Glial cell line-derived neurotrophic factor expression in the brain of adult zebrafish (Danio rerio)

In mammals, glial cell line-derived neurotrophic factor (GDNF) is a growth factor of many neuronal populations in the central, peripheral and autonomous nervous system. GDNF may also function as a morphogen during kidney development and may regulate spermatogonial differentiation. GDNF has been characterised in zebrafish embryos and was demonstrated experimentally to be critical for the development of the enteric nervous system. However, in adult zebrafish, no data exist regarding GDNF expression and localisation in the brain and in different organs. Thus, the aim of the present study was to investigate the expression of GDNF in the brain of adult zebrafish (Danio rerio). Transcripts of GDNF mRNA were observed in brain extracts by a standard RT-PCR. The presence of the protein in the brain homogenates was confirmed by SDS-PAGE electrophoresis and Western blotting analysis. Immunohistochemistry and in situ hybridization experiments showed that GDNF protein and mRNA were localised in various nuclei of the telencephalon, diencephalon, mesencephalon, cerebellum and medulla oblongata of the zebrafish brain. In conclusion, this study showed that the expression of GDNF was not restricted to developmental periods but it seems that this factor might be involved in adult zebrafish brain physiology, as observed in mammals.