Biology subjects

Carr, B. J.

Publications and source records attributed to Carr, B. J..

3 recordsLinked to original sources

bioRxiv2025

Polysialic acid is a versatile marker for retinal Müller glia in common vertebrate model organisms and systems

Muller glia are retinal support cells that play crucial roles in tissue structure, waste management, and repair. A challenge for the field has been to find Muller glia markers that detect non-reactive cells or work well in non-mammalian models. We introduce two novel markers for identifying reactive and non-reactive Muller glia in vertebrate retinas: a modified enzyme lectin (GFP-EndoNDM) and a monoclonal antibody (mAb735). These markers recognize polysialic acid (polySia), which is a highly conserved glycosylation modification in humans and vertebrates. In the retina, polySia is present on Muller glia predominantly in the form of polySia-NCAM. We used GFP-EndoNDM and mAb735 to investigate polySia distribution in Muller glia of fish, amphibians, reptiles, birds, rodents, retinal organoids, and humans. In adult retinas of most species, polySia was localized to the Muller glia and spanned outer to inner retina, with inner plexiform layer (IPL) sublaminae ramifications. Gliosis was also detectable in degenerating murine retinas. Notable species differences were that only outer retinal regions of Muller glia were labelled in adult zebrafish, whereas the outer Muller glia body up to the first IPL sublamina was labelled in adult turquoise killifish. There was no significant retinal polySia labeling in larval zebrafish, but it was present in the brain. Larval turquoise killifish have polySia throughout the retina, similar to other adult vertebrates. Labelling polySia expands the scientific toolbox for Muller glia markers, and offers a versatile way to visualize and monitor structural changes in non-reactive and reactive Muller glia across most vertebrate species. HighlightsO_LIPolySia is a highly conserved Muller glia marker in vertebrate retina and retinal organoids C_LIO_LILabeling Muller glia with markers of polySia, facilitates the analysis of fine Muller glia processes in the IPL sublaminae, whole Muller glia morphology, and degenerative gliosis C_LIO_LIPolySia can be labeled with an engineered lectin conjugate (GFP-EndoNDM) and a commercially-available monoclonal antibody C_LI

cell biology↗

bioRxiv2024

Prominin-1 null Xenopus laevis develop subretinal drusenoid-like deposits, cone-rod dystrophy, and dysmorphic retinal pigment epithelium.

Mutations in the PROMININ-1 (PROM1) gene are associated with inherited, non-syndromic vision loss. Here, we used CRISPR/Cas9 to induce truncating prom1-null mutations in Xenopus laevis to create a disease model. We then tracked progression of retinal degeneration in these animals from the ages of 6 weeks to 3 years old. We found that retinal degeneration caused by prom1-null is age-dependent and likely involves death or damage to the retinal pigment epithelium (RPE) that precedes photoreceptor degeneration. As prom1-null frogs age, they develop large cellular debris deposits in the subretinal space and outer segment layer which resemble subretinal drusenoid deposits (SDD) in their location, histology, and representation in color fundus photography and optical coherence tomography (OCT). In older frogs, these SDD-like deposits accumulate in size and number, and they are present before retinal degeneration occurs. Evidence for an RPE origin of these deposits includes infiltration of pigment granules into the deposits, thinning of RPE as measured by OCT, and RPE disorganization as measured by histology and OCT. The appearance and accumulation of SDD-like deposits and RPE thinning and disorganization in our animal model suggests an underlying disease mechanism for prom1-null mediated blindness of death and dysfunction of the RPE preceding photoreceptor degeneration, instead of direct effects upon photoreceptor outer segment morphogenesis, as was previously hypothesized.

cell biology↗

bioRxiv2020

Genetically-modified X. laevisindicate distinct roles for prominin-1 and photoreceptor cadherin in outer segment morphogenesis and retinal dystrophy

Mutations in prominin-1 (prom1) and photoreceptor cadherin (cdhr1) are associated with inherited retinal degenerative disorders such as retinitis pigmentosa, cone-rod dystrophy, and juvenile macular dystrophy. The proteins encoded by these genes are hypothesized to regulate photoreceptor outer segment disc morphogenesis, but their functions remain unknown. We used CRISPR/Cas9 to generate prom1-, cdhr1-, and prom1 + cdhr1-null X. laevis and then documented the effects of these mutations on photoreceptor structure and function. Prom1-null mutations resulted in dysmorphic photoreceptors comprised of overgrown and disorganized disc membranes. Cones were more severely affected than rods; outer segments were elongated and fragmented, and ERG response was impaired. Autofluorescent deposits in the outer segment layer of aging prom1-null animals indicate that secondary toxic effects to the retina or RPE drive retinal degeneration for this mutation, instead of direct effects on outer segment disc morphogenesis. Cdhr1-null photoreceptors did not appear grossly dysmorphic, but ultrastructural analysis revealed that some disc membranes were overgrown or aligned vertically within the plasma membrane. Prom1 + cdhr1-null mutants did not differ significantly from prom1-null mutants. Our results indicate that neither prom1 nor cdhr1 are necessary for outer segment disc membrane evagination or the membrane fusion event involved in disc sealing. Rather, they are necessary for higher-order organization of the nascent outer segment discs. Prom1 may align and reinforce interactions between the disc leading edges, a function more critical in cone photoreceptors for structural support. Cdhr1 may help to align nascent discs and maintain horizontal disc orientation prior to fusion.

cell biology↗