Biology subjects

Fisch, A. J.

Publications and source records attributed to Fisch, A. J..

3 recordsLinked to original sources

bioRxiv2025

A toolbox for navigating and analyzing the spatiotemporal properties of retinal waves

The precise development of the visual system is driven by retinal waves, which are bursts of spontaneous activity that propagate across retinal neurons in a wave-like fashion. In mice, retinal waves begin embryonically and continue until eye opening at the end of the second postnatal week. During this time, the mechanisms for generating and propagating retinal waves are changing, thus causing retinal waves to exhibit highly dynamic spatiotemporal properties from one day to the next. Critically, the spatiotemporal properties of retinal waves have been shown to instruct the development of the visual system, including eye-specific segregation, retinotopic mapping, direction selectivity, and potentially retinal vascularization. Currently, there is no method for the automatic detection and high-throughput quantitative analysis of the spatiotemporal properties of retinal waves. To overcome this barrier, we developed WaveMiner, an automated, high-throughput toolbox for detecting, segregating, and quantifying retinal waves from microelectrode-array (MEA) and calcium-imaging recordings. After first validating our toolbox, we use it to uncover novel dynamic spatiotemporal properties of retinal waves in the first two postnatal weeks. We also use this toolbox to analyze ultra long physiological recordings, revealing that waves exhibit both stable and dynamic spatiotemporal properties on an hourly basis. Finally, we demonstrate that this toolbox can detect waves in the presence of pharmacological agents that increase the baseline firing of neurons, enabling the discovery of novel factors that perturb the spatiotemporal properties of retinal waves and visual development. In summary, WaveMiner is a platform to standardize the detection and quantification of retinal waves across recording modalities and experimental conditions, enabling novel discoveries about their dynamic spatiotemporal properties and the factors that govern them.

neuroscience↗

bioRxiv2025

Pharmacological Tools to Modulate Ordered Membrane Domains and Order-Dependent Protein Function

Ordered membrane nanodomains colloquially known as "lipid rafts" have many proposed cellular functions. However, pharmacological tools to modulate protein affinity for rafts and to manipulate raft formation are currently lacking. We screened 24,000 small molecules for compounds that impact the raft affinity of a known raft-preferring protein, peripheral myelin protein 22 (PMP22), in giant plasma membrane vesicles (GPMVs). Hits were counter-screened against another raft protein, MAL, and also tested for their impact on raft stability. We identified three chemically distinct tools for manipulating lipid rafts. Two compounds were seen to both decrease PMP22 raft partitioning and to destabilize ordered domains (VU0607402 and VU0519975) while a third (primaquine diphosphate) increased PMP22 partitioning and stabilized ordered domains. While discovered in a PMP22-focused screen, all three were seen to modulate raft formation in a protein-independent manner by altering lipid-lipid interactions and membrane fluidity. Acute treatment of live cells with the raft destabilizing compound, VU0607402 was seen to modulate TRPM8 channel function, highlighting the utility of this compound in live-cell experiments for dissecting the role that membrane order and fluidity play in cell signaling. These compounds provide novel pharmacological tools for probing lipid raft properties and function in biophysical experiments and in living cells.

biophysics↗

bioRxiv2024

Small-molecule modulators of lipid raft stability and protein-raft partitioning

Development of an understanding of membrane nanodomains colloquially known as "lipid rafts" has been hindered by a lack of pharmacological tools to manipulate rafts and protein affinity for rafts. We screened 24,000 small molecules for modulators of the affinity of peripheral myelin protein 22 (PMP22) for rafts in giant plasma membrane vesicles (GPMVs). Hits were counter-screened against another raft protein, MAL, and tested for impact on raft, leading to two classes of compounds. Class I molecules altered the raft affinity of PMP22 and MAL and also reduced raft formation in a protein-dependent manner. Class II molecules modulated raft formation in a protein-independent manner. This suggests independent forces work collectively to stabilize lipid rafts. Both classes of compounds altered membrane fluidity in cells and modulated TRPM8 channel function. These compounds provide new tools for probing lipid raft function in cells and for furthering our understanding of raft biophysics. TeaserCompounds have been discovered that modulate the affinity of membrane proteins for lipid rafts as well as raft formation.

biophysics↗