3 IQ domain. These trends were entirely corroborated by population analysis of multiple neurons (Figure 4A3), particularly over the 0mV–10mV range where CaV1.3 channel CDI would likely predominate (Figures S6A and S6B). In this regard, despite the contribution of other Ca2+ channel subtypes to overall current (Cloues and Sather, 2003), most of the observed RNA-editing effects on CDI could be attributed Talazoparib to CaV1.3 channels, because little CDI was observed upon pharmacological blockade of CaV1.3 channels (Figure S6C), and a comparatively high level of intracellular Ca2+ buffering was used (5 mM

EGTA) to preferentially suppress CaV2 channel CDI (Liang et al., 2003,

Soong et al., 2002 and Tadross et al., 2008). Having explicitly established effects of RNA editing on CDI within SCN neurons, we tested for potential corresponding consequences on SCN rhythmicity. Under current clamp of SCN neurons in acute slices of wild-type mice (GluR-BR/R), we observed spontaneous discharges of sodium action potentials (“Na spikes”) characteristic of this preparation (Figure 4B, top black). By contrast, SCN neurons of ADAR2 knockout mice (ADAR2−/−/GluR-BR/R) (Higuchi et al., 2000) exhibited Na spikes that fired at clearly lower frequencies (Figure 4B, bottom red; and Figure 4D), with a decreased depolarization rate preceding Na action potentials (Figure 4C). This suite of effects in the ADAR2-deficient setting is consistent with a loss of RNA editing leading to increased CaV1.3 CDI, with Bortezomib corollary diminution of CaV1.3 pacemaking current. Two important controls warrant mention. First, the “wild-type”

GluR-BR/R mice used as baseline were engineered for constitutive expression of the R-containing form of GluR-B subunits at the Q/R-editing site (Higuchi et al., 2000); hence, the alteration of Na spike activity seen upon transitioning to ADAR2 knockout animals (Figures 4B–4D) could not have arisen trivially from a loss of Q/R editing of GluR-B subunits. Second, we determined Phosphoprotein phosphatase that Q/R editing of GluR-B subunits in the SCN of non-engineered wild-type mice was complete (Figure S4B), thus excluding the possibility that engineering wild-type mice for constitutive expression of the R-form of GluR-B would, in itself, alter baseline excitability. Nonetheless, altering RNA editing of targets other than those considered thus far could still account for the rhythmicity effects up to this point. Accordingly, we analyzed the actions of ADAR2 elimination upon a persistent pattern of membrane potential oscillations that persists after application of a saturating concentration of TTX, as illustrated by the exemplar trace from a wild-type mouse (Figure 4E, upper black trace).