AUTHOR=Sheikh Imran S. , Keefe Kathleen M. , Sterling Noelle A. , Junker Ian P. , Eneanya Chidubem I. , Liu Yingpeng , Tang Xiao-Qing , Smith George M. TITLE=Retrogradely Transportable Lentivirus Tracers for Mapping Spinal Cord Locomotor Circuits JOURNAL=Frontiers in Neural Circuits VOLUME=12 YEAR=2018 URL=https://www.frontiersin.org/journals/neural-circuits/articles/10.3389/fncir.2018.00060 DOI=10.3389/fncir.2018.00060 ISSN=1662-5110 ABSTRACT=

Retrograde tracing is a key facet of neuroanatomical studies involving long distance projection neurons. Previous groups have utilized a variety of tools ranging from classical chemical tracers to newer methods employing viruses for gene delivery. Here, we highlight the usage of a lentivirus that permits highly efficient retrograde transport (HiRet) from synaptic terminals within the cervical and lumbar enlargements of the spinal cord. By injecting HiRet, we can clearly identify supraspinal and propriospinal circuits innervating motor neuron pools relating to forelimb and hindlimb function. We observed robust labeling of propriospinal neurons, including high fidelity details of dendritic arbors and axon terminals seldom seen with chemical tracers. In addition, we examine changes in interneuronal circuits occurring after a thoracic contusion, highlighting populations that potentially contribute to spontaneous behavioral recovery in this lesion model. Our study demonstrates that the HiRet lentivirus is a unique tool for examining neuronal circuitry within the brain and spinal cord.