The human HYMAI/PLAGL1 differentially methylated region acts as an imprint control region in mice

Imprinting centers (IC) can be defined as cis-elements that are recognized in the germ line and are epigenetically modified to bring about the full imprinting program in a somatic cell. Two paternally expressed human genes, HYMAI and PLAGL1 (LOT1/ZAC), are located within human chromosome 6q24. Within this region lies a 1-kb CpG island that is differentially methylated in somatic cells, unmethylated in sperm, and methylated in mature oocytes in mice, characteristic features of an IC. Loss of methylation of the homologous region in humans is observed in patients with transient neonatal diabetes mellitus and hypermethylation is associated with a variety of cancers, suggesting that this region regulates the expression of one or more key genes in this region involved in these diseases. We now report that a transgene carrying the human HYMAI/PLAGL1 DMR was methylated in the correct parent-origin-specific manner in mice and this was sufficient to confer imprinted expression from the transgene. Therefore, we propose that this DMR functions as the IC for the HYMAI/PLAGL1 domain.     

Effects of host nutritional status and seasonality on the nitrogen status of zooxanthellae in the temperate coral Plesiastrea versipora (Lamarck)

The nitrogen status of endosymbiotic dinoflagellates (zooxanthellae) in the temperate coral Plesiastrea versipora (Lamarck) was determined by measuring the extent to which ammonium (40 μM NH₄⁺) enhanced the rate of zooxanthellar dark carbon fixation above that seen in filtered seawater (FSW) alone; the enhancement ratio was expressed as [dark NH₄⁺ rate/dark FSW rate]. V_D′/V_L, a further index of nitrogen status, was also calculated where V_D′ = [dark NH₄⁺ rate − dark FSW rate] and V_L = rate of carbon fixation in the light. When corals were starved for 2-8 weeks, zooxanthellar nitrogen deficiency became apparent at ≥ 4 weeks, with NH₄⁺/FSW and V_D′/V_L averaging up to 2.08 and 0.0061, respectively. A decrease in light-saturated photosynthesis per zooxanthella also occurred, with the photosynthetic rate after 4-6 weeks being just 81% of that seen prior to starvation. In comparison, when corals were fed 5 times per week for 8 weeks the addition of ammonium had little effect, indicating nitrogen sufficiency; NH₄⁺/FSW and V_D′/V_L were 1.03 and 0.0003, respectively. Photosynthetic rates of zooxanthellae from well-fed corals were up to 1.7 times greater than those of zooxanthellae from starved corals. The nitrogen status of zooxanthellae from corals in the field exhibited seasonal differences. Autumn samples were nitrogen sufficient, with NH₄⁺/FSW = 1.003 and V_D′/V_L = 0.0001. In contrast, a small degree of nitrogen deficiency was seen in winter and spring, when NH₄⁺/FSW averaged 1.075 and 1.249, and V_D′/V_L averaged 0.0013 and 0.0014, respectively. The greatest degree of nitrogen deficiency was observed in summer, when NH₄⁺/FSW averaged 1.318 and V_D′/V_L averaged 0.0036. Given the clear links between food supply and nitrogen status seen under experimental conditions, and the likelihood that the zooxanthellae are also able to take up nutrients directly from the seawater, the fluctuations in nitrogen status may reflect temporal fluctuations in seawater nutrient concentrations and plankton abundance. The nutrient status of these temperate zooxanthellae in the field is in contrast to the marked nitrogen deficiency seen in zooxanthellae from nutrient-poor coral reef waters, and raises the possibility that temperate zooxanthellae can store nitrogen for use when exogenous nutrients and food are less readily available. This, in turn, may contribute to the considerable stability of temperate zooxanthellar populations under highly variable environmental conditions.     

Shrimps survive white spot syndrome virus challenge following treatment with Vibrio bacterin

Taking an innovative approach, a vaccination study using five bacterial strains viz. Vibrio campbelli (B60), V. alginolyticus (B73), V. parahaemolyticus-like (B79), V. parahaemolyticus (R8) and V. harveyi (RG203) was conducted in Penaeus monodon against white spot syndrome virus (WSSV) infection, considered as one of the serious pathogens of shrimps. Oral challenge with shrimps infected with WSSV showed a relative percentage survival of 5 and 47% in the P. monodon juveniles vaccinated with V. parahaemolyticus and V. harveyi, respectively. Results showed that there is a possibility of specifically immunising the shrimps against WSSV using bacterin prepared out of Vibrio harveyi isolates taken from shrimps infected with WSSV. Also, there was a level of protection attained by the shrimps due to immunisation with Vibrio strains.     

Chromatin signatures of pluripotent cell lines

Epigenetic genome modifications are thought to be important for specifying the lineage and developmental stage of cells within a multicellular organism. Here, we show that the epigenetic profile of pluripotent embryonic stem cells (ES) is distinct from that of embryonic carcinoma cells, haematopoietic stem cells (HSC) and their differentiated progeny. Silent, lineage-specific genes replicated earlier in pluripotent cells than in tissue-specific stem cells or differentiated cells and had unexpectedly high levels of acetylated H3K9 and methylated H3K4. Unusually, in ES cells these markers of open chromatin were also combined with H3K27 trimethylation at some non-expressed genes. Thus, pluripotency of ES cells is characterized by a specific epigenetic profile where lineage-specific genes may be accessible but, if so, carry repressive H3K27 trimethylation modifications. H3K27 methylation is functionally important for preventing expression of these genes in ES cells as premature expression occurs in embryonic ectoderm development (Eed)-deficient ES cells. Our data suggest that lineage-specific genes are primed for expression in ES cells but are held in check by opposing chromatin modifications.     

Polymorphic DNA sequences of the fungal honey bee pathogen Ascosphaera apis

The pathogenic fungus Ascosphaera apis is ubiquitous in honey bee populations. We used the draft genome assembly of this pathogen to search for polymorphic intergenic loci that could be used to differentiate haplotypes. Primers were developed for five such loci, and the species specificities were verified using DNA from nine closely related species. The sequence variation was compared among 12 A.?apis isolates at each of these loci, and two additional loci, the internal transcribed spacer of the ribosomal RNA (ITS) and a variable part of the elongation factor 1α (Ef1α). The degree of variation was then compared among the different loci, and three were found to have the greatest detection power for identifying A.?apis haplotypes. The described loci can help to resolve strain differences and population genetic structures, to elucidate host-pathogen interaction and to test evolutionary hypotheses for the world's most important pollinator: the honey bee and one of its most common pathogens.     

A mechanical model of cell segregation driven by differential adhesion

From simulations that begin with a random mix of two cell types, we monitor progress towards segregation driven by contact-mediated linkage of model cells, which is equivalent to the cell-cell adhesion of real cells. In comparison with real cell experiments, we show that this mechanical model can account for the observed extent of segregation obtained by differential adhesion in a 2D cell culture assay of cells with differentially expressed cadherin molecules. Calibration of virtual to real time allowed us to estimate a time course for these experiments that was within 50% agreement for the simulations compared to differential adhesion of cells. In contrast, simulations of differential adhesion do not account for the rate of segregation driven by interactions between EphB2 receptor and ephrinB1 expressing cells which occurs an order of magnitude faster. The latter result suggests that mechanisms additional or alternative to differential adhesion contribute to Eph-ephrin mediated cell segregation.     

Action in the axon: generation and transport of signaling endosomes

Neurons extend axonal processes over long distances, necessitating efficient transport mechanisms to convey target-derived neurotrophic survival signals from remote distal axons to cell bodies. Retrograde transport, powered by dynein motors, supplies cell bodies with survival signals in the form of 'signaling endosomes'. In this review, we will discuss new advances in our understanding of the motor proteins that bind to and move signaling components in a retrograde direction and discuss mechanisms that might specify distinct neuronal responses to spatially restricted neurotrophin signals. Disruption of retrograde transport leads to a variety of neurodegenerative diseases, highlighting the role of retrograde transport of signaling endosomes for axonal maintenance and the importance of efficient transport for neuronal survival and function.     

Phosphorylation of cysteine string protein on Serine 10 triggers 14-3-3 protein binding

Cysteine string protein (CSP) is a neuronal chaperone that maintains normal neurotransmitter exocytosis and is essential for preventing presynaptic neurodegeneration. CSP is phosphorylated in vivo on a single residue, Ser10, and this phosphorylation regulates its cellular functions, although the molecular mechanisms involved are unclear. To identify novel phosphorylation-specific binding partners for CSP, we used a pull-down approach using synthetic peptides and recombinant proteins. A single protein band was observed to bind specifically to a Ser10-phosphorylated CSP peptide (residues 4-14) compared to a non-phosphorylated peptide. This band was identified as 14-3-3 protein of various isoforms using mass spectrometry and Western blotting. PKA phosphorylation of full-length CSP protein stimulated 14-3-3 binding, and this was abolished in a Ser10-Ala mutant CSP, confirming the binding site as phospho-Ser10. As both CSP and 14-3-3 proteins are implicated in neurotransmitter exocytosis and neurodegeneration, this novel phosphorylation-dependent interaction may help maintain the functional integrity of the synapse.     

Molecular Analysis of the β-Globin Gene Cluster in the Niokholo Mandenka Population Reveals a Recent Origin of the βS Senegal Mutation

A large and ethnically well-defined Mandenka sample from eastern Senegal was analyzed for the polymorphism of the beta-globin gene cluster on chromosome 11. Five RFLP sites of the 5' region were investigated in 193 individuals revealing the presence of 10 different haplotypes. The frequency of the sickle-cell anemia causing mutation (beta(S)) in the Mandenka estimated from this sample is 11.7%. This mutation was found strictly associated with the single Senegal haplotype. Approximately 600 bp of the upstream region of the beta-globin gene were sequenced for a subset of 94 chromosomes, showing the presence of four transversions, five transitions, and a composite microsatellite polymorphism. The sequence of 22 beta(S) chromosomes was also identical to the previously defined Senegal haplotype, suggesting that this mutation is very recent. Monte Carlo simulations (allowing for a specific balancing selection model, a logistic growth of the population, and variable initial frequencies of the Senegal haplotype) were used to estimate the age of the beta(S) mutation. Resulting maximum-likelihood estimates are 45-70 generations (1,350-2,100 years) for very different demographic scenarios. Smallest confidence intervals (25-690 generations) are obtained under the hypothesis that the Mandenka population is large (N(e) >5,000) and stationary or that it has undergone a rapid demographic expansion to a current size of >5,000 reproducing individuals, which is quite likely in view of the great diversity found on beta(A) chromosomes.