Complex sentence: Inhibition of Grb2 function impairs developmental processes in various organisms and blocks transformation and proliferation of various cell types, and so it is not surprising that a targeted gene disruption of Grb2 in mouse is lethal at an early embryonic stage.
Split into simpler sentences: Inhibition of Grb2 function impairs developmental processes in various organisms and blocks transformation and proliferation of various cell types. It is thus not surprising that targeted gene disruption of Grb2 in mice is lethal at an early embryonic stage.