Elsevier

Developmental Biology

Volume 405, Issue 2, 15 September 2015, Pages 225-236
Developmental Biology

Postnatal reduction of BDNF regulates the developmental remodeling of taste bud innervation

https://doi.org/10.1016/j.ydbio.2015.07.006Get rights and content
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Highlights

  • • BDNF expression in taste buds decreases between postnatal days 5 and 10.

  • • BDNF is reduced specifically from progenitor cells and not taste receptor cells.

  • • Innervation density in the taste bud is reduced between postnatal days 5 and 10.

  • • BDNF overexpression blocks the refinement of innervation.

Abstract

The refinement of innervation is a common developmental mechanism that serves to increase the specificity of connections following initial innervation. In the peripheral gustatory system, the extent to which innervation is refined and how refinement might be regulated is unclear. The initial innervation of taste buds is controlled by brain-derived neurotrophic factor (BDNF). Following initial innervation, taste receptor cells are added and become newly innervated. The connections between the taste receptor cells and nerve fibers are likely to be specific in order to retain peripheral coding mechanisms. Here, we explored the possibility that the down-regulation of BDNF regulates the refinement of taste bud innervation during postnatal development. An analysis of BDNF expression in BdnflacZ/+ mice and real-time reverse transcription polymerase chain reaction (RT-PCR) revealed that BDNF was down-regulated between postnatal day (P) 5 and P10. This reduction in BDNF expression was due to a loss of precursor/progenitor cells that express BDNF, while the expression of BDNF in the subpopulations of taste receptor cells did not change. Gustatory innervation, which was identified by P2X3 immunohistochemistry, was lost around the perimeter where most progenitor/precursor cells are located. In addition, the density of innervation in the taste bud was reduced between P5 and P10, because taste buds increase in size without increasing innervation. This reduction of innervation density was blocked by the overexpression of BDNF in the precursor/progenitor population of taste bud cells. Together these findings indicate that the process of BDNF restriction to a subpopulation of taste receptor cells between P5 and P10, results in a refinement of gustatory innervation. We speculate that this refinement results in an increased specificity of connections between neurons and taste receptor cells during development.

Keywords

Precursor/progenitor taste cells
Taste receptor cells
Innervation density
Fungiform taste buds
BDNF overexpression
β-galactosidase

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