Cripto binds transforming growth factor beta (TGF-beta) and inhibits TGF-beta signaling

Cripto is a developmental oncoprotein and a member of the epidermal growth factor-Cripto, FRL-1, Cryptic family of extracellular signaling molecules. In addition to having essential functions during embryogenesis, Cripto is highly expressed in tumors and promotes tumorigenesis. During development, Cripto acts as an obligate coreceptor for transforming growth factor beta (TGF-beta) ligands, including nodals, growth and differentiation factor 1 (GDF1), and GDF3. As an oncogene, Cripto is thought to promote tumor growth via mechanisms including activation of mitogenic signaling pathways and antagonism of activin signaling. Here, we provide evidence supporting a novel mechanism in which Cripto inhibits the tumor suppressor function of TGF-beta. Cripto bound TGF-beta and reduced the association of TGF-beta with its type I receptor, TbetaRI. Consistent with its ability to block receptor assembly, Cripto suppressed TGF-beta signaling in multiple cell types and diminished the cytostatic effects of TGF-beta in mammary epithelial cells. Furthermore, targeted disruption of Cripto expression by use of small inhibitory RNA enhanced TGF-beta signaling, indicating that endogenous Cripto plays a role in restraining TGF-beta responses.     

The correlation between the synthesis of skeletal muscle actin,myosin heavy chain,and myosin light chain and the accumulation of corresponding mRNA sequences during myogenesis

Cloned cDNA probes were used to measure the accumulation of myosin heavy chain, myosin light chain 2, and actin mRNA during differentiation of rat skeletal muscle cell cultures. This was compared with the changes in the rate of synthesis of the corresponding proteins. Accumulation of those mRNA sequences was detectable a few hours before the onset of the phase of cell fusion; however, the main increase in hybridizable RNA occurred during the phase of rapid cell fusion. A close correlation was found between the amounts of mRNAs coding for these proteins and the rate of synthesis of the proteins. The results suggest that the activation of stored mRNA is not a major mechanism for controlling the time at which these proteins are synthesized.     

Sibling species of bean bruchids: a morphological and phylogenetic study of Acanthoscelides obtectus Say and Acanthoscelides obvelatus Bridwell

Acanthoscelides Schilsky is a large genus of neotropical bruchid beetles, in which most species show host plant specialization. Acanthoscelides obtectus and Acanthoscelides obvelatus are two sibling species specialized on Phaseolus beans, and are therefore considered pests. Up to now, the status of these two taxa has remained unclear, the few studies conducted having failed to elucidate whether these are two differentiated species or a single morphologically variable species. In addition, A. obvelatus has not been taken into account in the great majority of studies of bean bruchids. In this morphological and genetic study, we show that A. obtectus and A. obvelatus are two 'true' non-hybridizing species, which diverged about 22 Mya. Although the two species demonstrate only few morphological differences, we point out some diagnostic characters that enable their identification in the field. We also address a genetic method of differentiation of the two species, based on species-specific microsatellite loci. The strong morphological resemblance of these two species, despite their ancient divergence, may be the result of evolutionary stasis, which could be the consequence of stabilizing selection. Niche differentiation could enable the two species to coexist indefinitely.     

Oxidized cellulose binding to allergens with a carbohydrate-binding module attenuates allergic reactions

Grass and mite allergens are of the main causes of allergy and asthma. A carbohydrate-binding module (CBM) represents a common motif to groups I (β-expansin) and II/III (expansin-like) grass allergens and is suggested to mediate allergen-IgE binding. House dust mite group II allergen (Der p 2 and Der f 2) structures bear strong similarity to expansin's CBM, suggesting their ability to bind carbohydrates. Thus, this study proposes the design of a carbohydrate-based treatment in which allergen binding to carbohydrate particles will promote allergen airway clearance and prevent allergic reactions. The aim of the study was to identify a polysaccharide with high allergen-binding capacities and to explore its ability to prevent allergy. Oxidized cellulose (OC) demonstrated allergen-binding capacities toward grass and mite allergens that surpassed those of any other polysaccharide examined in this study. Furthermore, inhalant preparations of OC microparticles attenuated allergic lung inflammation in rye grass-sensitized Brown Norway rats and OVA-sensitized BALB/c mice. Fluorescently labeled OC efficiently cleared from the mouse airways and body organs. Moreover, long-term administration of OC inhalant to Wistar rats did not result in toxicity. In conclusion, many allergens, such as grass and dust mite, contain a common CBM motif. OC demonstrates a strong and relatively specific allergen-binding capacity to CBM-containing allergens. OC's ability to attenuate allergic inflammation, together with its documented safety record, forms a firm basis for its application as an alternative treatment for prevention and relief of allergy and asthma.     

Pleiotrophin (PTN) Expression and Function and in the Mouse Mammary Gland and Mammary Epithelial Cells

Expression of the heparin-binding growth factor, pleiotrophin (PTN) in the mammary gland has been reported but its function during mammary gland development is not known. We examined the expression of PTN and its receptor ALK (Anaplastic Lymphoma Kinase) at various stages of mouse mammary gland development and found that their expression in epithelial cells is regulated in parallel during pregnancy. A 30-fold downregulation of PTN mRNA expression was observed during mid-pregnancy when the mammary gland undergoes lobular-alveolar differentiation. After weaning of pups, PTN expression was restored although baseline expression of PTN was reduced significantly in mammary glands of mice that had undergone multiple pregnancies. We found PTN expressed in epithelial cells of the mammary gland and thus used a monoclonal anti-PTN blocking antibody to elucidate its function in cultured mammary epithelial cells (MECs) as well as during gland development. Real-time impedance monitoring of MECs growth, migration and invasion during anti-PTN blocking antibody treatment showed that MECs motility and invasion but not proliferation depend on the activity of endogenous PTN. Increased number of mammospheres with laminin deposition after anti-PTN blocking antibody treatment of MECs in 3D culture and expression of progenitor markers suggest that the endogenously expressed PTN inhibits the expansion and differentiation of epithelial progenitor cells by disrupting cell-matrix adhesion. In vivo, PTN activity was found to inhibit ductal outgrowth and branching via the inhibition of phospho ERK1/2 signaling in the mammary epithelial cells. We conclude that PTN delays the maturation of the mammary gland by maintaining mammary epithelial cells in a progenitor phenotype and by inhibiting their differentiation during mammary gland development.     

Xyloglucan for Generating Tensile Stress to Bend Tree Stem

In response to environmental variation, angiosperm trees bend their stems by forming tension wood, which consists of a cellulose-rich G （gelatinous）-Iayer in the walls of fiber cells and generates abnormal tensile stress in the secondary xylem. We produced transgenic poplar plants overexpressing several endoglycanases to reduce each specific polysaccharide in the cell wall, as the secondary xylem consists of primary and secondary wall layers. When placed horizontally, the basal regions of stems of transgenic poplars overexpressing xyloglucanase alone could not bend upward due to low strain in the tension side of the xylem. In the wild-type plants, xyloglucan was found in the inner surface of G-layers during multiple layering. In situ xyloglucan endotransglucosylase （XET） activity showed that the incorporation of whole xyloglucan, potentially for wall tightening, began at the inner surface layers S1 and S2 and was retained throughout G-layer development, while the incorporation of xyloglucan heptasaccharide （XXXG） for wall loosening occurred in the primary wall of the expanding zone. We propose that the xyloglucan network is reinforced by XET to form a further connection between wall-bound and secreted xyloglucans in order to withstand the tensile stress created within the cellulose G-layer micro fibrils.     

Rabies Virus Hijacks and Accelerates the p75NTR Retrograde Axonal Transport Machinery

Rabies virus (RABV) is a neurotropic virus that depends on long distance axonal transport in order to reach the central nervous system (CNS). The strategy RABV uses to hijack the cellular transport machinery is still not clear. It is thought that RABV interacts with membrane receptors in order to internalize and exploit the endosomal trafficking pathway, yet this has never been demonstrated directly. The p75 Nerve Growth Factor (NGF) receptor (p75NTR) binds RABV Glycoprotein (RABV-G) with high affinity. However, as p75NTR is not essential for RABV infection, the specific role of this interaction remains in question. Here we used live cell imaging to track RABV entry at nerve terminals and studied its retrograde transport along the axon with and without the p75NTR receptor. First, we found that NGF, an endogenous p75NTR ligand, and RABV, are localized in corresponding domains along nerve tips. RABV and NGF were internalized at similar time frames, suggesting comparable entry machineries. Next, we demonstrated that RABV could internalize together with p75NTR. Characterizing RABV retrograde movement along the axon, we showed the virus is transported in acidic compartments, mostly with p75NTR. Interestingly, RABV is transported faster than NGF, suggesting that RABV not only hijacks the transport machinery but can also manipulate it. Co-transport of RABV and NGF identified two modes of transport, slow and fast, that may represent a differential control of the trafficking machinery by RABV. Finally, we determined that p75NTR-dependent transport of RABV is faster and more directed than p75NTR-independent RABV transport. This fast route to the neuronal cell body is characterized by both an increase in instantaneous velocities and fewer, shorter stops en route. Hence, RABV may employ p75NTR-dependent transport as a fast mechanism to facilitate movement to the CNS.