Title

Stochastic Simulation in Biology

Speakers

J N Tavares and Ricardo Cruz (CMUP)

Date/Venue

29th January 2015, 17h. Anfiteatro A IBMC, Rua do Campo Alegre 823, Porto

Abstract

Many processes in cell and molecular biology can be described by biochemical reaction networks. It is useful to study these networks using computer simulations because they allow us to quantitatively investigate hypotheses about the networks. Deterministic simulations are sufficient to predict average behaviors at the population level, but they cannot address questions about noise, random switching between stable states of the system, or the behaviors of systems with very few molecules of key species. These topics are investigated with stochastic simulations.
In this first Bridges talk, we will review, in an intuitive, and hopeffuly comprehensive manner, some key Stochastic Simulation Algorithms used in Sistems Biology. We will give several illustrations of these methods [pdf presentation]

Title

Mechanics of the contractile ring during cytokinesis

Speakers

Ana Carvalho (IBMC) (see >>>>)

Abstract

Brief background and aims of our lab:
We have been exploring the power of quantitative live imaging assays to study cytokinesis in the early C. elegans embryo.

Cytokinesis requires the assembly and constriction of a contractile ring at the equator of the mother cell. The contractile ring is an acto-myosin filamentous structure which constricts while bringing behind it the plasma membrane, generating a physical barrier between the two daughter cells. The ring is thought to constrict via the action of myosin motor activity that slides actin filaments past one another and actin filament depolymerization.

The whole process of assembly and constriction of the ring takes 6 minutes in our system. Due to the contractile ring highly transient and dynamic nature, the understanding of its mechanics is challenging and yet poorly understood.

Mathematical models exist but suffer from a lack of quantitative in vivo data. They generally use parameters from in vitro data obtained from a mix of experimental setups/ molecules of different organisms. The aim of our lab is to gather quantitative information about the dynamic behavior of contractile ring components, the roles of actin filament dynamics, myosin II motility, and actin regulators during contractile ring constriction, as well as about the ultra-structural organization of the contractile ring. We expect that these parameters, all derived from the same experimental system, will allow us to significantly improve our understanding of the mechanics of the contractile ring as well as develop computational models aimed at recapitulating the process of contractile ring assembly and constriction. To generate new models, whose predictions we will be able to test in our highly tractable experimental system, we are currently seeking to establish collaborations with mathematicians and biophysicists.

Topics I would like to address in the seminar:
The seminar I propose to present would be entitled "Mechanics of the contractile ring during cytokinesis"
and would consist of the description of results we have already obtained:
1) when we use a laser microsurgery assay to probe how the constricting contractile ring responds to discontinuities in its structure
2) when we follow constricting rings in the presence of myosin mutants that have already been characterized in vitro and are known to slide actin filaments at different velocities.