Differing Transcriptomic Responses in High Titer versus Low Titer Mosquitoes after Oral Infection with Sindbis Virus.

Oral infection of mosquitoes by arboviruses often results in a large degree of variation in the amount of infectious virus between individual mosquitoes, even when the mosquitoes are from inbred laboratory strains. This variability in arbovirus load has been shown to affect virus transmissibility. Previously, our group described population genetic and specific infectivity differences between the virus populations found in high and low titer mosquitoes that had been orally infected with Sindbis virus (SINV).

Comparative basolateral amygdala connectomics reveals dissociable single-neuron projection patterns to frontal cortex in macaques and mice.

Basolateral amygdala (BLA) is a key hub for affect in the brain, and dysfunction within this area contributes to a host of psychiatric disorders. BLA is extensively and reciprocally interconnected with frontal cortex, and some aspects of its function are evolutionarily conserved across rodents, anthropoid primates, and humans. Neuron density in BLA is substantially lower in primates compared to murine rodents, and frontal cortex (FC) is dramatically expanded in primates, particularly the more anterior granular and dysgranular areas.

The mouse dorsal peduncular cortex encodes fear memory.

The rodent medial prefrontal cortex (mPFC) is functionally organized across the dorsoventral axis, where dorsal and ventral subregions promote and suppress fear, respectively. As the ventral-most subregion, the dorsal peduncular cortex (DP) is hypothesized to function in fear suppression. However, this role has not been explicitly tested.

Extreme infectious titer variability in individual Aedes aegypti mosquitoes infected with Sindbis virus is associated with both differences in virus population structure and dramatic disparities in specific infectivity.

Variability in how individuals respond to pathogens is a hallmark of infectious disease, yet the basis for individual variation in host response is often poorly understood. The titer of infectious virus among individual mosquitoes infected with arboviruses is frequently observed to vary by several orders of magnitude in a single experiment, even when the mosquitoes are highly inbred. To better understand the basis for this titer variation, we sequenced populations of Sindbis virus (SINV) obtained from individual infected Aedes aegypti mosquitoes that, despite being from a highly inbred laboratory colony, differed in their titers of infectious virus by approximately 10,000-fold.

Comparative basolateral amygdala connectomics reveals dissociable single-neuron projection patterns to frontal cortex in macaques and mice.

The basolateral amygdala (BLA) projects to the frontal cortex (FC) in both rodents and primates, but the comparative organization of single-neuron BLA-FC projections is unknown. Using a barcoded connectomic approach, we found that BLA neurons are more likely to project to multiple distinct parts of FC in mice than in macaques. Further, while single BLA neuron projections to nucleus accumbens are similarly organized in mice and macaques, BLA-FC connections differ.

Single basolateral amygdala neurons in macaques exhibit distinct connectional motifs with frontal cortex.

Basolateral amygdala (BLA) projects widely across the macaque frontal cortex, and amygdalo-frontal projections are critical for appropriate emotional responding and decision making. While it is appreciated that single BLA neurons branch and project to multiple areas in frontal cortex, the organization and frequency of this branching has yet to be fully characterized. Here, we determined the projection patterns of more than 3,000 macaque BLA neurons.

The mouse dorsal peduncular cortex encodes fear memory.

The rodent medial prefrontal cortex (mPFC) is a locus for both the promotion and suppression (e.g. extinction) of fear and is composed of four anatomically distinct subregions, including anterior cingulate 1 (Cg1), prelimbic (PL), infralimbic (IL), and the dorsal peduncular (DP) cortex.

Factors Affecting Arbovirus Midgut Escape in Mosquitoes.

Arboviral diseases spread by mosquitoes cause significant morbidity and mortality throughout much of the world. The treatment and prevention of these diseases through medication and vaccination is often limited, which makes controlling arboviruses at the level of the vector ideal. One way to prevent the spread of an arbovirus would be to stop its vector from developing a disseminated infection, which is required for the virus to make its way to the saliva of the mosquito to be potentially transmitted to a new host.

High-throughput sequencing of macaque basolateral amygdala projections reveals dissociable connectional motifs with frontal cortex.

The basolateral amygdala (BLA) projects widely across the macaque frontal cortex, and amygdalo-frontal projections are critical for optimal emotional responding and decision-making. Yet, little is known about the single-neuron architecture of these projections: namely, whether single BLA neurons project to multiple parts of the frontal cortex. Here, we use MAPseq to determine the projection patterns of over 3000 macaque BLA neurons.

Ensemble-specific deficit in neuronal intrinsic excitability in aged mice.

With the prevalence of age-related cognitive deficits on the rise, it is essential to identify cellular and circuit alterations that contribute to age-related memory impairment. Increased intrinsic neuronal excitability after learning is important for memory consolidation, and changes to this process could underlie memory impairment in old age. Some studies find age-related deficits in hippocampal neuronal excitability that correlate with memory impairment but others do not, possibly due to selective changes only in activated neural ensembles.

Expressing the Pro-Apoptotic Reaper Protein via Insertion into the Structural Open Reading Frame of Sindbis Virus Reduces the Ability to Infect Mosquitoes.

Arboviruses continue to threaten a significant portion of the human population, and a better understanding is needed of the determinants of successful arbovirus infection of arthropod vectors. Avoiding apoptosis has been shown to be one such determinant. Previous work showed that a Sindbis virus (SINV) construct called MRE/rpr that expresses the pro-apoptotic protein Reaper via a duplicated subgenomic promoter had a reduced ability to orally infect mosquitoes at 3 days post-blood meal (PBM), but this difference diminished over time as virus variants containing deletions in the inserted gene rapidly predominated.

Control of fear by discrete prefrontal GABAergic populations encoding valence-specific information.

Neurons activated by learning have been ascribed the unique potential to encode memory, but the functional contribution of discrete cell types remains poorly understood. In particular, it is unclear whether learning engages specific GABAergic interneurons and, if so, whether they differ functionally from interneurons recruited by other experiences. Here, we show that fear conditioning activates a heterogeneous neuronal population in the medial prefrontal cortex (mPFC) that is largely comprised of somatostatin-expressing interneurons (SST-INs).

Investigation of Biological Factors Contributing to Individual Variation in Viral Titer after Oral Infection of Mosquitoes by Sindbis Virus.

The mechanisms involved in determining arbovirus vector competence, or the ability of an arbovirus to infect and be transmitted by an arthropod vector, are still incompletely understood. It is well known that vector competence for a particular arbovirus can vary widely among different populations of a mosquito species, which is generally attributed to genetic differences between populations. What is less understood is the considerable variability (up to several logs) that is routinely observed in the virus titer between individual mosquitoes in a single experiment, even in mosquitoes from highly inbred lines.

GABAergic basal forebrain projections to the periaqueductal gray promote food consumption, reward and predation.

Behaviors central to the procurement and consumption of food are among those most fundamental to survival, but their inappropriate expression can lead to overeating and obesity. Nevertheless, we have a poor understanding of circuits that promote feeding independent of physiological demand. Here we demonstrate that activation of basal forebrain (BF) GABAergic neurons results in consumption of food as well as non-food items in well-fed mice, and performance of fictive eating in the absence of ingestible materials.

GABAergic microcircuitry of fear memory encoding.

The paradigm of fear conditioning is largely responsible for our current understanding of how memories are encoded at the cellular level. Its most fundamental underlying mechanism is considered to be plasticity of synaptic connections between excitatory projection neurons (PNs). However, recent studies suggest that while PNs execute critical memory functions, their activity at key stages of learning and recall is extensively orchestrated by a diverse array of GABAergic interneurons (INs).

Infection of Aedes aegypti Mosquitoes with Midgut-Attenuated Sindbis Virus Reduces, but Does Not Eliminate, Disseminated Infection.

Arboviruses are transmitted by specific vectors, and the reasons for this specificity are not fully understood. One contributing factor is the existence of tissue barriers within the vector such as the midgut escape barrier. We used microRNA (miRNA) targeting of Sindbis virus (SINV) to study how replication in midgut cells contributes to overcoming this barrier in the mosquito Aedes aegypti.

Effects of Manipulating Fibroblast Growth Factor Expression on Sindbis Virus Replication In Vitro and in Mosquitoes.

Fibroblast growth factors (FGFs) are conserved among vertebrate and invertebrate animals and function in cell proliferation, cell differentiation, tissue repair, and embryonic development. A viral fibroblast growth factor (vFGF) homolog encoded by baculoviruses, a group of insect viruses, is involved in escape of baculoviruses from the insect midgut by stimulating basal lamina remodeling. This led us to investigate whether cellular FGF is involved in the escape of an arbovirus from mosquito midgut.

Adolescent frontal top-down neurons receive heightened local drive to establish adult attentional behavior in mice.

Frontal top-down cortical neurons projecting to sensory cortical regions are well-positioned to integrate long-range inputs with local circuitry in frontal cortex to implement top-down attentional control of sensory regions. How adolescence contributes to the maturation of top-down neurons and associated local/long-range input balance, and the establishment of attentional control is poorly understood. Here we combine projection-specific electrophysiological and rabies-mediated input mapping in mice to uncover adolescence as a developmental stage when frontal top-down neurons projecting from the anterior cingulate to visual cortex are highly functionally integrated into local excitatory circuitry and have heightened activity compared to adulthood.

The role of intrinsic excitability in the evolution of memory: Significance in memory allocation, consolidation, and updating.

Memory is a dynamic process that is continuously regulated by both synaptic and intrinsic neural mechanisms. While numerous studies have shown that synaptic plasticity is important in various types and phases of learning and memory, neuronal intrinsic excitability has received relatively less attention, especially regarding the dynamic nature of memory. In this review, we present evidence demonstrating the importance of intrinsic excitability in memory allocation, consolidation, and updating.

Orexin signaling in GABAergic lateral habenula neurons modulates aggressive behavior in male mice.

Heightened aggression is characteristic of multiple neuropsychiatric disorders and can have various negative effects on patients, their families and the public. Recent studies in humans and animals have implicated brain reward circuits in aggression and suggest that, in subsets of aggressive individuals, domination of subordinate social targets is reinforcing. In this study, we showed that, in male mice, orexin neurons in the lateral hypothalamus activated a small population of glutamic acid decarboxylase 2 (GAD2)-expressing neurons in the lateral habenula (LHb) via orexin receptor 2 (OxR2) and that activation of these GAD2 neurons promoted male-male aggression and conditioned place preference for aggression-paired contexts.

Prefrontal parvalbumin interneurons require juvenile social experience to establish adult social behavior.

Social isolation during the juvenile critical window is detrimental to proper functioning of the prefrontal cortex (PFC) and establishment of appropriate adult social behaviors. However, the specific circuits that undergo social experience-dependent maturation to regulate social behavior are poorly understood. We identify a specific activation pattern of parvalbumin-positive interneurons (PVIs) in dorsal-medial PFC (dmPFC) prior to an active bout, or a bout initiated by the focal mouse, but not during a passive bout when mice are explored by a stimulus mouse.

Prefrontal somatostatin interneurons encode fear memory.

Theories stipulate that memories are encoded within networks of cortical projection neurons. Conversely, GABAergic interneurons are thought to function primarily to inhibit projection neurons and thereby impose network gain control, an important but purely modulatory role. Here we show in male mice that associative fear learning potentiates synaptic transmission and cue-specific activity of medial prefrontal cortex somatostatin (SST) interneurons and that activation of these cells controls both memory encoding and expression.

Inhibition of dicer activity in lepidopteran and dipteran cells by baculovirus-mediated expression of Flock House virus B2.

Prior studies have suggested that insect DNA viruses are negatively affected by dicer-2-mediated RNA interference (RNAi). To examine this further, we utilized an in vitro assay to measure dicer activity in lepidopteran and dipteran cells, combined with baculoviruses expressing the RNAi suppressor B2 from Flock House virus or Aedes aegypti dicer-2 (Aedicer-2) using a constitutive heat shock promoter. Addition of cell lysates containing baculovirus-expressed B2 to lysates from dipteran (S2, Aag2) or lepidopteran (Sf9) cells inhibited endogenous dicer activity in a dose-dependent manner, while expression of Aedicer-2 restored siRNA production in Ae.