Chitin protects the gut epithelial barrier in a protochordate model of DSS-induced colitis.

The gastrointestinal tract of , a solitary tunicate that siphon-filters water, shares similarities with its mammalian counterpart. The gut exhibits other features that are unique to protochordates, including certain immune molecules, and other characteristics, e.g.

An Immune Effector System in the Protochordate Gut Sheds Light on Fundamental Aspects of Vertebrate Immunity.

A variety of germline and somatic immune mechanisms have evolved in vertebrate and invertebrate species to detect a wide array of pathogenic invaders. The gut is a particularly significant site in terms of distinguishing pathogens from potentially beneficial microbes. Ciona intestinalis, a filter-feeding marine protochordate that is ancestral to the vertebrate form, possesses variable region-containing chitin-binding proteins (VCBPs), a family of innate immune receptors, which recognize bacteria through an immunoglobulin-type variable region.

Evolution of the complement system C3 gene in Antarctic teleosts.

Notothenioidei are typical Antarctic teleosts evolved to adapt to the very low temperatures of the Antarctic seas. Aim of the present paper is to investigate sequence and structure of C3, the third component of the complement system of the notothenioid Trematomus bernacchii and Chionodraco hamatus. We determined the complete nucleotide sequence of two C3 isoforms of T.

Expression of Ciona intestinalis variable region-containing chitin-binding proteins during development of the gastrointestinal tract and their role in host-microbe interactions.

Variable region-containing chitin-binding proteins (VCBPs) are secreted, immune-type molecules that have been described in both amphioxus, a cephalochordate, and sea squirt, Ciona intestinalis, a urochordate. In adult Ciona, VCBP-A, -B and -C are expressed in hemocytes and the cells of the gastrointestinal tract. VCBP-C binds bacteria in the stomach lumen and functions as an opsonin in vitro.

The gut of geographically disparate Ciona intestinalis harbors a core microbiota.

It is now widely understood that all animals engage in complex interactions with bacteria (or microbes) throughout their various life stages. This ancient exchange can involve cooperation and has resulted in a wide range of evolved host-microbial interdependencies, including those observed in the gut. Ciona intestinalis, a filter-feeding basal chordate and classic developmental model that can be experimentally manipulated, is being employed to help define these relationships.

Immune competence of the Ciona intestinalis pharynx: complement system-mediated activity.

In the tunicate Ciona intestinalis, the ciliated pharynx, which connects the external environment to a highly developed and compartmentalized gastrointestinal system, represents the natural portal of entry for a vast and diverse, potentially pathogenic microbial community. To address the role of the pharynx in immune surveillance in Ciona, we asked whether C3, the key component of the complement system, was expressed in this organ and whether the encoded protein was functionally active. We found by real-time PCR that C3, constitutively expressed in the pharynx, is up-regulated by LPS injection.

A Basal chordate model for studies of gut microbial immune interactions.

Complex symbiotic interactions at the surface of host epithelia govern most encounters between host and microbe. The epithelium of the gut is a physiologically ancient structure that is comprised of a single layer of cells and is thought to possess fully developed immunological capabilities. Ciona intestinalis (sea squirt), which is a descendant of the last common ancestor of all vertebrates, is a potentially valuable model for studying barrier defenses and gut microbial immune interactions.

A role for variable region-containing chitin-binding proteins (VCBPs) in host gut-bacteria interactions.

A number of different classes of molecules function as structural matrices for effecting innate and adaptive immunity. The most extensively characterized mediators of adaptive immunity are the immunoglobulins and T-cell antigen receptors found in jawed vertebrates. In both classes of molecules, unique receptor specificity is effected through somatic variation in the variable (V) structural domain.

ciCD94-1, an ascidian multipurpose C-type lectin-like receptor expressed in Ciona intestinalis hemocytes and larval neural structures.

C-type lectins play an important role in the immune system and are part of a large superfamily that includes C-type lectin-like domain (CTLD)-containing proteins. Divergent evolution, acting on the CTLD fold, has generated the Ca2+-dependent carbohydrate-binding lectins and molecules, as the lectin-like natural killer (NK) receptors that bind proteins, rather than sugars, in a Ca(2+)-independent manner. We have studied ciCD94-1, a CTLD-containing protein from the tunicate Ciona intestinalis, which is a homolog of the CD94 vertebrate receptor that is expressed on NK cells and modulates their cytotoxic activity by interacting with MHC class I molecules.

Ammonium channel expression is essential for brain development and function in the larva of Ciona intestinalis.

Ammonium uptake into the cell is known to be mediated by ammonium transport (Amt) proteins, which are present in all domains of life. The physiological role of Amt proteins remains elusive; indeed, loss-of-function experiments suggested that Amt proteins do not play an essential role in bacteria, yeast, and plants. Here we show that the reverse holds true in the tunicate Ciona intestinalis.

First identification of a chemotactic receptor in an invertebrate species: structural and functional characterization of Ciona intestinalis C3a receptor.

In mammals, the bioactive fragment C3a, released from C3 during complement activation, is a potent mediator of inflammatory reactions and exerts its functional activity through the specific binding to cell surface G protein-coupled seven-transmembrane receptors. Recently, we demonstrated a Ciona intestinalis C3a (CiC3a)-mediated chemotaxis of hemocytes in the deuterostome invertebrate Ciona intestinalis and suggested an important role for this molecule in inflammatory processes. In the present work, we have cloned and characterized the receptor molecule involved in the CiC3a-mediated chemotaxis and studied its expression profile.

CiC3-1a-mediated chemotaxis in the deuterostome invertebrate Ciona intestinalis (Urochordata).

Deuterostome invertebrates possess complement genes, and in limited instances complement-mediated functions have been reported in these organisms. However, the organization of the complement pathway(s), as well as the functions exerted by the cloned gene products, are largely unknown. To address the issue of the presence of an inflammatory pathway in ascidians, we expressed in Escherichia coli the fragment of Ciona intestinalis C3-1 corresponding to mammalian complement C3a (rCiC3-1a) and assessed its chemotactic activity on C.

Genomic analysis of immunity in a Urochordate and the emergence of the vertebrate immune system: "waiting for Godot".

Genome-wide sequence analysis in the invertebrate chordate, Ciona intestinalis, has provided a comprehensive picture of immune-related genes in an organism that occupies a key phylogenetic position in vertebrate evolution. The pivotal genes for adaptive immunity, such as the major histocompatibility complex (MHC) class I and II genes, T-cell receptors, or dimeric immunoglobulin molecules, have not been identified in the Ciona genome. Many genes involved in innate immunity have been identified, including complement components, Toll-like receptors, and the genes involved in intracellular signal transduction of immune responses, and show both expansion and unexpected diversity in comparison with the vertebrates.

Complement in urochordates: cloning and characterization of two C3-like genes in the ascidian Ciona intestinalis.

The recent identification of complement components in deuterostome invertebrates has indicated the presence of a complement system operating via an alternative pathway in echinoderms and tunicates and via a MBL-mediated pathway thus far identified only in tunicates. Here, we report the isolation of two C3-like genes, CiC3-1 and CiC3-2, from blood cell total RNA of the ascidian Ciona intestinalis. The deduced amino acid sequences of both Ciona C3-like proteins exhibit a canonical processing site for alpha and beta chains, a thioester site with an associated catalytic histidine and a convertase cleavage site, thus showing an overall similarity to the other C3 molecules already characterized.

Specific induction of self-discrimination by follicle cells in Ciona intestinalis oocytes.

Self-incompatibility, a mechanism that prevents self-fertilization in ascidians, is based on the ability of the oocyte vitelline coat to distinguish and accept only heterologous spermatozoa. In Ciona intestinalis self-discrimination is established during late oogenesis and is contributed or controlled by products of the overlying follicle cells. In this study we have further investigated the role of the follicle cells in the onset of self-discrimination by using in vitro maturation of ovarian oocytes deprived of the follicle cells and incubated with either autologous or heterologous follicle cells.

Plasma Membrane Glycoproteins of Ciona intestinalis Spermatozoa that Interact with the Egg : (Ascidians/sperm-egg interaction/spermatozoa/sperm plasma membrane/Con A-binding proteins).

In the ascidian Ciona intestinalis the species-specific interaction between the spermatozoon and the egg occurs between the vitelline coat (VC) of the egg and the plasma membrane of the apical part of the head of the spermatozoa. Concanavalin A (Con A)-binding sites are present on this area of the sperm surface. We used Con A to identify and isolate the spermatozoon plasma membrane components that may be involved in the interaction with the VC.

Isolation and Partial Characterization of a Glycoprotein Complex with Sperm-Receptor Activity from Ciona intestinalis Ovary : (Ascidians/sperm-egg interaction/sperm receptors/vietelline coat).

Sperm-egg interaction in the ascidian Ciana intestinalis is mediated by a fucosyl-glycoprotein (FP) component of the egg vitelline coat. FP are responsible for sperm binding, sperm activation and the acrosome reaction. In this paper we report a detailed biochemical and functional characterization of FP purified from the ovaries by affinity chromatography.

The Differentiation of the Vitelline Envelope of Xenopus Oocytes*: (xenopus/oocyte/vitelline envelope/differentiation/fucosyl glycoproteins).

We have studied the differentiation of the vitelline envelope (V.E.) of the oocyte of the anuran Xenopus laevis.