Anatomical and Molecular Properties of Long Descending Propriospinal Neurons in Mice.

Long descending propriospinal neurons (LDPNs) are interneurons that form direct connections between cervical and lumbar spinal circuits. LDPNs are involved in interlimb coordination and are important mediators of functional recovery after spinal cord injury (SCI). Much of what we know about LDPNs comes from a range of species, however, the increased use of transgenic mouse lines to better define neuronal populations calls for a more complete characterisation of LDPNs in mice.

Identification of spinal circuits transmitting and gating mechanical pain.

Pain information processing in the spinal cord has been postulated to rely on nociceptive transmission (T) neurons receiving inputs from nociceptors and Aβ mechanoreceptors, with Aβ inputs gated through feed-forward activation of spinal inhibitory neurons (INs). Here, we used intersectional genetic manipulations to identify these critical components of pain transduction. Marking and ablating six populations of spinal excitatory and inhibitory neurons, coupled with behavioral and electrophysiological analysis, showed that excitatory neurons expressing somatostatin (SOM) include T-type cells, whose ablation causes loss of mechanical pain.

V1 and v2b interneurons secure the alternating flexor-extensor motor activity mice require for limbed locomotion.

Reciprocal activation of flexor and extensor muscles constitutes the fundamental mechanism that tetrapod vertebrates use for locomotion and limb-driven reflex behaviors. This aspect of motor coordination is controlled by inhibitory neurons in the spinal cord; however, the identity of the spinal interneurons that serve this function is not known. Here, we show that the production of an alternating flexor-extensor motor rhythm depends on the composite activities of two classes of ventrally located inhibitory neurons, V1 and V2b interneurons (INs).

Cell-type specific regulation of cortical excitability through the allatostatin receptor system.

Recent technical advances enable the regulation of neuronal circuit activity with high spatial and temporal resolution through genetic delivery of molecular activation or inactivation systems.Among them, the allatostatin receptor (AlstR)/ligand system has been developed for selective and quickly reversible silencing of mammalian neurons. However, targeted AlstR-mediated inactivation of specific neuronal types, particularly diverse types of inhibitory interneurons, remains to be established.

V3 spinal neurons establish a robust and balanced locomotor rhythm during walking.

A robust and well-organized rhythm is a key feature of many neuronal networks, including those that regulate essential behaviors such as circadian rhythmogenesis, breathing, and locomotion. Here we show that excitatory V3-derived neurons are necessary for a robust and organized locomotor rhythm during walking. When V3-mediated neurotransmission is selectively blocked by the expression of the tetanus toxin light chain subunit (TeNT), the regularity and robustness of the locomotor rhythm is severely perturbed.

V1 spinal neurons regulate the speed of vertebrate locomotor outputs.

The neuronal networks that generate vertebrate movements such as walking and swimming are embedded in the spinal cord. These networks, which are referred to as central pattern generators (CPGs), are ideal systems for determining how ensembles of neurons generate simple behavioural outputs. In spite of efforts to address the organization of the locomotor CPG in walking animals, little is known about the identity and function of the spinal interneuron cell types that contribute to these locomotor networks.

Brn3a-expressing retinal ganglion cells project specifically to thalamocortical and collicular visual pathways.

Retinal ganglion cells (RGCs) innervate several specific CNS targets serving cortical and subcortical visual pathways and the entrainment of circadian rhythms. Recent studies have shown that retinal ganglion cells express specific combinations of POU- and LIM-domain transcription factors, but how these factors relate to the subsequent development of the retinofugal pathways and the functional identity of RGCs is mostly unknown. Here, we use targeted expression of an genetic axonal tracer, tau/beta-galactosidase, to examine target innervation by retinal ganglion cells expressing the POU-domain factor Brn3a.

Pax6 and engrailed 1 regulate two distinct aspects of renshaw cell development.

Many of the interneuron cell types present in the adult spinal cord contribute to the circuits that control locomotion and posture. Little is known, however, about the embryonic origin of these cell types or the molecular mechanisms that control their differentiation. Here we provide evidence that V1 interneurons (INs), an embryonic class of interneurons that transiently express the En1 transcription factor, differentiate as local circuit inhibitory interneurons and form synapses with motor neurons.