North Shore Hebrew Academy High School
Great Neck, NY
Teacher: Lisa Runco
Retinitis pigmentosa (RP) is a degenerative retinal disease that affects approximately 1.5 million people worldwide (Churchill et al., 2013). RP patients gradually lose vision as rod and cone photoreceptors in the eyes deteriorate (Natarajan, 2011). Symptoms generally begin with night blindness, followed by constriction of visual fields, causing tunnel vision and ultimately complete vision loss in some patients (Ferrari et al., 2011)…
One of the most severe forms of RP is X-linked recessive (XLRP), which affects 10-15% of RP patients (Ferrari et al., 2011). XLRP primarily impacts men and symptoms typically begin in adolescence. Genetic mapping of XLRP has identified six loci with genetic defects: RP2, RP3, RP6, RP23, RP24, and RP34 (Beltran et al., 2015). Over 70% of XLRP cases have mutations in RP3, which affects the retinitis pigmentosa GTPase regulator (RPGR) gene (Murga-Zamalloa et al., 2010)…
…Gene supplementation therapy introduces healthy genes to replace defective or absent ones through delivery in a genetically engineered vector, such as a virus (Collins et al., 2015). Research on canine models with XLRP found that introduction of adeno-associated virus 2/5–vectored human RPGR via injection into the subretinal region caused the function of both rods and cones to improve (Beltran et al., 2011). This demonstrated the promise of gene therapy in treating XLRP
The CRISPR technology was recently used by Bassuk et al. to repair the RPGR point mutation that causes XLRP. XLRP patients with RPGR mutations underwent skin biopsies to remove fibroblasts, which were converted into induced pluripotent stem cells (iPSCs). The iPSCs contained the harmful RPGR genetic mutation, so CRISPR-Cas9 was used to repair the point mutation. CRISPR gRNAs were programmed to target the mutation in the ORF15 region of RPGR, enabling Cas9 to cleave the DNA. Then, homology-directed repair (HDR) was used to correct the mutation and reconnect the cut DNA, resulting in a iPSCs that contain a healthy RPGR gene (Bassuk et al., 2016). Researchers intend to further this work by differentiating the corrected iPSCs into retinal cells for autologous transplantation into XLRP patients, which may treat their disease. This exciting research will hopefully succeed, enabling people with XLRP to no longer suffer vision loss.