Intermediate expression of CCRL1 reveals novel subpopulations of medullary thymic epithelial cells that emerge in the postnatal thymus.

Cortical and medullary thymic epithelial cells (cTECs and mTECs, respectively) provide inductive microenvironments for T-cell development and selection. The differentiation pathway of cTEC/mTEC lineages downstream of common bipotent progenitors at discrete stages of development remains unresolved. Using IL-7/CCRL1 dual reporter mice that identify specialized TEC subsets, we show that the stepwise acquisition of chemokine (C-C motif) receptor-like 1 (CCRL1) is a late determinant of cTEC differentiation. Although cTECs expressing high CCRL1 levels (CCRL1(hi) ) develop normally in immunocompetent and Rag2(-/-) thymi, their differentiation is partially blocked in Rag2(-/-) Il2rg(-/-) counterparts. These results unravel a novel checkpoint in cTEC maturation that is regulated by the cross-talk between TECs and immature thymocytes. Additionally, we identify new Ulex europaeus agglutinin 1 (UEA)(+) mTEC subtypes expressing intermediate CCRL1 levels (CCRL1(int) ) that conspicuously emerge in the postnatal thymus and differentially express Tnfrsf11a, Ccl21, and Aire. While rare in fetal and in Rag2(-/-) thymi, CCRL1(int) mTECs are restored in Rag2(-/-) Marilyn TCR-Tg mice, indicating that the appearance of postnatal-restricted mTECs is closely linked with T-cell selection. Our findings suggest that alternative temporally restricted routes of new mTEC differentiation contribute to the establishment of the medullary niche in the postnatal thymus.We thank James Di Santo, Jocelyne Demengeot, and Thomas Boehm for Rag2−/−Il2rg−/−, CCRL1-reporter, and Marilyn-Rag2−/− mice, respectively. We thank Dr. Catarina Leit˜ao for critical reading of the manuscript and technical assistance. We thank FEDER funds through the Operational Competitiveness Programme – COMPETE and by National Funds through Fundaçao para a Ciência e a Tecnologia (FCT) under the project PTDC/SAU-IMU/117057/2010 funded this work. N.L.A., A.R.R.,C.M., and P.M.R. are supported by FCT Investigator program and PhD fellowships

Performance related factors are the main determinants of the von Willebrand factor response to exhaustive physical exercise

Background: Physical stress triggers the endothelium to release von Willebrand Factor (VWF) from the Weibel Palade bodies. Since VWF is a risk factor for arterial thrombosis, it is of great interest to discover determinants of VWF response to physical stress. We aimed to determine the main mediators of the VWF increase by exhaustive physical exercise. Methods: 105 healthy individuals (18-35 years) were included in this study. Each participant performed an incremental exhaustive exercise test on a cycle ergometer. Respiratory gas exchange measurements were obtained while cardiac function was continuously monitored. Blood was collected at baseline and directly after exhaustion. VWF antigen (VWF:Ag) levels, VWF collagen binding (VWF:CB) levels, ADAMTS13 activity and common variations in Syntaxin Binding Protein-5 (STXBP5, rs1039084 and rs9399599), Syntaxin-2 (STX2, rs7978987) and VWF (promoter, rs7965413) were determined. Results: The median VWF:Ag level at baseline was 0.94 IU/mL [IQR 0.8-1.1] and increased with 47% [IQR 25-73] after exhaustive exercise to a median maximum VWF:Ag of 1.38 IU/mL [IQR 1.1-1.8] (p<0.0001). VWF:CB levels and ADAMTS13 activity both also increased after exhaustive exercise (median increase 43% and 12%, both p<0.0001). The strongest determinants of the VWF:Ag level increase are performance related (p<0.0001). We observed a gender difference in VWF:Ag response to exercise (females 1.2 IU/mL; males 1.7 IU/mL, p = 0.001), which was associated by a difference in performance. Genetic variations in STXBP5, STX2 and the VWF promoter were not associated with VWF:Ag levels at baseline nor with the VWF:Ag increase. Conclusions: VWF:Ag levels strongly increase upon exhaustive exercise and this increase is strongly determined by physical fitness level and the intensity of the exercise, while there is no clear effect of genetic variation in STXBP5, STX2 and the VWF promoter

Lymphotoxin-β receptor in microenvironmental cells promotes the development of T-cell acute lymphoblastic leukaemia with cortical/mature immunophenotype.

Lymphotoxin-mediated activation of the lymphotoxin-β receptor (LTβR; LTBR) has been implicated in cancer, but its role in T-cell acute lymphoblastic leukaemia (T-ALL) has remained elusive. Here we show that the genes encoding lymphotoxin (LT)-α and LTβ (LTA, LTB) are expressed in T-ALL patient samples, mostly of the TAL/LMO molecular subtype, and in the TEL-JAK2 transgenic mouse model of cortical/mature T-ALL (Lta, Ltb). In these mice, expression of Lta and Ltb is elevated in early stage T-ALL. Surface LTα1 β2 protein is expressed in primary mouse T-ALL cells, but only in the absence of microenvironmental LTβR interaction. Indeed, surface LT expression is suppressed in leukaemic cells contacting Ltbr-expressing but not Ltbr-deficient stromal cells, both in vitro and in vivo, thus indicating that dynamic surface LT expression in leukaemic cells depends on interaction with its receptor. Supporting the notion that LT signalling plays a role in T-ALL, inactivation of Ltbr results in a significant delay in TEL-JAK2-induced leukaemia onset. Moreover, young asymptomatic TEL-JAK2;Ltbr(-/-) mice present markedly less leukaemic thymocytes than age-matched TEL-JAK2;Ltbr(+/+) mice and interference with LTβR function at this early stage delayed T-ALL development. We conclude that LT expression by T-ALL cells activates LTβR signalling in thymic stromal cells, thus promoting leukaemogenesis.Grants from Fundação para a Ciencia e a Tecnologia (PTDC/SAU-OBD/103336/2008 and PEst-OE/EQB/LA0023/2013), Nucleo Regional Sul da Liga Portuguesa Contra o Cancro (NRS/LPCC-Terry Fox) and Fundacao MSD to NRdS; grants from the Sao Paulo Research Foundation (FAPESP 08/10034-1 and 12/12802-1) to JAY; and Plan Cancer Action 29 to ED. MTF (SFRH/BD/75137/2010) MNG (SFRH/BD/80503/2011), and RKK (SFRH/BPD/70718/2010) were recipients of FCT PhD or postdoctoral fellowships. ABS and JAY are supported by PhD and Productivity Fellowships, respectively, from the Brazilian National Council for Scientific and Technological Development (CNPq). NRdS has been supported by FCT Ciencia 2007 and FCT Investigator contracts (IF/00056/2012)

The use of phylogeny to interpret cross-cultural patterns in plant use and guide medicinal plant discovery: an example from Pterocarpus (Leguminosae)

The study of traditional knowledge of medicinal plants has led to discoveries that have helped combat diseases and improve healthcare. However, the development of quantitative measures that can assist our quest for new medicinal plants has not greatly advanced in recent years. Phylogenetic tools have entered many scientific fields in the last two decades to provide explanatory power, but have been overlooked in ethnomedicinal studies. Several studies show that medicinal properties are not randomly distributed in plant phylogenies, suggesting that phylogeny shapes ethnobotanical use. Nevertheless, empirical studies that explicitly combine ethnobotanical and phylogenetic information are scarce.In this study, we borrowed tools from community ecology phylogenetics to quantify significance of phylogenetic signal in medicinal properties in plants and identify nodes on phylogenies with high bioscreening potential. To do this, we produced an ethnomedicinal review from extensive literature research and a multi-locus phylogenetic hypothesis for the pantropical genus Pterocarpus (Leguminosae: Papilionoideae). We demonstrate that species used to treat a certain conditions, such as malaria, are significantly phylogenetically clumped and we highlight nodes in the phylogeny that are significantly overabundant in species used to treat certain conditions. These cross-cultural patterns in ethnomedicinal usage in Pterocarpus are interpreted in the light of phylogenetic relationships.This study provides techniques that enable the application of phylogenies in bioscreening, but also sheds light on the processes that shape cross-cultural ethnomedicinal patterns. This community phylogenetic approach demonstrates that similar ethnobotanical uses can arise in parallel in different areas where related plants are available. With a vast amount of ethnomedicinal and phylogenetic information available, we predict that this field, after further refinement of the techniques, will expand into similar research areas, such as pest management or the search for bioactive plant-based compounds

Stochastic Theory of Early Viral Infection: Continuous versus Burst Production of Virions

Viral production from infected cells can occur continuously or in a burst that generally kills the cell. For HIV infection, both modes of production have been suggested. Standard viral dynamic models formulated as sets of ordinary differential equations can not distinguish between these two modes of viral production, as the predicted dynamics is identical as long as infected cells produce the same total number of virions over their lifespan. Here we show that in stochastic models of viral infection the two modes of viral production yield different early term dynamics. Further, we analytically determine the probability that infections initiated with any number of virions and infected cells reach extinction, the state when both the population of virions and infected cells vanish, and show this too has different solutions for continuous and burst production. We also compute the distributions of times to establish infection as well as the distribution of times to extinction starting from both a single virion as well as from a single infected cell for both modes of virion production

Active dendrites enhance neuronal dynamic range

Since the first experimental evidences of active conductances in dendrites, most neurons have been shown to exhibit dendritic excitability through the expression of a variety of voltage-gated ion channels. However, despite experimental and theoretical efforts undertaken in the last decades, the role of this excitability for some kind of dendritic computation has remained elusive. Here we show that, owing to very general properties of excitable media, the average output of a model of active dendritic trees is a highly non-linear function of their afferent rate, attaining extremely large dynamic ranges (above 50 dB). Moreover, the model yields double-sigmoid response functions as experimentally observed in retinal ganglion cells. We claim that enhancement of dynamic range is the primary functional role of active dendritic conductances. We predict that neurons with larger dendritic trees should have larger dynamic range and that blocking of active conductances should lead to a decrease of dynamic range.Comment: 20 pages, 6 figure