Table 1.

Different methods employed for lineage tracing of aNSCs, highlighting some of their strongest advantages, and main weaknesses.

	Method	Strongest adventage	Main weakness
Cells not monitored by live imaging	Retroviral vector	Allows to label dividing cells in vivo and in vitro.	The entire clone is not labeled. Cell death, migration away of a labeled cell, or immigration of a non-related labeled cells to the field of view are not discriminated.
	Genetic recombination and multicolor reporter systems	Allows to discriminate clonally while labeling high numbers of progenitors.	Cell death, migration away of a labeled cell, or immigration of a non-related labeled cells to the field of view are not discriminated.
	Classical neurosphere assay	Classical assay to evaluate NSCs hallmarks. (Self-renewal and differentiation capacity).	Does not ensure clonality, does not guarantee to monitor the slow dividing NSCs. Mitogen factors exerts confounding effects on the NSCs.
Cells monitored by live imaging	In vitro live imaging in presence of feeder layers/mitogen factors	Allows for continuous monitoring. Presence of niche factors.	Mitogen factors exerts confounding effects on the NSCs.
	Mitogen-free in vitro live imaging system	Allows for continuous monitoring. Perfect tool to evaluate the effect of each niche factor at a time. In vivo studies confirm their conclusions.	Absence of niche environment.
	Live imaging by brain slices	Allows for continuous monitoring. Preserves neurogenic niche.	Usually comprises high doses of serum in the preparation protocol. Restricted time of preservation of the neurogenic niche properties.
	Live imaging in vivo	Intact neurogenic niche in an intact brain environment.	Not yet developed for a single cell resolution.