CPG15 regulates synapse stability in the developing and adult brain.

Use-dependent selection of optimal connections is a key feature of neural circuit development and, in the mature brain, underlies functional adaptation, such as is required for learning and memory. Activity patterns guide circuit refinement through selective stabilization or elimination of specific neuronal branches and synapses. The molecular signals that mediate activity-dependent synapse and arbor stabilization and maintenance remain elusive. We report that knockout of the activity-regulated gene cpg15 in mice delays developmental maturation of axonal and dendritic arbors visualized by anterograde tracing and diolistic labeling, respectively. Electrophysiology shows that synaptic maturation is also delayed, and electron microscopy confirms that many dendritic spines initially lack functional synaptic contacts. While circuits eventually develop, in vivo imaging reveals that spine maintenance is compromised in the adult, leading to a gradual attrition in spine numbers. Loss of cpg15 also results in poor learning. cpg15 knockout mice require more trails to learn, but once they learn, memories are retained. Our findings suggest that CPG15 acts to stabilize active synapses on dendritic spines, resulting in selective spine and arbor stabilization and synaptic maturation, and that synapse stabilization mediated by CPG15 is critical for efficient learning.

A phase I study of intravenous aflibercept with FOLFIRI in Japanese patients with previously treated metastatic colorectal cancer.

Aflibercept, a recombinant fusion protein, is a potent inhibitor of vascular endothelial growth factor (VEGF)-A, VEGF-B, and the placental growth factor (PlGF). The present study was an open-label, sequential-cohort, dose-escalation trial of intravenous aflibercept administered every 2 weeks in combination with 5-fluorouracil, levofolinate, and irinotecan (FOLFIRI) in patients with previously treated metastatic colorectal cancer (mCRC). We aimed to assess the safety, dose-limiting toxicities (DLTs), pharmacokinetics, and preliminary efficacy of the combination therapy to determine the recommended phase II dose (RPTD) for Japanese patients. Two doses of aflibercept (2.0 and 4.0 mg/kg) were set, and DLTs were evaluated in the first 2 cycles. The subjects comprised 16 patients (n = 3 and 13 for 2.0 and 4.0 mg/kg aflibercept, respectively) who received a total of 149 cycles of aflibercept with FOLFIRI. No DLTs were observed at both doses. The frequent adverse events encountered were leukopenia, neutropenia, anemia, diarrhea, fatigue, decreased appetite, stomatitis, dysphonia, nausea, and epistaxis. The most common grade 3/4 adverse events were neutropenia for both doses and hypertension for the 4.0 mg/kg dose. Free aflibercept exposure increased with the dose, whereas exposure to VEGF-bound aflibercept remained similar at both doses. The response rate and progression-free survival at 4.0 mg/kg was 8.3 % and 7.59 months, respectively. In conclusion, the combination of aflibercept and FOLFIRI was well tolerated at both doses. The RPTD of aflibercept in combination with FOLFIRI for Japanese patients with mCRC was determined to be 4.0 mg/kg every 2 weeks. ClinicalTrials.gov identifier: NCT00921661.

Effect of intra-ischemic hypothermia on the expression of c-Fos and c-Jun, and DNA binding activity of AP-1 after focal cerebral ischemia in rat brain.

It is unknown whether immediate early gene (IEG) induction and subsequent late gene regulation after ischemia is beneficial or deleterious. The aim of this study was to examine the effect of hypothermia on expression of c-Fos and c-Jun, and AP-1 DNA binding activity, after transient focal cerebral ischemia in rat brain, and clarify the role of IEGs and AP-1 after insults. Male Wistar rats underwent right middle cerebral artery occlusion for 1 h with the intraluminal suture method. During ischemia, animals were assigned to either normothermic (NT) or hypothermic (HT) groups. In the NT group, brain temperature was observed to spontaneously increase to 40 degrees C during ischemia. In the HT group, brain temperature decreased to 30 degrees C. Infarct volume in cortex was decreased in the HT group, compared with that in the NT group (P<0.001). Increased c-Fos immunoreactivity in the cortex was observed at 3 h after reperfusion in the HT, but not the NT group, while c-Jun expression was not affected by HT treatment. There was also a significant increase in AP-1 DNA binding activity at 3 h in the HT group when compared to the NT group (P<0.01). In conclusion, hypothermia decreased cerebral infarction in association with early increases in c-Fos expression and AP-1 DNA binding activity in peri-infarct cortex. It remains to be established whether such responses are a cause or consequence of cell survival, but these results clearly establish that altered transcription is a key feature of tissue spared following hypothermic focal ischemia.

cpg15 and cpg15-2 constitute a family of activity-regulated ligands expressed differentially in the nervous system to promote neurite growth and neuronal survival.

Many ligands that affect nervous system development are members of gene families that function together to coordinate the assembly of complex neural circuits. cpg15/neuritin encodes an extracellular ligand that promotes neurite growth, neuronal survival, and synaptic maturation. Here we identify cpg15-2 as the only paralogue of cpg15 in the mouse and human genome. Both genes are expressed predominantly in the nervous system, where their expression is regulated by activity. cpg15-2 expression increases by more than twofold in response to kainate-induced seizures and nearly fourfold in the visual cortex in response to 24 hours of light exposure following dark adaptation. cpg15 and cpg15-2 diverge in their spatial and temporal expression profiles. cpg15-2 mRNA is most abundant in the retina and the olfactory bulb, as opposed to the cerebral cortex and the hippocampus for cpg15. In the retina, they differ in their cell-type specificity. cpg15 is expressed in retinal ganglion cells, whereas cpg15-2 is predominantly in bipolar cells. Developmentally, onset of cpg15-2 expression is delayed compared with cpg15 expression. CPG15-2 is glycosylphosphatidylinositol (GPI) anchored to the cell membrane and, like CPG15, can be released in a soluble-secreted form, but with lower efficiency. CPG15 and CPG15-2 were found to form homodimers and heterodimers with each other. In hippocampal explants and dissociated cultures, CPG15 and CPG15-2 promote neurite growth and neuronal survival with similar efficacy. Our findings suggest that CPG15 and CPG15-2 perform similar cellular functions but may play distinct roles in vivo through their cell-type- and tissue-specific transcriptional regulation.

Regulation of cpg15 by signaling pathways that mediate synaptic plasticity.

Transcriptional activation is a key link between neuronal activity and long-term synaptic plasticity. Little is known about genes responding to this activation whose products directly effect functional and structural changes at the synapse. cpg15 is an activity-regulated gene encoding a membrane-bound ligand that regulates dendritic and axonal arbor growth and synaptic maturation. We report that cpg15 is an immediate-early gene induced by Ca(2+) influx through NMDA receptors and L-type voltage-sensitive calcium channels. Activity-dependent cpg15 expression requires convergent activation of the CaM kinase and MAP kinase pathways. Although activation of PKA is not required for activity-dependent expression, cpg15 is induced by cAMP in active neurons. CREB binds the cpg15 promoter in vivo and partially regulates its activity-dependent expression. cpg15 is an effector gene that is a target for signal transduction pathways that mediate synaptic plasticity and thus may take part in an activity-regulated transcriptional program that directs long-term changes in synaptic connections.