✍🏼 Vibhu Sahni, Julia Kaiser, Payal Patel, Samuel Fedde, Alexander Lammers, Matthew Kenwood, Asim Iqbal, Mark Goldberg

🏠 Burke Neurological Institute, Weill Cornell Medicine, NY, USA

📑 Research Square (2025)

Abstract
Skilled movement relies on descending cortical projections to the brainstem and spinal cord. While corticospinal neurons (CSN) have long been recognized for their role in fine motor control, the contribution of cortical projections to the brainstem remains poorly understood. Here, we identify a previously unrecognized direct cortico-brainstem circuit that emerges early in development and persists into adulthood. A subset of subcerebral projection neurons (SCPN) limit their projections to the brainstem from the earliest stages of axon extension without ever extending to the spinal cord. Using FACS purification and single-cell RNA sequencing, we show that these cortico-brainstem neurons (CBN) can be prospectively identified by the expression of Neuropeptide Y (Npy) in development. Functional silencing of Npy+ CBN in adulthood leads to impaired skilled forelimb reaching, demonstrating their essential role in adult motor control. Npy+ CBN project preferentially to rostral brainstem regions, including the midbrain reticular formation. These findings reveal developmental molecular signatures that define cortico-brainstem pathways for adult skilled movement. Our work provides new insights into the developmental logic that establishes descending cortical circuits and opens avenues for targeted investigation of their roles in motor function and recovery after injury.

How the WOLF is used in this Study
The authors used a WOLF cell sorter to prospectively purify specific neuronal populations from dissociated mouse brain tissue for downstream molecular analysis. Following enzymatic and mechanical dissociation of sensorimotor cortex samples containing fluorescently labeled subcerebral projection neurons (CBN and related cell types), the WOLF sorter was used to isolate target cells based on size and fluorescent marker expression from the heterogeneous single-cell suspension. This sorting step enriched for the specific neuronal subtypes of interest, enabling high-quality single-cell transcriptomic profiling that underlies the identification of molecular signatures defining cortico-brainstem projections during development.