Single cell RNAseq of mouse olfactory bulb reveals cellular heterogeneity and activity dependent molecular census of adult-born neurons

Cellular heterogeneity within the mammalian brain poses a challenge towards understanding its complex functions. Within the olfactory bulb (OB), odor information is processed by subtypes of inhibitory interneurons whose heterogeneity and functionality is influenced by ongoing adult neurogenesis. To investigate this cellular heterogeneity, and to better understand the developmental programs of adult-born neurons, we utilized single cell RNA sequencing and computational modeling to reveal diverse and transcriptionally distinct neuronal and non-neuronal cell types. We also analyzed molecular changes during adult-born interneuron maturation, and uncovered developmental programs within their gene expression profiles. Finally, we discovered that distinct neuronal subtypes are differentially affected by sensory experience. Together, these data provide a transcriptome-based foundation for investigating subtype-specific neuronal function in the OB, charting the molecular profiles that arise during the maturation and integration of adult-born neurons, and documenting activity-dependent changes in the cellular composition of the olfactory system. To develop a comprehensive profile of cellular heterogeneity within the OB, here we employed high-throughput single-cell RNA sequencing (scRNA-seq) (Zheng et al. 2017) of activity manipulated and wildtype mouse olfactory bulbs. This technique allows an in-depth categorization of single cell molecular signatures, and provides an analysis of potential developmental and activity-dependent changes that occur in adult-born neuron populations. Together, our data inform the heterogeneity of interneurons within the OB, provide a molecular blueprint of stereotyped developmental programs for OB interneurons, and reveal the transcriptional changes that govern activity-dependent circuit integration of adult-born neurons. Furthermore, our results suggest that distinct molecular mechanisms act on different subsets of adult-born neurons, driving diversity and survival of adult-born interneuron subsets in an activity-dependent manner.哺乳动物大脑内的细胞异质性（cellular heterogeneity）是解析其复杂功能的核心挑战。在嗅球（olfactory bulb, OB）中，气味信息由不同亚型的抑制性中间神经元完成处理，这类神经元的异质性与功能受到持续性成年神经发生（adult neurogenesis）的影响。为探究这一细胞异质性，并更深入理解成年新生神经元的发育程序，我们采用单细胞RNA测序（single cell RNA sequencing, scRNA-seq）与计算建模技术，揭示了多种转录特征迥异的神经元与非神经元细胞类型。我们还分析了成年新生中间神经元成熟过程中的分子变化，并从其基因表达谱中挖掘出特异性发育程序。最后，我们发现不同的神经元亚型会受到感觉经验的差异性影响。综上，本研究数据为探究嗅球内亚型特异性神经元功能提供了基于转录组的研究基础，梳理了成年新生神经元成熟与整合过程中出现的分子特征，并记录了嗅觉系统细胞组成中的活动依赖性变化。为全面解析嗅球内的细胞异质性，我们对经活动干预的小鼠嗅球与野生型小鼠嗅球开展了高通量单细胞RNA测序（high-throughput single-cell RNA sequencing, scRNA-seq）（Zheng等，2017）。该技术可实现单细胞分子特征的深度分类，并能分析成年新生神经元群体中潜在的发育与活动依赖性变化。综上，我们的数据阐明了嗅球内中间神经元的异质性，为嗅球中间神经元的定型发育程序提供了分子蓝图，并揭示了调控成年新生神经元活动依赖性环路整合的转录变化。此外，我们的研究结果表明，不同的分子机制会作用于不同的成年新生神经元亚群，以活动依赖性的方式驱动成年新生中间神经元亚群的多样性与存活。