Project description:In the studies of Inherited Retinal Diseases (IRDs), the knockout of traditional animal models like mice often fails to accurately replicate human phenotypes due to genetic and anatomical differences. Human retinal organoids (ROs) derived from stem cells have emerged as promising developmental models in retinal studies to delineate cell growth, but their ability to represent the characteristics of late-onset IRDs remains unclear. This study aims to validate ROs as a disease model for Stargardt's Disease (STGD) caused by Abca4 mutations. Using single-cell RNA sequencing, ROs from 2 STGD patients were compared with unaffected ROs at two developmental stages on both the cellular and transcriptomic levels. The results from gene-level comparisons show promising evidence that ROs successfully capture the underlying molecular variations between patient and control samples even at the early developmental stage, providing the potential of applying ROs to facilitate the study of IRDs and late-onset neurodegenerative diseases.
Project description:The eye is an intricate organ with limited representation in large-scale functional genomics datasets. The retinal pigment epithelium (RPE) serves vital roles in ocular development and retinal homeostasis. We interrogated the genetics of gene expression of cultured human fetal RPE (fRPE) cells under two metabolic conditions. Genes with disproportionately high fRPE expression are enriched for genes related to inherited ocular diseases. Variants near these fRPE-selective genes explain a larger fraction of risk for both age-related macular degeneration (AMD) and myopia than variants near genes enriched in 53 non-ocular human tissues. Increased mitochondrial oxidation of glutamine by fRPE promoted expression of lipid synthesis genes implicated in AMD. Expression and splice quantitative trait loci (e/sQTLs) analyses revealed shared and metabolic condition-specific loci of each type and several eQTLs not previously described in any tissue. Fine mapping of fRPE e/sQTLs across AMD and myopia genome-wide association data suggests new candidate genes, and mechanisms by which the same common variant of RDH5 contributes to both increased AMD risk and decreased myopia risk. Our study highlights the unique transcriptomic characteristics of fRPE and provides a resource to connect e/sQTLs in a critical ocular cell type to monogenic and complex eye disorders.
Project description:Many patients suffering from inherited diseases do not receive a genetic diagnosis and are therefore excluded as candidates for treatments, such as gene therapies. Analyzing disease-related gene transcripts from patient cells would improve detection of mutations that have been missed or misinterpreted in terms of pathogenicity during routine genome sequencing. However, the analysis of transcripts is complicated by the fact that a biopsy of the affected tissue is often not appropriate, and many disease-associated genes are not expressed in tissues or cells that can be easily obtained from patients. Here, using CRISPR/Cas-mediated transcriptional activation (CRISPRa) we developed a robust and efficient approach to activate genes in skin-derived fibroblasts and in freshly isolated peripheral blood mononuclear cells (PBMCs) from healthy individuals. This approach was successfully applied to blood samples from patients with inherited retinal dystrophies (IRD). We were able to efficiently activate several IRD-linked genes and detect the corresponding transcripts using different diagnostically relevant methods such as RT-(q)PCR, long- and short-read RNA sequencing. The detection and analysis of known and unknown mRNA isoforms demonstrates the potential of CRISPRa-mediated transcriptional activation in PBMCs. These results will contribute to ceasing the critical gap in the genetic diagnosis of patients with IRD or other inherited diseases.