Figure 4.

Scaling factors are persistently expressed and mediate cellular adaptive responses. SF levels fluctuate throughout a cell's lifespan, with higher levels generating greater specialization – in this example, more secretory granules. As long as SF levels remain within a certain range (in this example, 4-7), the cell functions normally; however, SF expression may fall outside the normal range, leading, in the depicted example, to a lack of balance among the cell's different sub-cellular domains and ultimately to cellular pathophysiology.