Loss of ABCA4 from photoreceptor discs triggers changes in glial cell homeostasis

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Abstract
Loss-of-function mutations in the ABCA4 gene cause Stargardt disease (STGD1), the most common inherited macular dystrophy leading to progressive central vision loss. Here, we generated hiPSC-derived retinal organoids harboring a premature stop codon in exon-24 of ABCA4 to evaluate the impact of this mutation on mRNA and protein levels in a human model. Immunofluorescence analysis revealed the absence of ABCA4 protein in the mutant photoreceptor outer segment discs, while single-cell RNA sequencing detected no major transcriptional alterations in rods and cones. Unexpectedly, differential gene expression and pathway enrichment analyses of Müller glial cells (MGCs) and astrocytes highlighted disruption of neuronal development, microenvironment of glial cells, intercellular communication, and programmed cell death pathways. These findings suggest that ABCA4 might play a role in maintaining the retinal microenvironment homeostasis, and that the early transcriptomic response of MGCs and astrocytes preceding photoreceptor degeneration could contribute to Stargardt disease development. Significance Statement: Human induced pluripotent stem cell (hiPSC)-derived retinal organoids provide a powerful platform to investigate inherited retinal diseases. In this study, we generated ABCA4 -mutant hiPSC lines and differentiated them into retinal organoids to model Stargardt disease. Despite complete loss of ABCA4 protein from the photoreceptor outer segment discs, rods and cones exhibited minimal transcriptional alterations. In contrast, the ABCA4 variant triggered changes in the glial cell homeostasis, suggesting that Müller glial cells and astrocytes might exhibit an early response to photoreceptor dysfunction in the absence of ABCA4. Abstract Figure: Human induced pluripotent stem cells (hiPSCs) were engineered to generate ABCA4 -mutant cell lines, later differentiated into retinal organoids as a model of Stargardt disease. The organoids showed loss of ABCA4 from the outer segment discs of rod and cone photoreceptors, while the mutant Müller glial cells and astrocytes exhibited transcriptional changes in pathways involved in neuronal development, microenvironment, and programmed cell death.
Funding Information
  • Stichting Oogfonds Nederland (UZ 2017-3)
  • Stichting Oogfonds Nederland (UZ 2019-9)
  • Stichting Oogfonds Nederland (UZ 2023-05)
  • Rotterdamse Stichting Blindenbelangen (UZ 2017-3)
  • Rotterdamse Stichting Blindenbelangen (UZ 2019-9)
  • Landelijke Stichting voor Blinden en Slechtzienden (UZ 2017-3)
  • Landelijke Stichting voor Blinden en Slechtzienden (UZ 2019-9)
  • Landelijke Stichting voor Blinden en Slechtzienden (UZ 2023-05)
  • Stichting Retina Fonds (UZ 2017-3)
  • Stichting Retina Fonds (UZ 2023-05)
  • Stichting Blindenhulp (UZ 2017-3)
  • Stichting Blindenhulp (UZ 2019-9)
  • Stichting Ushersyndroom (UZ 2023-05)

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