Calretinin expression in the chick brainstem auditory nuclei develops and is maintained independently of cochlear nerve input

Abstract

The expression of the calcium-binding protein calretinin (CR) in the chick brainstem auditory nuclei angularis (NA), laminaris (NL), and magnocelularis (NM) was studied during normal development and after deafening by surgical removal of the otocyst (embryonic precursor of the inner ear) or columella (middle ear ossicle). CR mRNA was localized by in situ hybridization by using a radiolabeled oligonucleotide chick CR probe. CR immunoreactivity (CR-IR) was localized on adjacent tissue sections. CR mRNA signal in the auditory nuclei was expressed at comparable levels at embryonic day (E)9 and E11 and increased thereafter to reach the highest levels in posthatch chicks. CR-IR neurons were apparent in NM and NA at E11 and in NL by E13, and CR-IR increased in all three auditory nuclei thereafter. Neither unilateral nor bilateral otocyst removal caused detectable changes in the intensity of CR mRNA expression or CR-IR in the auditory nuclei at any of the several ages examined. Similarly, columella removal at posthatching day 2 or 3 failed to significantly affect CR mRNA or CR-IR levels at 3 hours, 1 day, or 3-4 days survival times. We conclude that cochlear nerve input is not necessary for expression of either calretinin mRNA or protein and that the profound decrease in sound-evoked activity caused by columella removal does not affect the maintenance of CR expression after hatching.

Heterogeneous Calretinin Expression in the Avian Cochlear Nucleus Angularis

“…Calretinin is an EFhand calcium-binding protein whose distribution and localization have been well characterized. The rabbitderived polyclonal antibody has been used extensively to characterize the auditory pathways in mammalian and several avian species including chicken (Rogers 1989;Kubke et al 1999;Parks et al 1997;Fredrich et al 2009). The mouse monoclonal antibody was obtained by immunizing mice with recombinant human calretinin-22 k and its specificity verified by immunoblot in chickens according to the product information sheet provided by Swant.…”

“…The auditory brain stems of birds and mammals have been characterized by high expression levels of three calcium-binding proteins (CaBP): calretinin, calbindin, and parvalbumin (Braun 1990;Braun et al 1985Braun et al , 1991bCelio and Heizmann 1981;Friauf 1994;Kubke et al 1999;Lohmann and Friauf 1996;Parks et al 1997). The calcium buffering capability of these CaBPs may play a neuroprotective role against high activity levels or degeneration during hearing loss (Camp and Wijesinghe 2009;D'Orlando et al 2002;Idrizbegovic et al 2006;Parks et al 1997).…”

“…The calcium buffering capability of these CaBPs may play a neuroprotective role against high activity levels or degeneration during hearing loss (Camp and Wijesinghe 2009;D'Orlando et al 2002;Idrizbegovic et al 2006;Parks et al 1997). In the avian brain stem, neurons in the timing pathways are characterized by calretinin (CR) immunoreactivity, which also demarcates the terminal fields of these pathways in the midbrain (Takahashi et al 1987).…”

“…Calretinin immunoreactivity was found in the neuropil, presumably in the axon terminals of the eighth nerve, but was also localized to the cytoplasm of cell bodies in NA and NM (Kubke et al 1999;Parks et al 1997). Over development, progressive CR expression coincides with the tonotopic axes in NA, NM, and NL.…”

Calcium‐binding protein immunoreactivity characterizes the auditory system of Gekko gecko

“…They label neurons in the central auditory system of mammals such as rat (Lohmann and Friauf, 1996;Pór et al, 2005), guinea pig (Caicedo et al, 1996), and human (Bazwinsky et al, 2003); in birds such as chicken (Parks et al, 1997) and barn owl (Kubke et al, 1999;Takahashi et al, 1987); and in lizards (Dávila et al, 2000), turtles (Belekhova et al, 2004), and amphibians (Morona and González, 2009). We therefore used antibodies against calretinin (CR), parvalbumin (PV), and calbindin-D28k (CB), along with antibodies against glutamic acid decarboxylase (GAD) and synaptic vesicle protein 2 (SV2), to describe the gecko ascending auditory pathways.…”