Secreted Wnt "inhibitors" are not just inhibitors: regulation of extracellular Wnt by secreted Frizzled-related proteins

Gradient formation and signaling ranges of secreted proteins are crucial problems to understand how morphogens work for positional information and patterning in animal development. Yet, extracellular behaviors of secreted signaling molecules remain unexplored compared to their downstream pathways inside the cell. Recent advances in bioimaging make it possible to directly visualize morphogen molecules, and this simple strategy has, at least partly, succeeded in uncovering molecular behaviors of morphogens, such as Wnt (wingless-type MMTV integration site family member) and BMP (bone morphogenetic protein) as well as secreted Wnt binding proteins, sFRPs (secreted Frizzled-related proteins), in embryonic tissues. Here, we review the regulation of Wnt signaling by sFRPs, focusing on extracellular regulation of Wnt ligands in comparison with other morphogens. We also discuss evolutionary aspects with comprehensive syntenic and phylogenetic information about vertebrate sfrp genes. We newly annotated several sfrp genes including sfrp2-like 1 (sfrp2l1) in frogs and fishes and crescent in mammals.     

Development of the Drosophila entero-endocrine lineage and its specification by the Notch signaling pathway

In this paper we have investigated the developmental–genetic steps that shape the entero-endocrine system of Drosophila melanogaster from the embryo to the adult. The process starts in the endoderm of the early embryo where precursors of endocrine cells and enterocytes of the larval midgut, as well as progenitors of the adult midgut, are specified by a Notch signaling-dependent mechanism. In a second step that occurs during the late larval period, enterocytes and endocrine cells of a transient pupal midgut are selected from within the clusters of adult midgut progenitors. As in the embryo, activation of the Notch pathway triggers enterocyte differentiation and inhibits cells from further proliferation or choosing the endocrine fate. The third step of entero-endocrine cell development takes place at a mid-pupal stage. Before this time point, the epithelial layer destined to become the adult midgut is devoid of endocrine cells. However, precursors of the intestinal midgut stem cells (pISCs) are already present. After an initial phase of symmetric divisions which causes an increase in their own population size, pISCs start to spin off cells that become postmitotic and express the endocrine fate marker, Prospero. Activation of Notch in pISCs forces these cells into an enterocyte fate. Loss of Notch function causes an increase in the proliferatory activity of pISCs, as well as a higher ratio of Prospero-positive cells.     

Estimating the flexural rigidity of Arabidopsis inflorescence stems: Free-vibration test vs. three-point bending test

The mechanical strength of a plant stem (a load-bearing organ) helps the plant resist drooping, buckling and fracturing. We previously proposed a method for quickly evaluating the stiffness of an inflorescence stem in the model plant Arabidopsis thaliana based on measuring its natural frequency in a free-vibration test. However, the relationship between the stiffness and flexural rigidity of inflorescence stems was unclear. Here, we compared our previously described free-vibration test with the three-point bending test, the most popular method for calculating the flexural rigidity of A. thaliana stems, and examined the extent to which the results were correlated. Finally, to expand the application range, we present an example of a modified free-vibration test. Our results provide a reference for improving estimates of the flexural rigidity of A. thaliana inflorescence stems.     

RNP2 of RNA Recognition Motif 1 Plays a Central Role in the Aberrant Modification of TDP-43

Phosphorylated and truncated TAR DNA-binding protein-43 (TDP-43) is a major component of ubiquitinated cytoplasmic inclusions in neuronal and glial cells of two TDP-43 proteinopathies, amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Modifications of TDP-43 are thus considered to play an important role in the pathogenesis of TDP-43 proteinopathies. However, both the initial cause of these abnormal modifications and the TDP-43 region responsible for its aggregation remain uncertain. Here we report that the 32 kDa C-terminal fragment of TDP-43, which lacks the RNP2 motif of RNA binding motif 1 (RRM1), formed aggregates in cultured cells, and that similar phenotypes were obtained when the RNP2 motif was either deleted from or mutated in full-length TDP-43. These aggregations were ubiquitinated, phosphorylated and truncated, and sequestered the 25 kDa C-terminal TDP-43 fragment seen in the neurons of TDP-43 proteinopathy patients. In addition, incubation with RNase decreased the solubility of TDP-43 in cell lysates. These findings suggest that the RNP2 motif of RRM1 plays a substantial role in pathological TDP-43 modifications and that it is possible that disruption of RNA binding may underlie the process of TDP-43 aggregation.     

Chromone acyl glucosides and an ayanin glucoside from Dasiphora parvifolia

Two new chromone acyl glucosides, 5-hydroxy-7-O-(6-O-p-cis-coumaroyl-β-D-glucopyranosyl)-chromone (1) and 5-hydroxy-7-O-(6-O-p-trans-coumaroyl-β-D-glucopyranosyl)-chromone (2), and a new flavonoid glucoside, ayanin 3′-O-β-D-glucopyranoside (3) were isolated from aerial parts of Dasiphora parvifolia, together with flavonoid glycosides (4–10), catechins (11, 12), and hydrolysable tannins (13, 14). The chemical structures of these compounds were elucidated on the basis of spectroscopic data. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and the hyaluronidase inhibitory activity of these compounds were evaluated.     

The type of mutations induced by carbon-ion-beam irradiation of the filamentous fungus Neurospora crassa

Heavy-ion beams are known to cause great damage to cellular components and are particularly renowned for their ability to generate DNA double-strand breaks (DSBs). To gain insight into the mutagenic effect of carbon-ion beams and how such damage is repaired by the cell, Neurospora crassa mutants deficient in one of three components involved in the repair of DSBs, nonhomologous end-joining (NHEJ), homologous recombination repair (HR), and the Mre11-Rad50-Xrs2 (MRX) complex, were irradiated with a carbon-ion beam and killing effect, mutation frequencies, and the type of mutation incurred by survivors were analysed. The sensitivity of the NHEJ-deficient strain (mus-52) was higher than that of the wild-type and the HR-deficient (mei-3) strains at low doses of radiation, but was little changed as the level increased. As a result both the wild-type and HR-deficient strains were more sensitive than the NHEJ-deficient strain at high radiation levels. In addition, the frequency of forward mutation at the adenine-3 (ad-3) loci of the NHEJ-deficient mutant was lower than that of the wild-type strain at all levels, while the mutation frequency of the HR-deficient strain was consistently ∼3-fold higher than the wild-type. From the comparison of mutation type of each strain, deletions were frequently observed in wild-type strain, whilst base substitution and deletion in the mus-52 and mei-3 strains. These mutations resulting from carbon-ion-beam irradiation depend on the mechanism invoked to cope with DSBs. Furthermore, in wild-type cells, these mechanisms likely compete to repair DSBs.     

Specific Gene bciD for C7-Methyl Oxidation in Bacteriochlorophyll e Biosynthesis of Brown-Colored Green Sulfur Bacteria

The gene named bciD, which encodes the enzyme involved in C7-formylation in bacteriochlorophyll e biosynthesis, was found and investigated by insertional inactivation in the brown-colored green sulfur bacterium Chlorobaculum limnaeum (previously called Chlorobium phaeobacteroides). The bciD mutant cells were green in color, and accumulated bacteriochlorophyll c homologs bearing the 7-methyl group, compared to C7-formylated BChl e homologs in the wild type. BChl-c homolog compositions in the mutant were further different from those in Chlorobaculum tepidum which originally produced BChl c: (3¹ S)-8-isobutyl-12-ethyl-BChl c was unusually predominant.     

Homopiperazine Derivatives as a Novel Class of Proteasome Inhibitors with a Unique Mode of Proteasome Binding

The proteasome is a proteolytic machinery that executes the degradation of polyubiquitinated proteins to maintain cellular homeostasis. Proteasome inhibition is a unique and effective way to kill cancer cells because they are sensitive to proteotoxic stress. Indeed, the proteasome inhibitor bortezomib is now indispensable for the treatment of multiple myeloma and other intractable malignancies, but is associated with patient inconvenience due to intravenous injection and emerging drug resistance. To resolve these problems, we attempted to develop orally bioavailable proteasome inhibitors with distinct mechanisms of action and identified homopiperazine derivatives (HPDs) as promising candidates. Biochemical and crystallographic studies revealed that some HPDs inhibit all three catalytic subunits (ß 1, ß 2 and ß 5) of the proteasome by direct binding, whereas bortezomib and other proteasome inhibitors mainly act on the ß5 subunit. Proteasome-inhibitory HPDs exhibited cytotoxic effects on cell lines from various hematological malignancies including myeloma. Furthermore, K-7174, one of the HPDs, was able to inhibit the growth of bortezomib-resistant myeloma cells carrying a ß5-subunit mutation. Finally, K-7174 had additive effects with bortezomib on proteasome inhibition and apoptosis induction in myeloma cells. Taken together, HPDs could be a new class of proteasome inhibitors, which compensate for the weak points of conventional ones and overcome the resistance to bortezomib.