Reward-related behavior is complex and its dysfunction correlated with neuropsychiatric illness. Dopamine (DA) neurons of the ventral tegmental area (VTA) have long been associated with different aspects of reward function, but it remains to be disentangled how distinct VTA DA neurons contribute to the full range of behaviors ascribed to the VTA. Here, a recently identified subtype of VTA neurons molecularly defined by NeuroD6 (NEX1M) was addressed. Among all VTA DA neurons, less than 15% were identified as positive for NeuroD6. In addition to dopaminergic markers, sparse NeuroD6 neurons expressed the vesicular glutamate transporter 2 (Vglut2) gene. To achieve manipulation of NeuroD6 VTA neurons, NeuroD6(NEX)-Cre-driven mouse genetics and optogenetics were implemented. First, expression of vesicular monoamine transporter 2 (VMAT2) was ablated to disrupt dopaminergic function in NeuroD6 VTA neurons. Comparing Vmat2 lox/lox;NEX-Cre conditional knockout (cKO) mice with littermate controls, it was evident that baseline locomotion, preference for sugar and ethanol, and place preference upon amphetamine-induced and cocaine-induced conditioning were similar between genotypes. However, locomotion upon repeated psychostimulant administration was significantly elevated above control levels in cKO mice. Second, optogenetic activation of NEX-Cre VTA neurons was shown to induce DA release and glutamatergic postsynaptic currents within the nucleus accumbens. Third, optogenetic stimulation of NEX-Cre VTA neurons in vivo induced significant place preference behavior, while stimulation of VTA neurons defined by Calretinin failed to cause a similar response. The results show that NeuroD6 VTA neurons exert distinct regulation over specific aspects of reward-related behavior, findings that contribute to the current understanding of VTA neurocircuitry.

The subthalamic nucleus (STN) is crucial for normal motor, limbic and associative function. STN dysregulation is correlated with several brain disorders, including Parkinsonʼs disease and obsessive compulsive disorder (OCD), for which high-frequency stimulation of the STN is increasing as therapy. However, clinical progress is hampered by poor knowledge of the anatomical-functional organization of the STN. Today, experimental mouse genetics provides outstanding capacity for functional decoding, provided selective promoters are available. Here, we implemented single-nuclei RNA sequencing (snRNASeq) of the mouse STN followed through with histological analysis of 16 candidate genes of interest. Our results demonstrate that the mouse STN is composed of at least four spatio-molecularly defined domains, each distinguished by defined sets of promoter activities. Further, molecular profiles dissociate the STN from the adjoining para-STN (PSTN) and neighboring structures of the hypothalamus, mammillary nuclei and zona incerta. Enhanced knowledge of STN´s internal organization should prove useful towards genetics-based functional decoding of this clinically relevant brain structure.

Stem cell transplantation holds great hope for the replacement of damaged cells in the nervous system. However, poor long-term survival after transplantation and insufficiently robust differentiation of stem cells into specialized cell types in vivo remain major obstacles for clinical application. Here, we report the development of a novel technological approach for the local delivery of exogenous trophic factor mimetics to transplanted cells using specifically designed silica nanoporous particles. We demonstrated that delivering Cintrofin and Gliafin, established peptide mimetics of the ciliary neurotrophic factor and glial cell line-derived neurotrophic factor, respectively, with these particles enabled not only robust functional differentiation of motor neurons from transplanted embryonic stem cells but also their long-term survival in vivo. We propose that the delivery of growth factors by mesoporous nanoparticles is a potentially versatile and widely applicable strategy for efficient differentiation and functional integration of stem cell derivatives upon transplantation. STEM CELLS TRANSLATIONAL MEDICINE 2013;2:906 -915

Spinal root avulsion results in paralysis and sensory loss, and is commonly associated with chronic pain. In addition to the failure of avulsed dorsal root axons to regenerate into the spinal cord, avulsion injury leads to extensive neuroinflammation and degeneration of second-order neurons in the dorsal horn. The ultimate objective in the treatment of this condition is to counteract degeneration of spinal cord neurons and to achieve functionally useful regeneration/reconnection of sensory neurons with spinal cord neurons. Here we compare survival and migration of murine boundary cap neural crest stem cells (bNCSCs) and embryonic stem cells (ESCs)-derived, predifferentiated neuron precursors after their implantation acutely at the junction between avulsed dorsal roots L3-L6 and the spinal cord. Both types of cells survived transplantation, but showed distinctly different modes of migration. Thus, bNCSCs migrated into the spinal cord, expressed glial markers and formed elongated tubes in the peripheral nervous system (PNS) compartment of the avulsed dorsal root transitional zone (DRTZ) area. In contrast, the ESC transplants remained at the site of implantation and differentiated to motor neurons and interneurons. These data show that both stem cell types successfully survived implantation to the acutely injured spinal cord and maintained their differentiation and migration potential. These data suggest that, depending on the source of neural stem cells, they can play different beneficial roles for recovery after dorsal root avulsion. Copyright © 2014 John Wiley & Sons, Ltd.

BackgroundThe boundary cap is a transient group of neural crest-derived cells located at the presumptive dorsal root transitional zone (DRTZ) when sensory axons enter the spinal cord during development. Later, these cells migrate to dorsal root ganglia and differentiate into subtypes of sensory neurons and glia. After birth when the DRTZ is established, sensory axons are no longer able to enter the spinal cord. Here we explored the fate of mouse boundary cap neural crest stem cells (bNCSCs) implanted to the injured DRTZ after dorsal root avulsion for their potential to assist sensory axon regeneration.ResultsGrafted cells showed extensive survival and differentiation after transplantation to the avulsed DRTZ. Transplanted cells located outside the spinal cord organized elongated tubes of Sox2/GFAP expressing cells closely associated with regenerating sensory axons or appeared as small clusters on the surface of the spinal cord. Other cells, migrating into the host spinal cord as single cells, differentiated to spinal cord neurons with different neurotransmitter characteristics, extensive fiber organization, and in some cases surrounded by glutamatergic terminal-like profiles.ConclusionsThese findings demonstrate that bNCSCs implanted at the site of dorsal root avulsion injury display remarkable differentiation plasticity inside the spinal cord and in the peripheral compartment where they organize tubes associated with regenerating sensory fibers. These properties offer a basis for exploring the ability of bNCSCs to assist regeneration of sensory axons into the spinal cord and replace lost neurons in the injured spinal cord.