Brain Proteome and Behavioural Analysis in Wild Type, BDNF+/− and BDNF−/− Adult Zebrafish (Danio rerio) Exposed to Two Different Temperatures

Abstract

Experimental evidence suggests that environmental stress conditions can alter the expression of BDNF and that the expression of this neurotrophin influences behavioural responses in mammalian models. It has been recently demonstrated that exposure to 34 °C for 21 days alters the brain proteome and behaviour in zebrafish. The aim of this work was to investigate the role of BDNF in the nervous system of adult zebrafish under control and heat treatment conditions. For this purpose, zebrafish from three different genotypes (wild type, heterozygous BDNF+/− and knock out BDNF−/−) were kept for 21 days at 26 °C or 34 °C and then euthanized for brain molecular analyses or subjected to behavioural tests (Y-maze test, novel tank test, light and dark test, social preference test, mirror biting test) for assessing behavioural aspects such as boldness, anxiety, social preference, aggressive behaviour, interest for the novel environment and exploration. qRT-PCR analysis showed the reduction of gene expression of BDNF and its receptors after heat treatment in wild type zebrafish. Moreover, proteomic analysis and behavioural tests showed genotype- and temperature-dependent effects on brain proteome and behavioural responding. Overall, the absent expression of BDNF in KO alters (1) the brain proteome by reducing the expression of proteins involved in synapse functioning and neurotransmitter-mediated transduction; (2) the behaviour, which can be interpreted as bolder and less anxious and (3) the cellular and behavioural response to thermal treatment.

Temperature- and chemical-induced neurotoxicity in zebrafish

“…The transcriptome analysis of KO larvae have unveiled altered gene expression patterns related to nervous system development, cell morphogenesis, axon and dendrite development, neurotransmitter transport and secretion, as well as synaptic organisation ( D'Agostino et al, 2022 ). Further examination of the cerebral proteome in adult KO zebrafish has confirmed significant alteration in protein expression profiles attributable to neurotoxicity ( Maffioli et al, 2022 ). These results point to reduced expression of protein networks associated with neuronal development and morphology.…”

“…The available evidence strongly indicates that BDNF functions are conserved between zebrafish and mammals ( Cacialli et al, 2016 ), underscoring zebrafish’s suitability as model for studying BDNF. While most information regarding BDNF comes from mammalian studies, the last 15 years have witnessed a growing number of BDNF investigations conducted in zebrafish ( Lucini et al, 2018 ; Aragona et al, 2022 ), leading to the creation of mutant BDNF −/− zebrafish ( D'Agostino et al, 2022 ; Maffioli et al, 2022 ).…”

“…These results point to reduced expression of protein networks associated with neuronal development and morphology. Additionally, the diminished expression of proteins involved in the ubiquitin proteasome pathway suggests compromised proteostasis capacity ( Maffioli et al, 2022 ).…”

“…Proteomic analysis has also revealed that the absence of BDNF strongly impacts neurotransmission, leading to reduced expression of proteins within signalling pathways for several neurotransmitter systems, including histaminergic, GABAergic, dopaminergic, adrenergic, serotonergic, cholinergic, glutamatergic pathways. Furthermore, a decrease in FGF and EGF signalling pathways has been observed ( Maffioli et al, 2022 ). Notable among the downregulated proteins in KO zebrafish are abat (4-Aminobutyrate Aminotransferase), c3a .…”

“…It is also a valuable resource in behavioural neuroscience ( Gerlai, 2023 ), with numerous behavioural tests that can be applied depending on the developmental stage. Some of these tests for adult zebrafish include the novel tank diving, light and dark preference, social preference, mirror biting, and Y-Maze, validated for studying anxiety-like and boldness behaviour, social preference, aggressiveness, and explorative behaviour ( Toni et al, 2019a ; Angiulli et al, 2020 ; Fasano et al, 2021 ; Nonnis et al, 2021 ; Maffioli et al, 2022 ).…”