Figure 9. Loss of both NCKX2 and NCKX4 expressions severely compromises cone function.

Representative light responses recorded from isolated retinas of Nckx4^+/+ Cre⁺ (a), Nckx4^f/f Cre⁺ (b) and Nckx2^-/- Nckx4^f/f Cre⁺ (c) mice using ex vivo ERG method. Light flashes ranged from 390 to 460,000 photons (505 nm) μm⁻² in (a) and (b), and from 4000 to 1.4 * 10⁶ photons (505 nm) μm⁻². (d) Population averaged (mean ± SEM) responses to a dim flash normalized with Q (in photons μm⁻²) and maximal response amplitude (R_max) recorded from Nckx4^+/+ Cre⁺ control (black, N = 5 retinas from four mice), Nckx4^f/f Cre⁺ (red, N = 8 retinas from four mice) and Nckx2^-/- Nckx4^f/f Cre⁺ (blue, N = 4 retinas from three mice) retinas. The response from Nckx2^-/- Nckx4^f/f Cre⁺ mice shown in (d) is scaled up by 25-fold to facilitate comparison of response kinetics between the genotypes. The inset shows fractional dim flash responses of control (WT) and Nckx2^-/- cones modified from (Sakurai et al., 2016). (e) Normalized population averaged response amplitudes (R/Rmax) are plotted as a function of flash strength in photons μm⁻² for Nckx4^+/+ Cre⁺ control (black, N = 5), Nckx4^f/f Cre⁺ (red, N = 8), and Nckx2^-/- Nckx4^f/f Cre⁺ (blue, N = 4) mouse retinas. Smooth traces plot Eq. 3 with Q_1/2 = 5200 photons μm⁻² and 3900 photons μm⁻² for control (black) and Nckx4^f/f Cre⁺ (red) retinas, respectively. (f) Light adaptation persists in the cones from Nckx2^-/- Nckx4^f/f Cre⁺ mice. Representative response to a bright step of 530 nm light (I = 38,600,000 photons μm⁻² s⁻¹) recorded from Nckx2^-/- Nckx4f^/f Cre⁺ mouse retina. Light step timing is indicated on the bottom of the graph.

DOI: http://dx.doi.org/10.7554/eLife.24550.012