Memory discrimination is promoted by the expression of the transcription repressor WT1 in the dentate gyrus.

The hippocampus is critical for the precise formation of contextual memories. Overlapping inputs coming from the entorhinal cortex are processed by the trisynaptic pathway to form distinct memories. Disruption in any step of the circuit flow can lead to a lack of memory precision, and to memory interference. We have identified the transcriptional repressor Wilm's Tumor 1 (WT1) as an important regulator of synaptic plasticity involved in memory discrimination in the hippocampus. In male mice, using viral and transgenic approaches, we showed that WT1 deletion in granule cells of the dentate gyrus (DG) disrupts memory discrimination. With electrophysiological methods, we then identified changes in granule cells' excitability and DG synaptic transmission indicating that WT1 knockdown in DG granule cells disrupts the inhibitory feedforward input from mossy fibers to CA3 by decreasing mIPSCs and shifting the normal excitatory/inhibitory (E/I) balance in the DG → CA3 circuit in favor of excitation. Finally, using a chemogenetic approach, we established a causal link between granule cell hyperexcitability and memory discrimination impairments. Our results suggest that WT1 enables a circuit-level computation that drives pattern discrimination behavior.

Wilm's tumor 1 promotes memory flexibility.

Under physiological conditions, strength and persistence of memory must be regulated in order to produce behavioral flexibility. In fact, impairments in memory flexibility are associated with pathologies such as post-traumatic stress disorder or autism; however, the underlying mechanisms that enable memory flexibility are still poorly understood. Here, we identify transcriptional repressor Wilm's Tumor 1 (WT1) as a critical synaptic plasticity regulator that decreases memory strength, promoting memory flexibility. WT1 is activated in the hippocampus following induction of long-term potentiation (LTP) or learning. WT1 knockdown enhances CA1 neuronal excitability, LTP and long-term memory whereas its overexpression weakens memory retention. Moreover, forebrain WT1-deficient mice show deficits in both reversal, sequential learning tasks and contextual fear extinction, exhibiting impaired memory flexibility. We conclude that WT1 limits memory strength or promotes memory weakening, thus enabling memory flexibility, a process that is critical for learning from new experiences.

Genomic signatures defining responsiveness to allopurinol and combination therapy for lung cancer identified by systems therapeutics analyses.

The ability to predict responsiveness to drugs in individual patients is limited. We hypothesized that integrating molecular information from databases would yield predictions that could be experimentally tested to develop transcriptomic signatures for specific drugs. We analyzed lung adenocarcinoma patient data from The Cancer Genome Atlas and identified a subset of patients in which xanthine dehydrogenase (XDH) expression correlated with decreased survival. We tested allopurinol, an FDA-approved drug that inhibits XDH, on human non-small-cell lung cancer (NSCLC) cell lines obtained from the Broad Institute Cancer Cell Line Encyclopedia and identified sensitive and resistant cell lines. We utilized the transcriptomic profiles of these cell lines to identify six-gene signatures for allopurinol-sensitive and allopurinol-resistant cell lines. Transcriptomic networks identified JAK2 as an additional target in allopurinol-resistant lines. Treatment of resistant cell lines with allopurinol and CEP-33779 (a JAK2 inhibitor) resulted in cell death. The effectiveness of allopurinol alone or allopurinol and CEP-33779 was verified in vivo using tumor formation in NCR-nude mice. We utilized the six-gene signatures to predict five additional allopurinol-sensitive NSCLC cell lines and four allopurinol-resistant cell lines susceptible to combination therapy. We searched the transcriptomic data from a library of patient-derived NSCLC tumors from the Jackson Laboratory to identify tumors that would be predicted to be sensitive to allopurinol or allopurinol + CEP-33779 treatment. Patient-derived tumors showed the predicted drug sensitivity in vivo. These data indicate that we can use integrated molecular information from cancer databases to predict drug responsiveness in individual patients and thus enable precision medicine.

Activation of the histaminergic H3 receptor induces phosphorylation of the Akt/GSK-3 beta pathway in cultured cortical neurons and protects against neurotoxic insults.

Stimulation of histamine H(3) receptors (H(3)R) activates G(i/o)-proteins that inhibit adenylyl cyclase and triggers MAPK and phospholipase A(2). In a previous study, we showed that H(3)R-mediated phosphorylation of Akt at Ser473 occurs in primary cultures of rat cortical neurons, but neither the downstream targets nor the function of such activation were explored. In this report we address these questions. Western blotting experiments showed that H(3)R-mediated activation of Akt in cultured rat cortical neurons was inhibited by LY 294004 and U0126, suggesting that it depends on phosphoinositide-3-kinase and mitogen-activated protein kinase kinase. H(3)R activation phosphorylated, hence inactivated, the Akt downstream effector glycogen synthase kinase-3beta, increased the expression of the antiapoptotic protein Bcl-2 and protected cultured rat and mouse cortical neurons from neurotoxic insults in a dose-dependent manner. All these effects were inhibited by the H(3)R antagonist inverse/agonist thioperamide. Mouse cortical cells expressed H(3)R as revealed by immunostaining experiments, and stimulation of H(3)R phoshorylated Akt and decreased caspase 3 activity. Hence, we uncovered a yet unexplored action of the H(3)R that may help understand the impact of H(3)R signaling in the CNS.

The Akt/GSK-3beta axis as a new signaling pathway of the histamine H(3) receptor.

Drugs targeting the histamine H(3) receptor (H(3)R) are suggested to be beneficial for the treatment of neurodegenerative diseases, such as Alzheimer's and Parkinson's disease. The H(3)R activates G(i/o)-proteins to inhibit adenylyl cyclase activity and modulates phospholipase A(2) and MAPK activity. Herein we show that, in transfected SK-N-MC cells, the H(3)R modulates the activity of the Akt/Glycogen synthase kinase 3beta (GSK-3beta) axis both in a constitutive and agonist-dependent fashion. H(3)R stimulation with the H(3)R agonist immepip induces the phosphorylation of both Ser473 and Thr308 on Akt, a serine/threonine kinase that is important for neuronal development and function. The H(3)R-mediated activation of Akt can be inhibited by the H(3)R inverse agonist thioperamide, and by Wortmannin, LY294002 and PTX, suggesting the observed Akt activation occurs via a G(i/o)-mediated activation of phosphoinositide-3-kinase. H(3)R activation also results in the phosphorylation of Ser9 on GSK-3beta, which acts downstream of Akt and has a prominent role in brain function. In addition, we show the H(3)R-mediated phosphorylation of Akt at Ser473 to occur in primary rat cortical neurons and in rat brain slices. The discovery of this signaling property of the H(3)R adds new understanding to the roles of histamine and the H(3)R in brain function and pathology.

Role of the endothelin-1 system in the luteolytic process of pseudopregnant rabbits.

The aim of this study was to better understand the role of the endothelin-1 (ET-1) system in the process of controlling the corpora lutea (CL) life span in rabbits. ET-1 (10 microg iv) administration at d 9 and 12 of pseudopregnancy induced a functional luteolysis within 24 h of injection, but it was ineffective at both d 4 and 6. Pretreatments with Bosentan, a dual ET(A)/ET(B) receptor antagonist, or cyclooxygenase (COX) inhibitor blocked the luteolytic action of ET-1 but not that induced by prostaglandin F2alpha (PGF2alpha). In CL cultured in vitro, ET-1 increased (P