Experience-Dependent Behavioral Plasticity in Avoiding Epigallocatechin Gallate (EGCG) Requires DAF-16/FOXO in the AIY Interneurons of Caenorhabditis elegans.

Bitterness and astringency are the aversive tastes in mammals. In humans, aversion to bitterness and astringency may be reduced depending on the eating experience. However, the cellular and molecular mechanisms underlying plasticity in preference to bitter and astringent tastants remain unknown. This study aimed to investigate the preference plasticity to bitter and astringent tea polyphenols, including catechins and tannic acids, in the model animal Caenorhabditis elegans. C. elegans showed avoidance behavior against epigallocatechin gallate (EGCG), tannic acid, and theaflavin. However, they displayed diminishing avoidance against EGCG depending on their EGCG-feeding regime at larval stages. Additionally, the behavioral plasticity in avoiding EGCG required the transcription factor DAF-16/FOXO. Isoform-specific deletion mutant analysis and cell-specific rescue analysis revealed that the function of daf-16 isoform b in AIY interneurons is necessary for experience-dependent behavioral plasticity to EGCG.

An ALS-associated KIF5A mutant forms oligomers and aggregates and induces neuronal toxicity.

KIF5A is a kinesin superfamily motor protein that transports various cargos in neurons. Mutations in Kif5a cause familial amyotrophic lateral sclerosis (ALS). These ALS mutations are in the intron of Kif5a and induce mis-splicing of KIF5A mRNA, leading to splicing out of exon 27, which in human KIF5A encodes the cargo-binding tail domain of KIF5A. Therefore, it has been suggested that ALS is caused by loss of function of KIF5A. However, the precise mechanisms regarding how mutations in KIF5A cause ALS remain unclear. Here, we show that an ALS-associated mutant of KIF5A, KIF5A(Δexon27), is predisposed to form oligomers and aggregates in cultured mouse cell lines. Interestingly, purified KIF5A(Δexon27) oligomers showed more active movement on microtubules than wild-type KIF5A in vitro. Purified KIF5A(∆exon27) was prone to form aggregates in vitro. Moreover, KIF5A(Δexon27)-expressing Caenorhabditis elegans neurons showed morphological defects. These data collectively suggest that ALS-associated mutations of KIF5A are toxic gain-of-function mutations rather than simple loss-of-function mutations.