The earliest notable changes of converted iN cells are morphological, with the generation of a round soma protruding one small and thin process (Vierbuchen et al., 2010, see also Figure 4B). Gradually, more processes are generated which begin to branch. At first all neurites express both axonal and dendritic markers but early during differentiation one process gains characteristics of an axon whereas the remaining neurites become dendrites (e.g. MAP2 vs. Tau, see Silverman et al., 2001). During early stages of neurogenesis, newly born neurons become immunoreactive for the nuclear epitope NeuN (Mullen et al., 1992) and Poly-Sialated Neural Cell Adhesion Molecule (PSA-NCAM) (Bonfanti et al., 1992).
