Early Transcriptional Changes in Rabies Virus-Infected Neurons and Their Impact on Neuronal Functions

Rabies is a zoonotic disease caused by rabies virus (RABV). As rabies advances, patients develop a variety of severe neurological symptoms that inevitably lead to coma and death. Unlike other neurotropic viruses that can induce symptoms of a similar range, RABV-infected post-mortem brains do not show significant signs of inflammation nor the structural damages on neurons. This suggests that the observed neurological symptoms possibly originate from dysfunctions of neurons. However, many aspects of neuronal dysfunctions in the context of RABV infection are only partially understood, and therefore require further investigation. In this study, we used differentiated neurons to characterize the RABV-induced transcriptomic changes at the early time-points of infection. We found that the genes modulated in response to the infection are particularly involved in cell cycle, gene expression, immune response, and neuronal function-associated processes. Comparing a wild-type RABV to a mutant virus harboring altered matrix proteins, we found that the RABV matrix protein plays an important role in the early down-regulation of host genes, of which a significant number is involved in neuronal functions. The kinetics of differentially expressed genes (DEGs) are also different between the wild type and mutant virus datasets. The number of modulated genes remained constant upon wild-type RABV infection up to 24 h post-infection, but dramatically increased in the mutant condition. This result suggests that the intact viral matrix protein is important to control the size of host gene modulation. We then examined the signaling pathways previously studied in relation to the innate immune responses against RABV, and found that these pathways contribute to the changes in neuronal function-associated processes. We further examined a set of regulated genes that could impact neuronal functions collectively, and demonstrated in calcium imaging that indeed the spontaneous activity of neurons is influenced by RABV infection. Overall, our findings suggest that neuronal function-associated genes are modulated by RABV early on, potentially through the viral matrix protein-interacting signaling molecules and their downstream pathways.

Deficiency of Intellectual Disability-Related Gene Brpf1 Attenuated Hippocampal Excitatory Synaptic Transmission and Impaired Spatial Learning and Memory Ability

Patients with monoallelic bromodomain and PHD finger-containing protein 1 (BRPF1) mutations showed intellectual disability. The hippocampus has essential roles in learning and memory. Our previous work indicated that Brpf1 was specifically and strongly expressed in the hippocampus from the perinatal period to adulthood. We hypothesized that mouse Brpf1 plays critical roles in the morphology and function of hippocampal neurons, and its deficiency leads to learning and memory deficits. To test this, we performed immunofluorescence, whole-cell patch clamp, and mRNA-Seq on shBrpf1-infected primary cultured hippocampal neurons to study the effect of Brpf1 knockdown on neuronal morphology, electrophysiological characteristics, and gene regulation. In addition, we performed stereotactic injection into adult mouse hippocampus to knock down Brpf1 in vivo and examined the learning and memory ability by Morris water maze. We found that mild knockdown of Brpf1 reduced mEPSC frequency of cultured hippocampal neurons, before any significant changes of dendritic morphology showed. We also found that Brpf1 mild knockdown in the hippocampus showed a decreasing trend on the spatial learning and memory ability of mice. Finally, mRNA-Seq analyses showed that genes related to learning, memory, and synaptic transmission (such as C1ql1, Gpr17, Htr1d, Glra1, Cxcl10, and Grin2a) were dysregulated upon Brpf1 knockdown. Our results showed that Brpf1 mild knockdown attenuated hippocampal excitatory synaptic transmission and reduced spatial learning and memory ability, which helps explain the symptoms of patients with BRPF1 mutations.

The Impact of Three Genospecies of Borrelia on Expression of Genes Associated with Chemokines and Their Receptors in Normal Human Dermal Fibroblasts in Vitro

An important role in pathomechanism of Lyme disease is played by the ability of spirochetes to spread within tissues, and to adhere (to platelets, erythrocytes and vascular epithelium). The principal factors regulating that process are chemokines, cytokines and adhesion particles. The aim of this study was to select genes related to the chemokines and their receptors, differentiating the type of infection in the system model, i.e. a culture of normal human diploid fibroblasts infected with three different spirochete genospecies: B. afzelii, B. garinii and B. burgdorferii sensu stricto, by comparing the infected fibroblast culture with that of the control fibroblast. The differences in the expression of genes selected on the basis of a scientific database Affymetrix were analysed by comparing transcriptomes from the four cultures of fibroblasts, using the oligonucleotide microarrays HG_U133A. In the result of infection of fibroblast cultivation with a specific Borrelia genospecies, a variable expression of the chemokines and their receptors, specific for one genospecies was observed. The fibroblast infected with B. afzelii expressed CCL4, CCL1, CCL2 and CCR10; with B. garinii - CXCL12, IL6, CCR3 and CXCR5; and with B. burgorferii sensu stricto - CCL5, CCR1, CCL3, CCL16, CXCR6, IL8, CXCR7 and CXCR3.