Biology subjects

Dsouza, A.

Publications and source records attributed to Dsouza, A..

5 recordsLinked to original sources

bioRxiv2026

A synaptic wiring diagram underlying modality-specific ascending pathways of the superficial spinal dorsal horn

The spinal cord dorsal horn transforms tactile, thermal, pruritic, and nociceptive signals from peripheral somatosensory neurons into outputs to the brain, but how dorsal horn circuits organize diverse inputs into modality-selective ascending pathways is poorly understood. Using dSC1, a large-scale electron microscopy dataset of the mouse dorsal horn, we mapped the circuitry connecting primary sensory afferents to projection neurons of the anterolateral tract (ALT), a principal pathway conveying somatosensory information to the brain. We find that afferents encoding distinct modalities are routed onto connectivity-defined populations of ALT projection neurons. Nociceptors and cold thermoreceptors directly innervate distinct lamina I ALT projection neuron populations specialized for conveying noxious and cooling signals, respectively, whereas tactile and pruritic signals instead pass through a recurrent, multilayered network involving interneurons called vertical cells before reaching a separate ALT projection population. This distinction, direct versus polysynaptic wiring, underlies marked differences in sensory convergence and establishes segregated ascending channels for conveying signals encoding the principal somatosensory modalities. Together, our findings define an architectural logic by which the dorsal horn integrates and routes tactile, thermal, pruritic, and nociceptive information into distinct ALT output pathways to the brain.

neuroscience↗

bioRxiv2026

Embedded transport accelerates interaction-limited biosensing

Phenotypic biosensors that measure bacterial viability and antimicrobial susceptibility are essential for rapid infectious disease diagnostics, yet their speed is fundamentally limited by the rate at which bacteria encounter reporter molecules, a transport bottleneck that has been typically addressed by complex microfluidic solutions. Here we show that this bottleneck can be overcome by engineering transport directly into the sensing material. A multifunctional ionic hydrogel matrix, co-encapsulating bacterial growth medium and the redox reporter resazurin, exploits swelling-driven convective transport to dramatically accelerate bacteria-reporter interactions without any change to assay chemistry. By systematically tailoring the hydrogel crosslinking density and optimizing the encapsulated nutrient-osmotic microenvironment, we maximize metabolic signal generation to achieve a 12-to-48-fold reduction in detection time relative to solution-phase and conventional hydrogel assays. Deployed in a standard 96-well format for urinary tract infection (UTI) diagnosis of 48 clinical samples, the platform rapidly detects infection in 15 minutes to 2 hours, achieving 95% sensitivity and 100% specificity for bacterial detection, and 100% sensitivity and 98% specificity for antimicrobial susceptibility profiling, compared to time-consuming gold-standard urine culture-based methods. Results are readable both quantitatively on a plate reader and visually as a colorimetric assay, enabling point-of-care deployment without additional instrumentation. Thus, embedding transport enhancement within the sensing matrix, represents a general and scalable design principle for accelerating interaction-limited biosensing, which has excellent scope for rapid diagnostic development.

bioengineering↗

bioRxiv2025

Dynamic Bacterial Growth Modulation in Structurally Distinct and Functionally Tuneable Agarose Hydrogels

Bacterial adaptability to diverse environments drives infection, persistence, and antibiotic resistance. Although hydrogels are increasingly used to model such conditions, the factors governing hydrogel-dependent bacterial growth is complex. Here, we focus on agarose hydrogels and investigate how their material properties influence bacterial proliferation. Using two agarose types - hydroxyethyl substituted and unsubstituted - at varying concentrations, we tested four bacterial species (E. coli, P. fluorescens, S. aureus, B. subtilis) across five nutrient media yielding 120 conditions. Growth consistently decreased with increasing hydrogel stiffness and water loss in unsubstituted and substituted agarose hydrogels, regardless of species. Media effects were largely due to their impact on hydrogel properties rather than nutrient content. Furthermore, electrostatic repulsion between Gram positive bacteria and anionic unsubstituted agarose suppressed growth in high concentration gels. These findings demonstrate that bacterial growth in agarose systems is primarily shaped by gel mechanics and surface interactions, informing the design of infection models and antibacterial materials.

microbiology↗

bioRxiv2021

A large-volume sputum dry storage and transportation device for molecular and culture-based diagnosis of tuberculosis

Technologies for preservation of specimens in the absence of cold chains are essential for optimum utilization of existing laboratory services in the developing world. We present a prototype called specimen transportation tube (SPECTRA-tube) for the collection, exposure-free drying, ambient transportation, and liquid state recovery of large-volume (>1 mL) specimens. Specimens introduced into SPECTRA-tube are dried in glass fiber membranes, which are critical for efficient liquid-state sample recovery by rehydration and centrifugation. Mycobacterium smegmatis (Msm)-spiked mock sputum dried in native Standard 17 glass fiber was stable for molecular testing after 10-day storage at 45{degrees}C, and for culture testing after 10- and 5-day storage at 37{degrees}C and 45{degrees}C, respectively. Compatibility with human sputum storage was demonstrated by dry storing Mycobacterium bovis-spiked pooled human sputum in SPECTRA-tube for 5 days at room temperature followed by successful qPCR detection. By significantly increasing the volume of samples that can be transported in the dry state and enabling recovery of the entire sample in liquid state, SPECTRA-tube presents a potential universal solution for the preservation and transportation of liquid specimens.

bioengineering↗

bioRxiv2020

Wnt-inducible Lrp6-APEX2 Interacting Proteins identify ESCRT Machinery and Trk-Fused Gene as Components of the Wnt Signaling Pathway

The canonical Wnt signaling pathway serves as a hub connecting diverse cellular physiological processes, such as {beta}-catenin signaling, differentiation, growth, protein stability, macropinocytosis, and nutrient acquisition in lysosomes. We have proposed that sequestration of {beta}-catenin destruction complex components in multivesicular bodies (MVBs) is required for sustained canonical Wnt signaling. In this study, we investigated the events that follow activation of the canonical Wnt receptor Lrp6 using an APEX2-mediated proximity labeling approach. The Wnt co-receptor Lrp6 was fused to APEX2 and used to biotinylate targets that are recruited near the receptor during Wnt signaling at different time periods. Lrp6 proximity targets were identified by mass spectrometry, and revealed that many components of the ESCRT (Endocytic Sorting Components Required for Transport) machinery interacted with Lrp6 within 5 minutes of Wnt3a treatment. This supports the proposal of a central role of multivesicular endosomes in canonical Wnt signaling. Interestingly, proteomic analyses identified the Trk-fused gene (TFG), previously known to regulate the cell secretory pathway and to be rearranged in thyroid and lung cancers, as being strongly enriched in the proximity of Lrp6. We provide evidence that TFG specifically co-localized with MVBs after Wnt stimulation. TFG depletion with siRNA, or knock-out with CRISPR/Cas9, significantly reduced Wnt/{beta}-catenin signaling in cell culture. In vivo, studies in the Xenopus system showed that TFG is required for endogenous Wnt-dependent embryonic patterning. The results suggest that the multivesicular endosomal machinery and the novel player TFG have important roles in Wnt signaling. SignificanceWnt/{beta}-catenin signaling is a conserved pathway involved in cell differentiation and in the regulation of many other processes, including cell growth and proliferation, macropinocytosis, and cell metabolism. Endocytosis is required to regulate Wnt signaling, but the precise factors at play are still elusive. Here, we describe a biotin-dependent proximity labeling approach using ascorbate peroxidase-tagged Lrp6, a Wnt co-receptor. Proteomic analysis of biotinylated-enriched targets identified numerous multivesicular endosome proteins that were recruited to the receptor shortly after addition of Wnt protein. Additionally, we identified the protein TFG as one of the strongest interactors with Lrp6. TFG co-localized with Wnt-induced multivesicular endosomes. Xenopus embryo assays revealed that TFG is required in vivo for canonical Wnt signaling.

cell biology↗