Targeted disruption of the Tab1 gene causes embryonic lethality and defects in cardiovascular and lung morphogenesis

The transforming growth factor-beta (TGF-beta) superfamily consists of a group of secreted signaling molecules that perform important roles in the regulation of cell growth and differentiation. TGF-beta activated kinase-1 binding protein-1 (TAB1) was identified as a molecule that activates TGF-beta activated kinase-1 (TAK1). Recent studies have revealed that the TAB1-TAK1 interaction plays an important role in signal transduction in vitro, but little is known about the role of these molecules in vivo. To investigate the role of TAB1 during development, we cloned the murine Tab1 gene and disrupted it by homologous recombination. Homozygous Tab1 mutant mice died, exhibiting a bloated appearance with extensive edema and hemorrhage at the late stages of gestation. By histological examinations, it was revealed that mutant embryos exhibited cardiovascular and lung dysmorphogenesis. Tab1 mutant embryonic fibroblast cells displayed drastically reduced TAK1 kinase activities and decreased sensitivity to TGF-beta stimulation. These results indicate a possibility that TAB1 plays an important role in mammalian embryogenesis and is required for TAK1 activation in TGF-beta signaling.     

3-(4-Methyl-3-pentenyl)-2(5H)-furanone, alpha,alpha-acariolide and 4-(4-methyl-3-pentenyl)-2(5H)-furanone, alpha,beta-acariolide: new monoterpene lactones from the astigmatid mites, Schwiebea araujoae and Rhizoglyphus sp. (Astigmata: Acaridae)

A new monoterpene lactone from the acarid mite, Schwiebea araujoae, was elucidated without its isolation by GC/FT-IR and GC/MS analyses to be 3-(4-methyl-3-pentenyl)-2(5H)-furanone (1) and tentatively named as alpha,alpha-acariolide. The structure of 1 was identified by its synthesis from alpha-bromo-gamma-butyrolactone via 4 reaction steps. The synthesized compound gave the same GC/MS and GC/FT-IR spectra as those of the natural product. The other monoterpene lactone was likewise elucidated from the unidentified Rhizoglyphus mite to be 4-(4-methyl-3-pentenyl)-2(5H)-furanone (2) and named as alpha,beta-acariolide; it was also identified by its synthesis in 5 reaction steps from the same butyrolactone as the starting material. GC/MS and GC/FT-IR spectra of the preparation were identical to those of the natural product.     

The role of CD98 in astrocytic neoplasms

The high expression of CD98 was reported in some normal tissues, including blood brain barrier, activated lymphocytes, the basal layer of skin, proximal tubles of kidney, placenta, testis and a wide variety of tumors. The CD98 complex consists of an 80-85kD heavy chain (4F2hc/FRP-1) and a 40-45kD light chain. CD98hc, 4F2hc, and FRP-1 are the same glycosylated protein each other and define antigenicity of CD98. LAT1, the sodium-independent L-type amino acid transporter 1, has been identified as a light chain of the CD98 heterodimer from C6 glioma cells. LAT1 also corresponds to TA1, an oncofetal antigen that is expressed primarily in fetal tissues and cancer cells such as glioma cells. Increased LAT1 expression was found in various malignancies including human gliomas. Several studies implicated the important role of LAT1 and 4F2hc in malignant transformation and carcinogenesis. The LAT1-CD98 pathway may represent a unique therapeutic target for cancer intervention.     

Identification of mono-, oligo-, and polysaccharides secreted from soybean roots

The mist culture system was conducted to study secreted polysaccharides from soybean ( Glycine max) roots grown for 15 days. Roots were rinsed with distilled water (DW) for 15 min, then with 30 mM oxalic acid (OXA) for 15 min to remove ionically bound sugar. Released sugars were further fractionated into low (L) and high (H) molecular weight fractions with Sephadex G-10. DW rinsing released 190 microg neutral sugar (NS) and 62 microg uronic acid (UA) per plant, while 374 microg NS and 70 microg UA per plant were released by OXA rinsing. Acetylation analysis revealed that the L fraction by DW and OXA mainly consisted of glucose (Glc), pinitol, and UA, whereas the H fraction mainly consisted of arabinose (Ara), galactose (Gal), Glc, and UA. The presence of rhamnose (2%-6%) in both fractions suggests secretion of rhamnogalacturonans. Methylation analysis revealed that the H fraction by DW and OXA contained T-Ara, 3-, 6-, and 3,6-Gal, suggesting the presence of type II arabinogalactan and arabinogalactan proteins. HPLC analysis detected mono-, di-, and tri-GalA in the L fraction by DW and OXA. Substances corresponding to sucrose, kojibiose, cello- and laminari-oligosaccharides were also found in root exudates.     

Development of an analytical method for the determination of betaines in higher plants by capillary electrophoresis at low pH

In recent years the role of betaines in higher plants has been extensively investigated in relation to environmental stress response. This paper reports the establishment of a simple, rapid and reliable method for the determination of betaines using capillary electrophoresis (CE) at low pH. Betaines were first converted to their phenacyl esters and the crude reaction mixture was then applied directly to CE without any pre-treatment. Employing an electrolyte running solution at pH 3 gave a well-resolved electropherogram for the esters of glycine betaine (1), trigonelline, proline betaine, gamma-butyro betaine, and carnitine. The content of 1 and its variation in plant samples collected from high-salinity areas in north China and west Australia are presented.     

Position dependent expression of GL2-type homeobox gene, Roc1: significance for protoderm differentiation and radial pattern formation in early rice embryogenesis

In early plant embryogenesis, the determination of cell fate in the protodermal cell layer is considered to be the earliest event in radial pattern formation. To elucidate the mechanisms of epidermal cell fate determination and radial pattern formation in early rice embryogenesis, we have isolated a GL2-type homeobox gene Roc1 (Rice outermost cell-specific gene1), which is specifically expressed in the protoderm (epidermis). In early rice embryogenesis, cell division occurs randomly and the morphologically distinct layer structure of the protoderm cannot be observed until the embryo reaches more than 100 microm in length. Nonetheless, in situ hybridization analyses revealed that specific expression of Roc1 in the outermost cells is established shortly after fertilization, much earlier than protoderm differentiation. In the regeneration process from callus, the Roc1 gene is also expressed in the outermost cells of callus in advance of tissue and organ differentiation, and occurs independently of whether the cells will differentiate into epidermis in the future or not. Furthermore, this cell-specific Roc1 expression could be induced flexibly in the newly produced outermost cells when we cut the callus. These findings suggest that the expression of Roc1 in the outermost cells may be dependent on the positional information of cells in the embryo or callus prior to the cell fate determination of the protoderm (epidermis). Furthermore, the Roc1 expression is downregulated in the inner cells of ligule, which have previously been determined as protodermal cells, also suggesting that the Roc1 expression is position dependent and that this position dependent Roc1 expression is important also in post-embryonic protoderm (epidermis) differentiation.     

Mammalian hyaluronan synthases

Three mammalian hyaluronan (HA) synthase genes, HAS1, HAS2, and HAS3, have been cloned and expressed, allowing the mechanisms for regulation of HA biosynthesis and function to be studied. The hyaluronan synthase (HAS) isoforms differ in kinetic characteristics and product size. The expression of each HAS isoform is controlled in a different fashion when mammalian cells are stimulated by various cytokines and the expression patterns are both spatially and temporally regulated during embryonic development. The existence of three different HAS isoforms with different characteristics implies that the broad range of biological and physiological roles performed by HA are regulated by controlling the activities and expression of the HAS isoforms. This review focuses on recent findings on the regulatory mechanisms for controlling HA biosynthesis and provides new insights into the enzymic basis for the functional regulation of HA.     

Regulation of Lck and Fyn tyrosine kinase activities by transmembrane protein tyrosine phosphatase leukocyte common antigen-related molecule

Leukocyte common antigen-related molecule (LAR) is a receptor-like protein tyrosine phosphatase (PTPase) with two PTPase domains. In the present study, we detected the expression of LAR in the brain, kidney, and thymus of mice using anti-LAR PTPase domain subunit monoclonal antibody (mAb) YU1. In the thymus, LAR was expressed on CD4(-)CD8(-) and CD4(-)CD8(low) thymocytes. The development of thymocytes in CD45 knockout mice is blocked partially in the maturation of CD4(-)CD8(-) to CD4(+)CD8(+). We postulated that LAR regulates Lck and Fyn in the immature thymocytes. Transfection of wild-type LAR activated extracellular signal-regulated kinase signal transduction pathway in CD45-deficient Jurkat cells stimulated with anti-CD3 mAb. LAR mutants, with Cys to Ser mutation in the catalytic center of PTPase D1, bound to tyrosine-phosphorylated Lck and Fyn, and LAR PTPase domain 2 was tyrosine phosphorylated by Fyn tyrosine kinase. The phosphorylated LAR was associated with Fyn Src homology 2 domain. Moreover, LAR dephosphorylated phosphorylated tyrosine residues in both the COOH terminus and kinase domain of Fyn in vitro. Our results indicate that Lck and Fyn would be substrates of LAR in immature thymocytes and that each LAR PTPase domain plays distinct functional roles in phosphorylation and dephosphorylation.     

Receptors for recombinant feline interferon-omega in hemocytes of the Japanese pearl oyster Pinctada fucata martensii

In a previous study we determined that administration of recombinant feline interferon-omega (rFeIFN-omega) could protect Japanese pearl oysters Pinctada fucata martensii from akoya-virus infection. Our results suggested that rFeIFN-omega enhanced the potential of agranulocytes to phagocytize necrotic cells and to produce collagen fibers that repair the lesions caused by the akoya-virus. In the present study, using an indirect immunofluorescence technique with an anti-rFeIFN-omega rabbit serum, we examined whether hemocytes bear receptors that bind rFeIFN-omega. rFeIFN-omega receptors were present on agranulocytes and bound rFeIFN-omega, and appeared as green fluorescent spots in the cytoplasm under a fluorescent microscope. Around 56% of agranulocytes in Japanese pearl oysters bore the rFeIFN-omega receptors.