A Single Amino Acid Mutation in SNAP-25 Induces Anxiety-Related Behavior in Mouse

Synaptosomal-associated protein of 25 kDa (SNAP-25) is a presynaptic protein essential for neurotransmitter release. Previously, we demonstrate that protein kinase C (PKC) phosphorylates Ser187 of SNAP-25, and enhances neurotransmitter release by recruiting secretory vesicles near to the plasma membrane. As PKC is abundant in the brain and SNAP-25 is essential for synaptic transmission, SNAP-25 phosphorylation is likely to play a crucial role in the central nervous system. We therefore generated a mutant mouse, substituting Ser187 of SNAP-25 with Ala using “knock-in” technology. The most striking effect of the mutation was observed in their behavior. The homozygous mutant mice froze readily in response to environmental change, and showed strong anxiety-related behavior in general activity and light and dark preference tests. In addition, the mutant mice sometimes exhibited spontaneously occurring convulsive seizures. Microdialysis measurements revealed that serotonin and dopamine release were markedly reduced in amygdala. These results clearly indicate that PKC-dependent SNAP-25 phosphorylation plays a critical role in the regulation of emotional behavior as well as the suppression of epileptic seizures, and the lack of enhancement of monoamine release is one of the possible mechanisms underlying these defects

Larval pufferfish protected by maternal tetrodotoxin

Marine pufferfish contain tetrodotoxin (TTX), an extremely potent neurotoxin. All species of the genus Takifugu accumulate TTX in the liver and ovaries, although the tissue(s) in which it is localized can differ among species. TTX is the major defense strategy the pufferfish appears to use against predators. TTX is also used as a male-attracting pheromone during spawning. Here we demonstrate an additional (and unexpected) use of maternal TTX in the early larval stages of the Takifugu pufferfish. Predation experiments demonstrated that juveniles of all the species of fish used as predators ingested pufferfish larvae, but spat them out promptly. Liquid Chromatography-Tandem Mass Spectrometry (LC-MSMS) analysis revealed that the pufferfish larvae contain a small quantity of TTX, which is not enough to be lethal to the predators. Immunohistochemical analysis with anti-TTX monoclonal antibody revealed that the TTX is primarily localized in the body surface of the larvae as a layer of protection. Our study showed the female parent of the Takifugu pufferfish vertically transfers TTX to the larvae through its accumulation in the ovaries, and subsequent localization on the body surface of the larvae