遗传编码的钙指标(GECIs),如GCaMP,是神经科学中使用光学成像监测神经元活动的宝贵工具。GECIs的病毒转导通常用于将表达靶向特定的大脑区域,可以方便地与任何感兴趣的小鼠品系一起使用,而无需事先与GECI小鼠品系杂交,并避免由于发育过程中GECIs的慢性表达而产生的潜在危害。用指标监测神经元活动的关键要求是指标本身对活动的影响最小。这里,使用常见的腺相关病毒(AAV)转导程序,我们描述了由突触素启动子驱动的GCaMP6,GCaMP7或R-CaMP1.07表达后缓慢通过海马的空间受限异常Ca2微波,并以滴度依赖性方式进行AAV依赖性基因转移。Ca2微波在海马CA1和CA3中发育,但不在齿状回或新皮质中发育,通常在病毒转导后4周首次观察到,并坚持至少8周。该现象是稳健的,并且在具有各种实验者和设置的实验室中观察到。我们的结果表明,异常海马Ca2+微波依赖于GECI的启动子和病毒滴度,表达密度,以及目标大脑区域。我们使用了GCaMP的替代病毒转导方法,可以避免这种假象。结果表明,常用的Ca2指示剂AAV转导程序可以产生人为的Ca2响应。我们的目标是提高人们对这些人工转导诱导的Ca2微波的认识,我们提供了一个潜在的解决方案。
Genetically encoded calcium indicators (GECIs) such as GCaMP are invaluable tools in neuroscience to monitor neuronal activity using optical imaging. The viral transduction of GECIs is commonly used to target expression to specific brain regions, can be conveniently used with any mouse strain of interest without the need for prior crossing with a
GECI mouse line, and avoids potential hazards due to the chronic expression of GECIs during development. A key requirement for monitoring neuronal activity with an indicator is that the indicator itself minimally affects activity. Here, using common adeno-associated viral (AAV) transduction procedures, we describe spatially confined aberrant Ca2+ microwaves slowly travelling through the hippocampus following expression of GCaMP6, GCaMP7, or R-CaMP1.07 driven by the synapsin promoter with AAV-dependent gene transfer in a titre-dependent fashion. Ca2+ microwaves developed in hippocampal CA1 and CA3, but not dentate gyrus nor neocortex, were typically first observed at 4 wk after viral transduction, and persisted up to at least 8 wk. The phenomenon was robust and observed across laboratories with various experimenters and setups. Our results indicate that aberrant hippocampal Ca2+ microwaves depend on the promoter and viral titre of the
GECI, density of expression, as well as the targeted brain region. We used an alternative viral transduction method of GCaMP which avoids this artefact. The results show that commonly used Ca2+-indicator AAV transduction procedures can produce artefactual Ca2+ responses. Our aim is to raise awareness in the field of these artefactual transduction-induced Ca2+ microwaves, and we provide a potential solution.