Biology subjects

Donaldson, K. J.

Publications and source records attributed to Donaldson, K. J..

3 recordsLinked to original sources

bioRxiv2024

High resolution imaging and interpretation of three-dimensional RPE sheet structure

The retinal pigment epithelium (RPE), a monolayer of pigmented cells, is critical for visual function through its interaction with the neural retina. In healthy eyes, RPE cells exhibit a uniform hexagonal arrangement, but under stress or disease, such as age-related macular degeneration (AMD), dysmorphic traits like cell enlargement and apparent multinucleation emerge. Multinucleation has been hypothesized to result from cellular fusion, a compensatory mechanism to maintain cell to cell contact, barrier function, and conserve resources in unhealthy tissue. However, traditional two-dimensional (2D) imaging using apical border markers alone may misrepresent multinucleation due to the lack of lateral markers. We present high-resolution confocal images enabling three-dimensional (3D) visualization of apical (ZO-1) and lateral (alpha-catenin) markers alongside nuclei. In two RPE damage models, we find that seemingly multinucleated cells are often single cells with displaced neighboring nuclei and lateral membranes. This emphasizes the need for 3D analyses to avoid misinterpreting multinucleation and underlying fusion mechanisms. Lastly, images from the NaIO3 oxidative damage model reveal variability in RPE damage, with elongated, dysmorphic cells showing increased ZsGreen reporter protein expression driven by EMT-linked CAG promoter activity, while more regular RPE cells displayed somewhat reduced green signal more typical of epithelial phenotypes.

molecular biology↗

bioRxiv2021

The evolution of cold nociception in drosophilid larvae and identification of a neural basis for cold acclimation

Cold temperatures can be fatal to insects, but many species have evolved the ability to cold acclimate, thereby increasing their cold tolerance. While there is a growing body of knowledge concerning the mechanisms underlying cold tolerance, relatively little is known concerning how insects sense noxious cold (cold nociception), or how cold nociception might function in cold tolerance. It has been previously shown that Drosophila melanogaster larvae perform highly stereotyped, cold-evoked behaviors under the control of noxious cold-sensing neurons (nociceptors) innervating the barrier epidermis. In the present study, we first sought to describe cold-nociceptive behavior among 11 drosophilid species with differing cold tolerances and from differing climates. Behavioral analyses revealed that the predominant cold-evoked response among drosophilid larvae is a head-to-tail contraction (CT) behavior, which is likely inherited from a common ancestor. However, despite lack of phylogenetic signal (suggesting trait lability), the CT behavior was transient and there was no clear evidence that cold sensitivity was related to thermal environment; collectively this suggests that the behavior might not be adaptive. We therefore sought to uncover an alternative way that cold nociception might be protective. Using a combination of cold-shock assays, optogenetics, electrophysiology, and methods to genetically disrupt neural transmission, we demonstrate that cold sensing neurons in Drosophila melanogaster (Class III nociceptors) are sensitized by and critical to cold acclimation. Moreover, we demonstrate that cold acclimation can be optogenetically-evoked, sans cold. Collectively, these findings reveal that cold nociception constitutes a peripheral neural basis for Drosophila larval cold acclimation. Significance StatementMany insects adapt to cold in response to developmental exposure to cool temperatures. While there is a growing body of knowledge concerning the mechanisms underlying cold tolerance, it is unknown how sensory neurons might contribute. Here, we show that noxious cold sensing (cold nociception) is widely present among drosophilid larvae, and that cold-sensing neurons (Class III cold nociceptors) are necessary and sufficient drivers of cold acclimation. This suggests that cold acclimation has, at least in part, a neural basis.

neuroscience↗

bioRxiv2019

The Secretomes of Painful Versus Nonpainful Human Schwannomatosis Tumor Cells Differentially Influence Sensory Neuron Gene Expression and Sensitivity

Schwannomatosis is a multiple tumor syndrome in which patients develop benign tumors along peripheral nerves throughout the body. The first symptom with which schwannomatosis patients often present, prior to discovery of tumors, is pain. This pain can be debilitating and is often inadequately alleviated by pharmacological approaches. Schwannomatosis-associated pain can be localized to the area of a tumor, or widespread. Moreover, not all tumors are painful, and the occurrence of pain is often unrelated to tumor size or location. We speculate that some individual tumors, but not others, secrete factors that act on nearby nerves to augment nociception by producing neuronal sensitization or spontaneous neuronal firing. We created cell lines from human SWN tumors with varying degrees of pain. We have found that conditioned medium (CM) collected from painful SWN tumors, but not that from nonpainful SWN tumors, sensitized DRG neurons, causing increased sensitivity to depolarization by KCl, increased response to noxious TRPV1 and TRPA1 agonists and also upregulated the expression of pain-associated genes in DRG cultures. Multiple cytokines were also detected at higher levels in CM from painful tumors. Taken together our data demonstrate a differential ability of painful versus non-painful human schwannomatosis tumor cells to secrete factors that augment sensory neuron responsiveness, and thus identify a potential determinant of pain heterogeneity in schwannomatosis.

neuroscience↗