Activated somatostatin interneurons orchestrate memory microcircuits

Despite recent advancements in identifying engram cells, our understanding of their regulatory and functional mechanisms remains in its infancy. To provide mechanistic insight into engram cell functioning, we introduced a novel local microcircuit labeling technique that enables the labeling of intraregional synaptic connections. Utilizing this approach, we discovered a unique population of somatostatin (SOM) interneurons in the mouse basolateral amygdala (BLA). These neurons are activated during fear memory formation and exhibit a preference for forming synapses with excitatory engram neurons. Post-activation, these SOM neurons displayed varying excitability based on fear memory retrieval. Furthermore, when we modulated these SOM neurons chemogenetically, we observed changes in the expression of fear-related behaviors, both in a fear-associated context and in a novel setting. Our findings suggest that these activated SOM interneurons play a pivotal role in modulating engram cell activity. They influence the expression of fear-related behaviors through a mechanism that is dependent on memory cues.

Hippocampal engram networks for fear memory recruit new synapses and modify pre-existing synapses in vivo

As basic units of neural networks, ensembles of synapses underlie cognitive functions such as learning and memory. These synaptic engrams show elevated synaptic density among engram cells following contextual fear memory formation. Subsequent analysis of the CA3-CA1 engram synapse revealed larger spine sizes, as the synaptic connectivity correlated with the memory strength. Here, we elucidate the synapse dynamics between CA3 and CA1 by tracking identical synapses at multiple time points by adapting two-photon microscopy and dual-eGRASP technique in vivo. After memory formation, synaptic connections between engram populations are enhanced in conjunction with synaptogenesis within the hippocampal network. However, extinction learning specifically correlated with the disappearance of CA3 engram to CA1 engram (E-E) synapses. We observed "newly formed" synapses near pre-existing synapses, which clustered CA3-CA1 engram synapses after fear memory formation. Overall, we conclude that dynamics at CA3 to CA1 E-E synapses are key sites for modification during fear memory states.

Synaptic ensembles between raphe and D1R-containing accumbens shell neurons underlie postisolation sociability in males

Social animals expend considerable energy to maintain social bonds throughout their life. Male and female mice show sexually dimorphic behaviors, yet the underlying neural mechanisms of sociability and their dysregulation during social disconnection remain unknown. Dopaminergic neurons in dorsal raphe nucleus (DRN^TH) is known to contribute to a loneliness-like state and modulate sociability. We identified that activated subpopulations in DRN^TH and nucleus accumbens shell (NAc^sh) during 24 hours of social isolation underlie the increase in isolation-induced sociability in male but not in female mice. This effect was reversed by chemogenetically and optogenetically inhibiting the DRN^TH-NAc^sh circuit. Moreover, synaptic connectivity among the activated neuronal ensembles in this circuit was increased, primarily in D₁ receptor-expressing neurons in NAc^sh. The increase in synaptic density functionally correlated with elevated dopamine release into NAc^sh. Overall, specific synaptic ensembles in DRN^TH-NAc^sh mediate sex differences in isolation-induced sociability, indicating that sex-dependent circuit dynamics underlie the expression of sexually dimorphic behaviors.

Synaptic correlates of associative fear memory in the lateral amygdala

Successful adaptation to the environment requires an accurate response to external threats by recalling specific memories. Memory formation and recall require engram cell activity and synaptic strengthening among activated neuronal ensembles. However, elucidation of the underlying neural substrates of associative fear memory has remained limited without a direct interrogation of extinction-induced changes of specific synapses that encode a specific auditory fear memory. Using dual-eGRASP (enhanced green fluorescent protein reconstitution across synaptic partners), we found that synapses among activated neuronal ensembles or activated synaptic ensembles showed a significantly larger spine morphology at auditory cortex (AC)-to-lateral amygdala (LA) projections after auditory fear conditioning in mice. Fear extinction reversed these enhanced synaptic ensemble spines, whereas re-conditioning with the same tone and shock restored the spine size of the synaptic ensemble. We suggest that synaptic ensembles encode and represent different fear memory states.

The essence of the engram: Cellular or synaptic?

Memory is composed of various phases including cellular consolidation, systems consolidation, reconsolidation, and extinction. In the last few years it has been shown that simple association memories can be encoded by a subset of the neuronal population called engram cells. Activity of these cells is necessary and sufficient for the recall of association memory. However, it is unclear which molecular mechanisms allow cellular engrams to encode the diverse phases of memory. Further research is needed to examine the possibility that it is the synapses between engram cells (the synaptic engram) that constitute the memory. In this review we summarize recent findings on cellular engrams with a focus on different phases of memory, and discuss the distinct molecular mechanism required for cellular and synaptic engrams.

Conditional knock out of transcription factor CTCF in excitatory neurons induces cognitive deficiency

CCCTC-binding factor (CTCF) is a transcription factor that is involved in organizing chromatin structure. A reduction of CTCF expression is known to develop distinct clinical features. Furthermore, conditional knock out (cKO) study revealed reactive gliosis of astrocytes and microglia followed by age-dependent cell death in the excitatory neurons of CTCF cKO mice. To assess the cognitive ability in CTCF cKO mice of over 20 weeks of age, we examined pairwise discrimination (PD), PD reversal learning (PDr), and different paired-associate learning (dPAL) tasks using a touch screen apparatus. We found cognitive impairment in dPAL touch screen tests, suggesting that prolonged Ctcf gene deficiency results in cognitive deficits.

Loss of the neuronal genome organizer and transcription factor CTCF induces neuronal death and reactive gliosis in the anterior cingulate cortex

CCCTC-binding factor (CTCF) is a genome organizer that regulates gene expression through transcription and chromatin structure regulation. CTCF also plays an important role during the developmental and adult stages. Cell-specific CTCF deletion studies have shown that a reduction in CTCF expression leads to the development of distinct clinical features and cognitive disorders. Therefore, we knocked out Ctcf (CTCF cKO) in the excitatory neurons of the forebrain in a Camk2a-Cre mouse strain to examine the role of CTCF in cell death and gliosis in the cortex. CTCF cKO mice were viable, but they demonstrated an age-dependent increase in reactive gliosis of astrocytes and microglia in the anterior cingulate cortex (ACC) from 16 weeks of age prior to neuronal loss observed at over 20 weeks of age. Consistent with these data, qRT-PCR analysis of the CTCF cKO ACC revealed changes in the expression of inflammation-related genes (Hspa1a, Prokr2 and Itga8) linked to gliosis and neuronal death. Our results suggest that prolonged Ctcf gene deficiency in excitatory neurons results in neuronal cell death and gliosis, possibly through functional changes in inflammation-related genes.

Strengthened connections between engrams encode specific memories

In previous studies, memory storage was localized to engram cells distributed across the brain. While these studies have provided an individual cellular profile of engram cells, their synaptic connectivity, or whether they follow Hebbian mechanisms, remains uncertain. Therefore, our recent study investigated whether synapses between engram cells exhibit selectively enhanced structural and functional properties following memory formation. This was accomplished using a newly developed technique called “dual-eGRASP”. We found that the number and size of spines on CA1 engram cells that receive inputs from CA3 engram cells were larger than at other synapses. We further observed that this enhanced connectivity correlated with induced memory strength. CA3 engram synapses exhibited increased release probability, while CA1 engram synapses produced enhanced postsynaptic responses. CA3 engram to CA1 engram projections showed strong occlusion of long-term potentiation. We demonstrated that the synaptic connectivity of CA3 to CA1 engram cells was strengthened following memory formation. Our results suggest that Hebbian plasticity occurs during memory formation among engram cells at the synapse level.

Interregional synaptic maps among engram cells underlie memory formation

Memory resides in engram cells distributed across the brain. However, the site-specific substrate within these engram cells remains theoretical, even though it is generally accepted that synaptic plasticity encodes memories. We developed the dual-eGRASP (green fluorescent protein reconstitution across synaptic partners) technique to examine synapses between engram cells to identify the specific neuronal site for memory storage. We found an increased number and size of spines on CA1 engram cells receiving input from CA3 engram cells. In contextual fear conditioning, this enhanced connectivity between engram cells encoded memory strength. CA3 engram to CA1 engram projections strongly occluded long-term potentiation. These results indicate that enhanced structural and functional connectivity between engram cells across two directly connected brain regions forms the synaptic correlate for memory formation.

Clinical benefit and residual kidney function of en bloc nephrectomy for perirenal retroperitoneal sarcoma

AIM

The purpose of this study was to evaluate the efficacy of en bloc nephrectomy for perirenal retroperitoneal sarcoma (RPS) with respect to postoperative kidney function and oncological benefits.

METHODS

We performed a comparative study of 114 patients undergoing surgery for primary RPS, classifying cases as nephrectomy (NPX, n = 65) versus no nephrectomy (no-NPX, n = 49). The Δ and % change between preoperative and postoperative estimated glomerulus filtration rate (eGFR) were analyzed to compare renal function changes after surgery. Kaplan-Meier analysis was performed to verify the incidence of local relapse between the two groups.

RESULTS

During a median follow-up of 29 months, median postoperative GFR of 65 patients in the NPX group decreased to 73.5% of preoperative eGFR. Although 38 patients (58%) in the NPX group experienced a progression in chronic kidney disease stage after nephrectomy, no patients progressed to end-stage renal disease (ESRD). In French Federation of Cancer Centers Sarcoma grade 2, the NPX group had statistically significant local control benefits, compared with the no-NPX group (P = 0.048).

CONCLUSIONS

Residual renal function after en bloc nephrectomy was stabilized without progression to ESRD. Moreover, en bloc nephrectomy for perirenal RPS might secure a complete resection margin for local tumor control.

Clinical Application of Targeted Deep Sequencing in Solid-Cancer Patients and Utility for Biomarker-Selected Clinical Trials

Molecular profiling of actionable mutations in refractory cancer patients has the potential to enable "precision medicine," wherein individualized therapies are guided based on genomic profiling. The molecular-screening program was intended to route participants to different candidate drugs in trials based on clinical-sequencing reports. In this screening program, we used a custom target-enrichment panel consisting of cancer-related genes to interrogate single-nucleotide variants, insertions and deletions, copy number variants, and a subset of gene fusions. From August 2014 through April 2015, 654 patients consented to participate in the program at Samsung Medical Center. Of these patients, 588 passed the quality control process for the 381-gene cancer-panel test, and 418 patients were included in the final analysis as being eligible for any anticancer treatment (127 gastric cancer, 122 colorectal cancer, 62 pancreatic/biliary tract cancer, 67 sarcoma/other cancer, and 40 genitourinary cancer patients). Of the 418 patients, 55 (12%) harbored a biomarker that guided them to a biomarker-selected clinical trial, and 184 (44%) patients harbored at least one genomic alteration that was potentially targetable. This study demonstrated that the panel-based sequencing program resulted in an increased rate of trial enrollment of metastatic cancer patients into biomarker-selected clinical trials. Given the expanding list of biomarker-selected trials, the guidance percentage to matched trials is anticipated to increase.

IMPLICATIONS FOR PRACTICE

This study demonstrated that the panel-based sequencing program resulted in an increased rate of trial enrollment of metastatic cancer patients into biomarker-selected clinical trials. Given the expanding list of biomarker-selected trials, the guidance percentage to matched trials is anticipated to increase.

The NEXT-1 (Next generation pErsonalized tX with mulTi-omics and preclinical model) trial: prospective molecular screening trial of metastatic solid cancer patients, a feasibility analysis

We conducted a prospective genomic screening trial with high throughput sequencing and copy number variation (CNV) assay, and immunohistochemistry array in metastatic solid cancer patients. We used Ion AmpliSeq Cancer Hotspot Panel v2 and nCounter Copy Number Variation Assay (21 genes) to identify molecular targets for potential matched therapy. Metastatic solid tumor patients were prospectively consented for molecular profiling tests. The primary outcome for this trial was the feasibility of molecular tests and response rate (matched vs non-matched treatment). Between November 2013 and August 2014, a total of 428 metastatic solid tumor patients were enrolled on to this study. The mutational profiles were obtained for 407 (95.1%) patients. CNV 21-gene assays were successfully performed in 281 (65.7%) of 428 patients. Of the 407 patients with molecular profiling results, 342 (84.0%) patients had one or more aberrations detected. Of the 342 patients, 103 patients were matched to molecularly targeted agents in the context of clinical trials or clinical practice. The response rate was significantly higher in the genome-matched treated group for gastrointestinal/hepatobiliary/rare tumors (matched vs non-matched treatment, 42.6% vs 24.3%, P = .009) and lung cancer cohort (matched vs non-matched treatment, 61.2% vs 28.6% < P = .001) when compared with the non-matched group. In this trial, we demonstrate that genome-matched treatment based on molecular profiling result in better treatment outcome in terms of response rate.

Ovarian large cell neuroendocrine carcinoma in the youngest woman

Large cell neuroendocrine carcinoma (LCNC) of the ovary is a rare tumor in gynecologic oncologic field. An 18-year-old woman presented with abdominal distention and a pelvic mass measuring ten cm in diameter, who previously underwent laparoscopic ovarian cystectomy due to large borderline mucinous ovarian neoplasm 18 months prior. A debulking operation was optimally performed, which included total abdominal hysterectomy with bilateral salpingo-oophorectomy, bilateral pelvic lymph node dissection, bilateral paraaortic lymph node dissection, omentectomy, optimal debulking of gastrohepatic mass and subdiaphragmatic mass, and pelvic peritonectomy. Despite adjuvant chemotherapy with paclitaxel and carboplatin, the patient died of progressive disease seven months after surgery. The authors report the youngest case of LCNC of the ovary, that failed chemotherapy and had the previous history of the conservative surgical treatment due to mucinous borderline tumor.

Multiple repressive mechanisms in the hippocampus during memory formation

Memory stabilization after learning requires translational and transcriptional regulations in the brain, yet the temporal molecular changes that occur after learning have not been explored at the genomic scale. We used ribosome profiling and RNA sequencing to quantify the translational status and transcript levels in the mouse hippocampus after contextual fear conditioning. We revealed three types of repressive regulations: translational suppression of ribosomal protein-coding genes in the hippocampus, learning-induced early translational repression of specific genes, and late persistent suppression of a subset of genes via inhibition of estrogen receptor 1 (ESR1/ERα) signaling. In behavioral analyses, overexpressing Nrsn1, one of the newly identified genes undergoing rapid translational repression, or activating ESR1 in the hippocampus impaired memory formation. Collectively, this study unveils the yet-unappreciated importance of gene repression mechanisms for memory formation.

Gastric duplication cysts in adults: a report of three cases

Gastric duplication cyst is a rare congenital anomaly of the gastrointestinal tract and is especially uncommon in adults. Most cases in adults are discovered incidentally on radiological examination or gastric endoscopy. Accurate diagnosis of these cysts before resection is difficult. Differential diagnoses are varied. Malignant transformation of a gastric duplication cyst is very rare. We present three cases of asymptomatic noncommunicating gastric duplication cysts in adults.

Nanostring-based multigene assay to predict recurrence for gastric cancer patients after surgery

Despite the benefits from adjuvant chemotherapy or chemoradiotherapy, approximately one-third of stage II gastric cancer (GC) patients developed recurrences. The aim of this study was to develop and validate a prognostic algorithm for gastric cancer (GCPS) that can robustly identify high-risk group for recurrence among stage II patients. A multi-step gene expression profiling study was conducted. First, a microarray gene expression profiling of archived paraffin-embedded tumor blocks was used to identify candidate prognostic genes (N=432). Second, a focused gene expression assay including prognostic genes was used to develop a robust clinical assay (GCPS) in stage II patients from the same cohort (N=186). Third, a predefined cut off for the GCPS was validated using an independent stage II cohort (N=216). The GCPS was validated in another set with stage II GC who underwent surgery without adjuvant treatment (N=300). GCPS was developed by summing the product of Cox regression coefficients and normalized expression levels of 8 genes (LAMP5, CDC25B, CDK1, CLIP4, LTB4R2, MATN3, NOX4, TFDP1). A prospectively defined cut-point for GCPS classified 22.7% of validation cohort treated with chemoradiotherapy (N=216) as high-risk group with 5-year recurrence rate of 58.6% compared to 85.4% in the low risk group (hazard ratio for recurrence=3.16, p=0.00004). GCPS also identified high-risk group among stage II patients treated with surgery only (hazard ratio=1.77, p=0.0053).

Prediction of complete necrosis of hepatocellular carcinoma treated with transarterial chemoembolization prior to liver transplantation

BACKGROUND/AIMS

Compact lipiodol uptake without enhancement on multiphasic helical computed tomography (CT) has been suggested as a radiologic response criterion in hepatocellular carcinoma (HCC) patients treated with transarterial chemoembolization (TACE) and subsequent partial hepatectomy. However, its usefulness has not been fully investigated in the explanted liver.

METHODS

Between 1998 and 2007, 81 patients with HCC underwent 1-9 sessions of TACE followed by liver transplantation (LT). Thirty-nine tumors in 29 patients showed a radiologic response on CT performed prior to LT. The radiologic response criteria and the duration of the response were evaluated to predict total necrosis in the explanted liver.

RESULTS

Among the 39 tumors, 34 nodules (87.2%) exhibited total pathological necrosis. While 13 out of 16 tumors (81.3%) with a radiologic response for 6 months or less were completely necrotic, 21 out of 23 tumors (91.3%) with a radiologic response of longer than 6 months showed total necrosis.

CONCLUSIONS

Our results suggested that the radiologic response criteria based on serial CT images might be useful for predicting total necrosis of TACE-pretreated HCC in LT.

Carney triad in an adult with aggressive behavior: the first case in Korea

Carney triad is a rare syndrome of unknown etiology characterized by having at least two out of three following neoplasms: gastrointestinal stromal tumor, pulmonary chondroma and extra-adrenal paraganglioma. About 100 cases have been reported worldwide. We report a case of Carney triad in a 42-year-old woman presented with a gastrointestinal stromal tumor in the stomach and a malignant functioning paraganglioma in the retroperitoneum that was fatal five years after diagnosis. The gastrointestinal stromal tumor was diagnosed as intermediate-risk of aggressive behavior and diffusely positive for c-kit whereas the retroperitoneal paraganglioma was negative for c-kit. Genetic analyses showed no mutations of KIT, PDGFRA, SDHB, SDHC, and SDHD genes in both tumors. To our best knowledge, this is the first case of Carney triad in Korea.

Prognostic stratification of high-risk gastrointestinal stromal tumors in the era of targeted therapy

BACKGROUND

Recently, a trial of adjuvant imatinib for primary R0-resected intermediate and high-risk gastrointestinal stromal tumors (GISTs) significantly improved recurrence-free survival. But identifying patients having higher chances of recurrence will reduce economic losses and prevent adverse side effects caused by adjuvant treatment.

METHODS

Tissue samples from 93 patients with high-risk GISTs were studied for p16, CD34, and CD44 protein expression and mutations of KIT and PDGFRA gene. Clinicopathologic, immunohistochemical, and mutation results were compared with clinical outcome by univariate and multivariate analyses.

RESULTS

KIT mutations were observed in 75 cases (81%) including 46 exon 11 deletion mutations and 31 deletions affecting codons 557-558. A novel 12 bp deletion mutation (KHNG484-488) on KIT exon 9 was detected in a small intestinal GIST. For recurrence-free survival, R0 resection, organ-confined disease stage, and female sex are better prognostic factors in univariate analysis and disease stage was the only factor predicting recurrence (P = 0.02) in multivariate analysis. In overall survival, mutation types, presence of mutation, location of GISTs, and mitosis were significant by univariate analysis. After multivariate analysis, mitotic counts and presence of KIT mutation corresponded to independent prognostic factors. Moreover, mitosis, KIT exon 11 deletion mutation, and deletions affecting exon 557-558 predict recurrence in R0-resected high-risk GISTs (P < 0.05).

CONCLUSION

Prognostic stratification in high-risk GISTs will help identify patients with high-risk GIST who may benefit from adjuvant therapy.

Expression of cyclooxygenase-2 in cholangiocarcinoma: correlation with clinicopathological features and prognosis

BACKGROUND AND AIMS

No information is available on the nature of the correlation between cyclooxygenase-2 (COX-2) expression and the clinicopathological features and prognosis of cholangiocarcinoma (CC). The goal of the present study was to determine the possible roles and clinical significance of COX-2 expression in CC.

METHODS

We investigated the immunohistochemical expression of COX-2 in 102 patients with CC with respect to clinicopathological characteristics, namely evidence of Clonorchis sinensis infection, proliferation index (PI, assessed by Ki-67 expression), apoptotic index (AI, assessed by TUNEL stain), and microvessel density (MVD, assessed by CD34 expression). Evidence of C. sinensis infection was assessed by the microscopic examination of stools for C. sinensis ova, serological testing (ELISA), and the detection of peripheral bile duct dilations by imaging studies.

RESULTS

An immunohistochemical investigation demonstrated the immunolabeling of tumor cells, mainly in the cytoplasmic and perinuclear regions, in 53 (52%) of the 102 patients with CC. No significant differences were found in terms of age, sex, tumor differentiation, involvement of the resection margin, presence of lymph nodes or liver metastases, or in pTNM stage between COX-2 positive and COX-2 negative patients. However, evidence of C. sinensis infection was more common in COX-2 positive patients (P < 0.05). No significant differences were found for PI, AI, MVD, or cumulative survival between COX-2 positive and COX-2 negative patients.

CONCLUSION

Clonorchis sinensis infection is related to aberrant COX-2 expression in patients with CC. However, COX-2 expression is not related to clinical outcome in CC patients.

Expression of corticotropin releasing factor, but not its binding protein, in CA1 pyramidal cells of gerbil hippocampus following transient ischemia

Recently, the ectopic expression of corticotropin-releasing factor (CRF) has been suggested as being associated with processes linked to neuronal injury and/or degeneration in response to a brain insult. However, there is little experimental data linking CRF directly to neuronal death induced by ischemia. Therefore, in the present study, we investigated the temporal and spatial alteration of CRF and its binding protein expressions in the hippocampus after transient ischemia. As a result, we found the selective increase of CRF immunoreactivity in the CA1 pyramidal cells and their processes at only 4 days post-ischemic insult. In contrast, CRF binding protein immunoreactivity was rarely detected in the CA1 region. These results suggest that transient ischemia may provoke selectively ectopic expression of CRF, but not of its binding protein, in vulnerable regions, and this enhancement of CRF may play important roles in the neurodegenerative process.

Increased levels of interleukin-6 are associated with lymphocytosis in bronchoalveolar lavage fluids of idiopathic nonspecific interstitial pneumonia

Local overexpression of interleukin-6 (IL-6) experimentally induces lymphocytic infiltration in the bronchial tree of rat. Among idiopathic interstitial pneumonia (IIP), nonspecific interstitial pneumonia/fibrosis (NSIP) has an increased number of lymphocytes in bronchoalveolar lavage (BAL) fluid when compared with usual interstitial pneumonia (UIP). To reveal a relation of IL-6 with the lymphocyte infiltration of NSIP, IL-6 was measured in BAL fluids of idiopathic NSIP (n = 7), idiopathic UIP (n = 16), and normal control subjects (n = 45). IL-6-producing sites were assessed by IL-6 protein stain on biopsy specimens of NSIP, UIP, and normal lung of mediastinal tumors. Lymphocyte numbers and IL-6 levels in BAL fluids were higher in NSIP than those in UIP (p < 0.01, respectively), which were also higher when compared with those of normal control subjects (p < 0.01, respectively). In NSIP, the levels of IL-6 correlated with the number of lymphocytes (r = 0.93, p < 0.01). UIP cases were divided into two groups: high-UIP (n = 7) or low-UIP (n = 9) according to IL-6 levels greater than or within the 95 percentile of normal control subjects, respectively. The high-UIP group had BAL lymphocytosis when compared with the low-UIP group (p < 0.05). IL-6 stained on epithelial cells of the bronchial tree and on alveolar macrophages of NSIP and UIP. In conclusion, the lymphocytosis in BAL fluid of patients with NSIP and a subgroup of UIP is associated with the high levels of IL-6 and its sources are the epithelial cells of the small airway and the alveolar macrophages.