 At Princeton, his early work on microtubules established their unusual molecular assembly from tubulin proteins and identified the first microtubule-stabilizing protein tau, later shown to be a major component of the neurofibrillary tangles in Alzheimer's disease.In studies at UC San Francisco of the frog embryo as a model system of cell development, Kirschner identified the first inducer of embryonic differentiation, fibroblast growth factor (FGF), an early finding in the field of signal transduction.Kirschner's lab is also known for uncovering basic mechanisms of the cell cycle in eukaryotic cells.