Epigenetic asymmetry of imprinted genes in plant gametes

Plant imprinted genes show parent-of-origin expression in seed endosperm, but little is known about the nature of parental imprints in gametes before fertilization. We show here that single differentially methylated regions (DMRs) correlate with allele-specific expression of two maternally expressed genes in the seed and that one DMR is differentially methylated between gametes. Thus, plants seem to have developed similar strategies as mammals to epigenetically mark imprinted genes.     

Radioprotectors from pyrodextrins

Cornstarch heated in the range of 230–280°C depolymerized into pyrodextrins characterized by two-component EPR signals of relatively stable free radicals. These thermally generated radicals could serve as efficient scavengers for free radicals generated from pyrodextrins with the 200 Gy dose of γ-radiation. The most efficient traps/scavengers were produced from cornstarch at 250–280°C. IR data indicated incorporation of the OH groups to the pyrodextrins. These groups most probably originated from the OH· radicals formed by the radiolysis of water. EPR spectra provided evidence for trapping free radicals generated by γ-irradiation and for their subsequent annihilation on contact with pyrodextrins. Water affected radical processes occurring in pyrodextrins caused by γ-irradiation.     

Rab5 is a signalling GTPase involved in actin remodelling by receptor tyrosine kinases

Rab5 is a small GTPase involved in the control of intracellular trafficking, both at the level of receptor endocytosis and endosomal dynamics. The finding that Rab5 can be activated by receptor tyrosine kinases (RTK) raised the question of whether it also participates in effector pathways emanating from these receptors. Here we show that Rab5 is indispensable for a form of RTK-induced actin remodelling, called circular ruffling. Three independent signals, originating from Rab5, phosphatidylinositol-3-OH kinase and Rac, respectively, are simultaneously required for the induction of circular ruffles. Rab5 signals to the actin cytoskeleton through RN-tre, a previously identified Rab5-specific GTPase-activating protein (GAP). Here we demonstrate that RN-tre has the dual function of Rab5-GAP and Rab5 effector. We also show that RN-tre is critical for macropinocytosis, a process previously connected to the formation of circular ruffles. Finally, RN-tre interacts with both F-actin and actinin-4, an F-actin bundling protein. We propose that RN-tre establishes a three-pronged connection with Rab5, F-actin and actinin-4. This may aid crosslinking of actin fibres into actin networks at the plasma membrane. Thus, we have shown that Rab5 is a signalling GTPase and have elucidated the major molecular elements of its downstream pathway.     

Different salt concentration requirement of nuclear and cytoplasmic Mn++-stimulated poly(A) synthetase activities from rat liver

Summary Mn⁺⁺-stimulated poly(A) synthetase activity of dialyzed ammonium sulfate fraction (0–50% saturation) of nuclear extracts from rat liver is dependent on salt addition to the incubation mixture. The corresponding soluble cytoplasmic activity is inhibited by the salt concentration required for nuclear activity.     

Ongoing therapeutic trials and outcome measures for Duchenne muscular dystrophy

Muscular dystrophy is a heterogeneous group of genetic disorders characterised by progressive muscle tissue degeneration. No effective treatment has been discovered for these diseases. Preclinical and clinical studies aimed at the development of new therapeutic approaches have been carried out, primarily in subjects affected with dystrophinopathies (Duchenne and Becker muscular dystrophy). In this review, we outline the current therapeutic approaches and past and ongoing clinical trials, highlighting both the advantages and limits of each one. The experimental designs of these trials were based on different rationales, including immunomodulation, readthrough strategies, exon skipping, gene therapy, and cell therapy. We also provide an overview of available outcome measures, focusing on their reliability in estimating meaningful clinical improvement in order to aid in the design of future trials. This perspective is extremely relevant to the field considering the recent development of novel therapeutic approaches that will result in an increasing number of clinical studies over the next few years.     

Role of vasostatin-1 C-terminal region in fibroblast cell adhesion

Fibroblast adhesion can be modulated by proteins released by neuroendocrine cells and neurons, such as chromogranin A (CgA) and its N-terminal fragment vasostatin-1 (VS-1, CgA_1–78). We have investigated the mechanisms of the interaction of VS-1 with fibroblasts and of its pro-adhesive activity and have found that the proadhesive activity of VS-1 relies on its interaction with the fibroblast membrane via a phospholipid-binding amphipathic α-helix located within residues 47–66, as well as on the interaction of the adjacent C-terminal region 67–78, which is structurally similar to ezrin–radixin–moesin-binding phosphoprotein 50 (a membrane-cytoskeleton adapter protein), with other cellular components critical for the regulation of cell cytoskeleton.     

The endocrine role for chromogranin A: A prohormone for peptides with regulatory properties

Chromogranin A (CgA) belongs to the granin family of uniquely acidic secretory proteins co-stored and co-secreted with other hormones and peptides in elements of the diffuse neuroendocrine system. The granins arise from different genes and are characterized by numerous sites for post-translational cleavage into shorter peptides with postulated regulatory properties. This review is directed towards endocrine aspects of CgA and its biologically active peptides. There is ample evidence from in vitro studies of distinct effects and targets for three CgA-derived peptides, vasostatin-I, pancreastatin and catestatin. Endocrine regulations are indicated from in vivo studies, consistent with the postulated prohormone function of CgA for peptides with regulatory properties. Most of the effects fit into patterns of direct or indirect, inhibitory modulations of major functions, implicating CgA peptides in regulation of calcium and glucose metabolism, cardiovascular functions, gastrointestinal motility and nociception, tissue repair, inflammatory responses and as host defense peptides in the first phase of microbial invasions. Received 1 June 2007; received after revision 11 July 2007; accepted 12 July 2007     

Distribution, silencing potential and evolutionary impact of promoter DNA methylation in the human genome

To gain insight into the function of DNA methylation at cis-regulatory regions and its impact on gene expression, we measured methylation, RNA polymerase occupancy and histone modifications at 16,000 promoters in primary human somatic and germline cells. We find CpG-poor promoters hypermethylated in somatic cells, which does not preclude their activity. This methylation is present in male gametes and results in evolutionary loss of CpG dinucleotides, as measured by divergence between humans and primates. In contrast, strong CpG island promoters are mostly unmethylated, even when inactive. Weak CpG island promoters are distinct, as they are preferential targets for de novo methylation in somatic cells. Notably, most germline-specific genes are methylated in somatic cells, suggesting additional functional selection. These results show that promoter sequence and gene function are major predictors of promoter methylation states. Moreover, we observe that inactive unmethylated CpG island promoters show elevated levels of dimethylation of Lys4 of histone H3, suggesting that this chromatin mark may protect DNA from methylation.     

T-antigen regulated expression reduces apoptosis of Tag-transformed human myoblasts

The generation of human myogenic cell lines could potentially provide a valuable source for cell transplantation in myopathies. The dysregulation of proliferative-differentiative signals by viral oncogenes can result in the induction of apoptosis. Whether apoptosis occurred in myogenic cells expressing large T antigen (Tag) from SV40 upon differentiation was unknown. Human muscle satellite cells were transfected with two different constructs, containing either an origin-defective SV40 genome or Tag under vimentin promoter control. When differentiation was triggered, Tag expression reduced the formation of myotubes and dead cells showing apoptotic features were present. However, the cells expressing SV40 Tag under vimentin promoter control retained their capacity to form myotubes and expressed the myofibrillar proteins as myosin heavy chain and dystrophin when Tag expression was silent. Their apoptotic rate was similar to that of untransfected cells. The observation that apoptosis can be prevented by the down-regulation of Tag suggests that the programmed cell death induced in transformed cells can be reversed, and confirms the regulatory efficiency of the human vimentin promoter.