Anatomy, Projectome and Functional Annotation of Mouse Spinal Cord Neural Diversity
Spinal cord gives rise to central somatosensation and orchestrates autonomic and motor control. How its cellular diversity achieves physiological functions across sex and along its longitudinal axis and links spinal cord to higher order brain centers remains poorly understood. Here we used retrograde viral tracing with spatial transcriptomics and multiomic profiling of >750k mouse spinal cord neurons to define its output logic and functional cellular repertoire. We identified 70 spinal projection neuron classes that link the spinal cord to hind-, mid-, and forebrain centers implicated in itch, touch, and pain revealing the output wiring logic of the spinal cord. Furthermore, we characterized >500 anatomically and transcriptomically distinct neuron types that revealed extensive (~50%) rostro-caudal cellular specialization as well as first sex specific neuron classes in the spinal cord.  Finally, we assembled a neuron-class-to-phenotype map of the structure based on genetically defined interventions. As a result, we deliver an anatomically and functionally annotated cellular atlas of the complete adult mouse spinal cord to guide future interrogation of the organ. Overall design: Cervical, thoracic, lumbar and sacral spinal cords were harvested from adult (p56) C57Bl6J male and female mice. Nuclei were extracted and NeuN+ neuronal nuclei were isolated with FACS sorting. Resulting neuronal suspensions were profiled with Chromium Next GEM Single Cell Multiome ATAC + Gene Expression kits from 10x Genomics. Altogether 3 biological replicates were acquired from all four spinal cord regions with three technical replicates each.