ZO-1, ZO-2, and ZO-3 are closely related scaffolding proteins that link tight junction (TJ) transmembrane proteins such as claudins, junctional adhesion molecules, and occludin to the actin cytoskeleton. Even though the zonula occludens (ZO) proteins are among the first TJ proteins to have been identified and have undergone extensive biochemical analysis, little is known about the physiological roles of individual ZO proteins in different tissues or during vertebrate development. Here, we show that ZO-3 knockout mice lack an obvious phenotype. In contrast, embryos deficient for ZO-2 die shortly after implantation due to an arrest in early gastrulation. ZO-2 ؊/؊ embryos show decreased proliferation at embryonic day 6.5 (E6.5) and increased apoptosis at E7.5 compared to wild-type embryos. The asymmetric distribution of prominin and E-cadherin to the apical and lateral plasma membrane domains, respectively, is maintained in cells of ZO-2 ؊/؊ embryos. However, the architecture of the apical junctional complex is altered, and paracellular permeability of a low-molecular-weight tracer is increased in ZO-2 ؊/؊ embryos. Leaky TJs and, given the association of ZO-2 with connexins and several transcription factors, effects on gap junctions and gene expression, respectively, are likely causes for embryonic lethality. Thus, ZO-2 is required for mouse embryonic development, but ZO-3 is dispensable. This is to our knowledge the first report showing that an individual ZO protein plays a nonredundant and critical role in mammalian development.Tight junctions (TJs) are regions of intimate contact between the plasma membrane domains of adjoining cells and are predominantly found in columnar epithelial and endothelial cells, where they are part of the apical junctional complex (reviewed in reference 47). TJs are also found in hepatocytes (13), keratinocytes (13), and Schwann cells (40).TJs contain integral membrane proteins, notably claudins, occludin, and junctional adhesion molecules, which engage in homotypic and heterotypic interactions through their extracellular domains with corresponding proteins on adjoining cells (reviewed in reference 3 and 52). On the cytoplasmic side, adaptor or scaffolding molecules tether the integral membrane TJ proteins to the actin cytoskeleton. The best-characterized adaptors that directly link transmembrane TJ proteins to the cytoskeleton are ZO-1, ZO-2, and ZO-3, three closely related proteins that are widely expressed in different tissues and organs (reviewed in reference 21). Zonula occludens (ZO) proteins carry three PDZ (PSD-95/Dlg/ZO-1) domains, an Src homology 3 domain, and a guanylate kinase-like domain, and hence belong to the membrane-associated guanylate kinaselike superfamily of proteins (reviewed in references 20 and 21). A growing number of both structural and regulatory proteins that associate with the different domains of ZO proteins have been identified (reviewed in reference 21). Some of these interacting partners bind selectively to an individual ZO protein; others bind to two...

One of the central issues in developmental neurobiology is how the forebrain is organized ontogenetically. The traditional view is that the anterior neuroectoderm first develops into mesencephalic and prosencephalic vesicles; the latter vesicle subsequently develops into the diencephalon and secondary prosencephalon, of which dorsal parts protrude to generate the telencephalon. The diencephalon yields the pretectum, thalamus, and prethalamus, and the telencephalon produces the archipallium, neopallium, and ganglionic eminences. By identifying cell descendants that once expressed Emx2 with use of the Cre knock-in mutant into the Emx2 locus and analyzing phenotypes of double mutants between Emx2 and Otx2/Otx1 and between Emx2 and Pax6, we propose that at the 3-6 somite stage, the anterior neuroectoderm develops into three primordia: midbrain, caudal forebrain, and rostral forebrain. The caudal forebrain primordium generates not only the pretectum, thalamus, and prethalamus but also the archipallium, cortical hem, choroid plexus, choroidal roof, and eminentia thalami. The primordium corresponds to the Emx2-or Pax6-positive region at the 3-6 somite stage that most probably does not include the future neopallium or commissural plate. Otx2 and Otx1 that are expressed in the entire future forebrain and midbrain cooperate with this Emx2 and Pax6 expression in the development of the caudal forebrain primordium; Emx2 and Pax6 functions are redundant. In the embryonic day 9.5 Emx2 Ϫ/Ϫ Pax6 Ϫ/Ϫ double mutant, the caudal forebrain remained unspecified and subsequently transformed into tectum in a mirror image of the endogenous one.

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The intestinal barrier plays a critical role in humans in the transport of nutrients and macromolecules. At the same time, it has to provide an effective barrier to harmful macromolecules and microorganisms. The tight junction (TJ) is an essential component of this barrier. The junctional complexes of the plasma membrane are not simply epithelial barriers in paracellular transport or barriers preventing diffusion in the plasma membrane, but also contain proteins involved in signal transduction and the maintenance of the physiological epithelial cell state. Occludin, claudin, junctional adhesion molecules, and the coxsackie virus and adenovirus receptor are the major components of TJs. This article highlights the structure and function of TJs as well as the molecular interactions occurring during permeation through TJs.

Polyunsaturated fatty acids (PUFAs) exhibit beneficial biological functions in carcinogenic processes. We examined the effects of PUFAs in the acid and phospholipid forms on three colon cancer cell lines (HT-29, Caco-2, and DLD-1). Docosahexaenoic acid (DHA) and eicosapentaenoic (EPA) in both acid and phospholipid forms showed growth inhibition effects on experimental colon cancer cell lines. But these PUFAs had the strongest growth-inhibitory effect on HT-29 than Caco-2 and DLD-1. Combined application of PUFAs and sodium butyrate (NaBt) increased the growth inhibition. Growth inhibition was apparently caused by increased lipid peroxidation. DHA or EPA in combination with NaBt significantly increased caspase-3 activity compared to control. DHA and DHA-rich phosphatidylcholine decreased Bcl-2 level in HT-29 and Caco-2 cells.

The influence of docosahexaenoic acid (DHA)-and eicosapentaenoic acid (EPA)-enriched phosphatidylcholine (PC) on the permeability, transport and uptake of phospholipids was evaluated in Caco-2 cells . The cells were grown on permeable polycarbonate transwell filters, thus allowing separate access to the apical and basolateral chambers . The monolayers of the cells were used to measure lucifer yellow permeability and transepithelial electrical resistance Our results show that DHA-and EPA-enriched PC increases tight junction permeability across the Caco-2 cell monolayer whereas soy PC has no effect on tight junction permeability .Transportation and uptake of DHA-and EPA-enriched PC SUV differed significantly (P<0.01) from those of soy PC SUV at all doses. We found that PC SUV transported across Caco-2 monolayer and was taken up by Caco-2 cells with very slight injury of the cell membrane up to 100 /-1M PC. Lactate dehydrogenase release and cell viability did not differ significantly between the treatment and control, emphasizing that injury was minimal. Our results suggest that DHA-and EPA-enriched PC enhance the permeability, transport and uptake of PC SUV across monolayers of Caco-2 cells.

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BackgroundThe World Health Organization recommends exclusive breastfeeding until 6 months followed by introduction of iron-rich complementary foods (CFs). The aim of this study was to determine the impact of different iron-rich CFs on infant gut inflammation and microbiota.MethodsEighty-seven exclusively breastfed infants were randomly assigned to receive one of the following as their first CF: iron-fortified cereal (Cer), iron-fortified cereal with fruit (Cer + Fr), or meat (M). Urine and stool samples were collected to assess reactive oxygen species (ROS) generation, gut microbiota and inflammation.ResultsFecal iron differed across feeding groups (p < 0.001); levels were highest in the Cer group and lowest in M group. A significant increase of fecal ROS formation (p < 0.002) after the introduction of CFs was observed, but did not differ across feeding groups. Fecal calprotectin increased within all groups after the introduction of CFs (p = 0.004). Gut microbiota richness increased after introduction of M or Cer + Fr. Regardless of feeding group, Coriobacteriaceae were positively correlated with ROS and Staphylococcaceae were negatively correlated with calprotectin.ConclusionsChoice of first CF may influence gut inflammation and microbiota, potentially due to variations in iron absorption from different foods. Further research is warranted to fully characterize these associations and to establish implications for infant health. This study was registered in the ClinicalTrial.gov registry (Identifier No. NCT01790542).Trial registrationThis study was registered in the ClinicalTrial.gov registry under the name “Assessment of Complementary Feeding of Canadian Infants” (Identifier No. NCT01790542) February 6, 2013.Electronic supplementary materialThe online version of this article (doi:10.1186/s12887-017-0805-0) contains supplementary material, which is available to authorized users.