The Journal of neuroscience : the official journal of the Society for Neuroscience
-
Key neuropathological hallmarks of Alzheimer's disease (AD) are elevated levels of amyloid β-peptide (Aβ) species generated via amyloid precursor protein (APP) endoproteolysis and cleavage by the rate-limiting β-site enzyme 1 (BACE1). Because rodents do not develop amyloid pathologies, we here investigated whether AD-like endophenotypes can be created in mice by expression of human bace1. To avoid pitfalls of existing models, we introduced hbace1 via knock-in under the control of the CaMKII α promoter into the safe HPRT locus. ⋯ Behaviorally, deficits in habituation to a novel environment and semantic-like memory (social transmission of food preference) were detected from 3 to 4 months of age. Impairments in spatial learning strategies in long-term reference (water maze) and working memory (Y-maze) tasks presented at 6 months, and were distinct from reductions in locomotor activity and anxiety. Overall, our data indicate for the first time that targeted, subtle forebrain-specific expression through single gene knock-in of hBACE1 is sufficient to generate AD-relevant cognitive impairments amid corresponding histopathologies, confirming human BACE as the key parameter in amyloid pathogenesis.
-
Temporal properties of spike firing in the central nervous system (CNS) are critical for neuronal coding and the precision of information storage. Chronic pain has been reported to affect cognitive and emotional functions, in addition to trigger long-term plasticity in sensory synapses and behavioral sensitization. Less is known about the possible changes in temporal precision of cortical neurons in chronic pain conditions. ⋯ Bath application of glutamate receptor antagonists CNQX and AP5 abolished the enhancement of jitter induced by CFA injection or nerve injury, suggesting that the increased jitter depends on the glutamatergic synaptic transmission. Activation of adenylyl cyclases (ACs) by bath application of forskolin increased jitter, whereas genetic deletion of AC1 abolished the change of jitter caused by CFA inflammation. Our study provides strong evidence for long-term changes of temporal precision of information coding in cortical neurons after peripheral injuries and explains neuronal mechanism for chronic pain caused cognitive and emotional impairment.
-
Failure of remyelination in diseases, such as multiple sclerosis (MS), leads to permanent axonal damage and irreversible functional loss. The mechanisms controlling remyelination are currently poorly understood. Recent studies implicate the cyclin-dependent kinase 5 (Cdk5) in regulating oligodendrocyte (OL) development and myelination in CNS. ⋯ The number of CC1(+) cells in the lesion sites was significantly reduced in Cdk5 cKO compared with wild-type animals although the total number of oligodendrocyte lineage cells (Olig2(+) cells) was increased, suggesting that Cdk5 loss perturbs the transition of early OL lineage cell into mature OL and subsequent remyelination. The failure of remyelination in Cdk5 cKO animals was associated with a reduction in signaling through the Akt pathway and an enhancement of Gsk-3β signaling pathways. Together, these data suggest that Cdk5 is critical in regulating the transition of adult oligodendrocyte precursor cells to mature OLs that is essential for myelin repair in adult CNS.
-
When the brain or spinal cord is injured, glial cells in the damaged area undergo complex morphological and physiological changes resulting in the formation of the glial scar. This scar contains reactive astrocytes, activated microglia, macrophages and other myeloid cells, meningeal cells, proliferating oligodendrocyte precursor cells (OPCs), and a dense extracellular matrix. Whether the scar is beneficial or detrimental to recovery remains controversial. ⋯ Viral-induced expression of Wnt3a in the normal adult mouse spinal cord induces an injury-like response in glia. Thus canonical Wnt signaling is both necessary and sufficient to induce injury responses among glial cells. These data suggest that targeting Wnt expression after SCI may have therapeutic potential in promoting axon regeneration.
-
MicroRNAs (miRs) are small noncoding RNAs that negatively regulate gene expression at the post-transcriptional level. To identify miRs that may regulate neuronal cell death after experimental traumatic brain injury (TBI), we profiled miR expression changes during the first several days after controlled cortical impact (CCI) in mice. miR-23a and miR-27a were rapidly downregulated in the injured cortex in the first hour after TBI. These changes coincided with increased expression of the proapoptotic Bcl-2 family members Noxa, Puma, and Bax. ⋯ Importantly, administration of miR-23a and miR-27a mimics significantly reduced activation of Puma, Noxa, and Bax as well as attenuated markers of caspase-dependent and -independent apoptosis after TBI. Furthermore, miR-23a and miR-27a mimics significantly attenuated cortical lesion volume and neuronal cell loss in the hippocampus after TBI. These findings indicate that post-traumatic decreases in miR-23a and miR-27a contribute to neuronal cell death after TBI by upregulating proapoptotic Bcl-2 family members, thus providing a novel therapeutic target.