Figure 2.

The origin, dedifferentiation and transdifferentiation of spermatogonial stem cells (SSCs). SSCs are derived from primordial germ cells whose precursors are formed in the epiblast. Human and rodent SSCs can dedifferentiate to become embryonic stem-like cells that give rise to numerous cells of all three germ layers, e.g. neurons, pancreatic cells and muscle cells. Notably, SSCs from neonatal mice can directly transdifferentiate into a variety of cell types including prostatic, uterine, skin epithelium, and mature hepatocyte-like cells. However, whether human and adult mouse SSCs can directly transdifferentiate to other lineage cells remains to be defined (as indicated as question marks).