Computation predicts rapidly adapting mechanotransduction currents cannot account for tactile encoding in Merkel cell-neurite complexes
Fig 4
Modeled response for the case of Atoh1 knockout animals.
By selectively deactivating sub-components of the generator function, IFF plots over time are generated (panel B) similar to those observed in electrophysiological recordings for Atoh1 knockout animals (panel A), in terms of attenuated temporal and spatial response compared to wildtype responses in Fig 3. Data from panel A were originally reported in Maksimovic, et. al. 2014 [3]. The two traces per plot represent two magnitudes of ramp and hold stimulation. Here, to model the Atoh1 knockout response, the SI component is removed entirely. In panel C, the current underlying the low magnitude stimulation case is shown in “Atoh1 CKO (USI and RI) Low stim.” As previously noted in panels C and G of Fig 3, an alternate approach to utilizing a USI term is to extend the duration of the SI term’s time constant. Aside from physiological feasibility, when the SI time constant is increased and USI not utilized, then the Atoh1CKO response—made up of USI and RI components—would revert to only an RI component (normalized to the magnitude of the USI and RI case) and its rate of decay does not match the Atoh1CKO current, panel C: “Atoh1 CKO (RI only, normalized).” In comparison to the electrophysiological recordings in panel A, its current decays to 0 IFF (where each line in panel C crosses the “approx. threshold for spike generation”) in 0.25 s whereas the IFF continues for 1–2 s in observed recordings. In fact, when the “Atoh1 CKO (RI only, normalized)” current is run through the full model, it produces just one spike.