Network traits predict ecological strategies in fungi.

Colonization of terrestrial environments by filamentous fungi relies on their ability to form networks that can forage for and connect resource patches. Despite the importance of these networks, ecologists rarely consider network features as functional traits because their measurement and interpretation are conceptually and methodologically difficult. To address these challenges, we have developed a pipeline to translate images of fungal mycelia, from both micro- and macro-scales, to weighted network graphs that capture ecologically relevant fungal behaviour. We focus on four properties that we hypothesize determine how fungi forage for resources, specifically: connectivity; relative construction cost; transport efficiency; and robustness against attack by fungivores. Constrained ordination and Pareto front analysis of these traits revealed that foraging strategies can be distinguished predominantly along a gradient of connectivity for micro- and macro-scale mycelial networks that is reminiscent of the qualitative 'phalanx' and 'guerilla' descriptors previously proposed in the literature. At one extreme are species with many inter-connections that increase the paths for multidirectional transport and robustness to damage, but with a high construction cost; at the other extreme are species with an opposite phenotype. Thus, we propose this approach represents a significant advance in quantifying ecological strategies for fungi using network information.

Effects of reclaimed waters on spectral properties and leaf traits of citrus orchards.

Effects resulting from the use of reclaimed waters on mandarins and grapefruits are evaluated by measuring the spectral responses of their canopies and the anatomy and the chlorophyll content of their leaves against control trees irrigated with waters provided by an interbasin transfer. Spectral responses from the red (R) and near-infrared (NIR) wavelength bands, and its normalized ratio (NDVI), were acquired from a hyperspatial flight conducted after a low-moderate exposition to reclaimed waters. Chlorophyll and leaf and palisade/spongy ratio thicknesses were analyzed after a moderate-high exposition. Significant differences between controls and treatments were detected in mandarins in R and leaf chlorophyll, but not in grapefruits, likely because of their higher tolerance to saline waters. Reused waters did not affect either NIR-NDVI or anatomy traits. Hyperspatial sensing techniques are suitable for detecting chlorophyll dynamics, but NIR information and related vegetation indices may mask the detection of periods of saline stress in citrus orchards.

The RING ubiquitin E3 RNF114 interacts with A20 and modulates NF-κB activity and T-cell activation.

Accurate regulation of nuclear factor-κB (NF-κB) activity is crucial to prevent a variety of disorders including immune and inflammatory diseases. Active NF-κB promotes IκBα and A20 expression, important negative regulatory molecules that control the NF-κB response. In this study, using two-hybrid screening we identify the RING-type zinc-finger protein 114 (RNF114) as an A20-interacting factor. RNF114 interacts with A20 in T cells and modulates A20 ubiquitylation. RNF114 acts as negative regulator of NF-κB-dependent transcription, not only by stabilizing the A20 protein but also IκBα. Importantly, we demonstrate that in T cells, the effect of RNF114 is linked to the modulation of T-cell activation and apoptosis but is independent of cell cycle regulation. Altogether, our data indicate that RNF114 is a new partner of A2O involved in the regulation of NF-κB activity that contributes to the control of signaling pathways modulating T cell-mediated immune response.

Identification of the NF-κB inhibitor A20 as a key regulator for human adipogenesis.

The zinc-finger protein A20 is a key player in the negative feedback regulation of the nuclear factor kappa-light-chain-enhancer of activated B-cell (NF-κB) pathway in response to multiple stimuli. Tumor necrosis factor alpha (TNFα), a cytokine with pleiotropic effects on cellular proliferation and differentiation, dramatically increases A20 expression in all tissues. As TNFα inhibits adipocyte differentiation, we have determined the contribution of A20 to the adipogenic capacity of human mesenchymal stromal cells (MSCs). Here we show that A20 is constitutively expressed in MSCs, which previously has been observed only in cells that are either tumor or immune cells (T/B lymphocytes). TNFα stimulation induced a rapid degradation of A20 protein mediated exclusively by the proteasome in MSCs and not by caspases. This degradation is concomitant to the induction of its own mRNA, which suggests that a tight regulation of NF-κB signaling in MSCs is fundamental. On one hand, we demonstrate that the knockdown of A20-mediated transcript dramatically decreases the adipogenic capacity of MSCs, which correlates with the phenotype observed in the presence of TNFα. On the other hand, A20 overexpression blocks NF-κB activation and drives to increased adipogenesis, even in the presence of TNFα treatment. In conclusion, our data demonstrate that the presence of A20 allows MSCs to differentiate into adipocytes by maintaining NF-κB signaling at a basal state.

p22phox-dependent NADPH oxidase activity is required for megakaryocytic differentiation.

Transient reactive oxygen species (ROS) production is currently proving to be an important mechanism in the regulation of intracellular signalling, but reports showing the involvement of ROS in important biological processes, such as cell differentiation, are scarce. In this study, we show for the first time that ROS production is required for megakaryocytic differentiation in K562 and HEL cell lines and also in human CD34(+) cells. ROS production is transiently activated during megakaryocytic differentiation, and such production is abolished by the addition of different antioxidants (such as N-acetyl cysteine, trolox, quercetin) or the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor diphenylene iodonium. The inhibition of ROS formation hinders differentiation. RNA interference experiments have shown that a p22(phox)-dependent NADPH oxidase activity is responsible for ROS production. In addition, the activation of ERK, AKT and JAK2 is required for differentiation, but the activation of phosphatidylinositol 3-kinase and c-Jun N-terminal kinase seems to be less important. When ROS production is prevented, the activation of these signalling pathways is partly inhibited. Taken together, these results show that NADPH oxidase ROS production is essential for complete activation of the main signalling pathways involved in megakaryocytopoiesis to occur. We suggest that this might also be important for in vivo megakaryocytopoiesis.

Mesenchymal stem cells and their use as cell replacement therapy and disease modelling tool.

Mesenchymal stem cells (MSCs) from adult somatic tissues may differentiate in vitro and in vivo into multiple mesodermal tissues including bone, cartilage, adipose tissue, tendon, ligament or even muscle. MSCs preferentially home to damaged tissues where they exert their therapeutic potential. A striking feature of the MSCs is their low inherent immunogenicity as they induce little, if any, proliferation of allogeneic lymphocytes and antigen-presenting cells. Instead, MSCs appear to be immunosuppressive in vitro. Their multilineage differentiation potential coupled to their immuno-privileged properties is being exploited worldwide for both autologous and allogeneic cell replacement strategies. Here, we introduce the readers to the biology of MSCs and the mechanisms underlying immune tolerance. We then outline potential cell replacement strategies and clinical applications based on the MSCs immunological properties. Ongoing clinical trials for graft-versus-host-disease, haematopoietic recovery after co-transplantation of MSCs along with haematopoietic stem cells and tissue repair are discussed. Finally, we review the emerging area based on the use of MSCs as a target cell subset for either spontaneous or induced neoplastic transformation and, for modelling non-haematological mesenchymal cancers such as sarcomas.

An endoplasmic reticulum retention function for the cytoplasmic tail of the human pre-T cell receptor (TCR) alpha chain: potential role in the regulation of cell surface pre-TCR expression levels.

The pre-T cell receptor (TCR), which consists of a TCR-beta chain paired with pre-TCR-alpha (pTalpha) and associated with CD3/zeta components, is a critical regulator of T cell development. For unknown reasons, extremely low pre-TCR levels reach the plasma membrane of pre-T cells. By transfecting chimeric TCR-alpha-pTalpha proteins into pre-T and mature T cell lines, we show here that the low surface expression of the human pre-TCR is pTalpha chain dependent. Particularly, the cytoplasmic domain of pTalpha is sufficient to reduce surface expression of a conventional TCR-alpha/beta to pre-TCR expression levels. Such reduced expression cannot be attributed to qualitative differences in the biochemical composition of the CD3/zeta modules associated with pre-TCR and TCR surface complexes. Rather, evidence is provided that the pTalpha cytoplasmic tail also causes a reduced surface expression of individual membrane molecules such as CD25 and CD4, which are shown to be retained in the endoplasmic reticulum (ER). Native pTalpha is also observed to be predominantly ER localized. Finally, sequential truncations along the pTalpha cytoplasmic domain revealed that removal of the COOH-terminal 48 residues is sufficient to release a CD4-pTalpha chimera from ER retention, and to restore native CD4 surface expression levels. As such a truncation in pTalpha also correlates with enhanced pre-TCR expression, the observed pTalpha ER retention function may contribute to the regulation of surface pre-TCR expression on pre-T cells.

Beta-selection is associated with the onset of CD8beta chain expression on CD4(+)CD8alphaalpha(+) pre-T cells during human intrathymic development.

T-cell precursors that undergo productive rearrangements at the T-cell receptor (TCR) beta locus are selected for proliferation and further maturation, before TCRalpha expression, by signaling through a pre-TCR composed of the TCRbeta chain paired with a pre-TCRalpha (pTalpha) chain. Such a critical developmental checkpoint, known as beta-selection, results in progression from CD4(-) CD8(-) double negative (DN) to CD4(+) CD8(+) double positive (DP) TCRalphabeta(-) thymocytes. In contrast to mice, progression to the DP compartment occurs in humans via a CD4(+) CD8(-) intermediate stage. Here we show that the CD4(+) CD8(-) to CD4(+) CD8(+) transition involves the sequential acquisition of the alpha and beta chains of CD8 at distinct maturation stages. Our results indicate that CD8alpha, but not CD8beta, is expressed in vivo in a minor subset of DP TCRalphabeta(-) thymocytes, referred to as CD4(+) CD8alphaalpha(+) pre-T cells, mostly composed of resting cells lacking cytoplasmic TCRbeta chain (TCRbeta(ic)). In contrast, expression of CD8alphabeta heterodimers was selectively found on DP TCRalphabeta(-) thymocytes that express TCRbeta(ic) and are enriched for cycling cells. Interestingly, CD4(+) CD8alphaalpha(+) pre-T cells are shown to be functional intermediates between CD4(+) CD8(-) TCRbeta(ic)(-) and CD4(+) CD8alphabeta(+) TCRbeta(ic)(+) thymocytes. More importantly, evidence is provided that onset of CD8beta and TCRbeta(ic) expression are coincident developmental events associated with acquisition of CD3 and pTalpha chain on the cell surface. Therefore, we propose that the CD4(+) CD8alphaalpha(+) to CD4(+) CD8alphabeta(+) transition marks the key control point of pre-TCR-mediated beta-selection in human T-cell development.

Identification of a late stage of small noncycling pTalpha- pre-T cells as immediate precursors of T cell receptor alpha/beta+ thymocytes.

During thymocyte development, progression from T cell receptor (TCR)beta to TCRalpha rearrangement is mediated by a CD3-associated pre-TCR composed of the TCRbeta chain paired with pre-TCRalpha (pTalpha). A major issue is how surface expression of the pre-TCR is regulated during normal thymocyte development to control transition through this checkpoint. Here, we show that developmental expression of pTalpha is time- and stage-specific, and is confined in vivo to a limited subset of large cycling human pre-T cells that coexpress low density CD3. This restricted expression pattern allowed the identification of a novel subset of small CD3(-) thymocytes lacking surface pTalpha, but expressing cytoplasmic TCRbeta, that represent late noncycling pre-T cells in which recombination activating gene reexpression and downregulation of T early alpha transcription are coincident events associated with cell cycle arrest, and immediately preceding TCRalpha gene expression. Importantly, thymocytes at this late pre-T cell stage are shown to be functional intermediates between large pTalpha+ pre-T cells and TCRalpha/beta+ thymocytes. The results support a developmental model in which pre-TCR-expressing pre-T cells are brought into cycle, rapidly downregulate surface pre-TCR, and finally become small resting pre-T cells, before the onset of TCRalpha gene expression.

Enhanced green fluorescent protein as an efficient reporter gene for retroviral transduction of human multipotent lymphoid precursors.

Owing to its autofluorescence properties, green fluorescent protein (GFP) has aroused increasing interest as a marker system for many research applications. In this study we investigated the suitability of the "enhanced" GFP (EGFP), a mutant version of GFP optimized for flow cytometry and microscopy detection, as a reporter gene for retroviral transduction protocols. EGFP was shown to display a bright and stably maintained emission pattern in transfected GP+envAm12 packaging cells. Stable fluorescent emission was observed as well after transduction in NIH 3T3 fibroblasts and in the human Jurkat T cell line, in which EGFP was shown to confer no deleterious effect or growth disadvantage on the expressing cells. Moreover, EGFP expression could be detected after short-term retroviral exposure, thus allowing a rapid and quantitative retroviral titering assay, alternative to the standard colony-formation procedure. Most importantly, we showed the feasibility of EGFP as a marker gene in retroviral-mediated transduction of primary lymphoid precursors. In particular, transduction of CD34+CD1- human thymocytes by short-term cocultivation yielded up to 30% of EGFP-expressing cells, while maintaining CD34 expression levels. Finally, when cultured under multicytokine-supported conditions, such transduced intrathymic progenitors were shown to efficiently generate lymphoid-related dendritic cells, which displayed a distinct EGFP expression. Therefore, because of its rapid and easy detectability and its nontoxic characteristics, EGFP proves itself to be a valuable reporter gene by allowing the transduction of multipotential progenitors and by being compatible with the developmental programs of lymphoid lineage generation.

Identification of a common developmental pathway for thymic natural killer cells and dendritic cells.

Current data support the notion that the thymus is seeded by a yet uncommitted progenitor cell able to generate T cells, B cells, natural killer (NK) cells, and dendritic cells (DCs). We assess in this report the developmental relationship of DCs and NK cells derived from a small subset of CD34(+) human postnatal thymocytes that, like the earliest precursors in the fetal thymus, display low CD33 surface expression. Culture of these isolated CD34(+) CD33(lo) thymic progenitors with a mixture of cytokines, including interleukin-7 (IL-7), IL-1alpha, IL-6, granulocyte-macrophage colony-stimulating factor, and stem cell factor, results in predominant generation of DCs. However, the addition of IL-2 to the cytokine mixture leads to the simultaneous development of DCs and NK cells. Both developmental pathways progress through a transient population of CD34(+)CD44(bright) CD5(lo/-)CD33(+) large-sized cells, distinct from small-sized T-lineage precursors, that contain bipotential NK/DC progenitors. These data provide evidence of linked pathways of NK cell and DC development from intrathymic precursors and suggest that NK cells and DCs branch off the T lineage through a common intermediate progenitor.

Herpesvirus saimiri immortalization of alpha beta and gamma delta human T-lineage cells derived from CD34+ intrathymic precursors in vitro.

Herpesvirus saimiri (HVS), an agent that can infect many human cell types, has been shown to immortalize selectively TCR alpha beta + CD3+ T lymphocytes. Human T cell precursors defined as CD34+CD3-CD4-CD8- were isolated from thymic samples and exposed to HVS in the presence of either IL-2 or IL-7. Cultures lacking the virus were non-viable by day 15. Test cultures, in contrast, showed a sustained proliferative activity lasting > 5 months, allowing the phenotypical and molecular analysis of the cellular progeny. In the presence of IL-7, TCR alpha beta + cells with three different phenotypes (mainly CD4+CD8-, but also CD4+CD8+ and CD4-CD8+) were immortalized, whereas no TCR gamma delta + cells were recovered. Kinetic studies showed that the expansion of immortalized TCR alpha beta + cells was preceded by a gradual loss of CD34+ cells followed by a transient accumulation of two distinct cell subsets: first CD1+CD4+CD3- cells and then CD4+CD8+ thymocytes. This resembles early phenotypic changes occurring during normal intrathymic T cell development. In the presence of IL-2, in contrast, only TCR gamma delta + cells were immortalized (mainly CD4-CD8+, but also CD4-CD8-). The results show that HVS can be used to read the CD3+ cellular outcome of T cell differentiation assays, including gamma delta + CD4-CD8+, gamma delta + CD4-CD8-, alpha beta + CD4+CD8-, alpha beta + CD4-CD8+ and alpha beta + CD4+CD8+ T cells. A clear role for different cytokines (IL-2 for gamma delta + cells, IL-7 for alpha beta + cells) in early T cell commitment was also apparent.

Regulation of pre-T cell receptor (pT alpha-TCR beta) gene expression during human thymic development.

In murine T cell development, early thymocytes that productively rearrange the T cell receptor (TCR) beta locus are selected to continue maturation, before TCR alpha expression, by means of a pre-TCR alpha- (pT alpha-) TCR beta heterodimer (pre-TCR). The aim of this study was to identify equivalent stages in human thymocyte development. We show here that variable-diversity-joining region TCR beta rearrangement and the expression of full-length TCR beta transcripts have been initiated in some immature thymocytes at the TCR alpha/beta- CD4+CD8- stage, and become common in a downstream subset of TCR alpha/beta- CD4+CD8+ thymocytes that is highly enriched in large cycling cells. TCR beta chain expression was hardly detected in TCR alpha/beta- CD4+CD8- thymocytes, whereas cytoplasmic TCR beta chain was found in virtually all TCR alpha/beta- CD4+CD8+ blasts. In addition, a TCR beta complex distinct from the mature TCR alpha/beta heterodimer was immunoprecipitated only from the latter subset. cDNA derived from TCR alpha/beta- CD4+CD8+ blasts allowed us to identify and clone the gene encoding the human pT alpha chain, and to examine its expression at different stages of thymocyte development. Our results show that high pT alpha transcription occurs only in CD4+CD8- and CD4+CD8+ TCR alpha/beta- thymocytes, whereas it is weaker in earlier and later stages of development. Based on these results, we propose that the transition from TCR alpha/beta- CD4+CD8- to TCR alpha/beta- CD4+CD8+ thymocytes represents a critical developmental stage at which the successful expression of TCR beta promotes the clonal expansion and further maturation of human thymocytes, independent of TCR alpha.

The development of T and non-T cell lineages from CD34+ human thymic precursors can be traced by the differential expression of CD44.

In addition to T-lineage cells, a small proportion of hematopoietic non-T cells are present in the human postnatal thymus. However, the origin of this minor non-T cell thymic compartment is presently unknown. In this study we have analyzed the developmental potential of the earliest human intrathymic precursors, characterized as CD34+ cells expressing intermediate levels of CD44. We show that these CD34+CD44int thymocytes cultured with interleukin 7 were able to develop simultaneously into both T- and non-T (monocytes and dendritic cells) -lineage cells. Both developmental pathways progress through a CD1+CD4+ intermediate stage, currently believed to be the immediate precursor of double positive thymocytes. However, separate progenitors for either T or non-T cells could be characterized within CD1+CD4+ thymocytes by their opposite expression of CD44. Downregulated levels of CD44 identified CD1+CD4+ T-lineage precursors, whereas CD44 upregulation occurred on CD1+CD4+ intermediates that later differentiated into non-T cells. Therefore, commitment of human early intrathymic precursors to either T or non-T cell lineages can be traced by the differential expression of the CD44 receptor.

Induced photolysis of rabbit red blood cells by several photosensitizers.

The photolysis of rabbit red blood cells induced by several photosensitizers has been studied. Membrane photohemolysis was found to be dependent on light dose (J/cm2) for hematoporphyrin (HP), methylene blue (MB) and toluidine blue (TB). No significant hemolysis was detected when mesotetra (4N-methylpyridyl) porphine (T4MPyP) plus light was used. Sodium azide inhibited, whereas deuterium oxide potentiated membrane lysis with HP, MB and TB. In the case of T4MPyP no differences were observed when using sodium azide or deuterium oxide.

Photodynamic induction of DNA-protein cross-linking in solution by several sensitizers and visible light.

The combined effect of several sensitizers and light on H2O or D2O solutions of DNA-histone complexes, as well as the significance of singlet oxygen (1O2), in this photosensitizing reaction has been studied. On H2O solutions, the production of 1O2, as well as the formation of DNA-protein cross-links (DPCs), were found to be dependent on light dose for all the sensitizers. Mesotetra (4N-methylpyridyl) porphine (T4MPyP), methylene blue (MB), and toluidine blue (TB) were the best photosensitizers with regard to tryptophan photolysis, followed by hematoporphyrin (HP), thioflavine T (TT), and pyronin G (PG). The formation of DPCs showed high initial rates, reaching a plateau at doses over 90 J/cm2. Under these irradiation conditions, the percentage of DPCs induced by the sensitizers decreases in the order T4MPyP > MB > TB >> HP approximately TT >> PG (approximately 0). These DPCs were totally destroyed with proteinase K (15 micrograms/ml). The irradiation of the DNA-histone-sensitizer solutions in the presence of L-carnosine (5 x 10(-4) M) produced approximately a 50% of DPCs inhibition for T4MPyP, MB, and TB, and a total inhibition for HP, TT, and PG. The substitution of H2O by D2O as solvent significantly increased the photodegradation of tryptophan, as well as the photoinduction of DPCs by the sensitizers. The results obtained indicate that singlet oxygen is the main agent responsible in the DNA-protein cross-linking formation.