Vladimir Kefalov, PhD

Dr. Bernard Becker and Janet R. Becker Distinguished Professor in Ophthalmology; Vice Chair for Research

“I have often had cause to feel that my hands are cleverer than my head. That is a crude way of characterizing the dialectics of experimentation. When it is going well, it is like a quiet conversation with Nature. One asks a question and gets an answer; then one asks the next question, and gets the next answer. An experiment is a device to make Nature speak intelligibly. After that one has only to listen.”

-George Wald
(The opening lines of his Nobel Prize lecture)

George Wald was awarded the Nobel Prize in Physiology and Medicine in 1967 (the year Vladimir was born!) for his monumental contributions to our understanding of the molecular basis of photoreception. We strive to live by his wise words and to have an intelligible dialogue with Nature. Our favorite topic of conversation is the function of rod and cone photoreceptor cells. Why don’t we see colors at night? How can our rod photoreceptors achieve the theoretical limit of light sensitivity and detect a single photon of light? How can our cone photoreceptors remain functional over an astonishing range of light intensities and still faithfully detect the intricate details of the world around us and nature’s palette of colors? Why do photoreceptors degenerate and how can we prevent their death? These are the questions that we are trying to address. We use a wide range of techniques for the investigation of photoreceptor physiology, including single-cell rod and cone recordings, ex vivo whole retina recordings, in vivo electroretinogram (ERG) recordings, optokinetic behavioral tests, and genetic manipulations.

Research Interests

Education

  • MSc, in Physics, Department of Physics, Sofia University, Sofia, Bulgaria, 1993
  • PhD, in Cellular Biophysics, Department of Physiology, Boston University School of Medicine, Boston, Massachusetts, 1993-1999
    Advisor: Carter Cornwall, Ph.D., Research Topic: Physiology of the early events in visual pigment regeneration.
  • Postdoctoral Fellow, Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland, 1999-2005
    Advisor: King-Wai Yau, Ph.D., Research Topic: Origins of the functional differences between retinal rod and cone photoreceptors.

Selected Publications

  • Xue Y., Shen S.Q., Corbo J.C., Kefalov V.J. (2015) Circadian and light-driven regulation of rod dark adaptation. Sci Rep 5 doi:10.1038/srep17616
  • Xue, Y, Shen, S.Q., Jui, J, Rupp, A.C., Byrne, L.C., Hattar, S, Flannery, J.G, Corbo, J.C., Kefalov, V.J. (2015) CRALBP supports the mammalian retina visual cycle and cone vision. J Clin Invest 125:727-738.
  • Palczewska, G., Vinberg, F., Stremplewski, P., Bircher, M.P., Salom?, D., Komar, K., Zhang, J., Cascella, M.#, Wojtkowski, M.#, Kefalov, V.J.#, Palczewski, K.# (2014) Human infrared vision is triggered by two-photon chromophore isomerization. Proc Natl Acad Sci USA 111:E5445-54.
  • Wang, J.S., Nymark, S., Frederiksen, R., Estevez, M.E., Shen, S.Q., Corbo, J.C., Cornwall, M.C., Kefalov, V.J. (2014) Chromophore supply rate-limits mammalian photoreceptor dark adaptation. J Neurosci 34:11212-11221.
  • Montana, C.L., Kolesnikov, A.V., Shen, S.Q., Myers, C.A., Kefalov, V.J., Corbo, J.C. (2013) Reprogramming of adult rod photoreceptors prevents retinal degeneration. Proc Natl Acad Sci USA 110, 1732-1737.
  • Sakurai, K., Chen, J., Kefalov, V.J., (2011). Role of guanylyl cyclase modulation in mouse cone phototransduction. J Neurosci 31, 7991-8000.
  • Kolesnikov, A.V., Tang, P.H., Parker, R.O., Crouch, R.K., Kefalov, V.J., (2011). The mammalian cone visual cycle promotes M/L-cone pigment regeneration independently of the interphotoreceptor retinoid-binding protein. J Neurosci 31, 7900-7909.
  • Wang, J. and Kefalov, V.J. (2009). An alternative pathway mediates the mouse and human cone visual cycle. Current Biology 19:1665-1669.
  • Wang, J., Estevez, M.E., Cornwell, M.C., and Kefalov, V.J. (2009). Intra-retinal visual cycle required for rapid and complete cone dark adaptation. Nature Neuroscience 12:295-302. (Journal Cover)
  • Kefalov, V.J., Estevez, M. E., Kono, M., Goletz, P. W., Crouch, R. K., Cornwall, M. C., and Yau, K.-W. (2005). Breaking the covalent bond – a pigment property that contributes to desensitization in cones. Neuron 46, 879-890.
  • Kefalov*, V.J., Fu*, Y., Marsh-Armstrong, N., and Yau, K.-W. (2003). Role of visual pigment properties in rod and cone phototransduction. Nature. 425, 526-531.
  • Kefalov, V.J., Crouch, R.K., and Cornwall, M.C. (2001). Role of noncovalent binding of 11-cis-retinal to opsin in dark adaptation of rod and cone photoreceptors. Neuron 29, 749-55.

(* equal contribution; # co-corresponding author)