Landscape genetics of an endangered lemur (Propithecus tattersalli) within its entire fragmented range

Habitat fragmentation may strongly reduce individuals’ dispersal among resource patches and hence influence population distribution and persistence. We studied the impact of landscape heterogeneity on the dispersal of the golden‐crowned sifaka (Propithecus tattersalli), an endangered social lemur species living in a restricted and highly fragmented landscape. We combined spatial analysis and population genetics methods to describe population units and identify the environmental factors which best predict the rates and patterns of genetic differentiation within and between populations. We used non‐invasive methods to genotype 230 individuals at 13 microsatellites in all the main forest fragments of its entire distribution area. Our analyses suggest that the Manankolana River and geographical distance are the primary structuring factors, while a national road crossing the region does not seem to impede gene flow. Altogether, our results are in agreement with a limited influence of forest habitat connectivity on gene flow patterns (except for North of the species’ range), suggesting that dispersal is still possible today among most forest patches for this species. Within forest patches, we find that dispersal is mainly among neighbouring social groups, hence confirming previous behavioural observations.     

The histological structure of the calcified lung of the fossil coelacanth Axelrodichthys araripensis (Actinistia: Mawsoniidae)

Abstract: The palaeohistological study of the calcified internal organ of Axelrodichthys araripensis Maisey, 1986, a coelacanthiform from the Lower Cretaceous of Brazil (Crato (Aptian) and Santana (Albian) formations of the Araripe Basin), shows that the walls of this organ consist of osseous blades of variable thickness separated from each other by the matrix. This indicates that, in the living individuals, the walls were reinforced by ossified plates, probably separated by conjunctive tissue. This calcified sheath present in Axelrodichthys, as well as in other fossil coelacanths, lies in ventral position relative to the gut and its single anterior opening is located under the opercle, suggesting a direct connection with the pharynx or the oesophagus. The calcified organ of Axelrodichthys, like that of other fossil coelacanths, is here regarded as an ‘ossified lung’ and compared with the ‘fatty lung’ of the extant coelacanth Latimeria. The reinforcement of the pulmonary walls by the overlying osseous blades could be interpreted as a means of adapting volumetric changes in the manner of bellows, a necessary function for ventilation in pulmonary respiration. Other functional hypotheses such as hydrostatic and/or acoustic functions are also discussed.     

A Repurposing Approach Identifies Off-Patent Drugs with Fungicidal Cryptococcal Activity,a Common Structural Chemotype,and Pharmacological Properties Relevant to the Treatment of Cryptococcosis

New, more accessible therapies for cryptococcosis represent an unmet clinical need of global importance. We took a repurposing approach to identify previously developed drugs with fungicidal activity toward Cryptococcus neoformans, using a high-throughput screening assay designed to detect drugs that directly kill fungi. From a set of 1,120 off-patent medications and bioactive molecules, we identified 31 drugs/molecules with fungicidal activity, including 15 drugs for which direct antifungal activity had not previously been reported. A significant portion of the drugs are orally bioavailable and cross the blood-brain barrier, features key to the development of a widely applicable anticryptococcal agent. Structural analysis of this set revealed a common chemotype consisting of a hydrophobic moiety linked to a basic amine, features that are common to drugs that cross the blood-brain barrier and access the phagolysosome, two important niches of C. neoformans. Consistent with their fungicidal activity, the set contains eight drugs that are either additive or synergistic in combination with fluconazole. Importantly, we identified two drugs, amiodarone and thioridazine, with activity against intraphagocytic C. neoformans. Finally, the set of drugs is also enriched for molecules that inhibit calmodulin, and we have confirmed that seven drugs directly bind C. neoformans calmodulin, providing a molecular target that may contribute to the mechanism of antifungal activity. Taken together, these studies provide a foundation for the optimization of the antifungal properties of a set of pharmacologically attractive scaffolds for the development of novel anticryptococcal therapies.     

Generation and characterization of antibodies specific for caspase-cleaved neo-epitopes: a novel approach

Apoptosis research has been significantly aided by the generation of antibodies against caspase-cleaved peptide neo-epitopes. However, most of these antibodies recognize the N-terminal fragment and are specific for the protein in question. The aim of this project was to create antibodies, which could identify caspase-cleaved proteins without a priori knowledge of the cleavage sites or even the proteins themselves. We hypothesized that many caspase-cleavage products might have a common antigenic shape, given that they must all fit into the same active site of caspases. Rabbits were immunized with the eight most prevalent exposed C-terminal tetrapeptide sequences following caspase cleavage. After purification of the antibodies we demonstrated (1) their specificity for exposed C-terminal (but not internal) peptides, (2) their ability to detect known caspase-cleaved proteins from apoptotic cell lysates or supernatants from apoptotic cell culture and (3) their ability to detect a caspase-cleaved protein whose tetrapeptide sequence differs from the eight tetrapeptides used to generate the antibodies. These antibodies have the potential to identify novel neo-epitopes produced by caspase cleavage and so can be used to identify pathway-specific caspase cleavage events in a specific cell type. Additionally this methodology may be applied to generate antibodies against products of other proteases, which have a well-defined and non-promiscuous cleavage activity.