Zorin, M. | Search bioRxiv

bioRxiv2025

Lost in communication: How Mueller glia cells fail to maintain retinal integrity in USH1C retinal organoids

Usher syndrome type 1, caused by pathogenic variants in the USH1C gene, leads to congenital deafness and progressive retinal degeneration resulting in vision loss. While auditory deficits can be compensated by cochlea implants and hearing aids, no treatment exists to prevent retinal degeneration. Here, we generated retinal organoids from induced pluripotent stem cells of two USH1C patients to elucidate the cellular and molecular mechanisms driving ocular pathogenesis. Single-cell RNA sequencing of both healthy and USH1C retinal organoids identified differential expression of genes related to phototransduction in photoreceptors, as well as alterations in cell adhesion and canonical Wnt signaling in Muller glia cells. Analysis of intercellular communication revealed an overall reduced signaling efficiency, particularly affecting Muller glia-mediated retinal adhesion processes. Morphological characterization of organoids confirmed transcriptome changes by showing degeneration of the outer limiting membrane and loss of adherens junction architecture. Moreover, photoreceptors revealed increased susceptibility to morphological and functional changes related to phototransduction. These results demonstrate that disruption of Muller glia signaling contributes to a loss of retinal integrity, providing novel insights into USH1C pathogenesis and offering targets for therapeutic interventions.

cell biology↗

bioRxiv2024

The adhesion GPCR ADGRV1 controls glutamate homeostasis in hippocampal astrocytes supporting neuron development: First insights into to pathophysiology of ADGRV1-associated epilepsy

ADGRV1 is the largest member of adhesion G protein-coupled receptor (aGPCR) family. In the cell, aGPCRs have dual roles in cell adhesion and signal transduction. Mutations in ADGRV1 have been linked not only to Usher syndrome (USH), which causes deaf-blindness, but recently also to various forms of epilepsy. While the USH defects are attributed to the loss of fiber links between membranes formed by the extracellular domain of ADGRV1, the pathomechanisms leading to epilepsy remain elusive to date. Here, we study the specific functions of ADGRV1 in astrocytes where it is highest expressed in the nervous system. Affinity proteomics showed the interaction of ADRGV1 with proteins enriched in astrocytes. Dysregulations of cellular processes important in astrocyte function were indicated by the different transcriptomes of patient-derived cells and Adgrv1-deficent mouse hippocampi compared to appropriate controls. Alteration in morphology and reduced numbers of astrocytes in the hippocampus of Adgrv1-deficent mice. Monitoring the glutamate uptake in colorimetric assay and by live cell imaging of a genetic glutamate reporter consistently showed that glutamate uptake from the extracellular environment is significantly reduced in Adgrv1-deficent astrocytes. Expression analyses of key enzymes of the glutamate-glutamine cycle in astrocytes and the glutamate metabolism indicated imbalanced glutamate homeostasis in Adgrv1-deficient astrocytes. Finally, we provide evidence that the supportive function of astrocytes in neuronal development also relies on ADGRV1 expression in astrocytes. Our data collectively provides first insights into the molecular pathophysiology underlying the development of epilepsy associated with mutations in ADGRV1. HighlightsO_LIADGRV1 deficiency reduces the number of astrocytes in CA1 and changes the morphology of astrocytes in the hippocampus. C_LIO_LIADGRV1 interacts with numerous proteins enriched in astrocytes. C_LIO_LIDifferential transcriptomes revealed differential expression of genes related to glutamate homeostasis and epilepsy in ADGRV1 deficient models. C_LIO_LIADGRV1 controls glutamate uptake and regulates homeostasis in astrocytes. C_LIO_LIADGRV1 in astrocytes is vital for neuron morphogenesis. C_LIO_LIFirst insights into the molecular pathophysiology underlying the development of epilepsy associated with mutations in ADGRV1. C_LI Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=197 SRC="FIGDIR/small/591120v1_ufig1.gif" ALT="Figure 1"> View larger version (54K): org.highwire.dtl.DTLVardef@1f1f749org.highwire.dtl.DTLVardef@a1ea01org.highwire.dtl.DTLVardef@a0be1org.highwire.dtl.DTLVardef@191f96a_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗