Identifying the Presence and Location of the PIEZO1 Channel in the Extraocular Muscles as a Possible Source of Proprioception

Abstract

The source of proprioception from the extraocular muscles (EOM) is currently unknown despite evidence of proprioceptive feedback in the brain from the EOM. The purpose of this study was to investigate the presence and location of the Piezo 1 protein in the EOM as a possible source of proprioception. Immunofluorescence microscopy was used to examine slides immunostained for Piezo 1. Furthermore, slides were stained for synaptobrevin and neurofilaments as presynaptic landmarks in the neuromuscular junction (NMJ) and nicotinic acetylcholine receptors as postsynaptic landmarks in the NMJ of the EOM of mice and rabbits to localize the Piezo 1 channel in the EOM. The Piezo 1 channel was found in the EOM of both mice and rabbits. The Piezo 1 channel was found to colocalize with synaptobrevin and neurofilaments in the EOM of mice. The Piezo 1 channel did not colocalize with nicotinic acetylcholine receptors in the EOM of mice or rabbits. This led to the hypothesis that the Piezo 1 channel resides presynaptically in the NMJ of the EOM. Due to its co-localization with synaptobrevin, the conclusion was made that the Piezo 1 channel was in a likely position to act as a local mechanosensitive proprioceptor to regulate EOM length. While this study does not uncover the mystery behind the source of proprioception in the EOM, it shows the presence and location of the Piezo 1 channel in the EOM and suggests a possible location for a local mechanosensitive proprioceptor.