Abstract
Aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) is a photoreceptor-specific chaperone that stabilizes the effector enzyme of phototransduction, cGMP phosphodiesterase 6 (PDE6). Mutations in the AIPL1 gene cause a severe inherited retinal dystrophy, Leber congenital amaurosis type 4 (LCA4), that manifests as the loss of vision during the first year of life. In this study, we generated three-dimensional (3D) retinal organoids (ROs) from human induced pluripotent stem cells (hiPSCs) derived from an LCA4 patient carrying a Cys89Arg mutation in AIPL1. This study aimed to (i) explore whether the patient hiPSC-derived ROs recapitulate LCA4 disease phenotype, and (ii) generate a clinically relevant resource to investigate the molecular mechanism of disease and safely test novel therapies for LCA4 in vitro. We demonstrate reduced levels of the mutant AIPL1 and PDE6 proteins in patient organoids, corroborating the findings in animal models; however, patient-derived organoids maintained retinal cell cytoarchitecture despite significantly reduced levels of AIPL1.
Highlights
Mutations in the aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) gene lead to early onset retinal disease and account for up to 5–10% of all mutations causing LCA3 resulting in a clinically severe form, LCA type 4 (LCA4, OMIM #604393)[4]
We employed a previously characterized human induced pluripotent stem cells (hiPSCs) line derived from a LCA patient with a confirmed homozygous mutation in Aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) (p.Cys89Arg)[29] to differentiate as retinal organoids according to a previously published protocol[24]
We examined the genesis of retinal cell types by following the expression of a panel of major retinal cell type markers spanning the 27 weeks of differentiation (Supplementary Fig. S5). hiPSC-derived retinal organoids (ROs) followed the temporal sequence of expression of human retinal cells[24], namely ganglion cells followed by photoreceptor progenitors, amacrine, and horizontal cell types
Summary
Mutations in the aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) gene lead to early onset retinal disease and account for up to 5–10% of all mutations causing LCA3 resulting in a clinically severe form, LCA type 4 (LCA4, OMIM #604393)[4]. FKBPs containing TPR domains represent a specific class of immunophilins, a subfamily of chaperones with peptidyl-prolyl cis-trans isomerase (PPIase) activity This activity interconverts isoforms of proline peptide bonds from cis to trans, a rate-limiting step in protein folding. The groundbreaking discovery of the Sasai group set the stage for the generation of pluripotent stem cell (PSC)-derived three-dimensional (3D) retinal organoids (ROs) that recapitulate major steps of retinogenesis and self-organize into stratified neural retina with maturing photoreceptor features[22,23,24,25] This approach offers a platform for the exploration of early human retinal development in vitro and supports photoreceptor cellular segmentation with nascent light-sensing outer segment (OS) formation within a native retina histoarchitecture that was impossible to achieve in classical two-dimensional cultures or cellular overexpression models. We examined the ability of mutation-bearing ROs to generate the entire retinal cell repertoire in correctly laminated retinal tissue and explored the advanced structural and molecular features of resultant photoreceptors
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