Overexpression of EphB6 and EphrinB2 controls soma spacing of cortical neurons in a mutual inhibitory way.

To establish functional circuitry, neurons settle down in a particular spatial domain by spacing their cell bodies, which requires proper positioning of the soma and establishing of a zone with unique connections. Deficits in this process are implicated in neurodevelopmental diseases. In this study, we examined the function of EphB6 in the development of cerebral cortex. Overexpression of EphB6 via in utero electroporation results in clumping of cortical neurons, while reducing its expression has no effect. In addition, overexpression of EphrinB2, a ligand of EphB6, also induces soma clumping in the cortex. Unexpectedly, the soma clumping phenotypes disappear when both of them are overexpressed in cortical neurons. The mutual inhibitory effect of EphB6/ EphrinB2 on preventing soma clumping is likely to be achieved via interaction of their specific domains. Thus, our results reveal a combinational role of EphrinB2/EphB6 overexpression in controlling soma spacing in cortical development.

Dystonia-like behaviors and impaired sensory-motor integration following neurotoxic lesion of the pedunculopontine tegmental nucleus in mice.

Introduction: The pedunculopontine nucleus (PPTg) is a vital interface between the basal ganglia and cerebellum, participating in modulation of the locomotion and muscle tone. Pathological changes of the PPTg have been reported in patients and animal models of dystonia, while its effect and mechanism on the phenotyping of dystonia is still unknown. Methods: In this study, a series of behavioral tests focusing on the specific deficits of dystonia were conducted for mice with bilateral and unilateral PPTg excitotoxic lesion, including the dystonia-like movements evaluation, different types of sensory-motor integrations, explorative behaviors and gait. In addition, neural dysfunctions including apoptosis, neuroinflammation, neurodegeneration and neural activation of PPTg-related motor areas in the basal ganglia, reticular formations and cerebellum were also explored. Results: Both bilateral and unilateral lesion of the PPTg elicited dystonia-like behaviors featured by the hyperactivity of the hindlimb flexors. Moreover, proprioceptive and auditory sensory-motor integrations were impaired in bilaterally lesioned mice, while no overt alterations were found for the tactile sensory-motor integration, explorative behaviors and gait. Similar but milder behavioral deficits were found in the unilaterally lesioned mice, with an effective compensation was observed for the auditory sensory-motor integration. Histologically, no neural loss, apoptosis, neuroinflammation and neurodegeneration were found in the substantia nigra pars compacta and caudate putamen (CPu) following PPTg lesion, while reduced neural activity was found in the dorsolateral part of the CPu and striatal indirect pathway-related structures including subthalamic nucleus, globus pallidus internus and substantia nigra pars reticular. Moreover, the neural activity was decreased for the reticular formations such as pontine reticular nucleus, parvicellular reticular nucleus and gigantocellular reticular nucleus, while deep cerebellar nuclei were spared. Conclusion: In conclusion, lesion of the PPTg could elicit dystonia-like behaviors through its effect on the balance of the striatal pathways and the reticular formations.

Dystonia and the pedunculopontine nucleus: Current evidences and potential mechanisms.

Being a major component of the midbrain locomotion region, the pedunculopontine nucleus (PPN) is known to have various connections with the basal ganglia, the cerebral cortex, thalamus, and motor regions of the brainstem and spinal cord. Functionally, the PPN is associated with muscle tone control and locomotion modulation, including motor initiation, rhythm and speed. In addition to its motor functions, the PPN also contribute to level of arousal, attention, memory and learning. Recent studies have revealed neuropathologic deficits in the PPN in both patients and animal models of dystonia, and deep brain stimulation of the PPN also showed alleviation of axial dystonia in patients of Parkinson's disease. These findings indicate that the PPN might play an important role in the development of dystonia. Moreover, with increasing preclinical evidences showed presence of dystonia-like behaviors, muscle tone changes, impaired cognitive functions and sleep following lesion or neuromodulation of the PPN, it is assumed that the pathological changes of the PPN might contribute to both motor and non-motor manifestations of dystonia. In this review, we aim to summarize the involvement of the PPN in dystonia based on the current preclinical and clinical evidences. Moreover, potential mechanisms for its contributions to the manifestation of dystonia is also discussed base on the dystonia-related basal ganglia-cerebello-thalamo-cortical circuit, providing fundamental insight into the targeting of the PPN for the treatment of dystonia in the future.

Deletion of Schizophrenia Susceptibility Gene Ulk4 Leads to Abnormal Cognitive Behaviors via Akt-GSK-3 Signaling Pathway in Mice.

OBJECTIVES: Despite of strenuous research in the past decades, the etiology of schizophrenia (SCZ) still remains incredibly controversial. Previous genetic analysis has uncovered a close association of Unc-51 like kinase 4 (ULK4), a family member of Unc-51-like serine/threonine kinase, with SCZ. However, animal behavior data which may connect Ulk4 deficiency with psychiatric disorders, particularly SCZ are still missing. METHODS: We generated Emx1-Cre:Ulk4flox/flox conditional knockout (CKO) mice, in which Ulk4 was deleted in the excitatory neurons of cerebral cortex and hippocampus. RESULTS: The cerebral cellular architecture was maintained but the spine density of pyramidal neurons was reduced in Ulk4 CKO mice. CKO mice showed deficits in the spatial and working memories and sensorimotor gating. Levels of p-Akt and p-GSK-3α/ß were markedly reduced in the CKO mice indicating an elevation of GSK-3 signaling. Mechanistically, Ulk4 may regulate the GSK-3 signaling via putative protein complex comprising of two phosphatases, protein phosphatase 2A (PP2A) and 1α (PP1α). Indeed, the reduction of p-Akt and p-GSK-3α/ß was rescued by administration of inhibitor acting on PP2A and PP1α in CKO mice. CONCLUSIONS: Our data identified potential downstream signaling pathway of Ulk4, which plays important roles in the cognitive functions and when defective, may promote SCZ-like pathogenesis and behavioral phenotypes in mice.

Dynamic muscle paralytic effects of a novel botulinum toxin A free of neurotoxin-associated proteins.

Structurally, botulinum toxin type A (BTX-A) is composed of neurotoxin and nontoxic complexing proteins (CPs), and the neurotoxin has the function of blocking acetylcholine release from the neuromuscular junction and therefore paralyzing muscles. Nowadays, a novel botulinum toxin A free of CPs (chinbotulinumtoxin A, A/Chin) is produced, and the present study comprehensively evaluated the dynamic paralytic effect of A/Chin on the gastrocnemius muscle of rats. Different doses (0.01, 0.1, 0.5, 1, 2, and 4 U) of A/Chin and other BTX-As with and without CPs were administered to the gastrocnemius muscles of rats and muscle strength was measured and compared at different postinjection timepoints (from day 0 to 84). With the dose increased, time-to-peak paralytic effect of other BTX-As varied from day 3 to day 14, while A/Chin groups showed rapid and steady time to peak on day 3. At the lowest dose of 0.01 U, A/Chin showed significantly better peak paralytic effect than the others on day 3. When the dose increased to 0.5 U and more, A/Chin group also showed significant paralytic effect when the paralytic effect of other BTX-As was worn off. Moreover, the paralytic effect of A/Chin was confirmed as muscle atrophy while hematoxylin-eosin staining was performed. In conclusion, compared with other BTX-As, A/Chin showed rapid and steady time-to-peak paralytic effect and long-term paralytic efficacy at the same dose level. And it might lay a solid foundation for further wide application of A/Chin in both clinical and cosmetic areas.

Synkinesis in primary and postparalytic hemifacial spasm: Clinical features and therapeutic outcomes of botulinum toxin A treatment.

Facial synkinesis can be present in both primary and postparalytic hemifacial spasm (HFS). The present retrospective study aimed to summarize the clinical features of synkinesis and explore an appropriate botulinum toxin A (BoNT-A) injection strategy to manage the synkinesis accompanying HFS. Video recordings of 234 patients with primary and postparalytic HFSs were analyzed. Improvements in the severity of spasm and synkinesis owing to BoNT-A treatment were monitored and compared among 36 primary and 12 postparalytic HFS patients with synkinesis and completed follow-up records. BoNT-A was injected into the voluntary facial region (VFR), the synkinetic facial region (SFR), or both VFR and SFR, and the efficacy of these strategies was evaluated and analyzed. Oral-ocular synkinesis in the primary group (32.8%) and ocular-oral synkinesis in the postparalytic group (81.0%) showed the highest incidence. Patients in both the primary and postparalytic groups exhibited a tremendous alleviation of spasm (97.2% vs. 91.7%, P > 0.05) following BoNT-A treatment. In both groups, coinjection and SFR injection were commonly used and effective in treatment of ocular and oral synkinesis, while VFR was frequently used but ineffective for frontal synkinesis. In addition, the improper muscle selection surrounding the mouth corner resulted in pattern change and treatment failure of oral synkinesis. Synkinesis mostly affected the ocular and oral regions. BoNT-A, via treatment of SFR, is effective against synkinesis accompanying HFS.