Comparative genomic analysis of mammalian NKG2D ligand family genes provides insights into their origin and evolution

NKG2D is a major activating receptor of natural killer cells. Its ligands are major histocompatibility complex (MHC) class I-like molecules whose expression is induced by cellular stresses such as infections and tumorigenesis. Humans have two families of NKG2D ligands (NKG2DL): MHC class I-related chains (MIC) encoded in the MHC and UL16-binding proteins (ULBP) encoded outside the MHC. By contrast, mice have only the latter family of ligands; instead, they have non-MHC-encoded MILL molecules that are closely related to MIC, but do not function as NKG2DL. To gain insights into the origin and evolution of MIC, ULBP, and MILL gene families, we conducted comparative genomic analysis of NKG2DL family genes in five mammalian species. In the opossum MHC, we identified a ULBP-like gene adjacent to a previously described MIC-like gene, suggesting that ULBP genes were originally encoded in the MHC. The opossum genome also contained a transcribed MILL-like gene in a region syntenic to the rodent regions encoding MILL molecules. These observations indicate that MIC-, ULBP-, and MILL-like genes emerged before the divergence of placental and marsupial mammals. Comparison of the human, cattle, rat, mouse, and opossum genomes indicates that after emigration from the MHC, ULBP genes underwent extensive duplications in each species. In mice, some of the ULBP genes appear to have been translocated telomerically on the same chromosome, forming a major cluster of existent NKG2DL genes.     

Rapid assessment of two major repair activities against DNA double-strand breaks in vertebrate cells

A linearized plasmid DNA, in which tandem repeats of 400bp flank the breakpoints, was transfected into vertebrate cells, and breakpoint junctions of plasmid DNA circularized in the cells were analyzed to assess the repair activities against DNA double-strand break (DSB) by non-homologous end joining and homology-directed repair (i.e., homologous recombinational repair and single-strand annealing). The circularization by non-homologous end joining repair of the breakpoints depended on the expression of DNA-PKcs, while that by homology-directed repair through the repeats depended on the length of the repeats, indicating that these two DSB repair activities can be rapidly assessed by this assay. Predominance in circularization by either non-homologous end joining or homology-directed repair differed among cells examined, and circularization was exclusively undertaken by homology-directed repair in DT40 cells known to show a high homologous recombination rate against gene-targeting vectors. Thus, this assay will be helpful in studies on mechanisms and inter-cellular variations of DSB repair.     

Expression of isoforms of NADPH oxidase components in rat pancreatic islets

Increased oxidative stress plays a role in the pathogenesis of beta-cell dysfunction and death. We studied isoforms of NADPH oxidase components in islets of Langerhans isolated from rat pancreas and tumoral rat beta-cell line RINm5F cells by RT-PCR and sequencing of its products. RT-PCR revealed that isolated islets constitutively expressed mRNA of NADPH oxidase components, Nox1, Nox2, Nox4 and p22(phox) as membrane-associated components and p47(phox), Noxo1 (homologue of p47(phox)), Noxa1 (homologue of p67(phox)), and p40(phox) as cytosolic components. RINm5F cells showed a similar pattern of expression but Nox2 mRNA was not detected. Expression of Nox1, Nox4, Noxo1 and Noxa1 was confirmed by sequencing the PCR products. Immunohistochemistry revealed the expression of NADPH oxidase component in beta-cells of rat pancreatic islets. Glucose-stimulated insulin secretion from isolated islets was suppressed by diphenyleneiodonium, a flavocytochrome inhibitor, but not by apocynin, an inhibitor of p47(phox) translocation to membranes. Our results suggest that the functional significance of NADPH oxidase in insulin secretion may merit further investigation.     

Variable domains in hagfish: NICIR is a polymorphic multigene family expressed preferentially in leukocytes and is related to lamprey TCR-like

The jawless vertebrates, represented by hagfish and lampreys, are the most advanced animals that apparently lack T cell and B cell receptors. As such, they offer unique opportunities for understanding the evolution of antigen receptors and variable (V)-type immunoglobulin (Ig)-like domains. In the present study, we describe four hagfish Ig superfamily (IgSF) members carrying V-type domains. None of them appeared to have direct counterparts in jawed vertebrates, indicating that many IgSF molecules have either evolved independently in jawed and jawless vertebrates or diverged to the extent that clear homology is no longer recognizable. One of the members encoded a molecule closely related to the previously described membrane protein designated novel ITAM (immunoreceptor tyrosine-based activation motif)-containing IgSF receptors (NICIR). We show here that NICIR is a polymorphic multigene family with at least three members and is expressed predominantly in peripheral blood leukocytes. Phylogenetic analysis indicates that among known proteins, NICIR is most closely related to the lamprey molecule recently proposed to be a potential ancestor of T cell receptors.Sequence data reported in this paper were submitted to the DDBJ/EMBL/GenBank databases under accession nos. AB234206-AB234210, AB242215-AB224219, and AB242221-AB242223.     

Study of hyaluronan synthase inhibitor, 4-methylumbelliferone derivatives on human pancreatic cancer cell (KP1-NL)

The structure of 4-methylumbelliferone (MU) consists of coumarin with 4-methyl group and 7-hydroxy group. MU inhibits HA synthesis and pericellular HA matrix formation. In this study, we used 10 MU derivatives which have hydroxy groups and methyl groups at various positions of coumarin to investigate a more effective HA inhibitor than MU. First, human pancreatic cancer cell (KP1-NL) growth assay was analyzed by Alamar Blue to determine the non-toxic concentration of MU derivatives, and the inhibitory effect on HA synthesis in the cell cultures was analyzed by HA measuring kit. Next, cell surfaces of cancer cells were analyzed by particle-exclusion assay. In conclusion, both hydroxy and methyl groups are necessary for HA inhibition by MU, and two hydroxy groups inhibited HA synthesis more strongly than MU.     

Capsule of Streptococcus pyogenes is essential for delayed death of mice in a model of streptococcal toxic shock syndrome

We have previously reported a mouse model of severe group A streptococcal infection (Microbiol. Immunol. 45: 777-786, 2001). When we injected Streptococcus pyogenes strains intramuscularly, the mice suffered from acute phase of infection for a few days but recovered from the illness and gained body weight. These mice, however, began to die after 3 weeks of infection, which we called 'delayed death.' Bacterial strains isolated from organs of the dead mice showed thick capsules. We, therefore, constructed a hyaluronic acid capsule gene, hasA, knockout mutant by homologous recombination and the effect of capsule on the death was observed. hasA knockout strain did not cause delayed death, though it caused acute death at high doses of infection. According to this result, the capsule is a critical pathogenic factor for causing the delayed death in our mouse model.     

Investigation of the fate of Sry-expressing cells using an in vivo Cre/loxP system

Sry (sex-determining region on Y chromosome) is expressed in the undifferentiated, bipotential genital ridges of mammalian XY fetuses. The expression of Sry initiates testis development, but the lineage of Sry-expressing cells is unclear. In this study, double-transgenic mice were analyzed using the Cre/loxP system. Cre under the control of the Sry promoter was expressed in the fetal gonads of transgenic mice similarly to endogenous Sry. The Sry/Cre-transgenic mice were crossed with CAG(cytomegalovirus immediate-early enhancer, chicken beta-actin promoter and fusion intron of chicken beta-actin and rabbit beta-globin)/loxP/CAT/loxP/LacZ-transgenic mice, in which the transgene expressed beta-galactosidase after a Cre-mediated recombination event. Sertoli cells, germ cells of testes and granulosa cells of ovaries of double-transgenic mice stained positive with X-gal. Cre expression was detected in germ cells and peritubular/Sertoli cells in adult testes. It is not clear whether beta-galactosidase expression in the Sertoli cells of the testes occurred as a result of Cre expression in the adult or in the fetal gonads. These analyses indicate that cells expressing Sry-inducing factors in female fetal gonads become granulosa cells.     

Validation of an HPLC Analytical Method Coupled to a Multifunctional Clean-up Column for the Determination of Deoxynivalenol

To evaluate a method using a multifunctional clean-up column coupled with high performance liquid chromatography as an official analytical method for the determination of deoxynivalenol in wheat used as food or feed, an inter-laboratory study was performed in 12 laboratories using four naturally contaminated wheat samples and one spiked sample. The relative standard deviations for repeatability (RSD_r) and reproducibility (RSD_R) of naturally contaminated wheat were in the range 5.8–11.3% and 12.0–20.7%, respectively. The HORRAT was less than 1.0 in each sample. From the spiking test, the recovery rate, RSD_r, RSD_R and HORRAT value were 100.0%, 11.2%, 10.3% and 0.5, respectively. The limit of quantification is 0.10 mg/kg from the range obtained in a linear calibration. Thus, it should be useful as a sensitive and validated analytical method for the determination of deoxynivalenol in wheat intended for use in food and feed.     

Strong immunostimulatory activity of AT-oligodeoxynucleotide requires a six-base loop with a self-stabilized 5'-C...G-3' stem structure

Lactobacillus gasseri OLL2716 has recently been discovered as a probiotic that suppresses the growth of Helicobacter pylori and reduces gastric mucosal inflammation in humans. This has resulted in the development of a new type of probiotic yoghurt 'LG21' in Japan. In our previous study, we found an immunostimulatory AT5ACL oligodeoxynucleotide (AT-ODN) containing a unique core sequence (5'-ATTTTTAC-3') in L. gasseri JCM1131(T). Interestingly, although the AT-ODN does not contain any CpG sequences, it exerts mitogenic activity in B cells and augments Th-1-type immune responses via Toll-like receptor 9. These findings prompted us to identify strong immunostimulatory non-CpG AT-ODNs that contain the 5'-ATTTTTAC-3' motif in the genomic sequence of L. gasseri OLL2716. We identified 280 kinds of AT-ODNs in the L. gasseri OLL2716 genome. Mitogenicity and NF-kappaB gene reporting assays showed that 13 of the 280 AT-ODNs were strongly immunostimulatory when in the TLR9 transfectant. Of these, AT-ODNs LGAT-145 and LGAT-243 were the most potent. With respect to the induction of Th-1-type cytokines, LGAT-243 had the greatest activity and was more potent than the swine prototype, ODN D25. We further found that a six-base secondary loop structure containing a self-stabilized 5'-C...G-3' stem sequence is important for potent immunostimulatory activity. These results show for the first time that AT-ODNs with a specific loop and stem structure are important factors for immunostimulatory activity. Finally, we found that novel strong immunostimulatory non-CpG AT-ODNs exist in the genome of probiotic lactic acid bacteria.