Segregated basal ganglia output pathways correspond to genetically divergent neuronal subclasses.

The basal ganglia control multiple sensorimotor behaviors though anatomically segregated and topographically organized subcircuits with outputs to specific downstream circuits. However, it is unclear how the anatomical organization of basal ganglia output circuits relates to the molecular diversity of cell types. Here, we demonstrate that the major output nucleus of the basal ganglia, the substantia nigra pars reticulata (SNr) is comprised of transcriptomically distinct subclasses that reflect its distinct progenitor lineages.

Divergent Hox Coding and Evasion of Retinoid Signaling Specifies Motor Neurons Innervating Digit Muscles.

The establishment of spinal motor neuron subclass diversity is achieved through developmental programs that are aligned with the organization of muscle targets in the limb. The evolutionary emergence of digits represents a specialized adaptation of limb morphology, yet it remains unclear how the specification of digit-innervating motor neuron subtypes parallels the elaboration of digits. We show that digit-innervating motor neurons can be defined by selective gene markers and distinguished from other LMC neurons by the expression of a variant Hox gene repertoire and by the failure to express a key enzyme involved in retinoic acid synthesis.

Sensory-Derived Glutamate Regulates Presynaptic Inhibitory Terminals in Mouse Spinal Cord.

Circuit function in the CNS relies on the balanced interplay of excitatory and inhibitory synaptic signaling. How neuronal activity influences synaptic differentiation to maintain such balance remains unclear. In the mouse spinal cord, a population of GABAergic interneurons, GABApre, forms synapses with the terminals of proprioceptive sensory neurons and controls information transfer at sensory-motor connections through presynaptic inhibition.

Activity Regulates the Incidence of Heteronymous Sensory-Motor Connections.

The construction of spinal sensory-motor circuits involves the selection of appropriate synaptic partners and the allocation of precise synaptic input densities. Many aspects of spinal sensory-motor selectivity appear to be preserved when peripheral sensory activation is blocked, which has led to a view that sensory-motor circuits are assembled in an activity-independent manner. Yet it remains unclear whether activity-dependent refinement has a role in the establishment of connections between sensory afferents and those motor pools that have synergistic biomechanical functions.