Biology subjects

Chaudhari, K.

Publications and source records attributed to Chaudhari, K..

5 recordsLinked to original sources

bioRxiv2026

The mechanotransduction channel Piezo2 refines axonal projections to the accessory optic system and regulates the optokinetic reflex

The optokinetic reflex (OKR) is an evolutionarily conserved reflexive behavior that ensures image stabilization on the retina during global motion. It consists of smooth eye tracking movements in the direction of the moving stimulus interspersed with rapid resetting saccades. This reflex is driven by retinal ON direction-selective ganglion cells (oDSGCs), which comprise distinct subtypes tuned either to vertical or horizontal motion. oDSGCs convey directional signals to the brain via precise axonal projections to specific accessory optic system (AOS) nuclei. However, the mechanisms that establish and maintain the specificity of these circuits remain poorly understood. Here, we identify a critical role for the mechanosensitive ion channel Piezo2 in refining AOS circuitry to ensure appropriate eye movement responses. Single-cell transcriptomic profiling revealed selective enrichment of Piezo2 in horizontally-tuned oDSGCs. We show that both loss and hyperactivation of Piezo2 in retinal neurons leads to cross-coupling of horizontal and vertical OKR responses, producing aberrant diagonal eye tracking movements during horizontal optokinetic stimulation. Mechanistically, Piezo2 regulates the developmental refinement of oDSGC axonal projections within the AOS, and disruption of this process results in persistent ectopic innervation that enables aberrant crosstalk between horizontal and vertical motion pathways. These findings reveal a channel activity-dependent mechanism that ensures the functional segregation of directional motion circuits underlying gaze stabilization. HIGHLIGHTSO_LIPiezo2 is selectively expressed in forward-tuned ON and ON-OFF DSGCs that innervate the accessory optic system C_LIO_LIBoth loss and overactivation of Piezo2 induce cross-coupling of horizontal and vertical optokinetic reflexes C_LIO_LIPiezo2 function in ON-OFF DSGCs is dispensable for normal optokinetic reflex responses C_LIO_LIRetinal Piezo2 refines axonal targeting to the accessory optic system nuclei, ensuring proper optokinetic reflex function C_LI

neuroscience↗

bioRxiv2026

Refactored genetic parts for modular assembly of the E. coli MccV type I secretion system used to screen class II microcin candidates from plant-associated bacteria

BackgroundMicrocins are small antibacterial proteins secreted by gram-negative bacteria. The activities of new microcins discovered using bioinformatic searches need to be validated and characterized to understand how they mediate competition in microbiomes and to evaluate their potential as new therapeutics for combating antibiotic resistance. Engineered plasmids containing the type I secretion system associated with Escherichia coli Microcin V (MccV) can secrete heterologous proteins, including other class II microcins, and this system functions in other bacterial hosts. However, existing microcin secretion constructs are not designed for easily swapping components -- such as origins of replication, resistance genes, promoters, and signal peptides -- that may need to be changed for compatibility with other chassis. ResultsWe refactored the E. coli MccV type I secretion system into genetic parts compatible with a modular Golden Gate assembly scheme and used these parts to construct two-plasmid microcin secretion systems. In our design, one plasmid encodes the type I secretion system proteins, and the other encodes a signal peptide fused to the cargo protein that will be secreted. We tested two versions of a system with inducible promoters separately controlling expression of the components on each plasmid. One used plasmids that replicate in E. coli and its close relatives. The other used broad-host-range plasmids. When induced to secrete MccV, both versions produced similar zones of inhibition against a susceptible strain of E. coli. Next, we identified putative class II microcins in genomes of bacteria from plant-associated genera (Pantoea, Erwinia, and Xanthomonas) using an existing bioinformatics pipeline. We screened 23 of these putative microcins for E. coli self-inhibition. Seven exhibited some inhibition, mostly later in growth curves, but none had effects that were comparable in strength to MccV. ConclusionsThe genetic parts we created can be assembled in various combinations into tailored systems for secreting small proteins from diverse bacterial chassis. These systems can be used to further characterize the targets of novel microcins and to secrete these or other small proteins for various applications. For example, beneficial bacteria used in crop protection could be engineered to secrete microcins that kill or inhibit plant pathogens to increase their efficacy.

synthetic biology↗

bioRxiv2025

Temporally-segregated dual functions for Gfi1 in the development of retinal direction-selectivity

There is great diversity in retinal ganglion cells subtypes in the mouse retina, but little is known about the molecular factors required to generate this subtype diversity. Here, we identify the transcription factor Gfi1 as a conserved driver of differentiation specifically in two downward-tuned direction selective ganglion cells (DSGCs). Further, we describe a post-differentiation role for Gfi1 in regulating dendritic development of Down ON-type DSGCs crucial for their ability to detect downward motion. These results define novel temporally-segregated dual functions for Gfi1 in the development of retinal direction-selective circuits, and they provide a framework for understanding fundamental mechanisms underlying direction-selectivity in the retina.

neuroscience↗

bioRxiv2022

A human DCC variant causing mirror movement disorder reveals an essential role for the Wave regulatory complex in Netrin/DCC signaling

The axon guidance cue, Netrin-1, signals through its receptor DCC to attract commissural axons to the midline. Pathogenic variants in DCC frequently lead to congenital mirror movements (CMM), but how these variants impact DCC function is largely unknown. Screening of DCC in individuals with CMM recently revealed a novel variant located in a conserved motif in the cytoplasmic tail of DCC that is predicted to bind to a central actin nucleation promoting factor, the WAVE regulatory complex (WRC). Here, we use biochemical and axon guidance assays to show that this CMM-associated DCC variant is pathogenic by disrupting the interaction between DCC and the WRC. This DCC-WRC interaction is evolutionarily conserved and is required for Netrin-1 mediated commissural axon outgrowth and guidance. Together, we identify the WRC as a pivotal component of Netrin-1/DCC signaling and further provide a molecular mechanism explaining how genetic variants in DCC may lead to CMM.

neuroscience↗

bioRxiv2020

Robo recruitment of the Wave Regulatory Complex plays an essential and conserved role in midline repulsion

The Roundabout (Robo) guidance receptor family induces axon repulsion in response to its ligand Slit by inducing local cytoskeletal changes; however, the link to the cytoskeleton and the nature of these cytoskeletal changes are unclear. Here we show that the heteropentameric Scar/Wave Regulatory Complex (WRC) which drives Arp2/3-induced branched actin polymerization, is a direct effector of Robo signaling. Biochemical evidence shows that Slit triggers WRC recruitment to the Robo receptors WIRS motif. In Drosophila embryos, mutants of the WRC enhance Robol-dependent midline crossing defects. Additionally, mutating Robo1s WIRS motif significantly reduces receptor activity in rescue assays in vivo, and CRISPR-Cas9 mutagenesis shows that the WIRS motif is essential for endogenous Robo1 function. Finally, axon guidance assays in mouse dorsal spinal commissural axons demonstrate that the WIRS motif is also required for Robo1 repulsion in mammals. Together, our data support an essential conserved role for the WRC in commissural axon repulsion.

developmental biology↗