Population coding of predator imminence in the hypothalamus.

Hypothalamic VMHdm SF1 neurons are activated by predator cues and are necessary and sufficient for instinctive defensive responses. However, such data do not distinguish which features of a predator encounter are encoded by VMHdm SF1 neural activity. To address this issue, we imaged VMHdm SF1 neurons at single-cell resolution in freely behaving mice exposed to a natural predator in varying contexts. Our results reveal that VMHdm SF1 neurons do not represent different defensive behaviors, but rather encode predator identity and multiple predator-evoked internal states, including threat-evoked fear/anxiety; neophobia or arousal; predator imminence; and safety. Notably, threat and safety are encoded bi-directionally by anti-correlated subpopulations. Finally, individual differences in predator defensiveness are correlated with differences in VMHdm SF1 response dynamics. Thus, different threat-related internal state variables are encoded by distinct neuronal subpopulations within a genetically defined, anatomically restricted hypothalamic cell class. Highlights: Distinct subsets of VMHdm SF1 neurons encode multiple predator-evoked internal states. Anti-correlated subsets encode safety vs. threat in a bi-directional mannerA population code for predator imminence is identified using a novel assay VMHdm SF1 dynamics correlate with individual variation in predator defensiveness.

Comprehensive Dual- and Triple-Feature Intersectional Single-Vector Delivery of Diverse Functional Payloads to Cells of Behaving Mammals.

The resolution and dimensionality with which biologists can characterize cell types have expanded dramatically in recent years, and intersectional consideration of such features (e.g., multiple gene expression and anatomical parameters) is increasingly understood to be essential. At the same time, genetically targeted technology for writing in and reading out activity patterns for cells in living organisms has enabled causal investigation in physiology and behavior; however, cell-type-specific delivery of these tools (including microbial opsins for optogenetics and genetically encoded Ca2+ indicators) has thus far fallen short of versatile targeting to cells jointly defined by many individually selected features. Here, we develop a comprehensive intersectional targeting toolbox including 39 novel vectors for joint-feature-targeted delivery of 13 molecular payloads (including opsins, indicators, and fluorophores), systematic approaches for development and optimization of new intersectional tools, hardware for in vivo monitoring of expression dynamics, and the first versatile single-virus tools (Triplesect) that enable targeting of triply defined cell types.

The discovery of potent nonstructural protein 5A (NS5A) inhibitors with a unique resistance profile-Part†2.

In ongoing studies towards novel hepatitis C virus (HCV) therapeutics, inhibitors of nonstructural protein 5A (NS5A) were evaluated. Specifically, starting from previously reported lead compounds, peripheral substitution patterns of a series of biaryl-linked pyrrolidine NS5A replication complex inhibitors were probed and structure-activity relationships were elucidated. Using molecular modelling and a supercritical fluid chromatographic (SFC) technique, intramolecular H-bonding and peripheral functional group topology were evaluated as key determinants of activity and membrane permeability. The novel compounds exhibited retained potency as compared with the lead compounds, and also showed promising results against a panel of resistance viruses. Together, the results of the study take us a step closer towards understanding the potency of daclatasvir, a clinical candidate upon which the compounds were based, and to designing improved analogues as second-generation antiviral agents targeting NS5A.