5. A signaling pathway that is important during embryonic development of animals is the notch signaling pathway. The diagram below shows an example of a notch system used in controlling the extent of differentiation of stem cells destined to become nerve cells. The diagram shows two cells. In the top cell, the genes Mash1 and Ngn2 induce the expression of the protein, Delta. Once synthesized, Delta becomes inserted into the cell membrane, where part of it sticks out into the extracellular space surrounding the cell. In this position, it is able to activate notch signaling in a second cell. Activation causes the notch protein in the second cell to be cleaved, forming the fragment NICD. NICD is released into the cytosol and moves into the cell nucleus. There it binds to the DNA-binding protein RBPj. This complex induces expression of several genes that block differentiation of that neuronal cell. As a result, the cell maintains its undifferentiated state. Explain how the cell-to-cell signaling in this example differs from the cell-to-cell signaling in the epinephrine induction of glycogen breakdown in muscle tissue. (3 points)

Cytoplasm Mash1, Ngn2 Delta Nucleus Delta NICD Notch NICD -CHOMO- RBPj --0000- NICD Hes1/Hes5 Hes1,Hes5 1 Mash1, Ngn2 Delta