jBillou edited Nuclear area predicts cell cycle phases.tex  over 9 years ago

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\subsection{Nuclear area predicts cell cycle phases (a little bit)}  In order to validate the use of the nuclear area to infer the cell cycle phased phases  we imaged NIH/3T3 fibroblasts containing the Fucci system. The Fucci system is a two color fluorescent reporter that allow to dinstinguish G1 phase from S/G2/M phase \cite{Sakaue-Sawano2008}. We modified our HMM to infer the cell cycle phase from the Fucci signal (denoted $\phi_F$) by multiplying the emmission probabilities of both colors (Figure \ref{fig:cellCycleFucci}A, Section \ref{sec:methods_fucci}) and independently infered the cell cycle phase $\phi_N$ from the nuclear area (Figure \ref{fig:cellCycleFucci}B). When comparing the two phases we found a reasonable agreement (Figure \ref{fig:cellCycleFucci}C). The two methods are very accurate close to divisions (the abrupt change in the signal at division contains a lot of information) but show more variations in the middle of the cycle.  To provide a more intuitive measure of the precision of our inferrences we estimated the durations of G1 and S/G2 from both phases (Figure \ref{fig:cellCycleFucci}D, A-B bottom), overall the S/G2 (G1) durations infered from the Fucci signal were predicted from nuclear area with an error of $\pm 2.2h$ ($2.4h$), compared to a mean duration of $14.5h$ ($10.7h$).