Fig. 3.

Systems analysis of signal transduction in vivo. A systems-analytical method can be combined with the in vivo imaging to study the regulation and function of the network of the signaling molecules in situ. The analysis typically consists of a defined set of input stimulations (for example, the cyclic pulsatile salt stimulation, whose parameters, such as the amplitude, frequency and duration of the stimulation pulses are varied) followed by measurement of output responses (i.e., MAPK activity) from which the system properties are deduced. An in vivo imaging of the signaling inside the target cell can be achieved using a genetically encoded sensor, which can be expressed by standard gene transferring methods (i.e., viral infection and DNA transfection)