Summary: A new study reports the production of a specific type of insulin receptor is required for gustatory memory during starvation in worms.
Source: University of Tokyo.
Insulin receptor in a single neuron directs behavior of worms.
Researchers at the University of Tokyo have demonstrated that production of a specific type of insulin receptor is required for gustatory memory during starvation in worms. The finding provides evidence that learning ability is influenced by functional diversity of a single gene in a single neuron.
C. elegans, a tiny roundworm that lives in soil, can remember concentrations of salts (NaCl etc.) to which it has been exposed during feeding or food deprivation and learn to approach or avoid those salt concentrations. The research group previously found that an insulin receptor, which is known to regulate blood glucose levels in humans, acts in a gustatory neuron that senses external salt concentrations in this learned behavior.
While the insulin receptor is encoded by a single gene in C. elegans, multiple types of insulin receptor are produced by switching RNA processing patterns. It was reported that a specific type of the insulin receptors, called DAF-2c, is required for the learned behavior in C. elegans. However, the detailed mechanism and the cell type that produces DAF-2c remained unclear.
Here, the research group of Assistant Professor Masahiro Tomioka and Professor Yuichi Iino at the University of Tokyo Graduate School of Science found that DAF-2c was produced only in a restricted subset of neurons, including the gustatory neuron. C. elegans has a compact nervous system, which consists of only 302 neurons, and the individual neurons play indispensable roles in behavioral and physiological functions. The research group unveiled the molecular mechanism by which the RNA processing pattern was switched and, as a result, DAF-2c was produced only in the restricted group of neurons. They further demonstrated that this mechanism underlies the learned salt avoidance under starvation conditions.
Visualization of RNA processing patterns of an insulin receptor gene in C. elegans.
“Our study unveiled a gene expression mechanism that generates neuronal properties underlying learning and memory in worms,” says Tomioka. “Similar mechanisms may underlie generation of neuronal properties required for learning and memory in higher organisms including mammals and offer future avenues for research.”
This research was carried out in collaboration with Dr. Hidehito Kuroyanagi of Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
Source: University of Tokyo
Image Source: This NeuroscienceNews.com image is credited to Masahiro Tomioka.
Video Source: The video is credited to University of Tokyo.
Original Research: Full open access research for “Splicing factors control C. elegans behavioural learning in a single neuron by producing DAF-2c receptor” by Masahiro Tomioka, Yasuki Naito, Hidehito Kuroyanagi and Yuichi Iino in Nature Communications. Published online May 20 2016 doi:10.1038/ncomms11645
Splicing factors control C. elegans behavioural learning in a single neuron by producing DAF-2c receptor
Alternative splicing generates protein diversity essential for neuronal properties. However, the precise mechanisms underlying this process and its relevance to physiological and behavioural functions are poorly understood. To address these issues, we focused on a cassette exon of the Caenorhabditis elegans insulin receptor gene daf-2, whose proper variant expression in the taste receptor neuron ASER is critical for taste-avoidance learning. We show that inclusion of daf-2 exon 11.5 is restricted to specific neuron types, including ASER, and is controlled by a combinatorial action of evolutionarily conserved alternative splicing factors, RBFOX, CELF and PTB families of proteins. Mutations of these factors cause a learning defect, and this defect is relieved by DAF-2c (exon 11.5+) isoform expression only in a single neuron ASER. Our results provide evidence that alternative splicing regulation of a single critical gene in a single critical neuron is essential for learning ability in an organism.
“Splicing factors control C. elegans behavioural learning in a single neuron by producing DAF-2c receptor” by Masahiro Tomioka, Yasuki Naito, Hidehito Kuroyanagi and Yuichi Iino in Nature Communications. Published online May 20 2016 doi:10.1038/ncomms11645