Probing the role of CREB homolog, CRH-1, in innate and learned behaviours in C. elegans

Abstract

Animals display innate behaviours that are genetically hardwired and can be performed in response to a cue. Although they are stereotypic, some innate be- haviours can be modified through experience. One such behaviour is chemotaxis towards an attractant isoamyl alcohol (IAA) in Caenorhabditis elegans. C. ele- gans is a soil dwelling nematode that lives on microbes for its food source. They move forward in a sinusoidal wave pattern and their forward movement is punc- tuated by frequent stops and events of backward movement called reversals. The main strategy is to reduce the frequency of reversals when the environment be- comes more favourable. crh-1 (homolog of mammalian CREB1) null mutants have severely compromised ability to change the reversal frequency in response to the gradient of attractant IAA. This defect is also manifested as a learning de- fect in crh-1 null worms. Our experiments employ a learning paradigm where the IAA was paired to heat and show that CRH-1c and CRH-1e (2 out of 6 CRH-1 isoforms) are required for innate behaviours as well as learned. Consistent with the behavioural data, the spatial localisation of ionotropic glutamate receptor sub- unit GLR-1 was found to be defective in CRH-1c and CRH-1e deletion lines. These experiments provide important insight into mechanistic understanding of CREB1/CRH-1 transcription factor in mediating innate and learned behaviours.