QLS seminar - Wed. 12 July at 11h00

[Quantitative Life Sciences]

Wednesday 12 July at 11:00

ICTP, Central Area, 2nd floor, old SISSA building, Via Beirut


Title: Mitotic waves in the early embryogenesis of Drosophila: 
bistability traded for speed


Speaker: Massimo Vergassola, UCSD


Abstract:

Early embryogenesis of most metazoans is characterized by rapid and 
synchronous cleavage divisions. In Drosophila embryos, waves of activity 
of Cdk1, the main regulator of the cell cycle, are responsible for the 
synchronization of cell divisions. After reviewing the phenomenology, I 
shall discuss the dynamics of the Ginzburg–Landau model that captures 
the in vivo dynamics of Cdk1. The main feature of the corresponding 
potential is that it features a time-dependent component, which accounts 
for the growing level of Cdk1 activation across the cell cycle. Two 
distinct regimes result. The first regime is experimentally observed in 
mutants that alter the regulation of the mitotic switch. In the 
resulting quasi-adiabatic regime, waves reflect the classical physical 
mechanism of invasion by a stable state of a metastable one. Conversely, 
the quasi-adiabatic approximation is violated in wild-type embryos, 
where the observed waves reflect the sweeping of spatial gradients of 
the Cdk1 field by the time-dependent component of the potential. This 
alternative mechanism leads to wave-like spreading, which is faster and 
depends on the dynamic parameters differently than bistable waves. For 
instance, the latter scale as the square root of the Cdk1 molecular 
diffusivity and weakly depend on the amplitude of the noise, whilst the 
former scale as 3/4 and 1/2 powers, respectively. Theoretical 
predictions are supported by experiments that couple quantitative 
measurements of Cdk1 and genetic perturbations.


Everyone interested is most welcome to attend!

-- 
Erica Sarnataro
Group Secretary
Quantitative Life Sciences
The Abdus Salam International Centre for Theoretical Physics (ICTP)
Trieste,  Italy
Tel. +39-040-2240623
e-mail: qls at ictp.it