NE cells are among the most interesting, but poorly understood cell types in the lung. Many are distributed apparently randomly in the bronchial epithelium, but others are organized into clusters of 20-30 NE cells called neuroepithelial bodies (NEBs) that are highly innervated by afferent and efferent fibers. They secrete a variety of vasoactive neuropeptides and amines and have many proposed functions in respiratory physiology, including airway oxygen sensing, mechanosensing, regulation of bronchial tone, and local control of pulmonary blood flow. NE cells also have a stem-cell function activated in lung injury and are tumor-initiating cells in small cell lung cancer (SCLC), a highly metastatic and the most deadly form of lung cancer. NE cells expand or show altered distributions in many respiratory diseases, however, little is known about their normal development, proliferation, placement, differentiation and physiologic function. The candidate for this career development award has performed a comprehensive study of NEB development in mice, revealing the cellular mechanism of their formation, including a novel form of targeted epithelial cell migration called slithering. This unexpected mode of epithelial cell rearrangement may explain the highly invasive and migratory nature of small cell lung cancer. This proposal aims to apply single cell whole- genome transcriptome analysis (single cell RNAseq) to developing mouse NE cells to elucidate the complete gene expression program of slithering. A system for conditional gene deletion in developing NE cells will be established, and used to determine the function of a candidate slithering gene identified in preliminary single cell RNAseq studies. In parallel, this emerging understanding of mouse NE cell development will be extended to humans by testing for human expression of slithering genes in developing NE cells. The primary site of research is within the Biochemistry Department, located in the Beckman Center for Molecular and Genetic Medicine, which also houses the Department of Developmental Biology and the Department of Molecular and Cellular Physiology, as well as the rest of the Howard Hughes Medical Institute. These Departments are among the premier departments in the world in these fields, and have been leading centers of innovation in biochemistry, molecular biology, genetics, and genomics for decades. The Beckman Center is attached to the hospital and centrally located on the Stanford Medical School campus, and across the street from the main Stanford University campus. The candidate's expertise in the most advanced genetic strategies in mice and strong knowledge of human respiratory diseases will complement the current training plan to learn single cell transcriptome analysis through collaborations with leaders in this innovative technology at Stanford to address important questions about NE cell development and disease. The long term goal of this work is to identify the molecular defects underlying pediatric and adult respiratory diseases associated with abnormalities in NE cell development, diversity, and function(s) in order to design effective therapies.
Pulmonary neuroendocrine (NE) cells are increased in small cell lung carcinoma, the most deadly lung cancer due to its highly metastatic nature, and abnormally distributed in several pediatric respiratory disorders including neuroendocrine cell hyperplasia of infancy, sudden infant death syndrome, and pulmonary hypertension. While NE cells expand and show altered distributions in many respiratory diseases, little is known about their normal development and physiologic function or their roles in diseases outside of their role as tumor-initiating cells in cancer. We have performed a comprehensive study of NE cells during development and discovered that NE cell precursors form large clusters called neuroepithelial bodies (NEBs) at highly stereotyped airway branchpoints by a novel form of epithelial cell migration called slithering. This developmental NE cell migratory program may be inappropriately activated later in small cell cancers, which originate from NE cells. We aim to elucidate the complete gene expression program of slithering using an innovative single cell whole genome transcriptome analysis and to test the function of a candidate slithering gene identified in preliminary studies. In parallel, this emerging understanding of mouse NE cell development will be extended to humans by testing for human expression of slithering genes in developing human NE cells. This fundamental work will reveal how abnormal execution of this developmental program perturbs respiratory function and causes or contributes to lung diseases in children and adults, and ultimately provide new avenues for treatment of a diverse group of NE cell-related respiratory diseases.
