A single-cell atlas of West African lungfish respiratory system reveals evolutionary adaptations to terrestrialization. A single-cell atlas of West African lungfish respiratory system reveals evolutionary adaptations to terrestrialization

The six species of lungfish possess both lungs and gills and are the closest extant relatives of tetrapods. Here, we report a single-cell transcriptome atlas of the West African lungfish (Protopterus annectens). This species manifests the most extreme form of terrestrialization, a life history strategy to survive dry periods in five lungfish species that can last for years, characterized by dormancy and reversible adaptive changes of the gills and lungs. Our atlas highlights the cell type diversity of the West African lungfish, including gene expression consistent with phenotype changes of terrestrialization. Comparisons with terrestrial tetrapods and ray-finned fishes revealed broad homology between the swim bladder and lung cell types as well as shared and idiosyncratic changes of the external gills of the West African lungfish and the internal gills of Atlantic salmon. The single-cell atlas presented here provides a valuable resource for further exploring the evolution of the vertebrate respiratory system and the diversity of lungfish terrestrialization. Overall design: Single cell expression profiling by high throughput sequencing of African lungfish lung and gill under freshwater and terrestrialization condition.

六种肺鱼兼具肺与鳃，是四足类（tetrapods）现存亲缘关系最近的类群。本研究报道了西非肺鱼（Protopterus annectens）的单细胞转录组图谱。该物种呈现出最为极端的陆生化（terrestrialization）表型：其拥有一套可应对长达数年干旱期的生活史策略，该策略为五种肺鱼共有，以休眠以及鳃与肺的可逆适应性变化为典型特征。本图谱揭示了西非肺鱼的细胞类型多样性，其中包含与陆生化表型变化相符的基因表达特征。通过与陆生四足类及辐鳍鱼类的对比分析，研究发现鳔与肺的细胞类型存在广泛同源性，同时揭示了西非肺鱼外鳃与大西洋鲑内鳃共有的及物种特异性的适应性变化。本研究构建的单细胞转录组图谱，为进一步探索脊椎动物呼吸系统的演化历程以及肺鱼陆生化的多样性提供了宝贵的研究资源。实验设计：采用高通量测序技术，对淡水环境及陆生化状态下的西非肺鱼鳃与肺组织进行单细胞表达谱分析。