Adeno‐associated virus (AAV) is one of the most common gene transfer vectors, but it has a limited capacity. A smaller fluorescent protein is urgently needed since it is more suitable to act as a reporter in AAV. In this study, a bilirubin‐dependent reporter smaller than EGFP, termed UnaG, was found to have the ability to label the neurons of a mouse brain as clearly as EGFP without the addition of exogenous bilirubin. We also found that UnaG's pH tolerance is better than that of EGFP; however, its fluorescence recovery after protonated quenching is not as good as that of EGFP. In addition, UnaG preserved its fluorescence better than EGFP in SeeDB clearing. Taken together, this study demonstrates that UnaG can act as a small intrinsically fluorescent reporter in the mouse brain without an additional ligand, thus providing an alternative over EGFP for AAV‐mediated neuron labeling in mammals.

中文翻译：

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UnaG作为腺相关病毒介导的生物医学成像基因转移的报告基因。

腺相关病毒（AAV）是最常见的基因转移载体之一，但容量有限。迫切需要更小的荧光蛋白，因为它更适合在AAV中充当报告基因。在这项研究中，发现一个小于EGFP的胆红素依赖性报告分子，称为UnaG，具有与EGFP一样清晰地标记小鼠大脑神经元的能力，而无需添加外源性胆红素。我们还发现UnaG的pH耐受性优于EGFP；然而，质子猝灭后其荧光恢复不如EGFP。此外，在SeeDB清除过程中，UnaG的荧光保存效果优于EGFP。两者合计，这项研究表明UnaG可以在没有额外配体的情况下充当小鼠大脑中的小型固有荧光报告分子，