Extreme value analysis of intracellular cargo transport by motor proteins
Extreme-value analysis (EVA) deals with deviations in the data from the median of the probability distributions. EVA serves various purposes such as predicting disasters and analyzing sports records. Herein, we extended the use of EVA to investigate the motility functions of nanoscale motor proteins in neurons of the living worm Caenorhabditis elegans (C. elegans). Motor proteins, such as kinesin and dynein, move along microtubules anterogradely and retrogradely, respectively, to deliver the cargo-containing materials needed for the cells. Although the essential difference between the two motors could not be inferred from the mean velocity values, the return-level EVA plots obtained from the velocity data revealed a difference. Shape parameters of the generalized extreme value distribution of EVA{xi} < 0 for anterograde transport and{xi} [≥] 0 for retrograde transport. Our findings extend the possibility and applicability of EVA for analyzing motility data of nanoscale proteins in vivo.