The unique combination of small size, translucency, and powerful genetic tools makes larval zebrafish a uniquely useful vertebrate system to investigate normal and pathological brain structure and function. While functional connectivity can now be assessed by optical imaging (via fluorescent calcium or voltage reporters) at the whole-brain scale, it remains challenging to systematically determine structural connections and identify connectivity changes during development or disease. To address this, we developed Tracer with Restricted Anterograde Spread (TRAS), a novel vesicular stomatitis virus (VSV)-based neural circuit labeling approach. TRAS makes use of replication-incompetent VSV (VSVΔG) and a helper virus (lentivirus) to enable anterograde transneuronal spread between efferent axons and their direct postsynaptic targets but restricts further spread to downstream areas. We integrated TRAS with the Z-Brain zebrafish 3D atlas for quantitative connectivity analysis and identified targets of the retinal and habenular efferent projections, in patterns consistent with previous reports. We compared retinofugal connectivity patterns between wild-type and down syndrome cell adhesion molecule-like 1 (dscaml1) mutant zebrafish and revealed differences in topographical distribution. These results demonstrate the utility of TRAS for quantitative structural connectivity analysis that would be valuable for detecting novel efferent targets and mapping connectivity changes underlying neurological or behavioral deficits.

中文翻译：

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斑马鱼的结构神经连通性分析，受限顺顺性跨神经元病毒标记和定量脑图分析。

小尺寸，半透明性和强大的遗传工具的独特组合使幼虫斑马鱼成为研究正常和病理性大脑结构和功能的独特有用的脊椎动物系统。尽管现在可以通过光学成像（通过荧光钙或电压报告仪）在全脑范围内评估功能连接性，但系统地确定结构连接并识别发育或疾病期间的连接性变化仍然具有挑战性。为了解决这个问题，我们开发了具有限制顺流传播的示踪剂（TRAS），这是一种基于水疱性口炎病毒（VSV）的新型神经回路标记方法。TRAS利用无复制能力的VSV（VSVΔG）和辅助病毒（lentivirus）来使传出的轴突与其直接突触后靶标之间顺行跨神经元扩散，但限制进一步扩散到下游区域。我们将TRAS与Z-Brain斑马鱼3D地图集集成在一起以进行定量连接分析，并以与以前的报告一致的方式确定了视网膜和哈贝状体传出投影的目标。我们比较了野生型和唐氏综合症细胞粘附分子样1（dscaml1）突变斑马鱼之间的视网膜视网膜连接模式，并揭示了地形分布的差异。