Tryptophan metabolism activation by indoleamine 2,3-dioxygenase in adipose tissue of obese women: an attempt to maintain immune homeostasis and vascular tone

Human obesity is characterized by chronic low-grade inflammation in white adipose tissue and is often associated with hypertension. The potential induction of indoleamine 2,3-dioxygenase-1 (IDO1), the rate-limiting enzyme in tryptophan/kynurenine degradation pathway, by proinflammatory cytokines, could be associated with these disorders but has remained unexplored in obesity. Using immunohistochemistry, we detected IDO1 expression in white adipose tissue of obese patients, and we focused on its contribution in the regulation of vascular tone and on its immunoregulatory effects. Concentrations of tryptophan and kynurenine were measured in sera of 36 obese and 15 lean women. The expression of IDO1 in corresponding omental and subcutaneous adipose tissues and liver was evaluated. Proinflammatory markers and T-cell subsets were analyzed in adipose tissue via the expression of CD14, IL-18, CD68, TNFα, CD3ε, FOXP3 [a regulatory T-cell (Treg) marker] and RORC (a Th17 marker). In obese subjects, the ratio of kynurenine to tryptophan, which reflects IDO1 activation, is higher than in lean subjects. Furthermore, IDO1 expression in both adipose tissues and liver is increased and is inversely correlated with arterial blood pressure. Inflammation is associated with a T-cell infiltration in obese adipose tissue, with predominance of Th17 in the omental compartment and of Treg in the subcutaneous depot. The Th17/Treg balance is decreased in subcutaneous fat and correlates with IDO1 activation. In contrast, in the omental compartment, despite IDO1 activation, the Th17/Treg balance control is impaired. Taken together, our results suggest that IDO1 activation represents a local compensatory mechanism to limit obesity-induced inflammation and hypertension.     

A single Na+-Pi cotransporter in Toxoplasma plays key roles in phosphate import and control of parasite osmoregulation

Inorganic ions such as phosphate, are essential nutrients required for a broad spectrum of cellular functions and regulation. During infection, pathogens must obtain inorganic phosphate (P_i) from the host. Despite the essentiality of phosphate for all forms of life, how the intracellular parasite Toxoplasma gondii acquires P_i from the host cell is still unknown. In this study, we demonstrated that Toxoplasma actively internalizes exogenous P_i by exploiting a gradient of Na⁺ ions to drive P_i uptake across the plasma membrane. The Na⁺-dependent phosphate transport mechanism is electrogenic and functionally coupled to a cipargarmin sensitive Na⁺-H⁺-ATPase. Toxoplasma expresses one transmembrane P_i transporter harboring PHO4 binding domains that typify the PiT Family. This transporter named TgPiT, localizes to the plasma membrane, the inward buds of the endosomal organelles termed VAC, and many cytoplasmic vesicles. Upon P_i limitation in the medium, TgPiT is more abundant at the plasma membrane. We genetically ablated the PiT gene, and ΔTgPiT parasites are impaired in importing P_i and synthesizing polyphosphates. Interestingly, ΔTgPiT parasites accumulate 4-times more acidocalcisomes, storage organelles for phosphate molecules, as compared to parental parasites. In addition, these mutants have a reduced cell volume, enlarged VAC organelles, defects in calcium storage and a slightly alkaline pH. Overall, these mutants exhibit severe growth defects and have reduced acute virulence in mice. In survival mode, ΔTgPiT parasites upregulate several genes, including those encoding enzymes that cleave or transfer phosphate groups from phosphometabolites, transporters and ions exchangers localized to VAC or acidocalcisomes. Taken together, these findings point to a critical role of TgPiT for P_i supply for Toxoplasma and also for protection against osmotic stresses.     

Munc13-4 is essential for cytolytic granules fusion and is mutated in a form of familial hemophagocytic lymphohistiocytosis (FHL3)

Secretion of cytolytic granules content at the immunological synapse is a highly regulated process essential for lymphocyte cytotoxicity. This process requires the rapid transfer of perforin containing lytic granules to the target cell interface, followed by their docking and fusion with the plasma membrane. Defective cytotoxicity characterizes a genetically heterogeneous condition named familial hemophagocytic lymphohistiocytosis (FHL), which can be associated with perforin deficiency. The locus of a perforin (+) FHL subtype (FHL3), observed in 10 patients, was mapped to 17q25. This region contains hMunc13-4, a member of the Munc13 family of proteins involved in vesicle priming function. HMunc13-4 mutations were shown to cause FHL3. HMunc13-4 deficiency results in defective cytolytic granule exocytosis, despite polarization of the secretory granules and docking with the plasma membrane. Expressed tagged hMunc13-4 localizes with cytotoxic granules at the immunological synapse. HMunc13-4 is therefore essential for the priming step of cytolytic granules secretion preceding vesicle membrane fusion.     

The ultimate effect of being cleaned: does ectoparasite removal have reproductive consequences for damselfish clients?

The mutualistic nature of cleaning symbioses has long remainedunconfirmed because of the difficulty in showing net benefitsfor clients. We have previously shown that cleaning gobies (Elacatinusspp.) within territories of Caribbean longfin damselfish (Stegastesdiencaeus) reduce the number of gnathiid isopod ectoparasiteson territory owners. We now investigate whether this benefitof being cleaned has reproductive consequences for male longfindamselfish. The mating success, rate of egg loss, and parentalaggression of 40 nest-guarding males were assessed during sixconsecutive monthly reproductive periods. Ten males had cleaningstations within their territory, 10 males were without cleaningstations, and 20 males initially with a cleaning station hadtheir cleaners removed half-way through the study. Ectoparasiteloads on our focal fish were very low; however, damselfish withcleaning stations still had significantly fewer ectoparasitesthan did fish without cleaning stations. There was, however,no significant difference in the number of eggs, clutches, orarea of clutches received, or in the number of eggs lost beforehatching between damselfish with and without cleaners. We alsofound no difference in parental male aggression between damselfishwith and without cleaners. We conclude that although ectoparasiteremoval appears to have no direct consequence for reproduction,at least for the levels of infestations observed on our studysite, it may still affect other aspects of damselfish fitnesssuch as survival.     

Plant genome archaeology: evidence for conserved ancestral chromosome segments in dicotyledonous plant species

We have developed genetic maps, based on expressed sequence tags (ESTs) that are homologous to Arabidopsis genes, in four dicotyledonous crop plant species from different families. A comparison of these maps with the physical map of Arabidopsis reveals common genome segments that appear to have been conserved throughout the evolution of the dicots. In the four crop species analysed these segments comprise between 16 and 33% of the Arabidopsis genome. Our findings extend the synteny patterns previously observed only within plant families, and indicate that structural and functional information from the model species will be, at least in part, applicable in crop plants with large genomes.     

Diverging patterns of mitochondrial and nuclear DNA diversity in subarctic black spruce: imprint of a founder effect associated with postglacial colonization

High-latitude ecotonal populations at the species margins may exhibit altered patterns of genetic diversity, resulting from more or less recent founder events and from bottleneck effects in response to climate oscillations. Patterns of genetic diversity were investigated in nine populations of the conifer black spruce (Picea mariana [Mill.] BSP.) in northwestern Québec, Canada, using seed-dispersed mitochondrial (mt) DNA and nuclear (nc) DNA. mtDNA diversity (mitotypes) was assessed at three loci, and ncDNA diversity was estimated for nine expressed sequence tag polymorphism (ESTP) loci. Sampling included populations from the boreal forest and the southern and northern subzones of the subarctic forest-tundra, a fire-born ecotone. For ncDNA, populations from all three vegetation zones were highly diverse with little population differentiation (thetaN = 0.014); even the northernmost populations showed no loss of rare alleles. Patterns of mitotype diversity were strikingly different: within-population diversity and population differentiation were high for boreal forest populations [expected heterozygosity per locus (HE) = 0.58 and thetaM = 0.529], but all subarctic populations were fixed for a single mitotype (HE = 0). This lack of variation suggests a founder event caused by long-distance seed establishment during postglacial colonization, consistent with palaeoecological data. The estimated movement of seeds alone (effective number of migrants per generation, NmM < 2) was much restricted compared to that estimated from nuclear variants, which including pollen movement (NmN > 17). This could account for the conservation of a founder imprint in the mtDNA of subarctic black spruce. After reduction, presumably in the early Holocene, the diversity in ncDNA would have been replenished rapidly by pollen-mediated gene flow, and maintained subsequently through vegetative layering during the current cooler period covering the last 3000 years.     

Egg cannibalism by Coleomegilla maculata lengi neonates: preference even in the presence of essential prey

Abstract 1. Egg cannibalism among coccinellids has been reported widely, however reasons why this type of behaviour is observed so frequently have been neglected. This experiment was undertaken to clarify whether cannibalistic behaviour is advantageous to Coleomegilla maculata lengi Thimberlake neonates and to understand the reasons for high levels of egg cannibalism.
2. Benefits gained by neonate cannibals were ascertained by comparing survival, developmental time, and second-instar weight of C. maculata larvae that were allowed to cannibalise conspecific eggs or not. Preference and behaviour tests were also conducted to assess the reasons for high levels of egg cannibalism.
3. Cannibal neonates grew faster and were heavier than non-cannibals. The developmental time of neonates was influenced more by prey vulnerability than by prey quality.
4. In choice tests, where three different proportions of conspecific eggs and aphids were offered (33–67, 50–50, and 67–33%), C. maculata neonates always consumed significantly more eggs. Manly's preference indexes indicated that neonates showed a consistent preference for conspecific eggs.
5. Seventy-five per cent of neonates observed went directly towards eggs and 90% of the first prey consumed by neonates were an egg. When aphids were painted with extract of crushed eggs and eggs with crushed aphids to determine whether neonates found eggs by chemical cues, neonates preferred aphids painted with egg extract to eggs painted with aphid extract.
6. It was concluded that C. maculata neonates benefited from cannibalistic behaviour. Moreover, egg cannibalism is not related only to frequency of encounter; chemical cues are also involved in egg searching.     

Rapid identification of lettuce seed germination mutants by bulked segregant analysis and whole genome sequencing

Lettuce (Lactuca sativa) seeds exhibit thermoinhibition, or failure to complete germination when imbibed at warm temperatures. Chemical mutagenesis was employed to develop lettuce lines that exhibit germination thermotolerance. Two independent thermotolerant lettuce seed mutant lines, TG01 and TG10, were generated through ethyl methanesulfonate mutagenesis. Genetic and physiological analyses indicated that these two mutations were allelic and recessive. To identify the causal gene(s), we applied bulked segregant analysis by whole genome sequencing. For each mutant, bulked DNA samples of segregating thermotolerant (mutant) seeds were sequenced and analyzed for homozygous single‐nucleotide polymorphisms. Two independent candidate mutations were identified at different physical positions in the zeaxanthin epoxidase gene (ABSCISIC ACID DEFICIENT 1/ZEAXANTHIN EPOXIDASE, or ABA1/ZEP) in TG01 and TG10. The mutation in TG01 caused an amino acid replacement, whereas the mutation in TG10 resulted in alternative mRNA splicing. Endogenous abscisic acid contents were reduced in both mutants, and expression of the ABA1 gene from wild‐type lettuce under its own promoter fully complemented the TG01 mutant. Conventional genetic mapping confirmed that the causal mutations were located near the ZEP/ABA1 gene, but the bulked segregant whole genome sequencing approach more efficiently identified the specific gene responsible for the phenotype.     

Antibody responses to NY-ESO-1 in primary breast cancer identify a subtype target for immunotherapy

The highly immunogenic human tumor antigen NY-ESO-1 (ESO) is a target of choice for anti-cancer immune therapy. In this study, we assessed spontaneous antibody (Ab) responses to ESO in a large cohort of patients with primary breast cancer (BC) and addressed the correlation between the presence of anti-ESO Ab, the expression of ESO in the tumors and their characteristics. We found detectable Ab responses to ESO in 1% of the patients. Tumors from patients with circulating Ab to ESO exhibited common characteristics, being mainly hormone receptor (HR)⁻ invasive ductal carcinomas of high grade, including both HER2⁻ and HER2⁺ tumors. In line with these results, we detected ESO expression in 20% of primary HR⁻ BC, including both ESO Ab⁺ and Ab⁻ patients, but not in HR⁺ BC. Interestingly, whereas expression levels in ESO⁺ BC were not significantly different between ESO Ab⁺ and Ab⁻ patients, the former had, in average, significantly higher numbers of tumor-infiltrated lymph nodes, indicating that lymph node invasion may be required for the development of spontaneous anti-tumor immune responses. Thus, the presence of ESO Ab identifies a tumor subtype of HR⁻ (HER2⁻ or HER2⁺) primary BC with frequent ESO expression and, together with the assessment of antigen expression in the tumor, may be instrumental for the selection of patients for whom ESO-based immunotherapy may complement standard therapy.