Background

Recent genetic technologies such as opto- and chemogenetics allow for the manipulation of brain circuits with unprecedented precision. Most studies employing these techniques have been undertaken in rodents, but a more human-homologous model for studying the brain is the nonhuman primate (NHP). Optimizing viral delivery of transgenes encoding actuator proteins could revolutionize the way we study neuronal circuits in NHPs.

New method

rAAV2-retro, a popular new capsid variant, produces robust retrograde labeling in rodents. Whether rAAV2-retro’s highly efficient retrograde transport would translate to NHPs was unknown. Here, we characterized the anatomical distribution of labeling following injections of rAAV2-retro encoding opsins or DREADDs in the cortico-basal ganglia and oculomotor circuits of rhesus macaques.

Results

rAAV2-retro injections in striatum, frontal eye field, and superior colliculus produced local labeling at injection sites and robust retrograde labeling in many afferent regions. In every case, however, a few brain regions with well-established projections to the injected structure lacked retrogradely labeled cells. We also observed robust terminal field labeling in downstream structures.

Comparison with existing method(s)

Patterns of labeling were similar to those obtained with traditional tract-tracers, except for some afferent labeling that was noticeably absent.

Conclusions

rAAV2-retro promises to be useful for circuit manipulation via retrograde transduction in NHPs, but caveats were revealed by our findings. Some afferently connected regions lacked retrogradely labeled cells, showed robust axon terminal labeling, or both. This highlights the importance of anatomically characterizing rAAV2-retro’s expression in target circuits in NHPs before moving to manipulation studies.

中文翻译：

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在恒河猴中使用 rAAV2-retro：电路操作的承诺和警告。

背景

最近的遗传技术，如光遗传学和化学遗传学，可以以前所未有的精度操纵大脑回路。大多数采用这些技术的研究都是在啮齿动物中进行的，但用于研究大脑的更与人类同源的模型是非人类灵长类动物 (NHP)。优化编码致动器蛋白的转基因的病毒传递可以彻底改变我们研究 NHP 中神经元回路的方式。

新方法

rAAV2-retro 是一种流行的新衣壳变体，可在啮齿动物中产生强大的逆行标记。rAAV2-retro 的高效逆行运输是否会转化为 NHP 尚不清楚。在这里，我们描述了在恒河猴的皮质基底节和动眼神经回路中注射 rAAV2-retro 编码视蛋白或 DREADD 后标记的解剖分布。

结果

rAAV2-retro 注射在纹状体、额眼区和上丘中，在注射部位产生局部标记，在许多传入区域产生强大的逆行标记。然而，在每种情况下，一些对注射结构具有良好预测的大脑区域缺乏逆行标记的细胞。我们还在下游结构中观察到强大的终端场标记。

与现有方法的比较

标记模式与使用传统束示踪剂获得的模式相似，除了一些明显不存在的传入标记。

结论

rAAV2-retro 有望通过 NHP 中的逆行转导用于电路操作，但我们的研究结果揭示了警告。一些传入连接的区域缺乏逆行标记的细胞，显示出强大的轴突末端标记，或两者兼而有之。这突出了在进行操作研究之前解剖学表征 rAAV2-retro 在 NHP 中目标回路中的表达的重要性。