Biology subjects

Faini, G.

Publications and source records attributed to Faini, G..

5 recordsLinked to original sources

bioRxiv2025

Lrrns define a visual circuit underlying brightness and contrast perception

Brightness and contrast are fundamental features of vision, crucial for object detection, environmental navigation, and feeding. Here, we identify a brightness-and contrast-processing circuit in the zebrafish visual system and uncover the role of Leucine-rich repeat neuronal (Lrrn) cell adhesion molecules (CAMs) in regulating its assembly. Deep-projecting retinal ganglion cells (RGCs) serve as the first synaptic relay to the brain requiring Lrrn2 and Lrrn3a for precise axonal targeting and connectivity within the optic tectum. Genetic targeting of these CAMs leads to circuit disorganization and impairments in contrast sensitivity, leading to deficits in visually guided behaviors. Additionally, ultrastructural circuit reconstruction and functional imaging analysis revealed their critical role in luminance processing. These studies define a fundamental visual processing pathway and establish Lrrn CAMs as essential molecular drivers of its assembly.

neuroscience↗

bioRxiv2024

Two-photon voltage imaging with rhodopsin-based sensors

The recent advances in sophisticated optical techniques, coupled with two-photon sensitive genetic voltage indicators (GEVIs), have enabled in-depth voltage imaging in vivo at single spike and single-cell resolution. To date, these results have been only achieved using ASAP-type sensors, as the complex photocycle of rhodopsin-based voltage indicators posed challenges for their two-photon use, restricting their application to one-photon approaches. In this work, we demonstrate that rhodopsin-based GEVIs (FRET-opsin) can be used under two-photon illumination when their peculiar light intensity dependence of kinetics and sensitivity are considered. We rationally engineer a fully genetically-encoded, rhodopsin-based voltage indicator with the brightest known fluorophore AaFP1, Jarvis, and demonstrate its utility under both one- and two-photon illumination. We also showed two-photon usability of the similar FRET-opsin sensor pAce. Our comparison of 2P scanless with fast 2P scanning illumination revealed that the latter approach is less suitable for this class of indicators and, on the contrary, both sensors responded well when scanless approaches were used. Furthermore, utilising Jarvis, we demonstrated high-fidelity, high-SNR action potential detection at kilohertz-imaging rates both in mouse hippocampal slices and in zebrafish larvae. To the best of our knowledge, this study represents the first report of a fully genetically-encoded rhodopsin-based voltage indicator for high contrast action potential detection under two-photon illumination in vitro and in vivo.

neuroscience↗

bioRxiv2021

Ultrafast Light Targeting for High-Throughput Precise Control of Neuronal Networks

Understanding how specific sets of neurons fire and wire together during cognitive-relevant activity is one of the most pressing questions in neuroscience. Two-photon, single-cell resolution optogenetics based on holographic light-targeting approaches enables accurate spatio-temporal control of individual or multiple neurons. Yet, currently, the ability to drive asynchronous activity in distinct cells is critically limited to a few milliseconds and the achievable number of targets to several dozens. In order to expand the capability of single-cell optogenetics, we introduce an approach capable of ultra-fast sequential light targeting (FLiT), based on switching temporally focused beams between holograms at kHz rates. We demonstrate serial-parallel photostimulation strategies capable of multi-cell sub-millisecond temporal control and many-fold expansion of the number of activated cells. This approach will be important for experiments that require rapid and precise cell stimulation with defined spatio-temporal activity patterns and optical control of large neuronal ensembles.

neuroscience↗

bioRxiv2021

Evolutionary divergence of locomotion in two related vertebrate species

Locomotion exists in diverse forms in nature and is adapted to the environmental constraints of each species1. However, little is known about how closely related species with similar neuronal circuitry can evolve different navigational strategies to explore their environments. We established a powerful approach in comparative neuroethology to investigate evolution of neuronal circuits in vertebrates by comparing divergent swimming pattern of two closely related larval fish species, Danionella translucida (DT) and Danio rerio or zebrafish (ZF)2,3. During swimming, we demonstrate that DT utilizes lower half tail-beat frequency and amplitude to generate a slower and continuous swimming pattern when compared to the burst-and-glide swimming pattern in ZF. We found a high degree of conservation in the brain anatomy between the two species. However, we revealed that the activity of a higher motor region, referred here as the Mesencephalic Locomotion Maintenance Neurons (MLMN) correlates with the duration of swim events and differs strikingly between DT and ZF. Using holographic stimulation, we show that the activation of the MLMN is sufficient to increase the frequency and duration of swim events in ZF. Moreover, we propose two characteristics, availability of dissolved oxygen and timing of swim bladder inflation, which drive the observed differences in the swim pattern. Our findings uncover the neuronal circuit substrate underlying the evolutionary divergence of navigational strategies and how they are adapted to their respective environmental constraints.

neuroscience↗

bioRxiv2018

Perineuronal nets set the strength of thalamic recruitment of interneurons in the adult visual cortex

In the neocortex, the closure of critical periods (CPs) of plasticity is paralleled by the accumulation of perineuronal nets (PNNs) around parvalbumin (PV)-positive inhibitory interneurons. Accordingly, PNN degradation in adult mammals re-opens cortical plasticity. However, how PNNs tune cortical function and plasticity is unknown. We found that PNNs modulated the gain of visual responses in the adult mouse visual cortex in vivo. Removal of PNNs in adult V1 strongly increased thalamic neurotransmission selectively on layer 4 PV cells. This produced a differential gating of feed-forward inhibition on principal neurons and other PV cells, with no alterations of unitary inhibitory synaptic transmission and neuronal excitability. These effects depended on visual input, as they were strongly attenuated by monocular deprivation in PNN-depleted adult mice. Thus, PNNs control visual processing and plasticity by selectively setting the strength of thalamic recruitment of PV cells. We conclude that PNN accumulation during circuit maturation likely prevents excessive thalamic excitation of PV cells at the expense of cortical plasticity.

neuroscience↗