Table 1. Strategies to express GECIs in astrocytes.

GECI	Expression approach	Ref
Cytosolic Yellow cameleon 3.60 mice	Transgenic mice driven by the S100β promoter	[49]
Cytosolic GCaMP3 and GCaMP6f	AAV 2/5 using the GfaABC1D promoter, in utero electroporation	[28, 31, 38, 42-44, 47]
Membrane tethered GCaMP3 and GCaMP6f (Lck tagged)	AAV 2/5 and GfaABC1D promoter, in utero electroporation	[28, 31, 43, 44, 47]
Cytosolic GCaMP3 mice	Knock-in at the ROSA26 locus	[37, 41]
Cytosolic YC-nano50 mice	Knock-in using tetracycline transactivator (tTa)-tet operator (tetO) strategy at Actb locus	[48]
Cytosolic GCaMP5G mice	Knock-in at the Polr2a locus	[53]
Cytosolic GCaMP6f and GCaMP6s mice	Knock-in mice at the ROSA26 and TIGRE loci	[38, 56]

Note: GCaMP3, GCaMP5G and GCaMP6f display Ca²⁺ affinities of 345, 447 and 375 nM, and k_off values of 2.57, 2.52 and 3.93 s^-1, respectively [24]. The Ca²⁺ affinity for YC-nano50 is 50 nM [48] and that for Yellow cameleon 3.6 is 250 nM [57].