Research Faculty

Edward S. Harkness Eye Institute
160 Fort Washington Avenue,
Room 513
New York, NY

Phone: 212-305-9535
Fax: 212-305-4987
Education and Training
MD, P&S 1998 and PhD. Columbia 1996
Jules Stein Eye Institute/UCLA 2003

Nikolai Artemyev Ph.D., University of Iowa
Gordon Fain Ph.D., UCLA
Criss Hartzell Ph.D., Emory
Randal Kaufman Ph.D., Sanford Burnham
Vinit Mahajan M.D., Ph.D., Iowa
Lawrence Yannuzzi MD, Vitreous-Retina-Macula Consultants

Internal Collaborations
Rando Allikmets, Ph.D. (Columbia University Medical Center)
Peter Gouras, M.D. (New York Presbyterian Hospital)
Donald Hood, Ph.D. (Columbia University)
Rudy Leibel, M.D. (Institute of Human Nutrition)
Janet Sparrow, Ph.D (Columbia University Medical Center)

Stephen Tsang, M.D. Ph.D.
Lazlo Z. Bito Associate Professor of Ophthalmology, Pathology and Cell Biology
Research Summary

Retinal degenerative diseases affect nine million Americans, including 6.5% of Americans older than 40 years of age. Other than cancer, blindness is the most feared of condition amongst Americans. Our New York State and NIH-R01EY018213 supported project investigates cell-based treatments for retinal diseases, and develops patient specific disease models relevant to drug development. The eye is an ideal testing ground for stem cell therapies because of its relative immune privilege and its ready accessibility for monitoring and imaging purposes. In the eye, various assays can be used to non-invasively quantify transplanted tissue at multiple time points. Furthermore, insight gained from the study of retinal disorders is applicable to other diseases and organ systems, thereby promoting the development of novel stem cell- and gene-based cures for a broad array of previously incurable maladies.

For example, in retinal gene therapy, the laboratory provided the preclinical feasibility data for an upcoming human trial. For cell therapy, laboratory was the first to restore visual function in mice using human induced pluripotent stem (iPS) cells – and to do so without inducing tumor formation. These achievements depended on novel preclinical models generated in the laboratory, including gene-targeted humanized mice and human iPS-derived cells – both with patient-specific mutations. The team also developed the first patient-specific model for an age-related retinal disease.

In addition to developing new therapeutics, the laboratory uses their models to study normal and disease physiology. For example, using a patient-specific cell model, they determined the function of risk factors identified by genome-wide-association studies – one of the first functional validations of GWAS. The laboratory’s genetically engineered mice provided a critical tool for studying phosphodiesterase (PDE6γ) metabolic pathways – a target in retinal degenerations. The team was the first to demonstrate in living neurons that GTPase regulation by PDE6 is rate limiting for the duration of the G-protein-coupled-receptor response, and light-induced post-translational modification of PDE6γ regulates light adaptation. Finally, the laboratory used non-invasive multi-modal imaging in patients and corresponding mouse models to identify new disease phenotypes, and correlated them with novel genes revealed by exome sequencing.


We established a stem cell line engineered to express green fluorescent protein (GFP) under control of the rod photoreceptor-specific Pde6g promoter through an internal ribosome entry site (IRES), Pde6g-IRES-GFP. The Pde6g-IRES-GFP cassette was introduced into mouse stem cells. The GFP marker is transcribed as a bicistronic message in conjunction with Pde6g. The GFP marker will only be expressed when these stem cells differentiate into rod photoreceptors (Fig. 2). Control retina is shown in the left (Fig. 1); whereas GFP marked photoreceptors are derived from stem cells found in Fig. 2. The Pde6g-IRES-GFP retinas show specific GFP marker expression in the outer nuclear layer marked by white arrows (Fig. 2).


A2E autofluorescence images (over 18 months, top to bottom) of non-exudate age-related macular degeneration, showing progressive retinal pigment epithelial (RPE) loss. Scattered, nonconfluent drusen are visible at the posterior pole, along with minor pigmentary alterations. Expanding spots of RPE loss can be seen in the area of increased autofluorescence nasal and superior to the large central spot of atrophy. A higher autofluorescence signal indicates excessive amounts of lipofuscin in the retinal sites that will continue to undergo RPE death, leading to absolute scotoma (areas of vision loss).


The human induced pluripotent stem (iPS) cells have been produced by reprogramming somatic cells (skin fibroblast) with a set of 4 transcription factors. The human iPS-cells show striking similarities in their morphological, gene expression, and functional characteristics to human ES-cells, and seem to have acquired the critical ES-cell characteristics of unlimited growth and potential to differentiate to all cell types of human body. Fibroblasts and iPS Cells. Fibroblasts taken from patient skin. (right) () Fibroblasts after treatment with OCT4, SOX2, KLF4, and cMYC. iPS colonies after SB431542 and PD0325901 selection. (left)


Retinal cells derived from human iPS (left) are morphologically similar to native human RPE cells (right).

Service Activities

Department and University Committees
2012-Present Member, Residency Selection Committee Harkness Eye Institute, Columbia
2011 Member, Review Committee for MS Program, Institute of Human
Nutrition, Columbia
2011-Present Member, Steering Committee for CME
2005-2011 Director, Basic Science Course in Ophthalmology
2005-Present Member, Basic Science Course in Ophthalmology Curriculum Committee

General Teaching Activities & Specific Courses
2005–Present Weekly Tuesday Retinal Degeneration Clinic, Columbia Ophthalmology
Consultants (3 trainees per year)
2005–Present Weekly Thursday Electrodiagnostic Clinic, NYPH
-Clinic provides consultations to Medicaid and NYPH private patients
with neuro-ophthalmic or retinal problems
2007–Present Nystagmus
-House-Staff Core Pediatrics Curriculum
2008-9 Age-Related Macular Degeneration and Macular Dystrophy Lecture, 2 hours
-Basic Science Course in Ophthalmology
2009–Present Morgan Stanley Children's Hospital Genetics Lectures Series, 4 hours
-Pediatric genetics residents attend this class yearly as a part of the Basic Science Course in Ophthalmology
2011–Present Medical Student Research Elective Coordinator (7 trainees per year)


Stem Cell Consortium
Vision Science
Selected Publications

Tsang S.H., Gouras P., Yamashita C.K., Fisher J., Farber D.B., and Goff SP (1996). Retinal Degeneration in Mice Lacking the γ subunit of cGMP phosphodiesterase. Science 272: 1026-1029.

Tsang S.H., Burns, M. E., Calvert, P. D., Gouras, P., Baylor, D. A., Goff, S. P., and
Arshavsky, V. Y. (1998). Role of the Target Enzyme in Deactivation of Photoreceptor G
Protein in Vivo. Science. 282, 117-21.

Salchow, D.J., Gouras, P., Doi, K., Goff, S.P., Schwinger, E, Tsang S.H. (1999). A point mutation (W70A) in the rod PDE6γ gene desensitizing and delaying murine Rod photoreceptors. Invest Ophthal Vis Sci 40: 3262-3267.*

Tsang S.H., Woodruff, M. L., Chen, C. K., Yamashita, C. Y., Cilluffo, M. C., Rao, A. L., Farber, D. B., and Fain, G. L. (2006). Modulation of phosphodiesterase6 turnoff during background illumination in mouse rod photoreceptors J Neurosci 26, 4472-4480.

Davis, R., Tosi, J., Janisch, K., Kasanuki, J., Wang, N.K., Kong, J., Tsui, I., Cilluffo, M., Woodruff, M., Fain, G.L., Lin C.S., Tsang S.H. (2008). Functional rescue of degenerating photoreceptors in mice homozygous for a hypomorphic cGMP phosphodiesterase 6 allele (Pde6bH620Q). Invest Ophthalmol Vis Sci. 2008 Jul 24.*

Wang N.K., Tosi J., Kasanuki J.M., Chou C.L., Kong J., Parmalee N., Wert K.J., Allikmets R., Lai C.C., Chien C.L., Nagasaki T., Lin C.S., Tsang S.H.Transplantation of reprogrammed embryonic stem cells improves visual function in a mouse model for retinitis pigmentosa. Transplantation 89, 911-919.*

Braunstein, A.L., Trief, D., Wang, N., Chang, S., and Tsang S.H. (2010). Vitamin A deficiency in New York City.Lancet. 2010 Jul 24;376(9737):267*

Tosi J, Davis RJ, Wang N, Naumann M, Lin C, Tsang S.H. shRNA knockdown of guanylate cyclase 2e or cyclic nucleotide gated channel alpha 1 increases photoreceptor survival in a cGMP phosphodiesterase mouse model of retinitis pigmentosa. J Cell Mol Med. 2010 Oct 15. doi: 10.1111/j 1582-4934.2010.01201.x.*

Tsang, S.H., Woodruff, M.L., Lin, C.S., Jacobson, B.D., Naumann, M.C., Hsu, C.W., Davis, R.J., Cilluffo, M.C., Chen, J., Fain, G.L. (2012) Effect of the ILE86TER mutation in the γ subunit of cGMP phosphodiesterase (PDE6) on rod photoreceptor signaling. Cell Signal. 24:181-188.

Tsang S.H., Woodruff ML, Hsu CW, Naumann MC, Cilluffo M, Tosi J, Lin CS. (2011) Function of the asparagine 74 residue of the inhibitory -subunit of retinal rod cGMP-phophodiesterase (PDE) in vivo. Cell Signal. 23(10), 1584-9

Sancho-Pelluz, J., Tosi, J., Hsu, C.W., Lee, F., Wolpert, K., Tabacaru, M.R., Greenberg, J.P., Tsang, S.H., Lin, C.S. (2012) Mice with a D190N mutation in the gene encoding rhodopsin: a model for human autosomal dominant Retinitis Pigmentosa Mol Med. Jan 11. doi: 10.2119/molmed.2011.00475.

Tosi, J., Sancho-Pelluz, J., Davis, R.J., Hsu, C.W., Wolpert, K.V., Sengillo, J.D., Lin, C.S., Tsang, S.H. (2011). Lentivirus-mediated expression of cDNA and shRNA slows degeneration in retinitis pigmentosa. Exp Biol Med (Maywood). 236(10), 1211-7 (2011).*

Wert KJ, Davis RJ, Sancho-Pelluz J, Nishina PM, Tsang SH. (2013) Gene therapy provides long-term visual function in a pre-clinical model of retinitis pigmentosa. Human Molecular Genetics. 22:558-567.

Davis RJ, Hsu CW, Tsai Y, Wert KJ, Sancho-Pelluz J, Lin CS, Tsang SH. (2013) Therapeutic margins in a novel preclinical model of retinitis pigmentosa. Journal of Neuroscience. 33:13475-83.

Li Y, Tsai Y-T, Hsu C-W, Erol D, Yang J, Wu W-H, Davis RJ, Egli D, Tsang SH. (2012) Long-term safety and efficacy of human induced pluripotent stem cell (iPS) grafts in a preclinical model of retinitis pigmentosa. Molecular Medicine. 18:1312-9.

Wert, K.J., Sancho-Pelluz, and Tsang, S.H. (2014). Mid-stage intervention achieves similar efficacy as conventional early-stage treatment using gene therapy in a pre-clinical model of retinitis pigmentosa Hum Mol Genet. 2014 2014 Jan 15;23(2):514-23. doi: 10.1093/hmg/ddt452. Epub 2013 Sep 18. PMID: 24101599

Yang J, Li Y, Chan L, Tsai YT, Wu WH, Nguyen HV, Hsu CW, Li X, Brown LM, Egli D, Sparrow JR, Tsang SH. (2014) Validation of genome-wide association study (GWAS)-identified disease risk alleles with patient-specific stem cell lines. Human Molecular Genetics. Jan 31. PMID: 24497574.

Li Y, Wu W-H, Hsu C-W, Nguyen H-V, Tsai Y-T, Nagasaki T, Maumenee IH, Yannuzzi LA, Hoang QV, Hua H, Egli D, Tsang SH. (2014) Gene therapy in patient-specific stem cell lines and mice with membrane frizzled-related protein defects. Molecular Therapy. (2014) 0:00

Koch SF, Tsai YT, Duong JK, Wu WH, Hsu CW, Wu WP, Bonet-Ponce L, Lin CS, TSANG SH. (2) Halting progressive neurodegeneration in advanced retinitis pigmentosa. 2015. Journal of Clinical Investigation. 2015 Sep;125(9):3704-13. doi: 10.1172/JCI82462. Epub 2015 Aug 24. PMID:26301813.

Wu WH, Tsai YT, Justus S, Lee TT, Zhang L, Lin CS, Bassuk AG, Mahajan VB, TSANG SH. CRISPR Repair Reveals Causative Mutation in a Preclinical Model of Retinitis Pigmentosa. Mol Ther. 2016 Aug;24(8):1388-94. doi: 10.1038/mt.2016.107. Epub 2016 May 20. PMID:27203441

Moshfegh Y, Velez G, Li Y, Bassuk AG, Mahajan VB, Moshfegh Y, Velez G, Li Y, Bassuk AG, Mahajan VB, TSANG SH. BESTROPHIN1 mutations cause defective chloride conductance in patient stem cell-derived RPE. Hum Mol Genet. 2016 May 18. pii: ddw126. PMID: 27193166. BESTROPHIN1 mutations cause defective chloride conductance in patient stem cell-derived RPE. Hum Mol Genet. 2016 May 18. pii: ddw126. PMID: 27193166

Zhang L, Justus S, Xu Y, Pluchenik T, Hsu CW, Yang J, Duong JK, Lin CS, Jia Y, Bassuk AG, Mahajan VB, Zhang L, Justus S, Xu Y, Pluchenik T, Hsu CW, Yang J, Duong JK, Lin CS, Jia Y, Bassuk AG, Mahajan VB, TSANG SH. Reprogramming towards anabolism impedes degeneration in a preclinical model of retinitis pigmentosa. Hum Mol Genet. 2016 Aug 11. pii: ddw256. PMID: 27516389. Reprogramming towards anabolism impedes degeneration in a preclinical model of retinitis pigmentosa. Hum Mol Genet. 2016 Aug 11. pii: ddw256. PMID: 27516389

Yang J, Bassuk AG, Merl-Pham J, Hsu CW, Colgan DF, Li X, Au KS, Zhang L, Smemo S, Justus S, Nagahama Y, Grossbach AJ, Howard MA 3rd, Kawasaki H, Feldstein NA, Dobyns WB, Northrup H, Hauck SM, Ueffing M, Mahajan VB, TSANG SH. Catenin delta-1 (CTNND1) phosphorylation controls the mesenchymal to epithelial transition in astrocytic tumors. Hum Mol Genet. 2016 Aug 11. pii: ddw253. PMID:27516388

Lijuan Zhang, Jianhai Du, Sally Justus, Chun-Wei Hsu, Luis Bonet-Ponce, Wen-Hsuan Wu, Yi-Ting Tsai, Wei-Pu Wu, Yading Jia, Jimmy K. Duong, Vinit B. Mahajan6, Chyuan-Sheng Lin, Shuang Wang, James B. Hurley, Stephen H. Tsang. Reprogramming Sirtuin 6 attenuates retinal degeneration. Journal of Clinical Investigation. 2016, 0:00

Current Projects

2008–2018 NIH-R01EY018213 (PI: Stephen Tsang)
Defining Barriers to Gene Therapy

2015-2017 R21AG050437 (Multiple-PI: Stephen Tsang)
Evaluating GWAS AMD Candidate Loci by Gene Editing in Human iPS Cells.

2015–2020 NIH-1R01EY024698-01 (PI: Stephen Tsang)
Gene Editing and Silencing in Phototransduction

2016–2020 NIH 1R01EY026682 (MPI: Stephen Tsang)
Childhood Blindness

2014-2017 New York State C029572 (PI: Stephen Tsang)
Comparative Effectiveness of Embryonic and Induced Pluripotent Stem Cell-based Therapies
Investigate the safety and efficacy of iPS-derived RPE grafts to restore vision in mouse models of both retinal damage and retinal degeneration.

2010–2016 Foundation Fighting Blindness Center C-NY05-0705-0312 (Co-PI: Stephen Tsang)
Electrodiagnostic Module.

Honors and Awards

Named Lectureships

1988 – 1989
Alpha Epsilon Delta, National Premedical Honor Society, Maryland Alpha (Historian)

Dean’s List, The Johns Hopkins University

Graduate with Departmental Honors

Recipient of Student Activities Award, The Johns Hopkins University

1989 – 1997
NIH-National Institute of General Medical Sciences Medical Scientist Training Program: MSTP fellowship PHS Grant # T32 GM 073667-14

ARVO/National Eye Institute Travel Fellowship Grant for the 1995 ARVO meeting

Dean’s Award for Excellence in Research, Graduate Sch of Arts & Sciences, Columbia U.

Dr. Alfred Steiner Award for Best Medical Student Research, Columbia U.

Best Overall Presentation at Eastern Student Research Forum sponsored by American Medical Association and the University of Miami

Travel Grant, European Students’ Conference at the Charité in Berlin

1998 - Edith McKane Award in Ophthalmology, College of Physicians and Surgeons, Columbia U.

John Lattimer Award in Urology, College of Physicians and Surgeons, Columbia U.

Jules Stein Eye Institute Research Award

RPB-Association of University Professors in Ophthalmology (AUPO) Resident Award

2001 – present
Fight for Sight/Grant-In-Aid Review Panel Member

Burroughs-Wellcome Fund Career Award in Biomedical Sciences

RPB Association of University Professors in Ophthalmology Resident Award

Nesburn Resident Award

Dennis W. Jahnigen Award, American Geriatrics Society

Becker-AUPO-RPB Award

Dr. Isaac Bekhor Lecturer, Doheny Eye Institute at University of Southern California

ARVO/Alcon Early Career Clinician Scientist Award

Charles E. Culpeper Award

Teacher Recognition Award, Columbia U.

2008 – 2009
Listed as one of “America’s Top Ophthalmologists” by Consumers’ Research Council of America

Patients' Choice Award for 2008
Elected to Macular Society

Keynote Speaker, GTCbio 2nd Annual Ocular Diseases & Drug Discovery conferen. May 28, 2010

Invited Lecturer, University of Geneva

2013 - 14
Dr. Paul Stringer Memorial Lectureship, McMaster University

Dr. Bradley Straastma Lecturer, Resident Graduation, UCLA

Elected by his peers for inclusion in Best Doctors in America®

ARVO Foundation Carl Camras Award

Foundation Fighting Blindness Visionary Award Recipient and “Banking on a Cure” Honoree

Dr. Joginder Nath Lecturer, West Virginia University School of Medicine

ARVO 2015 Annual Meeting Gene Editing Symposium Invited Speaker in Denver, Colorado

Elected to American Ophthalmological Society

Plenary lecture, Rensselaer Center for Stem Cell Research (RCSCR) - Symposium

Chair, Gene Editing/Rewriting the Genome Symposium, ASHG Annual Meeting

Elected to American Society for Clinical Investigation
Committees , Council, and Professional Society Memberships

2005–Present Member, The Harvey Society
2005–Present Member, Society for Neuroscience
1995–Present Member, ARVO
1989–Present Member, Society of Chinese Bioscientists in America
1988–Present Council Member, Association of Chinese Geneticists in America
1988–Present Member, American Society of Human Genetics (ASHG)

Federal and International Grant Review
2013 Ad Hoc Reviewer, Diseases and Pathophysiology of the Visual System Study Section, Center for Scientific Review, National Institutes of Health (NIH)
2013 Ad Hoc Reviewer, Biology of the Visual System Study Section,
Center for Scientific Review, National Institutes of Health (NIH)
2013 Reviewer, Israel Science Foundation
2012 Ad Hoc Reviewer, Biology of the Visual System Study Section,
Center for Scientific Review, National Institutes of Health (NIH)
2011 Ad Hoc Reviewer, Medical Research Council, UK
2011 Ad Hoc Reviewer, NIH Center for Scientific Review ZRG1 F05-A (20)
2009 Ad Hoc Reviewer, NIH Center for Scientific Review ZRG1 CB-N (58)

2013 Member, Diabetic Retinopathy Clinical Research Network’s Genetics Advisory Committee, National Institutes of Health (NIH)
2011 Consultant, FDA Cellular, Tissue and Gene Therapies Advisory Committee

Private -Grant Review
2012-Present Reviewer, Burroughs Wellcome Fund Career Awards for Medical Scientists Internal Selection Committee for Columbia University


Macular degenerations, Macular dystrophies, Stargardt disease, Best disease, Pattern Dystrophies, North Carolina macular dystrophy, Choroideremia, Retinitis pigmentosa, Leber congenital amaurosis, Cone dystrophies, Cone-rod dystrophies, Congenital Stationary night blindness, Bradyopsia, X-Linked Retinoschisis, Hereditary vitreoretinopathies, Refractive errors, Congenital nystagmus, Optic atrophies, Albinism, Foveal hypoplasia, Connective tissue disorders, and Inborn errors of metabolism, Stem cells, Regenerative medicine, Gene-targeting, Gene therapy, Molecular genetics

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