The emergence of transcriptional identity in somatosensory neurons

Primary somatosensory neurons are diverse neurons that report salient features of our internal and external environments. How specialized gene expression programs emerge during development to endow each somatosensory neuron subtype with unique properties is unclear. To analyze the developmental progression of transcriptional maturation of each principal somatosensory neuron subtype, we generated a transcriptomic atlas of cells traversing the somatosensory lineage. We find that somatosensory neurogenesis leads to neurons in a transcriptionally unspecialized state, characterized by trace expression of subtype-specific genes yet co-expression of transcription factors (TFs) that become restricted to select subtypes as development proceeds. Single cell transcriptomic analysis using sensory neurons from mutant mice lacking representative broad-to-restricted TFs revealed that they are essential for establishing subtype specific gene programs in subtypes where their expression is maintained, while leaving other subtypes unaffected. We also identify a role for neuronal targets by demonstrating that nerve growth factor influences subtype-restricted patterns of TFs. Our findings support a model in which extrinsic cues orchestrate somatosensory neuron diversification by influencing the expression pattern of TFs that promote transcriptional specialization of somatosensory neuron subtypes. Single-cell RNA-seq from dorsal root ganglia