Table 1.
Current H129-derived anterograde transneuronal tracers and their properties.
| H129-wt | H129dTK-TT | H129-EGFP | H129-G4 | H129-H8 | H129-dTK-tdT | H129-dTK-T2 | |
|---|---|---|---|---|---|---|---|
| Polysynaptic Tracing a | ✓ | ✓ | ✓ | ✓ | ✓ | ✗ | ✗ |
| Monosynaptic Tracing a | ✗ | ✗ | ✗ | ✗ | ✗ | ✓ | ✓ |
| Labeling Brightness b | - | +/++ | ++ | +++ | ++/+++ | + | + |
| Starter Neuron Specificity a | ✗ | Cre+ neuron | ✗ | ✗ | ✗ | Naïve/Cre+/Flp+/… (controlled by helper AAV expressing TK) | Naïve/Cre+/Flp+/… (controlled by helper AAV expressing TK) |
| Advantages | Works in primates | Polysynaptic tracing from Cre+ neurons | Increased labeling intensity | With the brightest labeling so far | Enhanced brightness | Monosynaptic tracer, suitable for starter neuron specific or nonspecific tracing | Monosynaptic tracer, suitable for starter neuron specific or nonspecific tracing, increased labeling intensity |
| Limitations | No fluorescence, requires immunostaining, potential retrograde labeling, high toxicity | Low labeling intensity, can’t trace from naïve neurons, potential retrograde labeling, high toxicity | No starter cell specificity, potential retrograde labeling, high toxicity | No starter cell specificity, potential retrograde labeling, high toxicity | No starter cell specificity | Low labeling intensity, requires immunostaining to visualize post-synaptic neurons, potential retrograde labeling, relatively high toxicity in the starter neuron | Relatively low labeling intensity, potential retrograde labeling, relatively low toxicity in the postsynaptic neurons but still high in the starter neurons |
| Original Articles | [17,51] | [48] | [59] | [18,49] | [70] | [18,49] | [49] |
| Application Articles c | [45,46,47,52,53,54] | [55,56,57,58] * | [60] | [61,62,63,64,65,66,67,68] | / | [64] | / |
a: ✓ Working; ✗ not working. b: - no fluorescence labeling; + weak labeling intensity; ++ moderate labeling intensity; +++ strong labeling intensity. c: * Not a full reference list, only representative articles are listed. / No published articles using these tracers so far.