Project description:Human plasma cells (PCs) and their precursors play an essential role in humoral immune response but are rare and difficult to harvest. We report the generation of human syndecan-1(+) and immunoglobulin secreting PCs starting from memory B cells in a 3-step and 10-day (D) culture, including a 6-fold cell amplification. We report the detailed phenotypic and Affymetrix gene expression profiles of these in vitro PCs as well as of intermediate cells (activated B cells and plasmablasts) compared with memory B cells and bone marrow PCs, which is accessible through an open web ATLAS (http://amazonia.transcriptome.eu/). We show this B cell-to-PC differentiation to involve IRF4 and AICDA expressions in D4 activated B cells, decrease of PAX5 and BCL6 expressions, and increase in PRDM1 and XBP1 expressions in D7 plasmablasts and D10 PCs. It involves down-regulation of genes controlled by Pax5 and induction of genes controlled by Blimp-1 and XBP1 (unfold protein response). The detailed phenotype of D10 PCs resembles that of peripheral blood PCs detected after immunization of healthy donors. This in vitro model will facilitate further studies in PC biology. It will likewise be helpful to study PC dyscrasias, including multiple myeloma.
Project description:Several evolutionary processes shape the genetic and phenotypic differentiation of populations. Among them, the joint effects of gene flow, selection and phenotypic plasticity are poorly known, especially when trying to understand how maladaptive plasticity affects population divergence. We extended a quantitative genetic model of Hendry et al. (2001) to describe these joint effects on phenotypic and additive genetic divergence between two populations, and their phenotypic and genetic differentiation (PST and QST). With individual-based simulations, we tested our model predictions and further modeled allelic differentiation at neutral (FST) and adaptive (FSTQ) loci. While adaptive phenotypic plasticity allows for large phenotypic divergence and differentiation despite high gene flow, maladaptive plasticity promotes genetic divergence and generates countergradient variation, under extensive migration with phenotypic differences sometimes opposed to genetic differences. Maladaptive plasticity can also promote adaptive phenotypic divergence by reducing the effective gene flow. Overall, plasticity decouples genetic from phenotypic differences between populations, and blurs the correlation between phenotypic divergence and local adaptation. By deriving models of population differentiation for three different life cycles, we further describe the effect of a species' ecology on evolution in structured populations.
Project description:The ability to succeed in diverse conditions is a key factor allowing introduced species to successfully invade and spread across new areas. Two non-exclusive factors have been suggested to promote this ability: adaptive phenotypic plasticity of individuals, and the evolution of locally adapted populations in the new range. We investigated these individual and population-level factors in Polygonum cespitosum, an Asian annual that has recently become invasive in northeastern North America. We characterized individual fitness, life-history, and functional plasticity in response to two contrasting glasshouse habitat treatments (full sun/dry soil and understory shade/moist soil) in 165 genotypes sampled from nine geographically separate populations representing the range of light and soil moisture conditions the species inhabits in this region. Polygonum cespitosum genotypes from these introduced-range populations expressed broadly similar plasticity patterns. In response to full sun, dry conditions, genotypes from all populations increased photosynthetic rate, water use efficiency, and allocation to root tissues, dramatically increasing reproductive fitness compared to phenotypes expressed in simulated understory shade. Although there were subtle among-population differences in mean trait values as well as in the slope of plastic responses, these population differences did not reflect local adaptation to environmental conditions measured at the population sites of origin. Instead, certain populations expressed higher fitness in both glasshouse habitat treatments. We also compared the introduced-range populations to a single population from the native Asian range, and found that the native population had delayed phenology, limited functional plasticity, and lower fitness in both experimental environments compared with the introduced-range populations. Our results indicate that the future spread of P. cespitosum in its introduced range will likely be fueled by populations consisting of individuals able to express high fitness across diverse light and moisture conditions, rather than by the evolution of locally specialized populations.
Project description:Highland populations living permanently under hypobaric hypoxia have been subject of extensive research because of the relevance of their physiological adaptations for the understanding of human health and disease. In this context, what is considered high altitude is a matter of interpretation and while the adaptive processes at high altitude (above 3000 m) are well documented, the effects of moderate altitude (below 3000 m) on the phenotype are less well established. In this study, we compare physiological and anthropometric characteristics as well as genetic variations in two Andean populations: the Calchaquíes (2300 m) and neighboring Collas (3500 m). We compare their phenotype and genotype to the sea-level Wichí population. We measured physiological (heart rate, oxygen saturation, respiration rate, and lung function) as well as anthropometric traits (height, sitting height, weight, forearm, and tibia length). We conducted genome-wide genotyping on a subset of the sample (n = 74) and performed various scans for positive selection. At the phenotypic level (n = 179), increased lung capacity stood out in both Andean groups, whereas a growth reduction in distal limbs was only observed at high altitude. At the genome level, Calchaquíes revealed strong signals around PRKG1, suggesting that the nitric oxide pathway may be a target of selection. PRKG1 was highlighted by one of four selection tests among the top five genes using the population branch statistic. Selection tests results of Collas were reported previously. Overall, our study shows that some phenotypic and genetic differentiation occurs at intermediate altitude in response to moderate lifelong selection pressures.
Project description:Systemic lupus erythematosus (SLE) is a generalized autoimmune disease characterized by abnormal B cell activation and the occurrence of increased frequencies of circulating plasma cells (PC). The molecular characteristics and nature of circulating PC and B cells in SLE have not been completely characterized. Microarray analysis of gene expression was used to characterize circulating PC in subjects with active SLE. Flow cytometry was used to sort PC and comparator B cell populations from active SLE blood, normal blood and normal tonsil. The gene expression profiles of the sorted B cell populations were then compared. SLE PC exhibited a similar gene expression signature as tonsil PC. The differences in gene expression between SLE PC and normal tonsil PC and tonsil plasmablasts (PB) suggest a mature Ig secreting cell phenotype in the former population. Despite this, SLE PC differed in expression of about half the genes from previously published gene expression profiles of normal bone marrow PC, indicating that these cells had not achieved a fully mature status. Abnormal expression of several genes, including CXCR4 and S1P(1), suggests a mechanism for the persistence of SLE PC in the circulation. All SLE B cell populations revealed an interferon (IFN) gene signature previously only reported in unseparated SLE peripheral blood mononuclear cells. These data indicate that SLE PC are a unique population of Ig secreting cells with a gene expression profile indicative of a mature, but not fully differentiated phenotype.
Project description:INTRODUCTION: While amniotic mesenchymal cells have been isolated and characterized in different species, amniotic epithelial cells (AECs) have been found only in humans and horses and are recently considered valid candidates in regenerative medicine. The aim of this work is to obtain and characterize, for the first time in the feline species, presumptive stem cells from the epithelial portion of the amnion (AECs) to be used for clinical applications. METHODS: In our study, we molecularly characterized and induced in vitro differentiation of feline AECs, obtained after enzymatic digestion of amnion. RESULTS: AECs displayed a polygonal morphology and the mean doubling time value was 1.94 ± 0.04 days demonstrating the high proliferating capacity of these cells. By RT-PCR, AECs expressed pluripotent (Oct4, Nanog) and some mesenchymal markers (CD166, CD44) suggesting that an epithelial-mesenchymal transition may occur in these cells that lack the hematopoietic marker CD34. Cells also showed the expression of embryonic marker SSEA-4, but not SSEA-3, as demonstrated by immunocytochemistry and flow cytometry. Moreover, the possibility to use feline AECs in cell therapies resides in their low immunogenicity, due to the absence of MHC-II antigen expression. After induction, AECs differentiated into the mesodermic and ectodermic lineages, demonstrating high plasticity. CONCLUSIONS: In conclusion, feline AECs appear to be a readily obtainable, highly proliferative, multipotent and non-immunogenic cell line from a source that may represent a good model system for stem cell biology and be useful in allogenic cell-based therapies in order to treat tissue lesions, especially with loss of substance.
Project description:Human Dental Pulp Stem Cells (hDPSCs) represent a type of adult mesenchymal stem cells that have the ability to differentiate in vitro in several lineages such as odontoblasts, osteoblasts, chondrocytes, adipocytes and neurons. In the current work, we used hDPSCs as the experimental model to study the role of recombinant prion protein 23⁻231 (recPrPC) in the neuronal differentiation process, and in the signal pathway activation of ERK 1/2 and Akt. We demonstrated that recPrPC was able to activate an intracellular signal pathway mediated by extracellular-signal-regulated kinase 1 and 2 (ERK 1/2) and protein kinase B (Akt). Moreover, in order to understand whether endogenous prion protein (PrPC) was necessary to mediate the signaling induced by recPrPC, we silenced PrPC, demonstrating that the presence of endogenous PrPC was essential for ERK 1/2 and Akt phosphorylation. Since endogenous PrPC is a well-known lipid rafts component, we evaluated the role of these structures in the signal pathway induced by recPrPC. Our results suggest that lipid rafts integrity play a key role in recPrPC activity. In fact, lipid rafts inhibitors, such as fumonisin B1 and MβCD, significantly prevented ERK 1/2 and Akt phosphorylation induced by recPrPC. In addition, we investigated the capacity of recPrPC to induce hDPSCs neuronal differentiation process after long-term stimulation through the evaluation of typical neuronal markers expression such as B3-Tubulin, neurofilament-H (NFH) and growth associated protein 43 (GAP43). Accordingly, when we silenced endogenous PrPC, we observed the inhibition of neuronal differentiation induced by recPrPC. The combined data suggest that recPrPC plays a key role in the neuronal differentiation process and in the activation of specific intracellular signal pathways in hDPSCs.