A simple qualitative method to detect impaired roaming behavior in C. elegans

C. elegans, as most animals, changes its behavior depending on the environment. We are characterizing mutants deficient in neurexin (nrx-1) and neuroligin (nlg-1) genes. These proteins are cell adhesion molecules present in excitatory and inhibitory synapses and they are required for correct neuron network function (Sudhof 2008). Previously we have shown that nlg-1 deficient mutants are defective in detecting osmotic strength (Calahorro et al. in press). Here we show a simple qualitative method to identify impaired roaming motion.

Description of the method:
1) Pick twenty L4 larval stage animals of each genotype from a fresh NGM plate containing OP50 E. coli and put them in the middle of a 9 cm plate containing 8 ml of agar medium (2% agar, 0,25% Tween20, 10 mM HEPES pH7,2) without bacteria.
2) Incubate the plate from 5 to 7 days at 20°C.
3) The fingerprinting of the worms is recognized by sight as a consequence of their roaming. A representative example is shown in Figure 1.

Figures

Figure 1: Roaming behavior assay. A. N2 (Bristol), wild-type strain; B. VC228 nlg-1(ok259) X; C. VC1416 nrx-1(ok1649) V; D. CRR21 nrx-1(ok1649) V; nlg-1(ok259) X. Petri’s dishes were scanned at 600-ppp resolution with an ordinary document scanner (Epson 4490 Photo) connected to an IBM-type PC. Neuroligin deficient mutants showed an increase in roaming movement compare to that of the N2 wild-type. However, the roaming behaviour of neurexin and double mutants was almost annulled. A representative experiment out of three is shown.

References

Calahorro C, Alejandre E, and Ruiz-Rubio M. (in press). Osmotic avoidance in Caenorhabditis elegans: synaptic function of two genes, orthologues of human NRXN1 and NLGN1, as candidates for autism. Journal of Visualized Experiments. http://www.jove.com/index/Details.stp?ID=1616

Sudhof TC. (2008). Neuroligins and neurexins link synaptic function to cognitive disease. Nature 455, 903-9011.