Biology subjects

Richards, S. E.

Publications and source records attributed to Richards, S. E..

3 recordsLinked to original sources

bioRxiv2024

APOE Impacts Lipid Trafficking in Retinal Pigment Epithelium Cells

Age-related macular degeneration (AMD) is typified by the formation of lipid-rich drusen under the retinal pigment epithelium (RPE) layer. Apolipoprotein E (APOE) is a known genetic risk factor for AMD and a substantial component of drusen, however, the mechanism by which APOE variants contribute to AMD pathology remains unclear. APOE is the primary cholesterol and lipid transport protein of the central nervous system, as well as a component circulating lipoproteins. To better understand how APOE-dependent lipid transport may impact AMD risk, we generated isogenic APOE iPS-RPE cells expressing each of the common human APOE isoforms, as well as an APOE knockout line. APOE knockout cells showed significant morphological and barrier function deficits, suggesting that APOE is essential for RPE health. Furthermore, we observed that APOE abundance is isoform-dependent in RPE cells and that lipid transport is deficient in APOE knockout RPE cells, as well as in RPE cells expressing APOE2, a variant associated with higher risk of AMD. Contrastingly, cells expressing APOE4 seem to respond strongly to lipid challenges by upregulating APOE to support efficient lipid transport. Our results suggest that disease associated APOE variants may impact lipid transport in RPE, contributing to the formation of drusen and impairing cellular function.

cell biology↗

bioRxiv2019

Experience-dependent development of dendritic arbors in mouse visual cortex

Despite the importance of dendritic arbors for proper neuronal function, our knowledge of how sensory experience influences these structures during postnatal cortical development is incomplete. We present a large-scale dataset of 849 three-dimensional reconstructions of pyramidal neuron basal arbors collected across early postnatal development in the mouse visual cortex. We found that the basal arbor underwent a 45% increase in total length between postnatal day 7 (P7) and P30. Surprisingly, comparisons of dark-reared and typically-reared mice revealed that only 15% of arbor length could be attributed to visual experience. Furthermore, we characterized the role of the activity-regulated small GTPase Rem2, showing that Rem2 is an experience-dependent negative regulator of dendritic segment number during the visual critical period. These data establish a detailed, quantitative analysis of the basal arbor that has high utility for understanding circuit development and providing a framework for computationalists wishing to generate anatomically accurate neuronal models.

neuroscience↗

bioRxiv2017

Rem2 regulates distinct homeostatic mechanisms in visual circuit plasticity

Activity-regulated genes sculpt neural circuits in response to sensory experience. These calcium-sensitive genes generally fall into two categories: transcription factors and proteins that function at synapses. Yet little is known about activity-regulated, cytosolic proteins that transduce signals between the neuronal membrane and the nucleus. Using the visual system as a model, we investigated the role of the activity-regulated, non-canonical Ras-like GTPase Rem2 in vivo. We demonstrate that Rem2-/- mice fail to exhibit normal ocular dominance plasticity during the critical period. At the circuit level, cortical layer 2/3 neurons in Rem2-/- mice show deficits in both postsynaptic scaling up of excitatory synapses and misregulation of intrinsic excitability. Further, we reveal that Rem2 plays a novel, cell-autonomous role in regulating neuronal intrinsic excitability. Thus, Rem2 is a critical regulator of neural circuit function and distinct homeostatic plasticity mechanisms in vivo.\n\nHIGHLIGHTSO_LIRem2 is required in excitatory cortical neurons for normal ocular dominance plasticity\nC_LIO_LIRem2 regulates postsynaptic homoeostatic synaptic scaling up\nC_LIO_LIRem2 alters the intrinsic excitability of neurons in a cell-autonomous manner\nC_LI

neuroscience↗