Model based dynamics analysis in live cell microtubule images

Background

The dynamic growing and shortening behaviors of microtubules are central to the fundamental roles played by microtubules in essentially all eukaryotic cells. Traditionally, microtubule behavior is quantified by manually tracking individual microtubules in time-lapse images under various experimental conditions. Manual analysis is laborious, approximate, and often offers limited analytical capability in extracting potentially valuable information from the data.

Results

In this work, we present computer vision and machine-learning based methods for extracting novel dynamics information from time-lapse images. Using actual microtubule data, we estimate statistical models of microtubule behavior that are highly effective in identifying common and distinct characteristics of microtubule dynamic behavior.

Conclusion

Computational methods provide powerful analytical capabilities in addition to traditional analysis methods for studying microtubule dynamic behavior. Novel capabilities, such as building and querying microtubule image databases, are introduced to quantify and analyze microtubule dynamic behavior.

     

Motor Dynamics Underlying Cargo Transport by Pairs of Kinesin-1 and Kinesin-3 Motors

Intracellular cargo transport by kinesin family motor proteins is crucial for many cellular processes, particularly vesicle transport in axons and dendrites. In a number of cases, the transport of specific cargo is carried out by two classes of kinesins that move at different speeds and thus compete during transport. Despite advances in single-molecule characterization and modeling approaches, many questions remain regarding the effect of intermotor tension on motor attachment/reattachment rates during cooperative multimotor transport. To understand the motor dynamics underlying multimotor transport, we analyzed the complexes of kinesin-1 and kinesin-3 motors attached through protein scaffolds moving on immobilized microtubules in vitro. To interpret the observed behavior, simulations were carried out using a model that incorporated motor stepping, attachment/detachment rates, and intermotor force generation. In single-molecule experiments, isolated kinesin-3 motors moved twofold faster and had threefold higher landing rates than kinesin-1. When the positively charged loop 12 of kinesin-3 was swapped with that of kinesin-1, the landing rates reversed, indicating that this “K-loop” is a key determinant of the motor reattachment rate. In contrast, swapping loop 12 had negligible effects on motor velocities. Two-motor complexes containing one kinesin-1 and one kinesin-3 moved at different speeds depending on the identity of their loop 12, indicating the importance of the motor reattachment rate on the cotransport speed. Simulations of these loop-swapped motors using experimentally derived motor parameters were able to reproduce the experimental results and identify best fit parameters for the motor reattachment rates for this geometry. Simulation results also supported previous work, suggesting that kinesin-3 microtubule detachment is very sensitive to load. Overall, the simulations demonstrate that the transport behavior of cargo carried by pairs of kinesin-1 and -3 motors are determined by three properties that differ between these two families: the unloaded velocity, the load dependence of detachment, and the motor reattachment rate.     

Microorganisms isolated from the bile of the patients who have undergone cholecystectomy and their antibiotic resistance pattern: multicenter prospective study

International Microbiology - Gallbladder and biliary tract infections are diseases with high mortality rates if they are not treated properly. Microbiological evaluation of perioperatively...     

The kinesin-like proteins,KAC1/2, regulate actin dynamics underlying chloroplast light-avoidance in Physcomitrella patens

In plants, light determines chloroplast position;these organelles show avoidance and accumulation re-sponses in high and low fluence-rate light, respectively. Chloroplast motility in response to light ...     

Myosin XI drives polarized growth by vesicle focusing and local enrichment of F-actin in Physcomitrium patens

In tip-growing plant cells, growth results from myosin XI and F-actin-mediated deposition of cell wall polysaccharides contained in secretory vesicles. Previous evidence showed that myosin XI anticipates F-actin accumulation at the cell’s tip, suggesting a mechanism where vesicle clustering via myosin XI increases F-actin polymerization. To evaluate this model, we used a conditional loss-of-function strategy by generating moss (Physcomitrium patens) plants harboring a myosin XI temperature-sensitive allele. We found that loss of myosin XI function alters tip cell morphology, vacuolar homeostasis, and cell viability but not following F-actin depolymerization. Importantly, our conditional loss-of-function analysis shows that myosin XI focuses and directs vesicles at the tip of the cell, which induces formin-dependent F-actin polymerization, increasing F-actin’s local concentration. Our findings support the role of myosin XI in vesicle focusing, possibly via clustering and F-actin organization, necessary for tip growth, and deepen our understanding of additional myosin XI functions.

Vesicle clustering by the molecular motor myosin XI enhances actin polymerization-dependent motility and polarized vesicle accumulation in tip-growing cells.     

Double Staining of Skeleton Using Microwave Irradiation

The fetal skeleton double staining method is used to reveal developmental abnormalities in the skeletal system. We used alizarin red S and al-cian blue successfully with microwave irradiation for skeletal double staining. The fixation time was reduced from 4-7 days to 2-2.5 min and the staining time was reduced from 4 days to 23 min.     

Introducing meta-services for biomedical information extraction

We introduce the first meta-service for information extraction in molecular biology, the BioCreative MetaServer (BCMS; http://bcms.bioinfo.cnio.es/). This prototype platform is a joint effort of 13 research groups and provides automatically generated annotations for PubMed/Medline abstracts. Annotation types cover gene names, gene IDs, species, and protein-protein interactions. The annotations are distributed by the meta-server in both human and machine readable formats (HTML/XML). This service is intended to be used by biomedical researchers and database annotators, and in biomedical language processing. The platform allows direct comparison, unified access, and result aggregation of the annotations.