Heterogeneous Calretinin Expression in the Avian Cochlear Nucleus Angularis

Research Article

DOI: 10.1007/s10162-014-0453-0

Cite this article as:
Bloom, S., Williams, A. & MacLeod, K.M. JARO (2014) 15: 603. doi:10.1007/s10162-014-0453-0

Abstract

Multiple calcium-binding proteins (CaBPs) are expressed at high levels and in complementary patterns in the auditory pathways of birds, mammals, and other vertebrates, but whether specific members of the CaBP family can be used to identify neuronal subpopulations is unclear. We used double immunofluorescence labeling of calretinin (CR) in combination with neuronal markers to investigate the distribution of CR-expressing neurons in brainstem sections of the cochlear nucleus in the chicken (Gallus gallus domesticus). While CR was homogeneously expressed in cochlear nucleus magnocellularis, CR expression was highly heterogeneous in cochlear nucleus angularis (NA), a nucleus with diverse cell types analogous in function to neurons in the mammalian ventral cochlear nucleus. To quantify the distribution of CR in the total NA cell population, we used antibodies against neuronal nuclear protein (NeuN), a postmitotic neuron-specific nuclear marker. In NA neurons, NeuN label was variably localized to the cell nucleus and the cytoplasm, and the intensity of NeuN immunoreactivity was inversely correlated with the intensity of CR immunoreactivity. The percentage of CR + neurons in NA increased from 31 % in embryonic (E)17/18 chicks, to 44 % around hatching (E21), to 51 % in postnatal day (P) 8 chicks. By P8, the distribution of CR + neurons was uniform, both rostrocaudal and in the tonotopic (dorsoventral) axis. Immunoreactivity for the voltage-gated potassium ion channel Kv1.1, used as a marker for physiological type, showed broad and heterogeneous postsynaptic expression in NA, but did not correlate with CR expression. These results suggest that CR may define a subpopulation of neurons within nucleus angularis.

Keywords

calretinin NeuN cochlear nucleus avian calcium binding protein Kv1.1 potassium channel 

Abbreviations

NA

Nucleus angularis

NM

Nucleus magnocellularis

NL

Nucleus laminaris

CR

Calretinin

PV

Parvalbumin

CaBP

Calcium-binding protein

NeuN

Neuronal nuclear protein

MAP2

Microtubule-associated protein 2

IC

Inferior colliculus

ICc

Central nucleus of the inferior colliculus

MLd

Nucleus mesencephalicus lateralis pars dorsalis (IC)

ITD

Interaural time difference

ILD

Interaural level difference

E

Embryonic (day)

P

Postnatal (day)

Supplementary material

10162_2014_453_MOESM1_ESM.mpg (3.2 mb)
Supplemental Video(MPG 3296 kb)

Copyright information

© Association for Research in Otolaryngology 2014

Authors and Affiliations

  1. 1.Department of BiologyUniversity of MarylandCollege ParkUSA
  2. 2.Neuroscience and Cognitive Science ProgramUniversity of MarylandCollege ParkUSA
  3. 3.Center for the Comparative and Evolutionary Biology of HearingUniversity of MarylandCollege ParkUSA

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