Meghan Raykoff
Research Mentor(s): Elise Savier
Mentor Department: Molecular & Integrative Physiology
Authors: Meghan Raykoff, Abdullah Masri, Elise Savier
Session: Session 2 (10:00am – 10:50am)
Presentation Type: Poster 88
Abstract
The extraocular muscles (EOM), located in the eye socket, are essential for moving the eyes. Palisade endings are specialized nerve terminals in which the axon ending takes a 180º turn, found in the myotendinous junction of some mammalian species’ EOM. In these species, they appear to an extent to replace EOM Golgi tendon organs and muscle spindles, two types of proprioceptive nerves found in the EOM of even-toed ungulates and elsewhere in the bodies of various species, which implies a sensory function (Blumer et al. 2016). However, in previous experiments palisade endings have been shown to be associated with choline acetyltransferase, an enzyme which helps produce acetylcholine to send signals to muscle fibers, implying a motor function. Hence, whether their function is primarily motor or sensory is not yet understood (Zimmermann et al. 2013). In addition, the presence of palisade endings in tree shrews has not yet been investigated; tree shrews are evolutionarily closely related to primates, which have palisade endings (Fuchs 2024) (Blumer et al. 2016). To search for the presence of palisade endings in tree shrews, immunostaining of synaptic markers, nerve fibers and muscle fibers was performed on the distal region of tree shrew EOM. These experiments will be followed by immunostaining for cholinergic transmission (motor markers, VAChT and ChAT) and mechanoreceptors (PIEZO2). Motor markers would suggest that palisade endings are involved in signaling to the EOM to move the eyes, while a high expression of PIEZO2 proteins associated with the palisade endings would indicate that palisade endings have a sensory function and send signals to the brain about EOM strain. More conclusive research about the function of these nerve endings is crucial to fully understanding how EOM in mammalian species move the eyes and send signals to the brain, and a more thorough understanding of human EOM can aid in the long-term in developing treatments for disorders of the EOM and eye movement.
