Piezo2, a pressure sensitive channel is expressed in select neurons of the mouse brain: a putative mechanism for synchronizing neural networks by transducing intracranial pressure pulses

Abstract

Piezo2 expression in the normal, young adult mouse brain was examined using an anti-PIEZO2 Ab generated against a C-terminal fragment of the human PIEZO2 protein. As a positive control for Ab staining of mouse neurons, the Ab was shown to stain the majority (~90%) of mouse dorsal root ganglia (DRG) neurons, consistent with recent in situ hybridization and transcriptomic studies that also indicate Piezo2 gene expression in ~90% mouse DRG neurons. As a negative control and stringent test for specificity, the Ab failed to stain DRG satellite glial cells, which do not express Piezo2 but rather its paralog, Piezo1. In slices of brains isolated from the same mice as the DRG, the Ab displayed high selectivity in staining only specific neuron types, including some pyramidal neurons in the neocortex and hippocampus, Purkinje cells in the cerebellar cortex, and most notably mitral cells within the olfactory bulb. Given the demonstrated role of Piezo2 channels in peripheral neurons as a low-threshold pressure sensor (i.e., [≤] 5 mm Hg) critical for gentle touch, proprioception, and the regulation of breathing and blood pressure, its expression in select brain neurons has interesting implications. In particular, we propose that the pressure sensitive channel may provide specific brain neurons with an intrinsic resonance that acts to synchronize their firing with the normal pulsatile changes in intracranial pressure (ICP) associated with breathing and cardiac cycles. This novel mechanism could serve to increase the robustness of the respiration entrained oscillations that have been recorded in both rodent and human brains across widely distributed neuronal networks. The idea of a "global rhythm" within the brain has been mainly related to the effect of nasal airflow activating mechanosensitive neurons within the olfactory epithelium, which in turn synchronize, through direct synaptic connections, mitral neurons within the olfactory bulb and then through their projections, the activity of neural networks in other brain regions, including the hippocampus and neocortex. Our proposed, non-synaptic, intrinsic resonance mechanism for tracking pulsatile ICP changes would have the advantage that spatially separated brain networks could be globally synchronized effectively at the speed of sound.