Responses of neurogenesis and neuroplasticity related genes to elevated CO ₂ levels in the brain of three teleost species

Abstract

The continuous increase of anthropogenic CO in the atmosphere resulting in ocean acidification has been reported to affect brain function in some fishes. During adulthood, cell proliferation is fundamental for fish brain growth and for it to adapt in response to external stimuli, such as environmental changes. Here we report the first expression study of genes regulating neurogenesis and neuroplasticity in brains of three-spined stickleback (), cinnamon anemonefish () and spiny damselfish () exposed to elevated CO The mRNA expression levels of the neurogenic differentiation factor (NeuroD) and doublecortin (DCX) were upregulated in three-spined stickleback exposed to high-CO compared with controls, while no changes were detected in the other species. The mRNA expression levels of the proliferating cell nuclear antigen (PCNA) and the brain-derived neurotrophic factor (BDNF) remained unaffected in the high-CO exposed groups compared to the control in all three species. These results indicate a species-specific regulation of genes involved in neurogenesis in response to elevated ambient CO levels. The higher expression of NeuroD and DCX mRNA transcripts in the brain of high-CO-exposed three-spined stickleback, together with the lack of effects on mRNA levels in cinnamon anemonefish and spiny damselfish, indicate differences in coping mechanisms among fish in response to the predicted-future CO level.

Long-term exposure to near-future ocean acidification does not affect the expression of neurogenesis- and synaptic transmission-related genes in the olfactory bulb of European sea bass (Dicentrarchus labrax)

“…The lack of regulation of DCX gene expression contrasts with previous data obtained in stickleback indicating up-regulation of this gene by OA, but is in line with responses observed in cinnamon anemonefish and spiny damselfish (Lai et al 2017a). Lai et al suggested that interspecies variability in the sensitivity of DCX gene expression to OA may reflect differential physiological plasticity between fish species (Lai et al 2017a). The absence of DCX gene regulation observed in the present study may not be related to a low molecular plasticity of European sea bass brain structure with respect to acidified condition.…”

“…The PCO2 levels associated to OA that we tested (i.e. ≈590 µatm for Control condition at PH total= 7.9; ≈980 µatm at pH7.7; ≈1520 µatm at pH7.5) were higher than those used in previous studies (Lai et al 2017a;Porteus et al 2018). However, the  PCO2 of ≈500 µatm and ≈1000 µatm that we have chosen to simulate OA were similar and based on IPCC RCP6.0 and RCP8.5 scenario (Collins 2014).…”

“…Additionally to molecular actors involved in neurotransmission, other genes related to brain plasticity and neurogenesis [e.g. Doublecortin (DCX)] have also been shown to be regulated by OA (Lai et al 2017a). Such a neurogenetic effect is characteristic to fish species which, unlike mammals, have a high potential to produce new neurons in the adult central nervous system (Zupanc 2001).…”

Toward a Mechanistic Understanding of Marine Invertebrate Behavior at Elevated CO2

“…In vertebrates, GABA can act as a trophic factor (a molecule supporting cell survival) through the GABA A R, influencing cell proliferation, migration and differentiation (Owens and Kriegstein, 2002;Sernagor et al, 2010). In a fish, the three-spined stickleback Gasterosteus aculeatus, genes involved in neurogenesis and neuroplasticity were upregulated after exposure to ∼1,000 µatm pCO 2 compared to control (∼330 µatm pCO 2 ) (Lai et al, 2017). Similarly, GABA induces cellular differentiation and proliferation in abalone larvae (Morse et al, 1980).…”

Social Plasticity in the Fish Brain: Neuroscientific and Ethological Aspects

“…Further, fishes are becoming valuable models to study impacts of anthropogenic noise, pollution, and climate change on sensory and brain function (Ashur et al, 2017;Braun, 2015;Fisher and Oleksiak, 2007;Lai et al, 2017), with important consequences for management and conservation. Sensory cues play an integral role in the daily lives and survival of marine and freshwater organisms, including influences on homing, settlement, predator detection and evasion, foraging, conspecific social interactions, and reproductive interactions.…”