Biology subjects

Redmond, T. M.

Publications and source records attributed to Redmond, T. M..

5 recordsLinked to original sources

bioRxiv2026

Structure of a secreted lancelet carotenoid cleavage dioxygenase (CCD), from an ancestral CCD clade

Carotenoid cleavage dioxygenases (CCDs) are a superfamily of non-heme iron-containing enzymes ubiquitous across all kingdoms of life. Previously, we identified a new subfamily of CCDs termed beta-carotene oxygenase-like (BCOL) proteins, a chordate expansion of an ancestral sister clade of metazoan CCDs, which are widely distributed in marine invertebrates, including mollusks and lancelets. Here we present the three-dimensional structure of a representative BCOL protein from the lancelet Branchiostoma floridae (BCOLg) at 2.4 [A] resolution and its functional properties. BCOLg symmetrically cleaves {beta}-carotene into all-trans retinal. RNAseq of wild-caught animals detected six of the seven annotated BCOL transcripts in Branchiostoma gut tissue. We expressed and crystallized recombinant BCOLg. BCOLg is heavily glycosylated, with four N-linked glycosylation sites, and adopts the seven-bladed propeller fold characteristic of the superfamily, with one disulfide bond contributing to structural stability. BCOLg and several other BCOL proteins contain Asp substitutions at two of three Glu positions found in other CCDs, stabilizing three of four His residues involved in Fe2+ coordination. Notably, BCOLg lacks the canonical -PDPCK- motif characteristic of other metazoan CCDs.

biochemistry↗

bioRxiv2024

Dual CRALBP isoforms unveiled: iPSC-derived retinal modelling and AAV2/5-RLBP1 gene transfer raise considerations for effective therapy

Inherited retinal diseases (IRDs) are clinically and genetically heterogeneous disorders characterised by progressive vision loss. Over 270 causative genes have been identified and variants within the same gene can give rise to clinically distinct disorders. Human induced pluripotent stem cells (iPSCs) have revolutionised disease modelling, by allowing pathophysiological and therapeutic studies in the patient and tissue context. The IRD gene RLBP1 encodes CRALBP, an actor of the rod and cone visual cycles in the retinal pigment epithelium (RPE) and Muller cells, respectively. Variants in RLBP1 lead to three clinical subtypes: Bothnia dystrophy, Retinitis punctata albescens and Newfoundland rod-cone dystrophy. We modelled RLBP1-IRD subtypes by patient-specific iPSC-derived RPE and identified pertinent therapeutic read-outs. We developed an AAV2/5-mediated gene replacement strategy and provided a proof-of-concept in the ex vivo human models that was validated in an in vivo Rlbp1-/- murine model. Most importantly, we identified a previously unsuspected smaller CRALBP isoform that is naturally and differentially expressed in both human and murine retina. The new isoform arises from an alternative methionine initiation site and plays a role in the visual cycle. This work provides novel insights into CRALBP expression and RLBP1-associated pathophysiology and raises important considerations for successful gene supplementation therapy.

molecular biology↗

bioRxiv2023

Human iPSC-derived Microglia Cells Integrated into Mouse Retina and Recapitulated Features of Endogenous Microglia Cells

Microglia exhibit both maladaptive and adaptive roles in the pathogenesis of neurodegenerative diseases and have emerged as a cellular target for central nervous system (CNS) disorders, including those affecting the retina. Replacing maladaptive microglia, such as those impacted by aging or over-activation, with exogenous microglia that can enable adaptive functions has been proposed as a potential therapeutic strategy for neurodegenerative diseases. To investigate microglia replacement as an approach for retinal diseases, we first employed a protocol to efficiently generate human-induced pluripotent stem cells (hiPSC)-derived microglia in quantities sufficient for in vivo transplantation. These cells demonstrated expression of microglia-enriched genes and showed typical microglial functions such as LPS-induced responses and phagocytosis. We then performed xenotransplantation of these hiPSC-derived microglia into the subretinal space of adult mice whose endogenous retinal microglia have been pharmacologically depleted. Long-term analysis post-transplantation demonstrated that transplanted hiPSC-derived microglia successfully integrated into the neuroretina as ramified cells, occupying positions previously filled by the endogenous microglia and expressed microglia homeostatic markers such as P2ry12 and Tmem119. Further, these cells were found juxtaposed alongside residual endogenous murine microglia for up to eight months in the retina, indicating their ability to establish a stable homeostatic state in vivo. Following retinal pigment epithelial (RPE) cell injury, transplanted microglia demonstrated responses typical of endogenous microglia, including migration, proliferation, and phagocytosis. Our findings indicate the feasibility of microglial transplantation and integration in the retina and suggest that modulating microglia through replacement may be a therapeutic strategy for treating neurodegenerative retinal diseases.

neuroscience↗

bioRxiv2021

Potential therapy for progressive vision loss due to PCDH15-associated Usher syndrome developed in an orthologous Usher mouse

Usher syndrome type I (USH1) is characterized by congenital deafness, vestibular areflexia, and progressive retinal degeneration with age. The protein-truncating p.Arg245* founder variant of PCDH15 has an ~2% carrier frequency among Ashkenazi Jews, accounting for nearly 60% of their USH1 cases. Here, longitudinal ocular phenotyping in thirteen USH1F individuals harboring the p.Arg245* variant revealed progressive retinal degeneration, leading to severe loss of vision with macular atrophy by the sixth decade. Half of the affected individuals met either the visual acuity or visual field loss definition for legal blindness by the middle of their fifth decade of life. Mice homozygous for p.Arg250* (Pcdh15R250X; equivalent to human p.Arg245*) also have early visual deficits evaluated using electroretinography. Light-dependent translocation of phototransduction cascade proteins, arrestin and transducin, was found to be impaired in Pcdh15R250X mice. Retinal pigment epithelium-(RPE) specific visual retinoid cycle proteins, RPE65 which converts all-trans retinoids to 11-cis retinoids and CRALBP that transports retinoids, and key retinoid levels were also reduced in Pcdh15R250X mice, suggesting a dual role for protocadherin-15 in photoreceptors and RPE. Administration of exogenous 9-cis retinal, an analog of the naturally occurring 11-cis retinal, improved ERG amplitudes in these mutant mice, suggesting a basis for a clinical trial of exogenous FDA approved retinoids to preserve vision in USH1F patients. SummaryIn a preclinical setting studying exogenous retinoids using a novel Usher syndrome mouse model, we describe a potential therapy to treat PCDH15-mediated visual dysfunction.

neuroscience↗

bioRxiv2020

Loss of CIB2 causes non-canonical autophagy deficits and visual impairment

Non-canonical autophagy or LC3-associated phagocytosis (LAP) is essential for the maintenance and functioning of the retinal pigment epithelium (RPE) and photoreceptors. Although molecular mechanisms still remain elusive, deficits in LAP have been found to be associated with age-related retinal pathology in both mice and humans. In this study, we found that calcium and integrin-binding protein 2 (CIB2) regulates LAP in the RPE. Mice lacking CIB2, both globally and specifically within RPE, have an impaired ability to process the engulfed photoreceptor outer segments due to reduced lysosomal capacity, which leads to marked accumulation of improperly digested remnants, lipid droplets, fused phago-melanosomes in RPE, and impaired visual function. In aged mice, we also found marked accumulation of drusen markers APOE, C3, and A{beta}, along with esterified cholesterol. Intriguingly, we were able to transiently rescue the photoreceptor function in Cib2 mutant mice by exogenous retinoid delivery. Our study links LAP and phagocytic clearance with CIB2, and their relevance to the sense of sight.

cell biology↗