Distribution of pejvakin in human spiral ganglion: An immunohistochemical study

Abstract

Up to 10% of permanent hearing impairments in children originate from lesions in the neuronal auditory pathway. This form of auditory neuron injury called auditory neuropathy features a preservation of outer hair cell integrity but an impaired inner hair cell function and/or neuronal transmission. DFNB59 gene encodes the protein pejvakin (PJVK) and its mutations cause autosomal recessive auditory neuropathy as well as other forms of sensorineural hearing loss. The finding of distinct forms of hearing anomalies was based on studies of consanguineous families from different ethnic groups as well as studies in mice with PJVK gene mutations. In the present immunohistochemical study, the distribution of pejvakin protein in surgically obtained human cochleae was for the first time investigated. The human cochleae had normal hearing thresholds before the operation. The expression of pejvakin was located in the cell bodies of all spiral ganglion neurons rather than the nerve fibers that were labeled with Tuj 1 antibody. As Tuj 1 antibody stained the cytoplasm of Type 1 cells, pejvakin antibody labeled both type 1 and type 2 cells. The nuclei of the neurons were also PJVK-positive. No labeling was seen in the structures within the organ of Corti and the stria vascularis. In the previous study, PJVK had been detected in the hair cells, the spiral ganglion, the cochlear nuclei, the superior olivary nucleus, and the inferior colliculus in mouse. Our study demonstrated for the first time the expression of PJVK in human spiral ganglion neurons. Its functional role in neural signal propagation and synchrony needs further elucidation.

Keywords:

• Human cochlea
• Spiral ganglion
• Neuron
• Organ of Corti
• Pejvakin
• Immunohistochemistry

Acknowledgement

This study was supported by ALF grants from Uppsala University Hospital and Uppsala University and by the Foundation ‘Tysta Skolan’, the Sellander Foundation, and the Swedish Deafness Foundation (HRF). Our research is part of the European Community 6th Framework Program on Research, Technological Development, and Demonstration (Nanotechnology-based Targeted Drug Delivery; contract number: NMP-2004–3.4.1.5-1-1, project acronym: NANOEAR; NINDC[NIH] 1 R 24 DC 008625) and 7th Framework Program Nanotechnology-based Implantable and Interfaceable Devices. Project acronym: NANOCI or Nanotechnology-based Cochlear Implant with Gapless Interface to Auditory Neurons (Grant no: 281056).