Research Faculty

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

Phone: 212-342-1189
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
William Hauswirth Ph.D., University of Florida
Randal Kaufman Ph.D., Sanford Burnham
Susanne Kohl, Ph.D., University of Tübingen
Vinit Mahajan M.D., Ph.D., Iowa
Marius Ueffing, Ph.D. (Dr. rer. nat.), University of Tübingen
Nicole Weisschuh, Ph.D., (Dr.rer. nat.) University of Tübingen
Bernd Wissinger, Ph.D., University of Tübingen
Lawrence Yannuzzi MD, Vitreous-Retina-Macula Consultants
King-Wai Yau Ph.D., Johns Hopkins
Eberhart Zrenner, M.D., Dr.h.c.mult., University of Tübingen

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

Stephen Tsang, M.D., Ph.D.'s research efforts are to find new treatments for photoreceptor degeneration in retinitis pigmentosa (RP), age-related macular degeneration, (AMD) and related retinal dystrophies, the most common forms of degenerative disease in the central nervous system, which all have profound impact on quality of life. Retinal degenerative diseases affect nine million Americans, including 6.5% of Americans older than 40 years of age. Of these conditions, RP is the most devastating. RP is a common form of inherited neurodegeneration, affecting 1.5 million people worldwide, and 1 in 10 Americans carry a recessive RP allele. RP is the most common cause of inherited blindness, named for the increased pigmentation that appears in the areas of retinal cell death during late manifestation of the disease. Initial symptoms include night blindness due to the death of rod photoreceptor cells--the light-sensing neurons at the peripheral retina—which results in "tunnel vision." In later stages, RP destroys cone photoreceptor cells in the macula, responsible for fine central vision. One in ten Americans is a carrier for a defect in one of the 180 genes associated with RP. Our research has illuminated the mechanisms by which the phosphodiesterase (PDE6) signaling network regulates rod and cone survival. Defects in the PDE6 gene account for approximately 75,000 yearly cases of RP worldwide.

Gene therapy is a potential means to strengthen or restore rod viability, thereby preventing secondary cone loss. However, the first human gene-therapy trial for RP found improved visual function but did not slow degeneration of photoreceptors. The goal of this gene therapy-oriented proposal is to determine whether therapy is achievable in the context of an already diseased retina. RP resulting from cGMP phosphodiesterase-6 (PDE6) deficiency is an ideal model for studying progressive cell-autonomous degeneration of rods and subsequent, non-cell-autonomous cone loss. We are determining whether mouse rods and cones can be rescued within a clinically relevant time window – that is, after the onset of degeneration when patients are usually diagnosed. To do this, we generate a novel inducible genetic rescue system that allows us to conditionally reverse PDE6-deficiency and to control numerical, temporal and spatial aspects of phenotypic reversal. We will use this nonsurgical and robust gene therapy approach to determine if vision restoration/preservation is influenced by the timing of rod rescue, the number of rods rescued, and non-autonomous effects of mutant rods.

Furthermore, we believe that cell transplantation in the human retina has the potential to restore lost vision and provide treatment for advanced stages of retinal degeneration featuring significant photoreceptor neuronal loss, noting that a major obstacle for this approach is the ability to produce sufficient patient specific photoreceptor cells for transplantation. Adult retinal stem cells, which reside in the ciliary body of the adult human eye, are one potential source of photoreceptors. The ciliary body surrounds the lens of the eye and maintains proper pressure in the eyeball. Fish regenerate retinal neurons from a population of stem cells that are intrinsic in the ciliary body; these cells reside within the differentiated retina throughout the lifetime of the animal. The progeny of fish stem cells can divide and migratory progenitors are the antecedents of photoreceptor precursors. It is these intrinsic adult retinal stem cells that allow the fish to regenerate photoreceptor neurons spontaneously when existing neurons are killed. Stem cell transplantation therefore has the potential to restore lost vision and provide treatment for advanced stages of retinal degeneration even in cases of significant photoreceptor loss in humans.

Our research paves the way toward "retinoplasty," the reconstruction of interfaces between photoreceptors and their environment after the onset of retinal degeneration. Our approach involves the culture of human retinal stem cells from the ciliary body in eye-bank globes; we then use these cultured cells to determine the combination of transcription factors involved in regulating their proliferation and differentiation into light-sensing photoreceptor neurons. These experiments will identify the effectors regulating human retinal stem cell differentiation and proliferation, as well as testing the ability of in vitro generated stem cells to repopulate the diseased retina. Future applications may include patient-specific stem cells obtained from fine-needle aspiration of their ciliary bodies in the operating room. Based on our findings, we foresee the ability to manipulate the patients' own stem cells to cure their specific disease. This approach will solve the problem of limited supply of allograft rejection by using a patient's own cells.


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

1. 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.

2. 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.

3. 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.*

4. 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.

5. 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.*

6. 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.*

7. 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*

8. 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.*

9. 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.

10. 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

11. 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.

12. 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).*

13. Wert, K.J., Sancho-Pelluz, J., Davis, R.J., Nishina, P.M., and Tsang, S.H. Long-term Visual Function in a Pre-clinical Model of Retinitis Pigmentosa. Hum Mol Genet. (2012).*

14. Li, Y., Tsai, Y.T., Hsu, C.W., Erol, D., Yang, J., Wu, W.H., Davis, R.J., Egli, D., and Tsang, S.H. (2012). Long-term safety and efficacy of human induced pluripotent stem cell (iPS) grafts in a preclinical model of retinitis pigmentosa.Mol Med. 2012 Aug 9. doi: 10.2119*

15. 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 In Press PMID: 24101599*

Current Projects

Toward mechanism and gene based therapies for retinal degeneration. (Supported by R01)
The major goal of this project is to develop control of retinal gene expression by tamoxifen.

Functional Analyses of Embryonic Stem Cell Derived Retinal Cells (Supported by NYSTEM)
The goal of the ES cell-derived RPE graft is to prevent secondary degeneration of photoreceptor neurons. The project is focused on investigating the use of ES cell-derived RPE grafts to prevent secondary degeneration of photoreceptor neurons. In contrast, the current proposal seeks to investigate the safety and efficacy of iPS-derived RPE grafts to restore vision in mouse models of both retinal damage and retinal degeneration. The ES-derived aspect of the current proposal is merely an adjunct to the iPS-derived elements of the project.

Clinical Electrodiagnostic Module (Supported by Foundation Fighting Blindness)
The goal of this study is to assess genotype and phenotype correlations of retinitis pigmentosa and ABCA4 –retinopathies. Specifically, this study would involve studying PDE6A and PDE6B patients, and determining whether the rate of progression in these patients differs from those found in other forms of RP.

Honors and Awards

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

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

Dr. Alfred Steiner Award for Best Medical Student Research, College of Physicians and Surgeons, Columbia U.

Jules Stein Eye Institute Research Award

Research to Prevent Blindness-Association of University Professors in Ophthalmology (AUPO) Resident Award

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

The Irma T. Hirschl Trust Scholar

ARVO/Alcon Early Career Clinician Scientist Award

Dr. Isaac Bekhor Lecturer, Doheny Eye Institute at University of Southern California (Sept 29th)

Charles E. Culpeper Prize

Resident Teaching Award

Listed as one of "America's Top Ophthalmologists" by Consumers' Research Council of America Consumer Research Council

NIH-R01EY018213 awarded for five years

Elected to Macular Society

Keynote Speaker, GTCbio 2nd Annual Ocular Diseases & Drug Discovery conference (May 28, 2010)

Invited Lecturer, University of Geneva

Bradley Straastma Lecture, Resident Graduation, UCLA

ARVO Foundation Carl Camras Award

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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