Statistical analysis of the velocity distributions of peroxisomes transported by molecular motors in Drosophila melanogaster S2 cells

DE ROSSI MC - WETZLER D - LEVI V; BRUNO L - SUED M ; D. RODRIGUEZ; DE ROSSI ME4

Buenos Aires

Conferencia; . Workshop Internacional Programa Raíces (MINCyT):"La matemática como herramienta para entender la biología / la biología como fuente de problemas matemáticos",; 2015

Cell survival and maintenance of several biological functions depend on an effective intracellular transport. Molecular motors transport a wide variety of cellular cargoes positioning them in the cytoplasm with high spatial?temporal precision. These proteins bind to specific cargoes and step along cytoskeletal filaments using energy provided by ATP hydrolysis. In particular, bidirectional transport along microtubules is driven by kinesin and dynein motors, which transport cargoes toward the plus and minus end of microtubule, respectively. The overall direction of motion results from the cooperation and/or competition between these opposed-polarity motors. In this work, we explored the transport of fluorescent peroxisomes in Drosophila S2 cells by using a fast-tracking routine. Since the distribution of the organelles velocities has been described to get insight into the population of motors driving transport, we proposed to determine the trajectories of peroxisomes and computed the segmental velocity for each opposite polarity motors. As those distributions presented multiple peaks, we proposed to develop a statistical method of analysis that explained the distribution of velocities as a mixture of normal populations of motors. Based on the density profile of distributions, we determined the best statistical model of a mixture of Gaussian functions that explained the experimental data following the Akaike information criterion (AIC). The model that exhibit the minimum value of AIC was used to establish the optimal parameters of each normal population which were further introduced into a bootstrap routine to compute the mean values of them with the respective confidence intervals. The results show that at least three populations of both motors, dynein and kinesin-1, transport the peroxisomes inside the cell. When we also compared the velocities obtained for wild type cells with those computed for cells expressing the slow kinesin Eg5, we observed that Eg5 only reduced the velocities of plus end directed peroxisomes indicating that this motor acts as an anchor to kinesin-1, reducing the forward stepping frequency.