Imaging the activity of Ras superfamily GTPase proteins in small subcellular compartments in neurons

Characterization of circular RNA expression profiles in the age-related thymic involution of Magang goose

The thymus is a vital immune organ, but its function gradually declines with age. Circular RNAs (circRNAs) are related to the development of tissues and organs. In this study, bioinformatics analysis showed that 1329, 755, and 417 circRNAs were differentially expressed between the comparison groups of 6-month age (M6) and 20-embryo age (E20), 3-day post-hatch (P3), and 3-month age (M3) Magang geese, respectively. Among them, 167 circRNAs were differentially co-expressed between thymic development (E20, P3, and M3) and involution (M6). Functional analysis showed significant enrichment of phosphorylation and positive regulation of GTPase activity. Furthermore, pathway analysis has shown that glycerolipid metabolism and the Wnt signaling pathway are critical pathways in the thymic involution process. Finally, we constructed the competitive endogenous RNA (ceRNA) network. The results of this study suggest that circRNAs may be involved in the age-related thymic involution of the Magang goose.

Rac1 is a downstream effector of PKCα in structural synaptic plasticity

Structural and functional plasticity of dendritic spines is the basis of animal learning. The rapid remodeling of actin cytoskeleton is associated with spine enlargement and shrinkage, which are essential for structural plasticity. The calcium-dependent protein kinase C isoform, PKCα, has been suggested to be critical for this actin-dependent plasticity. However, mechanisms linking PKCα and structural plasticity of spines are unknown. Here, we examine the spatiotemporal activation of actin regulators, including small GTPases Rac1, Cdc42 and Ras, in the presence or absence of PKCα during single-spine structural plasticity. Removal of PKCα expression in the postsynapse attenuated Rac1 activation during structural plasticity without affecting Ras or Cdc42 activity. Moreover, disruption of a PDZ binding domain within PKCα led to impaired Rac1 activation and deficits in structural spine remodeling. These results demonstrate that PKCα positively regulates the activation of Rac1 during structural plasticity.

Circular RNA profiling in the oocyte and cumulus cells reveals that circARMC4 is essential for porcine oocyte maturation

Thousands of circular RNAs (circRNAs) have been recently discovered in cumulus cells and oocytes from several species. However, the expression and function of circRNA during porcine oocyte meiotic maturation have been never examined. Here, we separately identified 7,067 and 637 circRNAs in both cumulus cells and oocytes via deep sequencing and bioinformatic analysis. Further analysis revealed that a faction of circRNAs is differentially expressed (DE) in a developmental stage-specific manner. The host genes of DE circRNAs are markedly enriched to multiple signaling pathways associated with cumulus cell function and oocyte maturation. Additionally, most DE circRNAs harbor several miRNA targets, suggesting that these DE circRNAs potentially act as miRNA sponge. Importantly, we found that maternal circARMC4 knockdown by siRNA microinjection caused a severely impaired chromosome alignment, and significantly inhibited first polar body extrusion and early embryo development. Taken together, these results demonstrate for the first time that circRNAs are abundantly and dynamically expressed in a developmental stage-specific manner in cumulus cells and oocytes, and maternally expressed circARMC4 is essential for porcine oocyte meiotic maturation and early embryo development.

Noninvasive Imaging of Ras Activity by Monomolecular Biosensor Based on Split-Luciferase Complementary Assay

Deregulated activity of Ras GTPases has been observed in many types of human cancers, and contributes to the diverse aspects of carcinogenesis. Although the significance in tumorigenesis has been widely accepted and many therapeutic drugs are under development, little attention has been dedicated to the development of sensors for the Ras activity in vivo. Therefore, based on the split firefly luciferase complementation strategy, we developed a monomolecular bioluminescent biosensor to image endogenous Ras activity in living subject. In this biosensor, two inactive luciferase fragments are sandwiched by Raf-1, whose conformation changes upon GTP-Ras binding. Thus, the Ras activity can be surrogated by the intensity of the complementary luciferase. The bioluminescence analyses demonstrated that this novel biosensor behaved the robust and sensitive reporting efficiency in response to the dynamical changes of Ras activity, both in living colorectal cancer cells and in vivo. Compared to the traditional method, such as the pull-down assay, the bioluminescent sensor is simply, noninvasive, faster and more sensitive for the analysis of the endogenous Ras activity. This innovative work opens up the way for monitoring the preclinical curative effect and high-throughput screening of therapeutic drugs targeting Ras pathways.

Biophysics of Biochemical Signaling in Dendritic Spines: Implications in Synaptic Plasticity

Dendritic spines are mushroom-shaped postsynaptic compartments that host biochemical signal cascades important for synaptic plasticity and, ultimately, learning and memory. Signaling events in spines involve a signaling network composed of hundreds of signaling proteins interacting with each other extensively. Synaptic plasticity is typically induced by Ca²⁺ elevation in spines, which activates a variety of signaling pathways. This leads to changes in the actin cytoskeleton and membrane dynamics, which in turn causes structural and functional changes of the spine. Recent studies have demonstrated that the activities of these proteins have a variety of spatiotemporal patterns, which orchestrate signaling activity in different subcellular compartments at different timescales. The diffusion and the decay kinetics of signaling molecules play important roles in determining the degree of their spatial spreading, and thereby the degree of the spine specificity of the signaling pathway.