CRISPR applications in ophthalmologic genome surgery

Abstract

Purpose of review This review seeks to summarize and discuss the application of CRISPR-Cas systems for genome editing, also called “genome surgery,” in the field of ophthalmology. Recent findings Precision medicine is an emerging approach for disease treatment and prevention that takes into account the variability of an individual’s genetic sequence. Various groups have used CRISPR-Cas genome editing to make significant progress in mammalian preclinical models of eye disease, the basic science of eye development in zebrafish, the in vivo modification of ocular tissue, as well as the correction of stem cells with therapeutic applications. Additionally, investigators have creatively used the targeted mutagenic potential of CRISPR-Cas systems to target pathogenic alleles in vitro. Summary Over the past year, CRISPR-Cas genome editing has been used to correct pathogenic mutations in vivo as well as in transplantable stem cells. While off-target mutagenesis remains a concern, improvement in CRISPR-Cas technology and careful screening for undesired mutations will likely lead to clinical eye therapeutics employing CRISPR-Cas systems in the near future.

Gene therapy and genome surgery in the retina

“…Moreover, Allergan is sponsoring a phase I/ II trial of an intravitreally delivered channelrhodospin-2-based optogenetic therapy, RST-100, in patients with advanced RP (174). Further developments in clinical application for other causative mutation retinal dystrophies are highly anticipated, as patients suffering from blinding inherited eye disease may gain options for previously untreatable conditions (175)(176)(177)(178)(179).…”

CRISPR-Mediated Ophthalmic Genome Surgery

“…In response to infection, the bacterium cuts the viral genome into smaller segments and incorporates them into its own genome in between short, highly repetitive sequences, called CRISPR (5–7). The viral genome is then transcribed into CRISPR RNAs (crRNA), which associate with trans-activating crRNA (tracrRNA).…”

“…ZFNs and TALENs are guided by protein-DNA binding, which limits their broad application due to difficulties in engineering new proteins for each target (3). On the other hand, the RNA-mediated CRISPR system offers efficient and versatile gene-modifying capabilities, allowing for diverse applications including deletions, insertions, knockouts, transcriptional control, epigenetic alterations, and more (3, 5, 13). These CRISPR strategies not only allow an expanded toolkit for studying implicated genes in relation to retinal development and physiology, but also may find success in treating inherited retinal dystrophies (5, 14–16).…”

“…Delivering the CRISPR system directly into the retina of patients as a therapeutic tool is still in pursuit (5). Efficacy of such a method was examined in adult Thy1 ::YFP transgenic mice via intravitreal injections using dual AAV delivery of SpCas9 and yellow fluorescent protein (YFP)-targeting gRNA (28).…”

“…Diverse CRISPR technologies have been applied to a variety of preclinical models contributing to furthering our understanding of disease models and to approaching feasible treatment options (5, 15). One disease which has been approached with CRISPR applications in the pre-clinical setting is retinitis pigmentosa (RP).…”