Many flaviviruses are significant human pathogens. The plus-strand RNA genome of a flavivirus contains a 5′ terminal cap 1 structure (m⁷GpppAmG). The flavivirus encodes one methyltransferase (MTase), located at the N-terminal portion of the NS5 RNA-dependent RNA polymerase (RdRp). Here we review recent advances in our understanding of flaviviral capping machinery and the implications for drug development. The NS5 MTase catalyzes both guanine N7 and ribose 2’-OH methylations during viral cap formation. Representative flavivirus MTases, from dengue, yellow fever, and West Nile virus (WNV), sequentially generate GpppA→m⁷GpppA→m⁷GpppAm. Despite the existence of two distinct methylation activities, the crystal structures of flavivirus MTases showed a single binding site for S-adenosyl-L-methionine (SAM), the methyl donor. This finding indicates that the substrate GpppA-RNA must be repositioned to accept the N7 and 2’-O methyl groups from SAM during the sequential reactions. Further studies demonstrated that distinct RNA elements are required for the methylations of guanine N7 on the cap and of ribose 2’-OH on the first transcribed nucleotide. Mutant enzymes with different methylation defects can trans complement one another in vitro, demonstrating that separate molecules of the enzyme can independently catalyze the two cap methylations in vitro. In the context of the infectious virus, defects in both methylations, or a defect in the N7 methylation alone, are lethal to WNV. However, viruses defective solely in 2’-O methylation are attenuated and can protect mice from later wild-type WNV challenge. The results demonstrate that the N7 methylation activity is essential for the WNV life cycle and, thus, methyltransferase represents a novel and promising target for flavivirus therapy.

Dendrites and the dendritic spines of neurons play key roles in the connectivity of the brain and have been recognized as the locus of long-term synaptic plasticity, which is correlated with learning and memory. The development of dendrites and spines in the mammalian central nervous system is a complex process that requires specific molecular events over a period of time. It has been shown that specific molecules are needed not only at the spine’s point of contact, but also at a distance, providing signals that initiate a cascade of events leading to synapse formation. The specific molecules that act to signal neuronal differentiation, dendritic morphology, and synaptogenesis are tightly regulated by genetic and epigenetic programs. It has been shown that the dendritic spine structure and distribution are altered in many diseases, including many forms of mental retardation (MR), and can also be potentiated by neuronal activities and an enriched environment. Because dendritic spine pathologies are found in many types of MR, it has been proposed that an inability to form normal spines leads to the cognitive and motor deficits that are characteristic of MR. Epigenetic mechanisms, including DNA methylation, chromatin remodeling, and the noncoding RNA-mediated process, have profound regulatory roles in mammalian gene expression. The study of epigenetics focuses on cellular effects that result in a heritable pattern of gene expression without changes to genomic encoding. Despite extensive efforts to understand the molecular regulation of dendrite and spine development, epigenetic mechanisms have only recently been considered. In this review, we will focus on epigenetic mechanisms that regulate the development and maturation of dendrites and spines. We will discuss how epigenetic alterations could result in spine abnormalities that lead to MR, such as is seen in fragile X and Rett syndromes. We will also discuss both general methodology and recent technological advances in the study of neuronal dendrites and spines.

Aging is the predominant risk factor for major neurodegenerative diseases. The underlying mechanisms are largely unknown. Members of the sirtuin family of protein deacetylases support and promote longevity in diverse organisms and can extend lifespan when upregulated. Sirtuins are involved in fundamental mechanisms in age-related neurodegenerative diseases, including protein aggregation and homeostasis, survival and stress responses, and inflammatory processes. In this review, we will discuss the neurobiology of sirtuins and their multifaceted roles in the pathogenesis of neurodegenerative diseases. We will also examine the potential and challenges of targeting sirtuin pathways to treat these devastating conditions.

Brugada syndrome (BrS) is a life-threatening cardiac rhythm disorder characterized by persistent ST-segment elevation in leads V1―V3 and right bundle branch block on electrocardiograms (ECG), and by syncope and sudden death from ventricular tachycardia (VT) and ventricular fibrillation (VF). BrS is responsible for nearly 4% of sudden cardiac deaths and considered to be the most common cause of natural death in males younger than 50 years in some Asian countries. Since the first disease-causing gene for BrS (the cardiac sodium channel gene SCN5A) was identified in 1998, extensive investigations on both clinical and basic aspects of BrS have occurred rapidly. SCN5A mutations remain the most common cause of BrS; nearly 300 SCN5A mutations have been identified and are responsible for 20%―30% of BrS cases. Commercial genetic testing is available for SCN5A. Recently, seven other disease-causing genes for BrS have been identified and include GPD1L (BrS2), CACNA1C (Cav1.2, BrS3), CACNB2 (Cavβ2, BrS4), SCN1B (Navβ1, BrS5), KCNE3 (MiRP2, BrS6), SCN3B (Navβ3, BrS7), and HCN4 (BrS8). This article will briefly review the progress made over the past decade in our understanding of the clinical, genetic and molecular aspects of BrS.

The discovery of the Hardy-Weinberg principle marked the beginning of the field of population genetics. Over the past hundred years, it has provided a starting point for many population genetic investigations. In this review, the Hardy-Weinberg principle, its statistical testing, and several of its applications in various modern population genetic research areas, including allelic variability and selection in the human leukocyte antigen region, microsatellite genotyping error detection, and accuracy of haplotype estimation, are discussed.

High throughput screening (HTS) is a widely used effective approach in genome-wide association and large scale protein expression studies, drug discovery, and biomedical imaging research. How to accurately identify candidate ‘targets’ or biologically meaningful features with a high degree of confidence has led to extensive statistical research in an effort to minimize both false-positive and false-negative rates. A large body of literature on this topic with in-depth statistical contents is available. We examine currently available statistical methods on HTS and aim to summarize some selected methods into a concise, easy-to-follow introduction for experimental biologists.

The Hedyotis diffusa Willd herbal compounds (HDWHCs) are commonly used as Chinese medicine to treat cancer patients with established clinical therapeutic efficacy in China. However, the underlying mechanisms remain to be elucidated. In this study, we used freeze-dried powder of the water extracts of HDWHCs to investigate the potential mechanisms of HDWHCs in cancer treatment. HDWHCs treatment significantly inhibited vascular endothelial growth factor (VEGF) mRNA levels and VEGF transcriptional activation in cancer cells. HDWHCs also had a remarkable inhibitory effect on the expression of hypoxia-inducible factor 1alpha (HIF-1alpha). Forced expression of HIF-1α restored VEGF transcriptional activation inhibited by HDWHCs, indicating that HDWHCs suppressed VEGF expression through decreasing HIF-1alpha expression. Moreover, HDWHCs inhibited cyclooxygenase-2 (COX-2) expression, and overexpression of HIF-1alpha restored HDWHCs’ inhibitory effect on COX-2 at transcriptional level. These findings may provide better understanding of HDWHCs’ anti-cancer mechanism in cancer treatment.

In dividing embryos, a localized elevation in intracellular Ca²⁺ ([Ca²⁺]_i) at the cleavage furrow has been shown to be essential for cytokinesis. However, the underlying mechanisms for generating and maintaining these [Ca²⁺]_i gradients throughout cytokinesis are not fully understood. In the present study, we analyzed the role of inositol 1,4,5-trisphosphate receptors (IP₃Rs) and endoplasmic reticulum (ER) distribution in determining the intracellular Ca²⁺ gradients in early zebrafish blastomeres. Application of the injected Ca²⁺ indicator, Indo-1, showed that during the first cell division a standing Ca²⁺ gradient was formed ~35min after fertilization, with the [Ca²⁺]_i spatially decaying from 500–600 nmol/L at the cleavage furrow to 100–200 nmol/L around the nucleus. While the IP₃R immunohistochemical fluorescence was relatively concentrated in the peri-furrow region, ER labeling was relatively enriched in both peri-furrow and peri-nuclear regions. Numeric simulation suggested that a divergence in the spatial distribution of IP₃R and the locations of Ca²⁺ uptake within the ER was essential for the formation of a standing Ca²⁺ gradient, and the Ca²⁺ gradient could only be well-established under an optimal stoichiometry of Ca²⁺ uptake and release. Indeed, while inhibition of IP₃R Ca²⁺ release blocked the generation of the Ca²⁺ gradient at a lower [Ca²⁺]_i level, both Ca²⁺ release stimulation by inositol 1,4,5-trisphosphate (IP₃) injection and ER Ca²⁺ pump inhibition by cyclopiazonic acid also eliminated the Ca²⁺ gradients at higher [Ca²⁺]_i levels. Our results suggest a dynamic relationship between ER-mediated Ca²⁺ release and uptake that underlies the maintenance of the peri-furrow Ca²⁺ gradient and is essential for cytokinesis of zebrafish embryos.