A phosphate transporter in VIPergic neurons of the suprachiasmatic nucleus gates locomotor activity during the light/dark transition in mice.

The suprachiasmatic nucleus (SCN) encodes time of day through changes in daily firing; however, the molecular mechanisms by which the SCN times behavior are not fully understood. To identify factors that could encode day/night differences in activity, we combine patch-clamp recordings and single-cell sequencing of individual SCN neurons in mice. We identify PiT2, a phosphate transporter, as being upregulated in a population of Vip+Nms+ SCN neurons at night. Although nocturnal and typically showing a peak of activity at lights off, mice lacking PiT2 (PiT2-/-) do not reach the activity level seen in wild-type mice during the light/dark transition. PiT2 loss leads to increased SCN neuronal firing and broad changes in SCN protein phosphorylation. PiT2-/- mice display a deficit in seasonal entrainment when moving from a simulated short summer to longer winter nights. This suggests that PiT2 is responsible for timing activity and is a driver of SCN plasticity allowing seasonal entrainment.