Biology subjects

Kay, J. N.

Publications and source records attributed to Kay, J. N..

9 recordsLinked to original sources

bioRxiv2026

Retinal degeneration in a mouse model of CRB1 disease rescued by the photoreceptor-specific CRB1-B isoform

Many genes involved in inherited diseases produce alternate mRNA isoforms that remain poorly characterized. Functional assessment of these isoforms could therefore unlock new insights into disease pathobiology or treatment. Here we investigated the function of the newly discovered B isoform of CRB1, a gene implicated in inherited retinal degenerations. CRB1-B is the most abundant retinal isoform, and differs from the canonical CRB1-A isoform in several important ways. Crucially, CRB1-B is the only isoform expressed by photoreceptors -- the cells vulnerable to degeneration. Using a mouse model of CRB1-associated degeneration with degraded visual acuity, we find that restoring CRB1-B to photoreceptors prevents degeneration and completely rescues visual function, despite the absence of other isoforms. The therapeutic mechanism involves preservation of adherens junctions between photoreceptors and supporting glia: We establish that progressive loss of these junctions is a key pathobiological mechanism underlying photoreceptor death, and that junction loss is prevented by restoring photoreceptor expression of CRB1-B. Our findings nominate CRB1-B replacement as a promising gene therapy strategy. More broadly, they suggest that exploring disease gene isoform diversity offers an untapped opportunity to devise novel therapeutics.

neuroscience↗

bioRxiv2026

Phosphatidylserine exposure by developing astrocytes initiates microglia-mediated developmental cell death

Developmental cell death is classically attributed to apoptosis, yet in mammalian retina, large numbers of developing astrocytes die non-apoptotically during a defined developmental window. Astrocyte death is important for patterning a cellular template that guides angiogenesis, but the underlying mechanism remains unknown. Here we show that healthy developing astrocytes initiate their own elimination by recruiting microglia via regulated exposure of the membrane lipid phosphatidylserine. Experimentally increasing phosphatidylserine exposure in astrocytes, but not neurons, accelerates their removal by microglia without changing how many astrocytes ultimately survive. This acceleration causes profound vascular defects resembling pathological features of retinopathy of prematurity. Genetic disruption of MFGE8, a phosphatidylserine-binding protein, suppresses microglia-mediated astrocyte killing and prevents vascular pathology despite continued phosphatidylserine exposure. This mechanism extends beyond the retina, because phosphatidylserine also initiates astrocyte death in developing cerebral cortex. Together, these findings identify phosphatidylserine exposure as a developmental signal that times microglia-mediated astrocyte elimination, with essential consequences for neurovascular development.

neuroscience↗

bioRxiv2025

Microglia and myeloid cell populations of the developing mouse retina

Microglia make important contributions to central nervous system (CNS) development, but the breadth of their distinct developmental functions remain poorly understood. The mouse retina has been a key model system for understanding fundamental mechanisms controlling assembly of the CNS. To gain insight into where and how microglia might influence retinal development, here we identified molecularly unique myeloid cell populations that are selectively present during development, and characterized their anatomical locations. Development-specific transcriptional states were identified using single-cell (sc) and single-nucleus RNA-sequencing (RNA-seq) across multiple timepoints. Transcriptional states were validated in vivo by histological staining for key RNA and/or protein markers. Several of these development-specific myeloid populations have been described before in brain scRNA-seq atlases but not validated in vivo, while others are unique to our retinal dataset. We identify two closely-related microglial populations, labeled by the Spp1 and Hmox1 genes, that are distinguished mainly by activity of the NRF2 transcription factor. Both types are present selectively within the developing retinal nerve fiber layer where they engulf neurons and astrocytes undergoing developmental cell death. Hmox1+ microglia were also localized selectively at the wavefront of developing vasculature during retinal angiogenesis, suggesting that developmental events associated with angiogenesis modulate NRF2 activity and thereby induce microglia to switch between the Spp1+ and Hmox1+ states. Overall, our results identify transcriptional profiles that define specific populations of retinal microglia, opening the way to future investigations of how these programs support microglial functions during development.

neuroscience↗

bioRxiv2023

Retinal neurons establish mosaic patterning by excluding homotypic somata from their dendritic territory

In vertebrate retina, individual neurons of the same type are distributed regularly across the tissue in a pattern known as a mosaic. Establishment of mosaics during development requires cell-cell repulsion among homotypic neurons, but the mechanisms underlying this repulsion remain unknown. Here we show that two mouse retinal cell types, OFF and ON starburst amacrine cells, establish mosaic spacing by using their dendritic arbors to repel neighboring homotypic somata. Using newly-generated transgenic tools and single cell labeling, we identify a transient developmental period when starburst somata receive extensive contacts from neighboring starburst dendrites; these serve to exclude somata from settling within the neighbors dendritic territory. Dendrite-soma exclusion is mediated by MEGF10, a cell-surface molecule required for starburst mosaic patterning. Our results implicate dendrite-soma exclusion as a key mechanism underlying starburst mosaic spacing, and suggest that this could be a general mechanism for mosaic patterning across many cell types and species.

neuroscience↗

bioRxiv2022

Rejection of inappropriate synaptic partners mediated by transcellular FLRT2-UNC5 signaling

During nervous system development, neurons choose synaptic partners with remarkable specificity; however, the cell-cell recognition mechanisms governing rejection of inappropriate partners remain enigmatic. Here we show that mouse retinal neurons avoid inappropriate partners using the FLRT2-UNC5 receptor-ligand system. Within the inner plexiform layer (IPL), FLRT2 is expressed by direction-selective (DS) circuit neurons, whereas UNC5C/D are expressed by non-DS neurons projecting to adjacent IPL sublayers. In vivo gain- and loss-of-function experiments demonstrate that FLRT2-UNC5 binding eliminates growing DS dendrites that have strayed from the DS circuit IPL sublayers. Abrogation of FLRT2-UNC5 binding allows mistargeted arbors to persist, elaborate, and acquire synapses from inappropriate partners. Conversely, UNC5C misexpression within DS circuit sublayers inhibits dendrite growth and drives arbors into adjacent sublayers. Mechanistically, UNC5s promote dendrite elimination by interfering with FLRT2-mediated adhesion. Based on their broad expression, FLRT-UNC5 recognition is poised to exert widespread effects upon synaptic partner choices across the nervous system.

neuroscience↗

bioRxiv2019

Thrombospondin-1 Promotes Circuit-Specific Synapse Formation via β1-Integrin

Glial cells regulate synaptic connectivity during development, but whether they selectively instruct the formation of specific synaptic circuits is not known. Here we show that the major perisynaptic glia of the retina, the Muller glia (MG), control the proper establishment of the direction-selective (DS) circuit by a synaptogenic protein, Thrombospondin 1 (TSP1). We found that TSP1 promotes excitatory synapse formation specifically in on-off Direction-Selective retinal Ganglion Cells (ooDSGCs). Lack of TSP1 leads to reduced synapse formation within the inner plexiform sublayers containing DS-circuit, resulting in deficits of ooDSGC function. Even though pan-TSP receptor, 2{delta}-1, interaction is required for TSP1-induced synapse formation, the ooDSGC-subtype specificity of TSP1 is conferred by a second neuronal TSP1 receptor, {beta}1-Integrin. Furthermore, conditional deletion of {beta}1-Integrin in ooDSGCs results in diminished excitatory synapse formation without disturbing laminar organization showing that MG-secreted TSP1 controls circuit-specific synapse formation via {beta}1-Integrin.

neuroscience↗

bioRxiv2019

Environmental Oxygen Regulates Astrocyte Proliferation to Guide Angiogenesis during Retinal Development

Angiogenesis in the developing mammalian retina requires patterning cues from astrocytes. Developmental disorders of retinal vasculature, such as retinopathy of prematurity (ROP), involve arrest or mispatterning of angiogenesis. Whether these vascular pathologies involve astrocyte dysfunction remains untested. Here we demonstrate that the major risk factor for ROP - transient neonatal exposure to hyperoxia - disrupts formation of the angiogenic astrocyte template. Exposing mice to hyperoxia (75% O2) from postnatal day (P)0-4 suppressed astrocyte proliferation, while return to room air (21% O2) at P4 triggered extensive proliferation, massively increasing astrocyte numbers and disturbing their spatial patterning prior to arrival of developing vasculature. Proliferation required astrocytic HIF2 and was also stimulated by direct hypoxia (10% O2), suggesting that astrocyte oxygen sensing regulates the number of astrocytes produced during development. Along with astrocyte defects, return to room air also caused vascular defects reminiscent of ROP. Strikingly, these vascular phenotypes were more severe in animals that had larger numbers of excess astrocytes. Together, our findings suggest that fluctuations in environmental oxygen dysregulate molecular pathways controlling astrocyte proliferation, thereby generating excess astrocytes that interfere with retinal angiogenesis.

neuroscience↗

bioRxiv2019

Large-scale death of retinal astrocytes duringnormal development mediated by microglia

Naturally-occurring cell death is a fundamental developmental mechanism for regulating cell numbers and sculpting developing organs. This is particularly true in the central nervous system, where large numbers of neurons and oligodendrocytes are eliminated via apoptosis during normal development. Given the profound impact of death upon these two major cell populations, it is surprising that developmental death of another major cell type - the astrocyte - has rarely been studied. It is presently unclear whether astrocytes are subject to significant amounts of developmental death, or how it occurs. Here we address these questions using mouse retinal astrocytes as our model system. We show that the total number of retinal astrocytes declines by over 3-fold during a death period spanning postnatal days 5-14. Surprisingly, these astrocytes do not die by apoptosis, the canonical mechanism underlying the vast majority of developmental cell death. Instead, we find that microglia kill and engulf astrocytes to mediate their developmental removal. Genetic ablation of microglia inhibits astrocyte death, leading to a larger astrocyte population size at the end of the death period. However, astrocyte death is not completely blocked in the absence of microglia, apparently due to the ability of astrocytes to engulf each other. Nevertheless, mice lacking microglia showed significant anatomical changes to the retinal astrocyte network, with functional consequences for the astrocyte-associated vasculature leading to retinal hemorrhage. These results establish a novel modality for naturally-occurring cell death, and demonstrate its importance for formation and integrity of the retinal gliovascular network.

neuroscience↗

bioRxiv2017

Formation of retinal direction-selective circuitry initiated by starburst amacrine cell homotypic contact

Impact statementSelective synapse formation in a retinal motion-sensitive circuit is orchestrated by starburst amacrine cells, which use homotypic interactions to initiate formation of a dendritic scaffold that recruits projections from circuit partners.\n\nSUMMARYA common strategy by which developing neurons locate their synaptic partners is through projections to circuit-specific neuropil sublayers. Once established, sublayers serve as a substrate for selective synapse formation, but how sublayers arise during neurodevelopment remains unknown. Here we identify the earliest events that initiate formation of the direction-selective circuit in the inner plexiform layer of mouse retina. We demonstrate that radially-migrating newborn starburst amacrine cells establish homotypic contacts on arrival at the inner retina. These contacts, mediated by the cell-surface protein MEGF10, trigger neuropil innervation resulting in generation of two sublayers comprising starburst-cell dendrites. This dendritic scaffold then recruits projections from circuit partners. Abolishing MEGF10-mediated contacts profoundly delays and ultimately disrupts sublayer formation, leading to broader direction tuning and weaker direction-selectivity in retinal ganglion cells. Our findings reveal a mechanism by which differentiating neurons transition from migratory to mature morphology, and highlight this mechanisms importance in forming circuit-specific sublayers.

neuroscience↗