Specific T-cell receptor beta-rearrangements of gluten-triggered CD8+ T-cells are enriched in celiac disease patients' duodenal mucosa

Celiac disease (CeD) is an autoimmune disorder affecting the small intestine with gluten as disease trigger. Infections including Influenza A, increase the CeD risk. While gluten-specific CD4+ T-cells, recognizing HLA-DQ2/DQ8 presented gluten-peptides, initiate and sustain the celiac immune response, CD8+ α/β intraepithelial T-cells elicit mucosal damage. Here, we subjected TCRs from a cohort of 56 CeD patients and 22 controls to an analysis employing 749 published CeD-related TCRβ-rearrangements derived from gluten-specific CD4+ T-cells and gluten-triggered peripheral blood CD8+ T-cells. We show, that in addition to TCRs from gluten-specific CD4+ T-cells, TCRs of gluten-triggered CD8+ T-cells are significantly enriched in CeD duodenal tissue samples. TCRβ-rearrangements of gluten-triggered CD8+ T-cells were even more expanded in patients than TCRs from gluten-specific CD4+ T-cells (p < 0.0002) and highest in refractory CeD. Sequence alignments with TCR-antigen databases suggest that a subgroup of these most likely indirectly gluten-triggered TCRs recognize microbial, viral, and autoantigens.

Functional chimeric genes in ciliates: An instructive case from Euplotes raikovi

In ciliates, with every sexual event the transcriptionally active genes of the sub-chromosomic somatic genome that resides in the cell macronucleus are lost. They are de novo assembled starting from 'Macronuclear Destined Sequences' that arise from the fragmentation of transcriptionally silent DNA sequences of the germline chromosomic genome enclosed in the cell micronucleus. The RNA-mediated epigenetic mechanism that drives the assembly of these sequences is subject to errors which result in the formation of chimeric genes. Studying a gene family that in Euplotes raikovi controls the synthesis of protein signal pheromones responsible for a self/not-self recognition mechanism, we identified the chimeric structure of an 851-bp macronuclear gene previously known to specify soluble and membrane-bound pheromone molecules through an intron-splicing mechanism. This chimeric gene, designated mac-er-1*, conserved the native pheromone-gene structure throughout its coding and 3' regions. Instead, its 5' region is completely unrelated to the pheromone gene structure at the level of a 360-bp sequence, which derives from the assembly with a MDS destined to compound a 2417-bp gene encoding a 696-amino acid protein with unknown function. This mac-er-1* gene characterization provides further evidence that ciliates rely on functional chimeric genes that originate in non-programmed phenomena of somatic MDS recombination to increase the species genetic variability independently of gene reshuffling phenomena of the germline genome.

Evaluation of mutagenic activity of platinum complexes in somatic cells of Drosophila melanogaster

Cisplatin, carboplatin, and oxaliplatin are some of the most often used alkylating chemotherapeutic agents. In view of the paucity of data on the genotoxicity of oxaliplatin, this study compares the mutagenic activity of cisplatin (0.006, 0.012, 0.025, 0.05 mM), carboplatin (0.1, 0.2, 0,5, 1.0 mM), and oxaliplatin (0.1, 0.2, 0,5, 1.0 mM) using the somatic mutation and recombination test (SMART) in Drosophila melanogaster. Standard and high-bioactivation crosses of the drosophilid were used, which present basal and high levels of cytochrome P450 (CYP450) metabolization enzymes, respectively. All concentrations of cisplatin and carboplatin induced lesions in genetic material in both crosses, while oxaliplatin was mutagenic only to high bioactivation flies treated with 0.1, 0.5 and 1 mM of the compound. No significant differences were observed between genotoxicity values of cisplatin and carboplatin. However, CYP450 enzymes may have affected the mutagenic action of oxaliplatin. Carboplatin induced mainly mutation events, while cisplatin triggered mostly mutation and recombination events when low and high doses were used. Most events induced by oxaliplatin were generated by somatic recombination. Important differences were observed in genotoxic potential of platinum chemotherapeutic compounds, possibly due to the origin and type of the lesions induced in DNA and the repair mechanisms involved.

Gene targeting and transgene stacking using intra genomic homologous recombination in plants

Modern agriculture has created a demand for plant biotechnology products that provide durable resistance to insect pests, tolerance of herbicide applications for weed control, and agronomic traits tailored for specific geographies. These transgenic trait products require a modular and sequential multigene stacking platform that is supported by precise genome engineering technology. Designed nucleases have emerged as potent tools for creating targeted DNA double strand breaks (DSBs). Exogenously supplied donor DNA can repair the targeted DSB by a process known as gene targeting (GT), resulting in a desired modification of the target genome. The potential of GT technology has not been fully realized for trait deployment in agriculture, mainly because of inefficient transformation and plant regeneration systems in a majority of crop plants and genotypes. This challenge of transgene stacking in plants could be overcome by Intra-Genomic Homologous Recombination (IGHR) that converts independently segregating unlinked donor and target transgenic loci into a genetically linked molecular stack. The method requires stable integration of the donor DNA into the plant genome followed by intra-genomic mobilization. IGHR complements conventional breeding with genetic transformation and designed nucleases to provide a flexible transgene stacking and trait deployment platform.

Evolution of Immunity and Pathogens

Host and pathogen engage in a constant evolutionary struggle known as a "Red Queen Paradigm". In this struggle, natural selection favours the pathogen which evolves effective virulence mechanisms and the host which is able to field adequate resistance strategies. A number of factors limit what each side can do. These include the fact that the elaboration of virulence or resistance mechanisms results in costs in genetic fitness and requires the use of ever more of the limited number of genes available in the genome. In addition, since the pathogen usually has a very much shorter generation time than the host, it can fix new virulence mutations much more quickly than the host can evolve matching resistance mechanisms. Finally, the host must ensure that its defence system does not result in unacceptable levels of collateral damage to its own tissues. This chapter briefly outlines how these considerations shape host-pathogen interactions.

Limited vegetative compatibility as a cause of somatic recombination in Trichoderma pseudokoningii

With the aim of a better characterization of the somatic recombination process in Trichoderma pseudokoningii, a progeny from crossings between T. pseudokoningii strains contrasting for auxotroph markers was characterized by RAPD markers and PFGE (electrophoretic karyotype). Cytological studies of the conidia, conidiogenesis and heterokaryotic colonies were also performed. The genotypes of the majority of the recombinant strains analyzed were similar to only one of the parental strains and the low frequency of polymorphic RAPD bands suggested that the nuclear fusions may not occur into the heterokaryon. In some heterokaryotic regions the existence of intensely staining hyphae might be related to cell death. We proposed that a mechanism of somatic recombination other than parasexuality might occur, being related to limited vegetative compatibility after postfusion events, as described for other Trichoderma species.