Developmental Changes in Peripherin-eGFP Expression in Spiral Ganglion Neurons

Abstract

The two types of spiral ganglion neurons (SGNs), types I and II, innervate inner hair cells and outer hair cells, respectively, within the mammalian cochlea and send another process back to cochlear nuclei in the hindbrain. Studying these two neuronal types has been made easier with the identification of unique molecular markers. One of these markers, peripherin, was shown using antibodies to be present in all SGNs initially but becomes specific to type II SGNs during maturation. We used mice with fluorescently labeled peripherin (Prph-eGFP) to examine peripherin expression in SGNs during development and in aged mice. Using these mice, we confirm the initial expression of Prph-eGFP in both types I and II neurons and eventual restriction to only type II perikarya shortly after birth. However, while Prph-eGFP is uniquely expressed within type II cell bodies by P8, both types I and II peripheral and central processes continue to express Prph-eGFP for some time before becoming downregulated. Only at P30 was there selective type II Prph-eGFP expression in central but not peripheral processes. By 9 months, only the type II cell bodies and more distal central processes retain Prph-eGFP expression. Our results show that Prph-eGFP is a reliable marker for type II SGN cell bodies beyond P8; however, it is not generally a suitable marker for type II processes, except for central processes beyond P30. How the changes in Prph-eGFP expression relate to subsequent protein expression remains to be explored.

ISL1 is necessary for auditory neuron development and contributes towards tonotopic organization

“…The formation of efferent intraganglionic spiral bundle was altered in Isl1CKO , indicating changes in efferent innervation in the cochlear region. Besides efferents, OHCs are innervated by the type II SGNs 86, 87 . Although the function of type II SGNs remains obscure, it is clear that these neurons are involved in auditory nociception 88 , and may also constitute the disputed sensory drive for the olivocochlear efferent reflex 89, 90 .…”

Association of cochlear outer hair cell - type II spiral ganglion afferents with protection from noise-induced hearing loss

“…Peripherin gene deletion similarly causes selective loss of small unmyelinated DRG fibres (Lariviere et al, 2002). In the mouse cochlea, peripherin is strongly biased to the unmyelinated type II SGN, over type I SGN from birth onward, and most strongly during early post-natal neurite extension and synaptic consolidation (Huang et al, 2012, Huang et al, 2007, Elliott et al, 2021. Spiral ganglion explants from the neonatal PrphKO mouse exhibit enhanced neurite outgrowth, suggesting altered response to guidance and/or stop cues (Barclay et al, 2010).…”

Age-Related Hearing Loss: Sensory and Neural Etiology and Their Interdependence

“…Two types of SGNs neurons are known, type I and type II, to innervate the inner hair cells (Petitpré et al, 2018 ; Shrestha et al, 2018 ; Sun et al, 2021 ) and the outer hair cells (Shrestha and Goodrich, 2019 ; Elliott et al, 2021a ), respectively. Innervation of the hair cells occurs in a progression, starting at E18 (Fritzsch et al, 1997 ) and finishing at about P14 (Petitpré et al, 2018 ; Shrestha and Goodrich, 2019 ).…”