Cross-Species Single-cell Comparative Analysis of Amygdala

The amygdala or amygdala-like structure in the brain are found in all vertebrates, and plays a critical role for emotional processing. But the cellular architecture of amygdala and how they evolved are still elusive. Here, we generated single-nucleus RNA-sequencing data for more than 200,000 cells in human, macaque, mouse and chicken amygdala. Abundant neuronal cell types derived from different subnuclei of amygdala were identified in all datasets. Cross-species analyses revealed GABAergic neurons and GABAergic neuron-enriched subnuclei of amygdala were well-conserved in cellular composition and marker gene expression, whereas glutamatergic neuron-enriched subnuclei were relatively divergent. Furthermore, we discovered that LAMP5+ interneurons were much more numerous in primates, while DRD2+ GABAergic neurons, LAMP5+ and SATB2+ glutamatergic neurons were predominant in the human central amygdalar nucleus (CEA) and basolateral amygdala complex (BLA), respectively. In addition, we also identified GABAergic neuron-enriched subnuclei of amygdala in the chicken. Altogether, our study highlight extremely cell-type diversity in the amygdala across species and their species-specifc adaptations. To transcriptomically characterize cell types of the amygdala in mammals and sauropsids, which have been the most diverse and successful group of land vertebrates, we applied snRNA-seq assays (Chromium v3) and focused on human, macaque, mouse and chicken. Human samples were from postmortem donors with very short postmortem interval (within 6 hours), and macaque, mouse and chicken amygdala were freshly dissected. We profiled a total of 17 specimens, including 3 human amygdala samples, 3 macaque amygdala samples, 2 chicken amygdala homolog samples, 4 mouse amygdala samples, 3 mouse basolateral amygdala complex (BLA; made up of the lateral (LA), basal (BA) and basomedial (BM) nucleus) samples, and 2 mouse central amygdalar nucleus (CEA) samples大脑中的杏仁核（amygdala）或类杏仁核结构存在于所有脊椎动物中，在情绪处理过程中发挥关键作用。然而，杏仁核的细胞结构及其演化机制至今仍未明确。本研究针对人类、猕猴、小鼠及鸡的杏仁核，生成了超过20万个细胞的单细胞核RNA测序数据。所有数据集均鉴定出源自杏仁核不同亚核的丰富神经元细胞类型。跨物种分析显示，杏仁核的γ-氨基丁酸能神经元（GABAergic neurons）及其富集的亚核在细胞组成与标记基因表达层面高度保守，而谷氨酸能神经元（glutamatergic neurons）富集的亚核则相对分化程度更高。此外，本研究发现LAMP5+中间神经元在灵长类动物中数量显著更多，而DRD2+ γ-氨基丁酸能神经元、LAMP5+与SATB2+谷氨酸能神经元分别是人类中央杏仁核（central amygdalar nucleus, CEA）与基底外侧杏仁核复合体（basolateral amygdala complex, BLA）的优势细胞类群。另外，本研究还在鸡的杏仁核中鉴定出了γ-氨基丁酸能神经元富集的亚核。综上，本研究揭示了跨物种杏仁核中极为丰富的细胞类型多样性及其物种特异性适应特征。为了在哺乳动物与蜥形类（sauropsids）这两类陆地脊椎动物中最具多样性与演化成功的类群中，从转录组层面表征杏仁核的细胞类型，我们采用了基于Chromium v3平台的单细胞核RNA测序实验，并聚焦于人类、猕猴、小鼠与鸡四个物种。人类样本来自死后间隔时间极短（6小时以内）的遗体捐赠者，而猕猴、小鼠与鸡的杏仁核组织均为新鲜解剖获取。本研究共对17份标本进行了测序分析，其中包括3份人类杏仁核样本、3份猕猴杏仁核样本、2份鸡杏仁核同源结构样本、4份小鼠杏仁核样本、3份小鼠基底外侧杏仁核复合体（BLA，由外侧杏仁核（LA）、基底杏仁核（BA）与基底内侧杏仁核（BM）组成）样本，以及2份小鼠中央杏仁核（CEA）样本。