Single nuclei analyses reveal transcriptional profiles and marker genes for diverse supraspinal populations

Abstract

The mammalian brain contains numerous neurons distributed across forebrain, midbrain, and hindbrain that project axons to the lower spinal cord and work in concert to control movement and achieve homeostasis. Extensive work has mapped the anatomical location of supraspinal cell types and continues to establish specific physiological functions. The patterns of gene expression that typify and distinguish these disparate populations, however, are mostly unknown. Here we combined retrograde labeling of supraspinal cell nuclei with fluorescence activated nuclei sorting and single nuclei RNA sequencing analyses to transcriptionally profile neurons that project axons from the mouse brain to lumbar spinal cord. We identified fourteen transcriptionally distinct cell types and used a combination of established and newly identified marker genes to assign an anatomical location to each. To validate the putative marker genes, we visualized selected transcripts and confirmed selective expression within lumbar-projecting neurons in discrete supraspinal regions. Finally, we illustrate the potential utility of these data by examining the expression of transcription factors that distinguish different supraspinal cell types and by surveying the expression of receptors for growth and guidance cues that may be present in the spinal cord. Collectively these data establish transcriptional differences between anatomically defined supraspinal populations, identify a new set of marker genes of use in future experiments, and provide insight into potential differences in cellular and physiological activity across the supraspinal connectome.