Yudowski, G. | bioRxiv Science

bioRxiv2020

Cnr2 is important for Ribbon Synapse Maturation and Function in Hair Cells and Photoreceptors

The role of the cannabinoid receptor 2 (CNR2) is still poorly described in sensory epithelia. We found strong cnr2 expression in hair cells (HCs) of the inner ear and the lateral line (LL), a superficial sensory structure in fish. Next, we demonstrated that sensory synapses in HCs were severely perturbed in zebrafish larvae lacking cnr2. Appearance and distribution of presynaptic ribbons and calcium channels (Cav1.3) were profoundly altered in mutant animals. Clustering of membrane-associated guanylate kinase (MAGUK) in post-synaptic densities (PSDs) was also heavily affected, suggesting a role for cnr2 for maintaining the structure of the sensory synapse. Furthermore, vesicular trafficking in HCs was strongly perturbed suggesting a retrograde action of the endocannabinoid system (ECs) mediated via cnr2 that was modulating HC mechanotransduction. We found similar perturbations in retinal ribbon synapses. Finally, we showed that larval swimming behaviors after sound and light stimulations were significantly different in mutant animals. Thus, we propose that cnr2 is critical for the processing of sensory information in the developing larva.

neuroscience↗

bioRxiv2018

Mitigation of coral bleaching by antioxidants

Coral bleaching, loss of symbiotic dinoflagellate algae from the coral holobiont, is a complex phenomenon that can result in coral death and reef degradation. Reactive oxygen species (ROS) have been suggested as a possible mechanism underlying this event. To determine if antioxidants can be used to reduce ROS production and coral bleaching, we tested the effects of thermal stress in Aiptasia pallida a model system for coral bleaching studies, and the scleractinian coral, Porites astreoides. We analyzed host ROS levels, symbiont dark-adapted quantum yield of photosystem II, and symbiont loss in the presence or absence of antioxidants. We found that a single dose of the antioxidant catechin, significantly reduced ROS levels in the hosts, mitigated the degradation of the symbionts quantum yield and reduced the loss of symbionts from thermally stressed P. astreoides but not from A. pallida. Taken together, these results support a key role of ROS and that antioxidants can prevent symbiont degradation and loss during thermally-induced bleaching in P. astreoides.

ecology↗