Origin of a Non-Clarke’s Column Division of the Dorsal Spinocerebellar Tract and the Role of Caudal Proprioceptive Neurons in Motor Function

• Atoh1-lineage cells form a non-Clarke’s column set of spinocerebellar neurons
• Spinocerebellar pathways derive from more than one progenitor domain
• Elimination of caudal Atoh1 leads to defects in coordinated movement
• Diverse proprioceptive pathways contribute differentially to motor output

SummaryProprioception, the sense of limb and body position, is essential for generating proper movement. Unconscious proprioceptive information travels through cerebellar-projecting neurons in the spinal cord and medulla. The progenitor domain defined by the basic-helix-loop-helix (bHLH) transcription factor, ATOH1, has been implicated in forming these cerebellar-projecting neurons; however, their precise contribution to proprioceptive tracts and motor behavior is unknown. Significantly, we demonstrate that Atoh1-lineage neurons in the spinal cord reside outside Clarke’s column (CC), a main contributor of neurons relaying hindlimb proprioception, despite giving rise to the anatomical and functional correlate of CC in the medulla, the external cuneate nucleus (ECu), which mediates forelimb proprioception. Elimination of caudal Atoh1-lineages results in mice with relatively normal locomotion but unable to perform coordinated motor tasks. Altogether, we reveal that proprioceptive nuclei in the spinal cord and medulla develop from more than one progenitor source, suggesting an avenue to uncover distinct proprioceptive functions.

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