Rajendra Kumar-Singh, PhD Associate Professor of Ophthalmology, Tufts University School of Medicine

Education

National University of Ireland, B.Sc, Physics and Biology

University of Dublin, Trinity College, Ireland, Ph.D, Retinitis Pigmentosa

Postdoctoral Training

University of Michigan, Ann Arbor, Adenovirus Vectors

Research Interests

Dr. Kumar-Singh is engaged in groundbreaking research in gene therapy. Specifically, his research interests are focused on development and application of gene therapy vectors for retinal diseases. Dr. Kumar-Singh is expected to lead work on important translational research opportunities within the fields of regenerative medicine and sensory neuroscience, research priorities identified in the strategic plan.

Gene therapy has already been shown to be efficacious in humans and animal models of disease. However, several important hurdles still exist to translate gene therapy from the laboratory to the clinic. These problems include vector toxicity, neoplasia and longevity of transgene expression. Dr. Kumar-Singh’s laboratory addresses each of these problems from several angles including the development of ‘gutted’ or helper-dependent adenovirus vectors that are capable of evading the immune system, pseudotyped (retargeted) adenovirus vectors that are redirected from their natural receptor (CAR, Coxsackie Adenovirus Receptor) to alternative receptors that are abundantly present on photoreceptor neurons and Adenovirus/Adeno Associated Virus hybrids that allow the normally episomal Adenovirus genome to integrate site specifically in human cells. This vector technology is used to rescue retinal degeneration in naturally occurring models of RP including the rd mouse, that has a mutation in the beta subunit of cGMP Phosphodiesterase and is the most common cause of autosomal recessive Retinitis Pigmentosa.

Dr. Kumar-Singh has recently developed a mutation independent approach to treating autosomal dominant RP (adRP) using short hairpin RNA (shRNA). A mutation- independent approach is extremely useful given that there are more than 100 different mutations present in the gene rhodopsin, any one of which can cause adRP. The difficulty of developing mutation specific therapies is hence obviated and makes it more likely to be able to economically develop therapies for adRP patients. Dr. Kumar-Singh hopes to take this technology to clinical trials in the future.

Dr. Kumar-Singh is also working on the development of shRNA’s that target Vascular Endothelial Growth Factor (VEGF) for treatment of macular degeneration. Several clinically approved therapies targeting VEGF are currently available but each one is associated with severe side effects. Dr. Kumar-Singh hopes to develop shRNA based therapies for macular degeneration that are efficacious and long lasting.

Finally, Dr. Kumar-Singh is working on the development of non-viral vector technology for gene transfer to neurons. Given that neurons are mitotically quiescent, the nuclear membrane does not dissolve and allow easy access to the nucleus. Overcoming these barriers is a key challenge for non viral gene therapy. Dr. Kumar-Singh is working on peptide mediated delivery of DNA to neurons. He believes that ultimately non viral gene transfer will be the most readily acceptable method to safely deliver genes to humans.

Representative Publications

1. Farrar, G.J., Jordan, S.A., Kenna, P., Humphries, M.M., Kumar-Singh, R., McWilliam, P., Allamand, V., Sharp, E. and Humphries, P. Autosomal dominant retinitis pigmentosa: localization of a disease gene (RP6) to the short arm of chromosome 6. Genomics 11:870-874, 1991.

2. Kumar-Singh, R., Bradley, D.G., Farrar, G.J., Lawler, M., Jordan, S.A. and Humphries, P. Autosomal dominant retinitis pigmentosa: a new multi-allelic marker (D3S621) genetically linked to the disease locus (RP4). Human Genetics 86:502-504, 1991.

3. Farrar, G.J., Kenna, P., Jordan, S.A., Kumar-Singh, R., Humphries, M.M., Sharp, E.M., Sheils, D.M. and Humphries, P. A three-base-pair deletion in the peripherin-RDS gene in one form of retinitis pigmentosa. Nature 354:478-480, 1991.

4. Kumar-Singh, R., Jordan, S.A., Farrar, G.J. and Humphries, P. Poly (T/A) polymorphism at the human retinal degeneration slow (RDS) locus. Nucleic Acids Research 19:5800, 1991.

5. Farrar, G.J., Kenna, P., Redmond, R., Shiels, D., McWilliam, P., Humphries, M.M., Sharp, E.M., Jordan, S., Kumar-Singh, R. and Humphries, P. Autosomal dominant retinitis pigmentosa: a mutation in codon 178 of the rhodopsin gene in two families of Celtic origin. Genomics 11:1170-1171, 1991.

6. Farrar, G.J., Kenna, P., Jordan, S.A., Kumar-Singh, R. and Humphries, P. A sequence polymorphism in the human peripherin/RDS gene. Nucleic Acids Research 19:6982, 1991.

7. Bleeker-Wagemakers, L.M., Gal, A., Kumar-Singh, R., Ingeborgh van den Born, L., Li, Y., Schwinger, E., Sandkuijl, L.A., Bergen, A.A., Kenna, P. and Humphries, P. Evidence for nonallelic genetic heterogeneity in autosomal recessive retinitis pigmentosa. Genomics 14:811-812, 1992.

8. Farrar, G.J., Findlay, J.B., Kumar-Singh, R., Kenna, P., Humphries, M.M., Sharpe, E. and Humphries, P. Autosomal dominant retinitis pigmentosa: a novel mutation in the rhodopsin gene in the original 3q linked family. Human Molecular Genetics 1:769-771, 1992.

9. Farrar, G.J., Kenna, P., Jordan, S.A., Kumar-Singh, R., Humphries, M.M., Sharp, E.M., Sheils, D. and Humphries, P. Autosomal dominant retinitis pigmentosa: a novel mutation at the peripherin/RDS locus in the original 6p-linked pedigree. Genomics 14:805-807, 1992.

10. Jordan, S.A., Farrar, G.J., Kumar-Singh, R., Kenna, P., Humphries, M.M., Allamand, V., Sharp, E.M. and Humphries, P. Autosomal dominant retinitis pigmentosa (adRP; RP6): cosegregation of RP6 and the peripherin-RDS locus in a late-onset family of Irish origin.American Journal of Human Genetics 50:634-639, 1992.

11. Humphries, M.M., Sheils, D.M., Jordan, S.A., Farrar, G.J., Kumar-Singh, R. and Humphries, P. Alu polymorphism in the human type I Keratin (KRT14) gene. Human Molecular Genetics 1:453, 1992.

12. Farrar, G.J., Kenna, P., Jordan, S.A., Kumar-Singh, R., Humphries, M.M., Sharp, E.M., Sheils, D. and Humphries, P. Autosomal dominant retinitis pigmentosa: a novel mutation at the peripherin/RDS locus in the original 6p-linked pedigree. Genomics 15:466, 1993.

13. Humphries, M.M., Sheils, D.M., Farrar, G.J., Kumar-Singh, R., Kenna, P.F., Mansergh, F.C., Jordan, S.A., Young, M. and Humphries, P. A mutation (Met-->Arg) in the type I keratin (K14) gene responsible for autosomal dominant epidermolysis bullosa simplex. Human Mutation 2:37-42, 1993.

14. Jordan, S.A., Farrar, G.J., Kenna, P., Humphries, M.M., Sheils, D.M., Kumar-Singh, R., Sharp, E.M., Soriano, N., Ayuso, C. and Benitez, J. Localization of an autosomal dominant retinitis pigmentosa gene to chromosome 7q . Nature Genetics 4:54-58, 1993.

15. Kumar-Singh, R., Wang, H., Humphries, P. and Farrar, G.J. Autosomal dominant retinitis pigmentosa: no evidence for nonallelic genetic heterogeneity on 3q. American Journal of Human Genetics 52:319-326, 1993.

16. Kumar-Singh, R., Farrar, G.J., Mansergh, F., Kenna, P., Bhattacharya, S., Gal, A. and Humphries, P. Exclusion of the involvement of all known retinitis pigmentosa loci in the disease present in a family of Irish origin provides evidence for a sixth autosomal dominant locus (RP8). Human Molecular Genetics 2:875-878, 1993.

17. Kumar-Singh, R. and Humphries, P. Isolation and genetic mapping of four microsatellite repeats from chromosome 3p21 using 40 CEPH pedigrees. Genomics 18:717-719, 1993.

18. Kumar-Singh, R., Kenna, P.F., Farrar, G.J. and Humphries, P. Evidence for further genetic heterogeneity in autosomal dominant retinitis pigmentosa. Genomics 15:212-215, 1993.

19. Mansergh, F.C., Jordan, S.A., Farrar, G.J., Kumar-Singh, R., Gal, A., Bhattacharya, S. and Humphries, P. Three sequence polymorphisms in the PDC gene. Human Molecular Genetics 3:2077, 1994.

20. Kumar-Singh, R., Wang, H., Carritt, B., Kruse, T.A., McCarthy, T.V., Vergnaud, G. and Humphries, P. The EUROGEM map of human chromosome 1. European Journal of  Human Genetics 2:204-205, 1994.

21. Schurmann, M., Muller, B., Duvigneau, C., Leutelt, J., Krey, S., Kumar-Singh, R., Lush, M., Swallow, D.M., Vergnaud, G. and Bakker, E. The EUROGEM map of human chromosome 3. European Journal of Human Genetics 2:208-209, 1994.

22. Terrenato, L., Jodice, C., Blasi, P., Loizedda, A., Contu, L., Buard, J., Vergnaud, G., Humphries, P., Kumar-Singh, R. and Massart, C. The EUROGEM map of human chromosome 6. European J of Human Genetics 2:214-215, 1994.

23. Mansergh, F.C., Kenna, P., Rudolph, G., Meitinger, T., Farrar, G. J., Kumar-Singh, R., Scorer, J., Hally, A.M., Mynett-Johnson, L., Humphries, M.M., Kiang, S., and Humphries, P.  Evidence for genetic heterogeneity in Best's vitelliform macular dystrophy.  Journal of Medical Genetics 32:855-858, 1995.

24. Kumar-Singh, R., and Chamberlain, J.S., Encapsidated Adenovirus Minichromosomes allow efficient delivery and expression of a 14Kb dystrophin cDNA to muscle cells  Human Molecular Genetics    5:913-921, 1996.

25. Hauser, M.A., Amalfitano A., Kumar-Singh R., Hauschka S.D., Chamberlain J.S.  Improved adenoviral vectors for gene therapy of Duchenne muscular dystrophy.  Neuromuscular Disorders 7(5):277-283, 1997

26. Kumar-Singh, R., and Farber, D.B. Encapsidated adenovirus minichromosome- mediated delivery of genes to the retina: application to the rescue of photoreceptor degeneration. Human Molecular Genetics  7(12):1893-1900, 1998.

27. Kumar-Singh, R., Tran, K., Yamashita, C. and Farber, D.B. Construction and use of encapsidated adenovirus minichromosomes (gutted vectors) for gene delivery to photoreceptors Methods in Enzymology316; 724-743,2000

28. Cashman,S., Sadowski, S., Morris D., Frederick, J., and Kumar-Singh, R.Intercellular trafficking of Adenovirus delivered HSV VP22 from the retinal pigment epithelium to the photoreceptors-implications for gene therapy. Molecular Therapy6: 813-823, 2002

29. Cashman,S., Morris, D., and Kumar-Singh, R. (2003) Evidence of protein transduction but not intercellular transport by proteins fused to HIV Tat in retinal cell culture and in vivo. Molecular Therapy 8: 130-142, 2003

30. Cashman,S., Morris, D., and Kumar-Singh, R. Adenovirus type 5 pseudotyped with adenovirus type 37 fiber uses sialic acid as a cellular receptor. Virology324: 129-39, 2004

31. Cashman, S. M., Binkley, E. A. and Kumar-Singh, R. (2005). Towards mutation-independent silencing of genes involved in retinal degeneration by RNA interference. Gene Ther12: 1223-1228.

Vision Research Laboratories

Tufts Center for Vision Research