Cell-Specific Imd-NF-κB Responses Enable Simultaneous Antibacterial Immunity and Intestinal Epithelial Cell Shedding upon Bacterial Infection.

Intestinal infection triggers potent immune responses to combat pathogens and concomitantly drives epithelial renewal to maintain barrier integrity. Current models propose that epithelial renewal is primarily driven by damage caused by reactive oxygen species (ROS). Here we found that in Drosophila, the Imd-NF-κB pathway controlled enterocyte (EC) shedding upon infection, via a mechanism independent of ROS-associated apoptosis. Mechanistically, the Imd pathway synergized with JNK signaling to induce epithelial cell shedding specifically in the context of bacterial infection, requiring also the reduced expression of the transcription factor GATAe. Furthermore, cell-specific NF-κB responses enabled simultaneous production of antimicrobial peptides (AMPs) and epithelial shedding in different EC populations. Thus, the Imd-NF-κB pathway is central to the intestinal antibacterial response by mediating both AMP production and the maintenance of barrier integrity. Considering the similarities between Drosophila Imd signaling and mammalian TNFR pathway, our findings suggest the existence of an evolutionarily conserved genetic program in immunity-induced epithelial shedding.

A novel GATA-like zinc finger transcription factor involving in hematopoiesis of Eriocheir sinensis.

GATA transcription factor is a family of DNA-binding proteins that can recognize and bind to sequence of (A/T) GATA (A/G). In the present study, a GATA-like protein (named as EsGLP) was characterized from Eriocheir sinensis, including an 834 bp full length open reading frame of EsGLP, encoding a polypeptide of 277 amino acids. The deduced amino acid sequence of EsGLP contained one conserved GATA-type zinc finger of the form Cys-X2-Cys-X17-Cys-X2-Cys, with four cysteine sites. The EsGLP mRNA transcripts were mainly detected in the hematopoietic tissue, hepatopancreas and gonad. The recombinant EsGLP protein was prepared for the antibody production. The EsGLP protein was mainly distributed in the edge of lobules in the HPT and the cytoplasm of hemocytes. The mRNA transcripts of EsGLP in hemocytes were significantly decreased at 24 h (0.39-fold and 0.27-fold, p < .05) and 48 h (0.35-fold and 0.16-fold, p < .05) after LPS and Aeromonas hydrophila stimulation, respectively. However, one peak of EsGLP mRNA transcripts were recorded at 24 h (8.71-fold, p < .05) in HPT after A. hydrophila stimulation. The expression level of EsGLP mRNA in HPT was significantly up-regulated at 2 h, 2.5 h and 9 h (41.74-fold, 45.38-fold and 26.07-fold, p < .05) after exsanguination stimulation. When EsGLP gene expression was inhibited by the injection of double-stranded RNA, both the total hemocytes counts and the rate of EdU-positive hemocytes were significantly decreased (0.32-fold and 0.56-fold compared to that in control group, p < .05). All these results suggested that EsGLP was an important regulatory factor in E. sinensis which involved in the hemocytes generation and the immune response against invading pathogens.

Common themes emerge in the transcriptional control of T helper and developmental cell fate decisions regulated by the T-box, GATA and ROR families.

Cellular differentiation requires the precise action of lineage-determining transcription factors. In the immune system, CD4(+) T helper cells differentiate into at least three distinct effector lineages, T helper type 1 (Th1), Th2 and Th17, with the fate of the cell at least in part determined by the transcription factors T-box expressed in T cells (T-bet), GATA-3 and retinoid-related orphan receptor gammat (RORgammat), respectively. Importantly, these transcription factors are members of larger families that are required for numerous developmental transitions from early embryogenesis into adulthood. Mutations in members of these transcription factor families are associated with a number of human genetic diseases due to a failure in completing lineage-specification events when the factor is dysregulated. Mechanistically, there are both common and distinct functional activities that are utilized by T-box, GATA and ROR family members to globally alter the cellular gene expression profiles at specific cell fate decision checkpoints. Therefore, understanding the molecular events that contribute to the ability of T-bet, GATA-3 and RORgammat to define T helper cell lineages can provide valuable information relevant to the establishment of other developmental systems and, conversely, information from diverse developmental systems may provide unexpected insights into the molecular mechanisms utilized in T helper cell differentiation.

T-cell regulation in asthmatic diseases.

Effector and regulatory T cells (Tregs) play a fundamental role in the airways in allergic asthma. Here, the role of T cells in the immunopathogenesis of human asthma as well as in animal models of allergic airway inflammation is reviewed. Recent data have shown that Th2 and Th17 effector T cells augment experimental airway inflammation, while Tregs have an important anti-inflammatory function. The local induction of Th2 cells is critically dependent on the balance between the transcription factors T-bet and GATA-3, while Th17 and Tregs require the transcription factors ROR-gammat and Foxp3, respectively. Cytokine signaling controls the development and activation of all the above T-cell subsets. For instance, local blockade of the membrane-bound interleukin (IL)-6R results in induction of lung CD4+CD25+ Foxp3+Tregs producing TGF-Beta and IL-10. In humans, it has been suggested that asthmatic patients have increased Th2 but decreased Tregs, however the role of Th17 cells in allergic asthma remains to be elucidated. However, the currently available data suggest that allergic asthma is a multifaceted disease that is actively controlled by T lymphocytes. A better understanding of effector and Treg activation will most likely lead to novel treatment strategies in the near future.

Polymorphisms in the 5' upstream region of the CXCR1 chemokine receptor gene, and their association with somatic cell score in Holstein cattle in Canada.

Identification of regulatory elements in 5' regions of chemokine genes is fundamental for understanding chemokine gene expression in response to infection diseases. The CXCR1 receptor is expressed on the surface of neutrophils and interacts primarily with CXCL8 (IL-8), the most potent chemoattractant for neutrophils. The aim of this study was to characterize the 5' upstream region (2.1 kb) of the bovine CXCR1 chemokine receptor gene for polymorphism content and to identify in silico potential transcription-factor binding sites. The 5' flanking region was found by mining the NCBI GenBank (www.ncbi.nlm.nih.gov/). A DNA sequence from the whole genome shotgun sequence project with reference number AC150887.4 contained the CXCR1 5' flanking sequence. Computer analysis revealed potential binding sites for the transcription factors nuclear factor kappaB (NF-kappaB), binding factor GATA-1, barbiturate inducible element (Barbie), nuclear factor of activated T-cells, and activator protein 1. Polymorphism discovery in this region was conducted by constructing an inclusive DNA pool including 2 phenotypic extreme groups, 20 bulls with high estimated breeding values (EBV) for somatic cell score (SCS), and 20 bulls with low EBV for SCS. Independent amplicons along the 5' flanking region of bovine CXCR1 were generated for polymorphism discovery by sequencing. Three novel single nucleotide polymorphisms (SNP), CXCR1c.-344T>C, CXCR1c.-1768T>A, and CXCR1c.-1830A>G, and a previously identified SNP in the coding region, CXCR1c.777G>C, were identified. The 4 SNP were genotyped in Canadian Holstein bulls (n = 338) using tetra-primer amplification refractory mutation system (ARMS)-PCR. Average allele substitution effects were estimated to investigate associations between the 4 SNP and EBV for SCS in first, second, and third and later lactations. Multiple trait analysis revealed that the SNP CXCR1c.-1768T>A was associated with EBV for SCS in the first and second lactations and over all 3 lactations. Haplotype analysis substantiated this association with EBV for SCS in the first lactation. Given the location of SNP CXCR1c.-1768T>A and the surrounding potential binding recognition sequences for NF-kappaB, GATA-1, and Barbie transcription-factors, this SNP may be implicated in gene regulation and warrants further research.

GATA factors participate in tissue-specific immune responses in Drosophila larvae.

Drosophila responds to infection by producing a broad range of antimicrobial agents in the fat body and more restricted responses in tissues such as the gut, trachea, and malpighian tubules. The regulation of antimicrobial genes in larval fat depends on linked Rel/NF-kappaB and GATA binding sites. Serpent functions as the major GATA transcription factor in the larval fat body. However, the transcriptional regulation of other tissue-specific responses is less well understood. Here, we present evidence that dGATAe regulates antimicrobial gene expression in the midgut. Regulatory regions for antimicrobial genes Diptericin and Metchnikowin require GATA sites for activation in the midgut, where Grain (dGATAc), dGATAd, and dGATAe are expressed in overlapping domains. Ectopic expression of dGATAe in the larval fat body, where it is normally absent, causes dramatic up-regulation of numerous innate immunity and gut genes, as judged by microarray analysis and in situ hybridization. Ectopic dGATAe also causes a host of symptoms reminiscent of hyperactive Toll (Toll(10b)) mutants, but without apparent activation of Toll signaling. Based on this evidence we propose that dGATAe mediates a Toll-independent immune response in the midgut, providing a window into the first and perhaps most ancient line of animal defense.

A conserved role for a GATA transcription factor in regulating epithelial innate immune responses.

Innate immunity is an ancient and conserved defense mechanism. Although host responses toward various pathogens have been delineated, how these responses are orchestrated in a whole animal is less understood. Through an unbiased genome-wide study performed in Caenorhabditis elegans, we identified a conserved function for endodermal GATA transcription factors in regulating local epithelial innate immune responses. Gene expression and functional RNAi-based analyses identified the tissue-specific GATA transcription factor ELT-2 as a major regulator of an early intestinal protective response to infection with the human bacterial pathogen Pseudomonas aeruginosa. In the adult worm, ELT-2 is required specifically for infection responses and survival on pathogen but makes no significant contribution to gene expression associated with intestinal maintenance or to resistance to cadmium, heat, and oxidative stress. We further demonstrate that this function is conserved, because the human endodermal transcription factor GATA6 has a protective function in lung epithelial cells exposed to P. aeruginosa. These findings expand the repertoire of innate immunity mechanisms and illuminate a yet-unknown function of endodermal GATA proteins.

GATA transcription factor required for immunity to bacterial and fungal pathogens.

In the past decade, Caenorhabditis elegans has been used to dissect several genetic pathways involved in immunity; however, little is known about transcription factors that regulate the expression of immune effectors. C. elegans does not appear to have a functional homolog of the key immune transcription factor NF-kappaB. Here we show that that the intestinal GATA transcription factor ELT-2 is required for both immunity to Salmonella enterica and expression of a C-type lectin gene, clec-67, which is expressed in the intestinal cells and is a good marker of S. enterica infection. We also found that ELT-2 is required for immunity to Pseudomonas aeruginosa, Enterococcus faecalis, and Cryptococcus neoformans. Lack of immune inhibition by DAF-2, which negatively regulates the FOXO transcription factor DAF-16, rescues the hypersusceptibility to pathogens phenotype of elt-2(RNAi) animals. Our results indicate that ELT-2 is part of a multi-pathogen defense pathway that regulates innate immunity independently of the DAF-2/DAF-16 signaling pathway.