Erratum for Woodruff et al., Modulation of Phosphodiesterase6 Turnoff during Background Illumination in Mouse Rod Photoreceptors

Correction for the article “Modulation of Phosphodiesterase6 Turnoff during Background Illumination in Mouse Rod Photoreceptors” by Michael L. Woodruff, Kerstin M. Janisch, Igor V. Peshenko, Alexander M. Dizhoor, Stephen H. Tsang, and Gordon L. Fain, which appeared on pages 2064–2074 of the February 27, 2008 issue.

According to the authors, “It has come to our attention that some of the animals used in Figure 10 of our paper were misidentified and did not contain the PDEγ T35A mutation but rather a different mutation of the PDEγ protein lacking both isoleucine 86 and isoleucine 87 at the C terminus. This confusion initially escaped our attention, because the physiology of the rod with this double-isoleucine deletion is nearly identical to that of rods from the T35A line we used for most of our experiments. We give below a new Figure 10, containing only data from T35A animals. The results are nearly identical to those in our paper; the time constant of recovery of T_sat after a bright flash was 76 s instead of the value of 67 s we initially reported. It is also possible that many or all of the animals used in Figure 4 of our paper contained this double-isoleucine deletion of PDEγ rather than the T35A mutation. It is unfortunately not possible for us to repeat these experiments with T35A animals, because the line of animals we used for the bulk of our experiments was inadvertently destroyed, and efforts to remake this line have thus far been unsuccessful.

Figure 10.

Each of nine dark-adapted T35A rods were stimulated with 20 ms flashes at a saturating intensity of 450 photons μm⁻². Each rod was then exposed to a saturating constant light of 2830 photons μm⁻² s⁻¹ for 3 min. When the constant light was extinguished, 20 ms flashes of 450 photons μm⁻² were resumed at 5–8 s after termination of the 3 min exposure and continued approximately each 10 s for a period of 3 min. The black trace is the mean of the dark-adapted responses from the nine T35A mouse rods normalized individually to their maximum amplitude. The red, blue, green, and pink traces are from these same rods at 5–8 s, 10–13 s, 15–18 s, and 50–53 s after the constant light was terminated. T_sat was obtained from the time of recovery of the response to 25% of the dark current (horizontal dashed line). The inset gives T_sat after exposure to 3 min illumination (triangles) normalized to its value in darkness (square) as a function of time after presentation of the 3 min exposure. The triangles have been fitted with a single exponential with a time constant of 76 s.

“We have recently redone all of the experiments of our paper on the PDEγ double-isoleucine animals, and we will describe these results in a future publication. These experiments strongly support the contention of our work, that mutations in the PDEγ molecule can nearly eliminate modulation of the declining phase of the light response in background light, and that modulation of GAP function plays an important role in rod light adaptation.”