Early Changes in Transcriptomic Profiles in Synaptodendrosomes Reveal Aberrant Synaptic Functions in Alzheimer's Disease.

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative disorders characterized by the progressive decline of cognitive functions, and is closely associated with the dysfunction of synapses, which comprise the basic structure that mediates the communication between neurons. Although the protein architecture and machinery for protein translation at synapses are extensively studied, the impact that local changes in the mRNA reservoir have on AD progression is largely unknown. Here, we investigated the changes in transcriptomic profiles in the synaptodendrosomes purified from the cortices of AD mice at ages 3 and 6 months, a stage when early signatures of synaptic dysfunction are revealed. The transcriptomic profiles of synaptodendrosomes showed a greater number of localized differentially expressed genes (DEGs) in 6-month-old AD mice compared with mice 3 months of age. Gene Ontology (GO) analysis showed that these DEGs are majorly enriched in mitochondrial biogenesis and metabolic activity. More specifically, we further identified three representative DEGs in mitochondrial and metabolic pathways-Prnp, Cst3, and Cox6c-that regulate the dendritic spine density and morphology in neurons. Taken together, this study provides insights into the transcriptomic changes in synaptodendrosomes during AD progression, which may facilitate the development of intervention strategies targeting local translation to ameliorate the pathological progression of AD.

EphB2 activates CREB-dependent expression of Annexin A1 to regulate dendritic spine morphogenesis.

Dendritic spines are the postsynaptic structure to mediate signal transduction in neural circuitry, whose function and plasticity are regulated by organization of their molecular architecture and by the expression of target genes and proteins. EphB2, a member of the Eph receptor tyrosine kinase family, potentiates dendritic spine maturation through cytoskeleton reorganization and protein trafficking. However, the transcriptional mechanisms underlying prolonged activation of EphB2 signaling during dendritic spine morphogenesis are unknown. Herein, we performed transcriptional profiling by stimulating EphB2 signaling and identified differentially expressed genes implicated in pivotal roles at synapses. Notably, we characterized an F-actin binding protein, Annexin A1, whose expression was induced by EphB2 signaling; the promotor activity of its coding gene Anxa1 is regulated by the activity of CREB (cAMP-response element-binding protein). Knockdown of Annexin A1 led to a significant reduction of mature dendritic spines without an obvious deficit in the complexity of dendrites. Altogether, our findings suggest that EphB2-induced, CREB-dependent Annexin A1 expression plays a key role in regulating dendritic spine morphology.

Coronin 2B regulates dendrite outgrowth by modulating actin dynamics.

Cytoskeletal remodeling is indispensable for the development and maintenance of neuronal structures and functions. However, the molecular machinery that controls the balance between actin polymerization and depolymerization during these processes is incompletely understood. Here, we report that coronin 2B, a conserved actin-binding protein, is concentrated at the tips of developing dendrites and that knockdown of coronin 2B inhibits the growth of dendrites. Importantly, coronin 2B interacts with actin and reduces the F-actin/G-actin ratio. Furthermore, the coiled-coil domain of coronin 2B is required for its oligomerization, thus confining coronin 2B to neurite tips. Our findings collectively suggest that coronin 2B is important for promoting dendrite outgrowth by limiting the speed of actin polymerization at growth cones.

Construction of a DNA vaccine and its protective effect on largemouth bass (Micropterus salmoides) challenged with largemouth bass virus (LMBV).

Largemouth bass virus (LMBV) is the causative agent of a disease causing high mortality rates in largemouth bass during summer. However, there is little information available about the development of vaccines for LMBV disease. Hence, a DNA vaccine, named pCDNA3.1(+)-MCP-Flag, was constructed by inserting the cloned LMBV major capsid protein (MCP) gene into the pCDNA3.1(+)-Flag plasmid. The expression of the recombinant plasmid was confirmed by Western blot (WB) and RT-PCR. The WB result revealed that the MCP protein produced a band of approximately 53 kDa, consistent with the expected result. The RT-PCR results also confirmed that MCP was transcribed in the EPC cells transfected with the recombinant plasmid. The largemouth bass in the DNA vaccine group were immunized with the pCDNA3.1(+)-MCP-Flag plasmid by pectoral fin base injection, and the relative percent survival (RPS) of fish challenged with LMBV was 63%. The relative immunological analyses were as follows. Compared with the PBS and pCDNA3.1(+) groups, the DNA vaccine group showed significantly upregulated expression of IL-1ß, IL-8, TNF-α and Mx in the spleen, head kidney and liver. All largemouth bass immunized with the DNA vaccine produced a high titre of LMBV-specific neutralizing antibody during the immunization period. The titre was 1:375 ± 40 and peaked at 14 days post-vaccination. The expression of the recombinant plasmid was analysed in the tissues of the DNA vaccine group by RT-PCR. The recombinant plasmid was expressed in the spleen, head kidney and liver, and MCP protein was successfully expressed after vaccination. In conclusion, the recombinant plasmid expressing LMBV MCP induced significant immune responses in largemouth bass, and might represent a potential LMBV vaccine candidate for largemouth bass.