Regional cellular heterogeneity is a fundamental feature of the human neocortex; however, details of this heterogeneity are still undefined. We used single-nucleus RNA-sequencing to examine cell-specific transcriptional features in the dorsolateral PFC (DLPFC) and the subgenual anterior cingulate cortex (sgACC), regions implicated in major psychiatric disorders. Droplet-based nuclei-capture and library preparation were performed on replicate samples from 8 male donors without history of psychiatric or neurologic disorder. Unsupervised clustering identified major neural cell classes. Subsequent iterative clustering of neurons further revealed 20 excitatory and 22 inhibitory subclasses. Inhibitory cells were consistently more abundant in the sgACC and excitatory neuron subclusters exhibited considerable variability across brain regions. Excitatory cell subclasses also exhibited greater within-class transcriptional differences between the two regions. We used these molecular definitions to determine which cell classes might be enriched in loci carrying a genetic signal in genome-wide association studies or for differentially expressed genes in mental illness. We found that the heritable signals of psychiatric disorders were enriched in neurons and that, while the gene expression changes detected in bulk-RNA-sequencing studies were dominated by glial cells, some alterations could be identified in specific classes of excitatory and inhibitory neurons. Intriguingly, only two excitatory cell classes exhibited concomitant region-specific enrichment for both genome-wide association study loci and transcriptional dysregulation. In sum, by detailing the molecular and cellular diversity of the DLPFC and sgACC, we were able to generate hypotheses on regional and cell-specific dysfunctions that may contribute to the development of mental illness.

SIGNIFICANCE STATEMENT Dysfunction of the subgenual anterior cingulate cortex has been implicated in mood disorders, particularly major depressive disorder, and the dorsolateral PFC, a subsection of the PFC involved in executive functioning, has been implicated in schizophrenia. Understanding the cellular composition of these regions is critical to elucidating the neurobiology underlying psychiatric and neurologic disorders. We studied cell type diversity of the subgenual anterior cingulate cortex and dorsolateral PFC of humans with no neuropsychiatric illness using a clustering analysis of single-nuclei RNA-sequencing data. Defining the transcriptomic profile of cellular subpopulations in these cortical regions is a first step to demystifying the cellular and molecular pathways involved in psychiatric disorders.

区域细胞异质性是人类新皮质的基本特征；然而，这种异质性的细节仍然不确定。我们使用单核 RNA 测序来检查背外侧 PFC (DLPFC) 和膝下前扣带皮层 (sgACC) 的细胞特异性转录特征，这些区域与主要精神疾病有关。对来自 8 名无精神或神经系统疾病史的男性捐赠者的重复样本进行了基于液滴的细胞核捕获和文库制备。无监督聚类识别了主要的神经细胞类别。随后的神经元迭代聚类进一步揭示了 20 个兴奋性亚类和 22 个抑制性亚类。sgACC 中的抑制性细胞始终更加丰富，而兴奋性神经元亚群在整个大脑区域表现出相当大的变异性。兴奋性细胞亚类在两个区域之间也表现出更大的类内转录差异。我们使用这些分子定义来确定哪些细胞类别可能富含全基因组关联研究中携带遗传信号的基因座或精神疾病中差异表达的基因。我们发现精神疾病的遗传信号在神经元中丰富，并且虽然批量 RNA 测序研究中检测到的基因表达变化主要由神经胶质细胞主导，但在特定类别的兴奋性和抑制性神经元中可以识别出一些改变。有趣的是，只有两种兴奋性细胞类别表现出全基因组关联研究位点和转录失调的伴随区域特异性富集。总之，通过详细描述 DLPFC 和 sgACC 的分子和细胞多样性，我们能够对可能导致精神疾病发展的区域和细胞特异性功能障碍提出假设。

意义声明膝下前扣带皮层的功能障碍与情绪障碍，特别是重度抑郁症有关，而背外侧前额叶皮层（PFC 中参与执行功能的一个部分）与精神分裂症有关。了解这些区域的细胞组成对于阐明精神和神经系统疾病的神经生物学至关重要。我们利用单核 RNA 测序数据的聚类分析，研究了没有神经精神疾病的人类膝下前扣带皮层和背外侧 PFC 的细胞类型多样性。定义这些皮质区域细胞亚群的转录组谱是揭开精神疾病相关细胞和分子通路神秘面纱的第一步。