BDNF, Brain, and Regeneration: Insights from Zebrafish

Abstract

Zebrafish (Danio rerio) is a teleost fish widely accepted as a model organism for neuroscientific studies. The adults show common basic vertebrate brain structures, together with similar key neuroanatomical and neurochemical pathways of relevance to human diseases. However, the brain of adult zebrafish possesses, differently from mammals, intense neurogenic activity, which can be correlated with high regenerative properties. Brain derived neurotrophic factor (BDNF), a member of the neurotrophin family, has multiple roles in the brain, due also to the existence of several biologically active isoforms, that interact with different types of receptors. BDNF is well conserved in the vertebrate evolution, with the primary amino acid sequences of zebrafish and human BDNF being 91% identical. Here, we review the available literature regarding BDNF in the vertebrate brain and the potential involvement of BDNF in telencephalic regeneration after injury, with particular emphasis to the zebrafish. Finally, we highlight the potential of the zebrafish brain as a valuable model to add new insights on future BDNF studies.

Keywords: Fish; Trk B; neuroregeneration; neurotrophins; p75.

Figure 1

Brain derived neurotrophic factor (BDNF) mRNA distribution in sagittal and cross sections of the zebrafish brain. Cells containing BDNF mRNA (red dots) are mature neurons. In several areas, they are close to radial glial (black dots) and proliferating (green dots) cells and Hu positive (azure dots) young neurons. Abbreviations: CCe: Cerebellar body; D: Dorsal telencephalon; Dc: Central area of dorsal telencephalon; Dm: Medial area dorsal telencephalon; Dp: Posterior area of dorsal telencephalon; Ha: Abenula; Hd: Dorsal zone of periventricular hypothalamus; Hv: Ventral zone of periventricular hypothalamus; OB: Olfactory bulb; PPa: Anterior part of parvocellular preoptic nucleus; PTN: Posterior tuberal nucleus; SRF/IMRF: Superior/intermediate reticular formation; TeO: Optic tect; Vd: Dorsal nucleus of ventral telencephalic area; Vv: Ventral nucleus of ventral telencephalic area.

Figure 2

BDNF mRNA distribution in cross sections of the zebrafish telencephalon after injury. Cells containing BDNF mRNA (red dots) are young (Hu positive, azure dots) and mature (Acetylated-Tubulin, blue dots) neurons. In several areas, they resulted close to proliferating cells (green dots). Abbreviations: CC: Cerebellar body; Dc: Central area of dorsal telencephalon; Dm: Medial area of dorsal telencephalon; Dp: Posterior area of dorsal telencephalon; Mo: Medulla oblongata; OB: Olfactory bulb; Tel: Telencephalon; TeO: Optic tect: Vd: Dorsal nucleus of ventral telencephalic area; Vv: Ventral nucleus of ventral telencephalic area.