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Gene Therapy Lab

Gene therapy can modify mutations in genes or deliver an extra, healthy copy of an allele to treat inherited forms of blindness. Dr. Mahajan was a surgeon in the recent trial for gene therapy using a viral vector that successfully rescued vision loss in patients with Leber Congenital Amaurosis. The development of pre-clinical models to test gene therapy approaches for other forms of blindness, as well as testing gene therapy treatments in these pre-clinical animal models, is necessary and important to lead to clinical trials for human patients.

We are treating human patient stem cells and translational animal models with gene therapy approaches. We are also developing animal models for various inherited retinal degenerative diseases by introducing human genes or human mutations into the animals.

Pluripotent stem cells are made in the lab from patient volunteers with retinal degenerations. We then use gene editing (CRISPR) to correct the patient mutations in their own cells. Our lab was the first to correct a human blindness gene in human stem cells. These gene-corrected cells can then be used to test therapies and create transplants that replace diseased retinas.


Fixing faulty genes.
Direct modification of DNA in living cells.
Gene therapy correction in pre-clinical models of retinal disease.


Aug 11 2020 | Posted In: 20/20 Blog
Palo Alto, CA — Gene therapy has become a viable option for people with inherited eye disease, but because it is still a novel treatment, patient progress following gene therapy often relies on subjective measurements
Apr 20 2020 | Posted In: 20/20 Blog
Palo Alto, CA — Is there something to feed retinal cells that can give them the energy to withstand gene mutations that make them sick?
Oct 16 2019 | Posted In: 20/20 Blog
Palo Alto, CA — A gene therapy clinical trial for Dry Age Related Macular Degeneration (AMD) is beginning at the Byers Eye Institute under the direction of Vinit Mahajan M.D., Ph.D., associate professor and Vice Chair for Research in Ophthalm
Oct 14 2019 | Posted In: 20/20 Blog
Palo Alto, CA – Dry macular degeneration is a common eye condition that usually occurs in people over 50. It is characterized by blurring of the central vision along with a decreased ability to see colors and fine details.
Sep 16 2019 | Posted In: 20/20 Blog
Palo Alto, CA – The Molecular Surgery Program in Stanford’s Ophthalmology Department held the first Bay Area Genetic Retinal Disease Case Conference at the 


Optical Gap Biomarker in Cone-Dominant Retinal Dystrophy., Oh, Jin Kyun, Ryu Joseph, de Carvalho Jose Ronaldo Li, Levi Sarah R., Lee Winston, Tsamis Emmanouil, Greenstein Vivienne C., Mahajan Vinit B., Allikmets Rando, and Tsang Stephen H. , Am J Ophthalmol, 2020 May 20, (2020)
Fundoscopy-directed genetic testing to re-evaluate negative whole exome sequencing results., Cho, Ahra, de Carvalho Jose Ronaldo Li, Tanaka Akemi J., Jauregui Ruben, Levi Sarah R., Bassuk Alexander G., Mahajan Vinit B., and Tsang Stephen H. , Orphanet J Rare Dis, 2020 Jan 30, Volume 15, Issue 1, p.32, (2020)
Whole-Exome Sequencing of Patients with Posterior Segment Uveitis., Li, Angela S., Velez Gabriel, Darbro Benjamin, Toral Marcus A., Yang Jing, Tsang Stephen H., Ferguson Polly J., Folk James C., Bassuk Alexander G., and Mahajan Vinit B. , Am J Ophthalmol, 2020 Jul 21, (2020)
Novel REEP6 gene mutation associated with autosomal recessive retinitis pigmentosa., Y., Lin, C.L. Xu, G. Velez, J. Yang, A.J. Tanaka, M.P. Breazzano, V.B. Mahajan, J.R. Sparrow, and S.H. Tsang , Doc Ophthalmol. 2020 Feb;140(1):67-75. doi: 10.1007/s10633-019-09719-1. Epub 2019 Sep 19., (2020)
CRISPR Repair Reveals Causative Mutation in a Preclinical Model of Retinitis Pigmentosa: A Brief Methodology, Wu, Wen-Hsuan, Tsai Yi-Ting, Justus Sally, Cho Galaxy Y., Sengillo Jesse D., Xu Yu, Cabral Thiago, Lin Chyuan-Sheng, Bassuk Alexander G., Mahajan Vinit B., et al. , Retinal Gene Therapy, p.191–205, (2018)
Translation of CRISPR Genome Surgery to the Bedside for Retinal Diseases., Xu, Christine L., Cho Galaxy Y., Sengillo Jesse D., Park Karen S., Mahajan Vinit B., and Tsang Stephen H. , Front Cell Dev Biol, 2018, Volume 6, p.46, (2018)