Two novel type II receptors mediate BMP signalling and are required to establish left-right asymmetry in zebrafish

Ligands of the transforming growth factor β (TGFβ) superfamily, like Nodal and bone morphogenetic protein (BMP), are pivotal to establish left-right (LR) asymmetry in vertebrates. However, the receptors mediating this process are unknown. Here we identified two new type II receptors for BMPs in zebrafish termed bmpr2a and bmpr2b that induce a classical Smad1/5/8 response to BMP binding. Morpholino-mediated knockdown of bmpr2a and bmpr2b showed that they are required for the establishment of concomitant cardiac and visceral LR asymmetry. Expression of early laterality markers in morphants indicated that bmpr2a and bmpr2b act upstream of pitx2 and the nodal-related southpaw (spaw), which are expressed asymmetrically in the lateral plate mesoderm (LPM), and subsequently regulate lefty2 and bmp4 in the left heart field. We demonstrated that bmpr2a is required for lefty1 expression in the midline at early segmentation while bmpr2a/bmpr2b heteromers mediate left-sided spaw expression in the LPM. We propose a mechanism whereby this differential interpretation of BMP signalling through bmpr2a and bmpr2b is essential for the establishment of LR asymmetry in the zebrafish embryo.     

Simple sequence repeat analyses of interspecific hybrids and MAALs of <Emphasis Type="Italic">Oryza </Emphasis><Emphasis Type="Italic">officinalis</Emphasis> and <Emphasis Type="Italic">Oryza sativa</Emphasis>

Wild rice is a valuable resource for the genetic improvement of cultivated rice (Oryza sativa L., AA genome). Molecular markers are important tools for monitoring gene introgression from wild rice into cultivated rice. In this study, Simple sequence repeat (SSR) markers were used to analyze interspecific hybrids of O. sativa-O. officinalis (CC genome), the backcrossing progenies and the parent plants. Results showed that most of the SSR primers (335 out of 396, 84.6%) developed in cultivated rice successfully amplified products from DNA samples of wild rice O. officinalis. The polymorphism ratio of SSR bands between O. sativa and O. officinalis was as high as 93.9%, indicating differences between the two species with respect to SSRs. When the SSR markers were applied in the interspecific hybrids, only a portion of SSR primers amplified O. officinalis-specific bands in the F(1) hybrid (52.5%), BC(1) (52.5%), and MAALs (37.0%); a number of the bands disappeared. Of the 124 SSR loci that detected officinalis-specific bands in MAAL plants, 96 (77.4%) showed synteny between the A and C-genomes, and 20 (16.1%) showed duplication in the C-genome. Sequencing analysis revealed that indels, substitution and duplication contribute to the diversity of SSR loci between the genomes of O. sativa and O. officinalis.     

One of the possible mechanisms for the inhibition effect of Tb(III) on peroxidase activity in horseradish (<Emphasis Type="Italic">Armoracia rusticana</Emphasis>) treated with Tb(III)

One of the possible mechanisms for the inhibition effect of Tb(III) on peroxidase activity in horseradish (Armoracia rusticana) treated with Tb(III) was investigated using some biophysical and biochemical methods. Firstly, it was found that a large amount of Tb(III) can be distributed on the cell wall, that some Tb(III) can enter into the horseradish cell, indicating that peroxidase was mainly distributed on cell wall, and thus that Tb(III) would interact with horseradish peroxidase (HRP) in the plant. In addition, peroxidase bioactivity was decreased in the presence of Tb(III). Secondly, a new peroxidase-containing Tb(III) complex (Tb–HRP) was obtained from horseradish after treatment with Tb(III); the molecular mass of Tb–HRP is near 44 kDa and the pI is about 8.80. Thirdly, the electrocatalytic activity of Tb–HRP is much lower than that of HRP obtained from horseradish without treatment with Tb(III). The decrease in the activity of Tb–HRP is due to the destruction (unfolding) of the conformation in Tb–HRP. The planarity of the heme active center in the Tb–HRP molecule was increased and the extent of exposure of Fe(III) in heme was decreased, leading to inhibition of the electron transfer. The microstructure change in Tb–HRP might be the result of the inhibition effect of Tb(III) on peroxidase activity in horseradish.     

Determining binding sites of drugs on human serum albumin using FIA-QCM

A simple and effective method was developed for determining binding sites of drugs on human serum albumin (HSA) by independent binding or competitive displacement of bilirubin using flow injection analysis-quartz crystal microbalance (FIA-QCM) system. Both independent and competitive bindings were entirely monitored in real time. Bilirubin as a site I-binding ligand was pre-bound to HSA sensor so as to occupy the drug-binding site I. When the model site II-binding drugs (ibuprofen, ketoprofen and flurbiprofen) were injected into the bilirubin pre-bound HSA system, the frequency continuously decreased by 6Hz, 4Hz and 5Hz, respectively, which was the same as that of their individual binding to HSA sensor. It indicated that the drug binding to site II was independent and did not interfere with bilirubin binding. However, when the model site I-binding drugs (iodipamide and magnesium salicylate) were introduced into the system, the frequency remained unchanged in the initial several minutes and then rapidly decreased by 4Hz for iodipamide and increased by 4Hz for magnesium salicylate. This phenomenon revealed site I-binding drugs competitively bound to HSA against bilirubin and displaced the pre-bound bilirubin. The results demonstrate FIA-QCM can be a valid approach for monitoring the dynamic interaction between drugs and HSA in real time further identifying drug-binding sites without the need of labels.     

Comparative analysis of meiotic progression in female mice bearing mutations in genes of the DNA mismatch repair pathway

The DNA mismatch repair (MMR) family functions in a variety of contexts to preserve genome integrity in most eukaryotes. In particular, members of the MMR family are involved in the process of meiotic recombination in germ cells. MMR gene mutations in mice result in meiotic disruption during prophase I, but the extent of this disruption often differs between male and female meiocytes. To address the role of MMR proteins specifically in female meiosis, we explored the progression of oocytes through prophase I and the meiotic divisions in mice harboring deletions in members of the MMR pathway (Mlh1, Mlh3, Exo1, and an ATPase-deficient variant of Mlh1, Mlh1(G67R)). The colocalization of MLH1 and MLH3, key proteins involved in stabilization of nascent crossovers, was dependent on intact heterodimer formation and was highly correlated with the ability of oocytes to progress through to metaphase II. The exception was Exo1(-/-) oocytes, in which normal MLH1/MLH3 localization was observed followed by failure to proceed to metaphase II. All mutant oocytes were able to resume meiosis after dictyate arrest, but they showed a dramatic decline in chiasmata (to less than 25% of normal), accompanied by varied progression through metaphase I. Taken together, these results demonstrate that MMR function is required for the formation and stabilization of crossovers in mammalian oocytes and that, in the absence of a functional MMR system, the failure to maintain chiasmata results in a reduced ability to proceed normally through the first and second meiotic divisions, despite near-normal levels of meiotic resumption after dictyate arrest.     

Structural and functional characterization of osmotically inducible protein C (OsmC) from Thermococcus kodakaraensis KOD1

Osmotically inducible protein C (OsmC) is involved in the cellular defense mechanism against oxidative stress caused by exposure to hyperoxides or elevated osmolarity. OsmC was identified by two-dimensional electrophoresis (2DE) analysis as a protein that is overexpressed in response to osmotic stress, but not under heat and oxidative stress. Here, an OsmC gene from T. kodakaraensis KOD1 was cloned and expressed in Escherichia coli. TkOsmC showed a homotetrameric structure based on gel filtration and electron microscopic analyses. TkOsmC has a significant peroxidase activity toward both organic and inorganic peroxides in high, but not in low temperature.     

合作行为的进化

达尔文在<物种起源>中阐释了生物体的竞争进化.但是合作行为和利他行为的发现却给了自然选择学说致命一击.20世纪60年代开始,进化生物学家开始重视对合作行为的研究.一方面,这些行为的本质至关重要,而且与基因学的观点相悖.另一方面,对合作行为和利他行为,尤其是实验室控制条件下行为的研究非常困难.阐述了合作行为进化发展的方式.同时综述了合作行为模式的框架,简要解释了这些模式的进化机制,以期为进一步理解合作行为的进化及其模式奠定基础.     

Hydrogen sulfide as an oxygen sensor in trout gill chemoreceptors

O2 chemoreceptors elicit cardiorespiratory reflexes in all vertebrates, but consensus on O2-sensing signal transduction mechanism(s) is lacking. We recently proposed that hydrogen sulfide (H2S) metabolism is involved in O2 sensing in vascular smooth muscle. Here, we examined the possibility that H2S is an O2 sensor in trout chemoreceptors where the first pair of gills is a primary site of aquatic O2 sensing and the homolog of the mammalian carotid body. Intrabuccal injection of H2S in unanesthetized trout produced a dose-dependent bradycardia and increased ventilatory frequency and amplitude similar to the hypoxic response. Removal of the first, but not second, pair of gills significantly inhibited H2S-mediated bradycardia, consistent with the loss of aquatic chemoreceptors. mRNA for H2S-synthesizing enzymes, cystathionine beta-synthase and cystathionine gamma-lyase, was present in branchial tissue. Homogenized gills produced H2S enzymatically, and H2S production was inhibited by O2, whereas mitochondrial H2S consumption was O2 dependent. Ambient hypoxia did not affect plasma H2S in unanesthetized trout, but produced a PO2-dependent increase in a sulfide moiety suggestive of increased H2S production. In isolated zebrafish neuroepithelial cells, the putative chemoreceptive cells of fish, both hypoxia and H2S, produced a similar approximately 10-mV depolarization. These studies are consistent with H2S involvement in O2 sensing/signal transduction pathway(s) in chemoreceptive cells, as previously demonstrated in vascular smooth muscle. This novel mechanism, whereby H2S concentration ([H2S]) is governed by the balance between constitutive production and oxidation, tightly couples tissue [H2S] to PO2 and may provide an exquisitely sensitive, yet simple, O2 sensor in a variety of tissues.     

Brain Atrophy in a Murine Model of Chronic Fatigue Syndrome and Beneficial Effect of Hochu-ekki-to (TJ-41)

Brain-derived neurotrophic factor (BDNF) is associated with the main symptoms of chronic fatigue sydrome (CFS) and neuron apoptosis. Nevertheless, no study has been performed directly to explore the relationship between CFS, BDNF and neuron apoptosis. We induced a CFS model by six injections of killed Brucella abortus antigen in BALB/c mice and treated them with Hochu-ekki-to (TJ-41). Daily running activity, body weight (BW), ratio of cerebral weight to BW (CW/BW) and expression levels of BDNF and Bcl-2 mRNA in the hippocampus were determined. The daily activity and CW/BW decreased significantly in the CFS model. BDNF and Bcl-2 mRNA expression levels in the hippocampus were suppressed in the CFS model and TJ-41 treated mice, while no significant difference was found between them. We improved a murine model to investigate the relationship between CFS and brain dysfunction. In this model, reduced daily activity might have been associated with decreased hippocampal BDNF mRNA expression, hippocampal apoptosis and brain atrophy. TJ-41 increased the daily running activity of the model, which was independent of brain recovery.