspecies were parapatric. We use a larger sample size than previous studies to examine variation in morphology and mitochondrial haplotype across the distribution of each subspecies and within the region of parapatry. The subspecies occurring to the west, Amytornis modestus indulkanna, had larger body size and longer and narrower bill than the subspecies occurring to the east, A. m. raglessi. Within the region of parapatry, females were morphologically similar to A. m. indulkanna but had eastern mitochondrial haplotypes while males had intermediate morphology and either eastern or western haplotypes. Additionally, haplotypes from the western mitochondrial clade were found in A. m. raglessi. These patterns of morphology and mitochondrial diversity reveal discordance within the region of parapatry and to the east. We suggest that the subspecies have undergone asymmetric expansion from west to east, made secondary contact, and are currently hybridising.

No abstract available.; Errata: Analysis of IgE binding patterns to house dust mite allergens in scabies-endemic communities: insights for both diseases. Clinical and Experimental Allergy (2016), Volume 46, Issue 3, pp.508: http://dx.doi.org/10.1111/cea.12713

Trisomy of human chromosome 21 (Hsa21) results in Down syndrome (DS), a disorder that affects many aspects of physiology, including hematopoiesis. DS children have greatly increased rates of acute lymphoblastic leukemia and acute megakaryoblastic leukemia (AMKL); DS newborns present with transient myeloproliferative disorder (TMD), a preleukemic form of AMKL. TMD and DS-AMKL almost always carry an acquired mutation in GATA1 resulting in exclusive synthesis of a truncated protein (GATA1s), suggesting that both trisomy 21 and GATA1 mutations are required for leukemogenesis. To gain further understanding of how Hsa21 contributes to hematopoietic abnormalities, we examined the Tc1 mouse model of DS, which carries an almost complete freely segregating copy of Hsa21, and is the most complete model of DS available. We show that although Tc1 mice do not develop leukemia, they have macrocytic anemia and increased extramedullary hematopoiesis. Introduction of GATA1s into Tc1 mice resulted in a synergistic increase in megakaryopoiesis, but did not result in leukemia or a TMD-like phenotype, demonstrating that GATA1s and trisomy of approximately 80% of Hsa21 perturb megakaryopoiesis but are insufficient to induce leukemia.

The histology of the spleen, lymph nodes, Gut-associated lymphoid tissue (GALT) and Bronchus-associated lymphoid tissue (BALT) are described for samples collected opportunistically from healthy and mycobacteria-affected specimens of the endangered marsupial Lagorchestes hirsutus, the Rufous Hare-wallaby. The structural elements, organization and distribution of T and B lymphocytes determined by immunohistological techniques using species cross-reactive antibodies in the lymph nodes, spleen and GALT of this species demonstrated lymphoid cell distributions that were consistent with other marsupial and eutherian mammals. The tissues of animals identified as acid-fast positive displayed immunopathology consistent with the responses to intracellular bacteria displayed in some eutherian mammals and included the presence of focal lesions, giant cells in the lung and lymphoid aggregations situated adjacent to blood and airway vessels. This is the first study to describe the lymphoid tissue of this rare macropod species and the first to document the tissue bed response to mycobacteria.

Down Syndrome (DS) is a highly prevalent developmental disorder, affecting 1/700 births. Intellectual disability, which affects learning and memory, is present in all cases and is reflected by below average IQ. We sought to determine whether defective morphology and connectivity in neurons of the cerebral cortex may underlie the cognitive deficits that have been described in two mouse models of DS, the Tc1 and Ts1Rhr mouse lines. We utilised in utero electroporation to label a cohort of future upper layer projection neurons in the cerebral cortex of developing mouse embryos with GFP, and then examined neuronal positioning and morphology in early adulthood, which revealed no alterations in cortical layer position or morphology in either Tc1 or Ts1Rhr mouse cortex. The number of dendrites, as well as dendrite length and branching was normal in both DS models, compared with wildtype controls. The sites of projection neuron synaptic inputs, dendritic spines, were analysed in Tc1 and Ts1Rhr cortex at three weeks and three months after birth, and significant changes in spine morphology were observed in both mouse lines. Ts1Rhr mice had significantly fewer thin spines at three weeks of age. At three months of age Tc1 mice had significantly fewer mushroom spines - the morphology associated with established synaptic inputs and learning and memory. The decrease in mushroom spines was accompanied by a significant increase in the number of stubby spines. This data suggests that dendritic spine abnormalities may be a more important contributor to cognitive deficits in DS models, rather than overall neuronal architecture defects.

Habitat heterogeneity can have considerable effects on gene flow and migration across a region of parapatry. Describing habitat across a region of parapatry is important for the development of eco-evolutionary theory. Two subspecies of thick-billed grasswren (Amytornis modestus) share a region of parapatry between the South Australian salt lakes, Lake Eyre and Lake Torrens. While the two subspecies remain morphologically diverged outside the region of parapatry, it is not known what factors within the region of parapatry may affect migration and gene flow. In this study, we test associations between habitat differences and subspecies distributions and discuss whether ecological barriers could play a role in mitigating gene flow between the subspecies. We compare dominant plant species (1) between the allopatric ranges of the subspecies and within their region of parapatry, and (2) in relation to presence or absence of grasswrens within their region of parapatry. We found that the dominant plant species differed between grasswren subspecies in their allopatric range and in their region of parapatry, and also differed in the region of parapatry at sites with or without grasswrens. Specifically, grasswrens were absent in vegetation that is typical of sand dunes. These findings are discussed in light of evidence for secondary contact and hybridisation between A. m. indulkanna and A. m. raglessi, and susceptibility to introgression.

Scabies, a parasitic skin infestation by the burrowing “itch” miteSarcoptes scabiei, causes significant health problems for children and adults worldwide. Crusted scabies is a particularly severe form of scabies in which mites multiply into the millions, causing extensive skin crusting. The symptoms and signs of scabies suggest host immunity to the scabies mite, but the specific resistant response in humans remains largely uncharacterized. We used 4 scabies mite recombinant proteins with sequence homology to extensively studied house dust mite allergens to investigate a differential immune response between ordinary scabies and the debilitating crusted form of the disease. Subjects with either disease form showed serum IgE against recombinantS. scabieicysteine and serine proteases and apolipoprotein, whereas naive subjects showed minimal IgE reactivity. Significantly (P< 0.05) greater serum IgE and IgG4 binding to mite apolipoprotein occurred in subjects with crusted scabies than in those with ordinary scabies. Both subject groups showed strong proliferative responses (peripheral blood mononuclear cells) to the scabies antigens, but the crusted scabies group showed increased secretion of the Th2 cytokines interleukin 5 (IL-5) and IL-13 and decreased Th1 cytokine gamma interferon (IFN-γ) in response to the active cysteine protease. These data confirm that a nonprotective allergic response occurs in the crusted disease form and demonstrate that clinical severity is associated with differences in the type and magnitude of the antibody and cellular responses to scabies proteins. A quantitative IgE inhibition assay identified IgE immunoreactivity of scabies mite antigens distinct from that of house dust mite antigens, which is potentially important for specific scabies diagnosis and therapy.

Aims Cardiac malformations are prevalent in trisomies of human chromosome 21 [Down's syndrome (DS)], affecting normal chamber separation in the developing heart. Efforts to understand the aetiology of these defects have been severely hampered by the absence of an accurate mouse model. Such models have proved challenging to establish because synteny with human chromosome Hsa21 is distributed across three mouse chromosomes. None of those engineered so far accurately models the full range of DS cardiac phenotypes, in particular the profound disruptions resulting from atrioventricular septal defects (AVSDs). Here, we present analysis of the cardiac malformations exhibited by embryos of the transchromosomic mouse line Tc(Hsa21)1TybEmcf (Tc1) which contains more than 90% of chromosome Hsa21 in addition to the normal diploid mouse genome. Methods and results Using high-resolution episcopic microscopy and three-dimensional (3D) modelling, we show that Tc1 embryos exhibit many of the cardiac defects found in DS, including balanced AVSD with single and separate valvar orifices, membranous and muscular ventricular septal defects along with outflow tract and valve leaflet abnormalities. Frequencies of cardiac malformations (ranging from 38 to 55%) are dependent on strain background. In contrast, no comparable cardiac defects were detected in embryos of the more limited mouse trisomy model, Dp(16Cbr1-ORF9)1Rhr (Ts1Rhr), indicating that trisomy of the region syntenic to the Down's syndrome critical region, including the candidate genes DSCAM and DYRK1A, is insufficient to yield DS cardiac abnormalities. Conclusion The Tc1 mouse line provides a suitable model for studying the underlying genetic causes of the DS AVSD cardiac phenotype.

Down syndrome (DS) results from trisomy of human chromosome 21 (Hsa21) and is associated with an increased risk of Alzheimer's disease (AD). Here, using the unique transchromosomic Tc1 mouse model of DS we investigate the influence of trisomy of Hsa21 on the protein tau, which is hyperphosphorylated in Alzheimer's disease. We show that in old, but not young, Tc1 mice increased phosphorylation of tau occurs at a site suggested to be targeted by the Hsa21 encoded kinase, dual-specificity tyrosine-(Y)-phosphorylation regulated kinase 1A (DYRK1A). We show that DYRK1A is upregulated in young and old Tc1 mice, but that young trisomic mice may be protected from accumulating aberrantly phosphorylated tau. We observe that the key tau kinase, glycogen synthase kinase3-β (GSK-3β) is aberrantly phosphorylated at an inhibitory site in the aged Tc1 brain which may reduce total glycogen synthase kinase3-β activity. It is possible that a similar mechanism may also occur in people with DS.