Instructive niches: environmental instructions that confound NG2 proteoglycan expression and the fate-restriction of CNS progenitors.

Cellullar deficits are replenished within the central nervous system (CNS) by progenitors to maintain integrity and recover function after injury. NG2 proteoglycan-expressing progenitors replenish oligodendrocyte populations, but the nature of NG2 proteoglycan may not indicate a restricted population of progenitors. After injury, restorative spatiotemporal cues have the potential ability to regulate divergent fate-choices for NG2 progenitors, and NG2 progenitors are known to produce multiple cell types in vitro. Recent data suggest that NG2 expression is attenuated while protein levels remain high within injurious tissue; thus, NG2 expression is not static but transiently controlled in response to a dynamic interplay of environmental cues. Therefore, NG2 proteoglycan expression could label newly generated cells or be inherited by resident cell populations that produce oligodendrocytes for remyelination, astrocytes that provide trophic support and other cells that contribute to CNS function.