Role of densin-180 in mouse ventral hippocampal neurons in 24-hr retention of contextual fear conditioning

CircularLRRC7 is a Potential Tumor Suppressor Associated With miR-1281 and PDXP Expression in Glioblastoma

Circular RNAs (circRNAs) are usually enriched in neural tissues, yet about 80% circRNAs have lower expression in gliomas relative to normal brains, highlighting the importance of circRNAs as tumor suppressors. However, the clinical impact as well as the pathways regulated by the tumor-suppressive circRNAs remain largely unknown in glioblastoma (GBM). Through bioinformatic analysis followed by experimental validation, we found that hsa_circ_0114014 (circLRRC7) was dramatically down-regulated in GBM when compared with normal brain tissues (p < 0.0001). GBM patients with a lower circLRRC7 expression had poorer progression-free survival (PFS, p < 0.05) and overall survival (OS, p < 0.05). Analyses of the predicted target miRNAs of circLRRC7 in CSCD and CRI databases, in combination with the miRNA expression data in GBMs and normal brains from GSE database, revealed miR-1281 as a potential downstream target of circLRRC7. Subsequently, the target genes of hsa-mir-1281 were predicted by TargetScan, miRDB and miRNATAR databases. Intersection analysis and correlation test indicated that PDXP was a potential target of miR-1281. In summary, circLRRC7 may be a tumor suppressor that associated with miR-1281 and PDXP expression in GBM, which may provide novel therapeutic targets for GBM treatment.

Isoxazole-9 reduces enhanced fear responses and retrieval in ethanol-dependent male rats

Plasticity in the dentate gyrus (DG) is strongly influenced by ethanol, and ethanol experience alters long-term memory consolidation dependent on the DG. However, it is unclear if DG plasticity plays a role in dysregulation of long-term memory consolidation during abstinence from chronic ethanol experience. Outbred male Wistar rats experienced 7 weeks of chronic intermittent ethanol vapor exposure (CIE). Seventy-two hours after CIE cessation, CIE and age-matched ethanol-naïve Air controls experienced auditory trace fear conditioning (TFC). Rats were tested for cue-mediated retrieval in the fear context either twenty-four hours (24 hr), ten days (10 days), or twenty-one days (21 days) later. CIE rats showed enhanced freezing behavior during TFC acquisition compared to Air rats. Air rats showed significant fear retrieval, and this behavior did not differ at the three time points. In CIE rats, fear retrieval increased over time during abstinence, indicating an incubation in fear responses. Enhanced retrieval at 21 days was associated with reduced structural and functional plasticity of ventral granule cell neurons (GCNs) and reduced expression of synaptic proteins important for neuronal plasticity. Systemic treatment with the drug Isoxazole-9 (Isx-9; small molecule that stimulates DG plasticity) during the last week and a half of CIE blocked altered acquisition and retrieval of fear memories in CIE rats during abstinence. Concurrently, Isx-9 modulated the structural and functional plasticity of ventral GCNs and the expression of synaptic proteins in the ventral DG. These findings identify that abstinence-induced disruption of fear memory consolidation occurs via altered plasticity within the ventral DG, and that Isx-9 prevented these effects.

Role of densin-180 in mouse ventral hippocampal neurons in 24-hr retention of contextual fear conditioning

INTRODUCTION

Densin-180 interacts with postsynaptic molecules including calcium/calmodulin-dependent protein kinase IIα (CaMKIIα) but its function in learning and memory process has been unclear.

METHODS

To investigate a role of hippocampal densin-180 in contextual fear conditioning (CFC) learning and memory processes, knockdown (KD) of densin-180 in hippocampal subareas was applied.

RESULTS

First, ventral hippocampal (vHC) densin-180 KD impaired single-trial CFC (stCFC) memory one day later. stCFC caused freezing behaviors to reach the peak about one hour later in both control and KD mice, but then freezing was disappeared at 2 hr postshock in KD mice. Second, stCFC caused an immediate and transient reduction of vHC densin-180 in control mice, which was not observed in KD mice. Third, stCFC caused phosphorylated-T286 (p-T286) CaMKIIα to change similarly to densin-180, but p-T305 CaMKIIα was increased 1 hr later in control mice. In KD mice, these effects were gone. Moreover, both basal levels of p-T286 and p-T305 CaMKIIα were reduced without change in total CaMKIIα in KD mice. Fourth, we found double-trial CFC (dtCFC) memory acquisition and retrieval kinetics were different from those of stCFC in vHC KD mice. In addition, densin-180 in dorsal hippocampal area appeared to play its unique role during the very early retrieval period of both CFC memories.

CONCLUSION

This study shows that vHC densin-180 is necessary for stCFC memory formation and retrieval and suggests that both densin-180 and p-T305 CaMKIIα at 1 ~ 2 hr postshock are important for stCFC memory formation. We conclude that roles of hippocampal neuronal densin-180 in CFC are temporally dynamic and differential depending on the pattern of conditioning stimuli and its location along the dorsoventral axis of hippocampal formation.