Abstract
Neurotrophins (NTs) and their signal-transducing Trk receptors play a crucial role in the development and maintenance of specific neuronal subpopulations in nervous and sensory systems. NTs are supposed to regulate two sensory systems in fish, the inner ear and the lateral line system (LLS). The latter is one of the major mechanosensory systems in fish. Considering that annual fishes of the genus Nothobranchius, with their short life expectancy, have become a suitable model for aging studies and that the occurrence and distribution of neurotrophin Trk receptors have never been investigated in the inner ear and LLS of killifish (Nothobranchius guentheri), our study aimed to investigate the localization of neurotrophin-specific Trk receptors in mechanosensory systems of N. guentheri. For histological and immunohistochemical analysis, adult specimens of N. guentheri were processed using antibodies against Trk receptors and S100 protein. An intense immunoreaction for TrkA and TrkC was found in the sensory cells of the inner ear as well as in the hair cells of LLS. Moreover, also the neurons localized in the acoustic ganglia displayed a specific immunoreaction for all Trk receptors (TrkA, B, and C) analyzed. Taken together, our results demonstrate, for the first time, that neurotrophins and their specific receptors could play a pivotal role in the biology of the sensory cells of the inner ear and LLS of N. guentheri and might also be involved in the hair cells regeneration process in normal and aged conditions.
Highlights
Mechanosensory systems in fish include the inner ear and lateral line system (LLS), forming together the acusticolateral system, known as the octavolateralis system
In fish, the mechanosensory organs are under the control of the neurotrophins, a family of growth factor acting on different neuronal subpopulations in the central and peripheral nervous systems regulating neuronal proliferation, synaptic plasticity, development, survival, growth, and differentiation [1]
TrkA binds the nerve growth factor (NGF), TrkB recognizes both brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4), and TrkC interacts with neurotrophin-3 (NT- 3)
Summary
Mechanosensory systems in fish include the inner ear and lateral line system (LLS), forming together the acusticolateral system, known as the octavolateralis system. We found it interesting to investigate the presence of neurotrophins and Trk-like proteins in the inner ear and lateral line in a model for aging studies, as a fish of Nothobranchius genus.
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