Molecular Taxonomy Links Transcriptional Identity to Functional Specialization in Brain-Wide Spinal Projecting Neurons
Background: Spinal projecting neurons (SPNs) transmit descending motor, sensory and autonomic commands from the brain to the spinal cord. Although their importance in voluntary movement and homeostatic regulation is well established, the molecular diversity and organization of SPNs across the entire brain have remained poorly characterized.
Hypothesis: This study hypothesized that distinct transcriptional signatures define discrete classes of SPNs, whose molecular identities correspond to their anatomical origins and functional specializations in motor and autonomic control.
Methods: The authors combined single-nucleus RNA sequencing using the 10x Genomics Chromium platform and SMART-Seq v4 with high-resolution spatial transcriptomics and anatomical mapping. Whole-brain reconstructions of retrogradely labeled neurons were acquired using the TissueCyte serial two-photon tomography platform. Image segmentation, registration and three-dimensional reconstruction of labeled nuclei were conducted with NeuroInfo. Quantification of labeled neurons and fluorescence intensity was performed using QuPath image analysis software.
Results: Sequencing of 65,002 SPN nuclei identified 76 molecularly distinct neuron types across three principal divisions: cortical, midbrain–hindbrain and modulatory. Reticulospinal neurons were organized by a LIM homeobox transcription factor “code” into five spatially distinct subclasses, and Spp1-positive rubrospinal neurons displayed larger soma size and fast-firing electrophysiological properties.
Conclusions: This study establishes a comprehensive molecular taxonomy of brain-wide SPNs, linking transcriptional identity to anatomical distribution and functional specialization in descending motor pathways.
Winter CC, Jacobi A, Su J, Chung L, van Velthoven CTJ, Yao Z, Lee C, Zhang Z, Yu S, Gao K, Duque Salazar G, Kegeles E, Zhang Y, Tomihiro MC, Zhang Y, Yang Z, Zhu J, Tang J, Song X, Donahue RJ, Wang Q, McMillen D, Kunst M, Wang N, Smith KA, Romero GE, Frank MM, Krol A, Kawaguchi R, Geschwind DH, Feng G, Goodrich LV, Liu Y, Tasic B, Zeng H, He Z. A transcriptomic taxonomy of mouse brain-wide spinal projecting neurons. Nature 2023;624(7991):403-414. doi: 10.1038/s41586-023-06817-8.
