Protons at the gate: DEG/ENaC ion channels help us feel and remember

The DEG/ENaC ion channel family contributes to channels of striking functional diversity. Neuronally expressed family members include the C. elegans degenerins that mediate touch and are thought to be mechanically gated, and the mammalian ASICs, which are gated by protons. ASICs affect a range of sensory functions that includes perception of gentle touch, harsh touch, heat, sour taste, and pain. Family member ASIC1 is now implicated in long-term potentiation, suggesting that minute fluxes in synaptic pH may activate ASICs to enhance learning.     

Ectomycorrhizae between <Emphasis Type="Italic">Alnus acuminata</Emphasis> H.B.K. and <Emphasis Type="Italic">Naucoria escharoides</Emphasis> (Fr.:Fr.) Kummer from Argentina

Field ectomycorrhizae of Naucoria escharoides on Alnus acuminata ("andean alder", "aliso del cerro") are described in detail for the first time. Naturally occurring ectomycorrhizal roots were sampled beneath sporocarps of N. escharoides. The samples were taken from four natural forest plots at two homogeneous A. acuminata sites (Tucumán and Catamarca Provinces, Argentina). The ectomycorrhizae were characterized morphologically and compared by means of PCR/RFLP analysis of the internal transcribed spacer region of the nuclear rDNA. The most important morphological features of the ectomycorrhizae are a white to pale yellow mantle, simple to monopodial branches, hyaline emanating hyphae, abundant hyphal bundles emerging more or less perpendicularly from a plectenchymatous mantle, and an acute or rounded apex with or without a mantle. N. escharoides fruitbodies have white basal mycelium with emanating hyphae similar to those of andean alder ectomycorrhizae. The RFLP profiles of sporocarps and mycorrhizae were the same.     

SakA MAP kinase is involved in stress signal transduction,sexual development and spore viability in Aspergillus nidulans

In eukaryotic cells, environmental stress signals are transmitted by evolutionarily conserved MAPKs, such as Hog1 in the budding yeast Saccharomyces cerevisiae, Spc1 in the fission yeast Schizosaccharomyces pombe and p38/JNK in mammalian cells. Here, we report the identification of the Aspergillus nidulans sakA gene, which encodes a member of the stress MAPK family. The sakA gene is able to complement the S. pombe spc1- defects in both osmo-regulation and cell cycle progression. Moreover, SakA MAPK is activated in response to osmotic and oxidative stress in both S. pombe and A. nidulans. However, in contrast to hog1 and spc1 mutants, the sakA null mutant is not sensitive to high osmolarity stress, indicating a different regulation of the osmostress response in this fungus. On the other hand, the DeltasakA mutant shows development and cell-specific phenotypes. First, it displays premature steA-dependent sexual development. Second, DeltasakA mutant produces asexual spores that are highly sensitive to oxidative and heat shock stress and lose viability upon storage. Indeed, SakA is transiently activated early after induction of conidiation. Our results indicate that SakA MAPK is involved in stress signal transduction and repression of sexual development, and is required for spore stress resistance and survival.     

Hereditary forms of intrahepatic cholestasis

Several genes that are mutated in hereditary forms of intrahepatic cholestasis have been identified or mapped, providing new insights into the process of enterohepatic bile acid circulation in health and disease and new tools with which to study this process. Murine models of several of these disorders have been generated. Unanticipated genetic heterogeneity has been identified.     

A high field NMR study of the products ensuing from konjak glucomannan C(6)-oxidation followed by enzymatic C(5)-epimerization

Konjak glucomannan (KGM) is a water-soluble linear copolymer of (1-->4) linked beta-D-mannopyranosyl and beta-D-glucopyranosyl units. It has been selectively C6-oxidized by a 2,2,6,6-tetramethylpiperidin-1-oxy mediated reaction to obtain the corresponding uronan. Oxidized KGM has been treated with three different C-5 epimerases, AlgE4, AlgE6, and AlgE1, to obtain uronans with a various content of alpha-L-gulopyranuronate residues, namely, KGME4, KGME6, and KGME1. By use of 1D selective and 2D NMR techniques, a full assignment of the high field (600 MHz) NMR spectra of the purified native KGM and of the oxidized and epimerized derivatives has been obtained. Since in the anomeric region of the (1)H NMR spectrum of native KGM, diads sensitivity is present, the glucose-glucose, glucose-mannose, mannose-mannose, and mannose-glucose distribution has been obtained. In the (13)C spectrum of oxidized KGM, due to the presence of triad sensitivity on the C-4 resonance of glucuronic and mannuronic units, a better sequential investigation has been possible. As a result the average length of mannuronic blocks, N(M) is obtained. When AlgE4, AlgE6, and AlgE1 enzymes are used for the epimerization of oxidized KGM, the reaction products differ significantly both in the proportion and in the distribution of the mannuronic and guluronic residues. In epimerized KGM derivatives, a careful deconvolution of (1)H spectra allows the measurement of the degree of epimerization. In the case of KGME1 and KGME6, the average blocks length, N(G), of the guluronic blocks introduced in the polysaccharidic chain with the epimerization has also been calculated. Due to the shortness of mannuronic blocks in the oxidized KGM before the epimerization, N(G) in the epimerized compounds is also very low.     

Jaw transformation with gain of symmetry after Dlx5/Dlx6 inactivation: Mirror of the past?

In modern vertebrates upper and lower jaws are morphologically different. Both develop from the mandibular arch, which is colonized mostly by Hox-free neural crest cells. Here we show that simultaneous inactivation of the murine homeobox genes Dlx5 and Dlx6 results in the transformation of the lower jaw into an upper jaw and in symmetry of the snout. This is the first homeotic-like transformation found in this Hox-free region after gene inactivation. A suggestive parallel comes from the paleontological record, which shows that in primitive vertebrates both jaws are essentially mirror images of each other. Our finding supports the notion that Dlx genes are homeotic genes associated with morphological novelty in the vertebrate lineage.