McMeekin, LJ;Joyce, KL;Jenkins, LM;Bohannon, BM;Patel, KD;Bohannon, AS;Patel, A;Fox, SN;Simmons, MS;Day, JJ;Kralli, A;Crossman, DK;Cowell, RM;
PMID: 34648866 | DOI: 10.1016/j.neuroscience.2021.10.007
Deficiency in peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) expression or function is implicated in numerous neurological and psychiatric disorders. PGC-1α is required for the expression of genes involved in synchronous neurotransmitter release, axonal integrity, and metabolism, especially in parvalbumin-positive interneurons. As a transcriptional coactivator, PGC-1α requires transcription factors to specify cell-type-specific gene programs; while much is known about these factors in peripheral tissues, it is unclear if PGC-1α utilizes these same factors in neurons. Here, we identified putative transcription factors controlling PGC-1α-dependent gene expression in the brain using bioinformatics, and then validated the role of the top candidate in a knockout mouse model. We transcriptionally profiled cells overexpressing PGC-1α and searched for over-represented binding motifs in the promoters of upregulated genes. Binding sites of the estrogen-related receptor (ERR) family of transcription factors were enriched and blockade of ERRα attenuated PGC-1α-mediated induction of mitochondrial and synaptic genes in cell culture. Localization in the mouse brain revealed enrichment of ERRα expression in parvalbumin-expressing neurons with tight correlation of expression with PGC-1α across brain regions. In ERRα null mice, PGC-1α-dependent genes were reduced in multiple regions, including neocortex, hippocampus, and cerebellum, though not to the extent observed in PGC-1α null mice. Behavioral assessment revealed ambulatory hyperactivity in response to amphetamine and impairments in sensorimotor gating without the overt motor impairment characteristic of PGC-1α null mice. These data suggest that ERRα is required for normal levels of expression of PGC-1α-dependent genes in neurons, but that additional factors may be involved in their regulation. Significance statement The transcription factors with which PGC-1α interacts determine specificity of the transcriptional program it drives across cell populations, but those mediating its functions in parvalbumin-expressing neurons are unknown. Relative to other PGC-1α-interacting transcription factors, ERRα is enriched in parvalbumin-expressing neurons and shows robust spatial and temporal correlation with PGC-1α expression throughout the brain. ERRα is also necessary for PGC-1α-dependent transcription both in vitro and in vivo for metabolic and neuronal transcripts. These data suggest that ERRα is an important player in cell-specific PGC-1α-dependent transcription in the CNS and may play a role in regulating parvalbumin-expressing neuron maturation and function.
Royan, M;Siddique, K;Nourizadeh-lillabadi, R;Weltzien, F;Henkel, C;FONTAINE, R;
| DOI: 10.2139/ssrn.4142092
In fish, prolactin-producing cells (lactotropes) are located in the anterior part of the pituitary and play an essential role in osmoregulation. However, small satellite lactotrope populations have been described in other parts of the pituitary in several species. The functional and developmental backgrounds of these extra populations are not known. We recently described two distinct prolactin-expressing cell types in Japanese medaka, a salinity tolerant fish, using single cell transcriptomics. In this study, we thus characterize the two transcriptomically distinct lactotrope cell types and explore the hypothesis that they represent the spatially distinct cell populations found in other species. Single cell RNA sequencing shows that one of the two lactotrope cell types exhibits an expression profile similar to that of stem cell populations. Using in situ hybridization, we show that the medaka pituitary often develops additional small satellite lactotrope cell groups, like in other teleost species. These satellite clusters arise early during development and grow in cell number throughout life regardless of the animal’s sex. Surprisingly, there seems to be no correspondence between the stem cell-like lactotropes and these newly emerging lactotrope populations. Instead, our data support a scenario in which the stem cell-like lactotropes are an intrinsic stage in the development of every spatially distinct lactotrope cluster. In addition, lactotrope activity in the medaka pituitary decreases when environmental salinity increases in the two spatially distinct lactotrope clusters, supporting their role in osmoregulation. However, this decrease appears weaker in the satellite lactotrope cell groups, suggesting that these lactotropes are differentially regulated.
Khom, S;Borgonetti, V;Vozella, V;Kirson, D;Rodriguez, L;Gandhi, P;Bianchi, P;Snyder, A;Vlkolinsky, R;Bajo, M;Oleata, C;Ciccocioppo, R;Roberto, M;
| DOI: 10.1016/j.ynstr.2023.100547
Impairments in the function of the hypothalamic-pituitary-adrenal (HPA) axis and enhanced glucocorticoid receptor (GR) activity in the central amygdala (CeA) are critical mechanisms in the pathogenesis of alcohol use disorder (AUD). The GR antagonist mifepristone attenuates craving in AUD patients, alcohol consumption in AUD models, and decreases CeA γ-aminobutyric acid (GABA) transmission in alcohol-dependent rats. Previous studies suggest elevated GR activity in the CeA of male alcohol-preferring Marchigian-Sardinian (msP) rats, but its contribution to heightened CeA GABA transmission driving their characteristic post-dependent phenotype is largely unknown. We determined Nr3c1 (the gene encoding GR) gene transcription in the CeA in male and female msP and Wistar rats using in situ hybridization and studied acute effects of mifepristone (10 μM) and its interaction with ethanol (44 mM) on pharmacologically isolated spontaneous inhibitory postsynaptic currents (sIPSCs) and electrically evoked inhibitory postsynaptic potentials (eIPSPs) in the CeA using ex vivo slice electrophysiology. Female rats of both genotypes expressed more CeA GRs than males, suggesting a sexually dimorphic GR regulation of CeA activity. Mifepristone reduced sIPSC frequencies (GABA release) and eIPSP amplitudes in msP rats of both sexes, but not in their Wistar counterparts; however, it did not prevent acute ethanol-induced increase in CeA GABA transmission in male rats. In msP rats, GR regulates CeA GABAergic signaling under basal conditions, indicative of intrinsically active GR. Thus, enhanced GR function in the CeA represents a key mechanism contributing to maladaptive behaviors associated with AUD.
Faltings, L;Sarowar, T;Virga, J;Singh, N;Kwa, B;Zhao, H;
| DOI: 10.1093/neuonc/noac079.046
Choroid plexus (CP) tumors are rare primary brain neoplasms found most commonly in children and are thought to arise from CP epithelial cells. Sox2 is a transcription factor that not only plays a role in development in the ventricular zone, CP, and roof plate, but also contributes to cancer stemness, tumorigenesis, and drug resistance. Gene expression studies demonstrate aberrant Sox2 expression in human CP tumors, suggesting a role in tumor development. A subset of CP tumors exhibit abnormal NOTCH pathway activity. Using animal models, we previously show that sustained NOTCH activity leads to CP tumors. Immunofluorescence, RT-qPCR, and RNA scope assays have revealed increased Sox2 levels in NOTCH-driven CP tumors compared to wild type CP in mice. To investigate the role of Sox2 in CP tumors, we eliminated Sox2 expression in NOTCH-driven CP tumors. Loss of Sox2 almost completely blocked NOTCH-driven CP tumor growth in these mice, supporting a role for Sox2 in these tumors. Ciliation regulation is one proposed functional pathway for tumorigenesis in CP tumors. Using immunofluorescence assays for cilia (ARL13b) and aquaporin transport protein 1 (AQP1) in combination with super resolution microscopy, we observe a stark contrast between wild type CP epithelial cells which are multiciliated and homogeneously express AQP1, indicative of normal epithelial differentiation, compared to NOTCH-driven CP tumors consisting of mono-ciliated cells with loss of AQP1 expression. In Sox2-deficient NOTCH-driven CP tumors, we observe tumor cells remain mono-ciliated and AQP1-negative, indicating that Sox2 loss does not affect the ciliation machinery. Together this warrants further study into the mechanisms of Sox2 functions in CP tumors. By unraveling the role of Sox2 in CP tumors, we may better understand their origin and biology to ultimately design improved treatment options.
Colijn S, Muthukumar V, Xie J, Gao S, Griffin CT
PMID: 31953345 | DOI: 10.1242/dmm.041962
Receptor-interacting protein kinase 3 (RIPK3) was recently implicated in promoting atherosclerosis progression through a proposed role in macrophage necroptosis. However, RIPK3 has been connected to numerous other cellular pathways, which raises questions about its actual role in atherosclerosis. Furthermore, RIPK3 is expressed in a multitude of cell types, suggesting that it may be physiologically relevant to more than just macrophages in atherosclerosis. In this study, Ripk3 was deleted in macrophages, endothelial cells, vascular smooth muscle cells or globally on the Apoe-/- background using Cre-lox technology. To induce atherosclerosis progression, male and female mice were fed a Western diet for three months before tissue collection and analysis. Surprisingly, necroptosis markers were nearly undetectable in atherosclerotic aortas. Furthermore, en face lesion area was increased in macrophage- and endothelial-specific deletions of Ripk3 in the descending and abdominal regions of the aorta. Analysis of bone-marrow-derived macrophages and cultured endothelial cells revealed that Ripk3 deletion promotes expression of monocyte chemoattractant protein 1 (MCP-1) and E-selectin in these cell types, respectively. Western blot analysis showed upregulation of MCP-1 in aortas with Ripk3-deficient macrophages. Altogether, these data suggest that RIPK3 in macrophages and endothelial cells protects against atherosclerosis through a mechanism that likely does not involve necroptosis. This protection may be due to RIPK3-mediated suppression of pro-inflammatory MCP-1 expression in macrophages and E-selectin expression in endothelial cells. These findings suggest a novel and unexpected cell-type specific and athero-protective function for RIPK3.This article has an associated First Person interview with the first author of the paper
Preston, SP;Stutz, MD;Allison, CC;Nachbur, U;Gouil, Q;Tran, BM;Duvivier, V;Arandjelovic, P;Cooney, JP;Mackiewicz, L;Meng, Y;Schaefer, J;Bader, SM;Peng, H;Valaydon, Z;Rajasekaran, P;Jennison, C;Lopaticki, S;Farrell, A;Ryan, M;Howell, J;Croagh, C;Karunakaran, D;Schuster-Klein, C;Murphy, JM;Fifis, T;Christophi, C;Vincan, E;Blewitt, ME;Thompson, A;Boddey, JA;Doerflinger, M;Pellegrini, M;
PMID: 36037995 | DOI: 10.1053/j.gastro.2022.08.040
Necroptosis is a highly inflammatory mode of cell death that has been implicated in causing hepatic injury including steatohepatitis/NASH. However, the evidence supporting these claims has been controversial. A comprehensive, fundamental understanding of cell death pathways involved in liver disease critically underpins rational strategies for therapeutic intervention. We sought to define the role and relevance of necroptosis in liver pathology.Several animal models of human liver pathology including diet induced steatohepatitis in male mice and diverse infections in both male and female mice were used to dissect the relevance of necroptosis in liver pathobiology. We applied necroptotic stimuli to primary mouse and human hepatocytes to measure their susceptibility to necroptosis. Paired liver biospecimens from patients with NASH, before and after intervention, were analysed. DNA methylation sequencing was also performed to investigate the epigenetic regulation of RIPK3 expression in primary human and mouse hepatocytes.Identical infection kinetics and pathological outcomes were observed in mice deficient in an essential necroptotic effector protein, MLKL, compared to control animals. Mice lacking MLKL were indistinguishable from wild-type mice when fed on a high fat diet to induce NASH. Under all conditions tested we were unable to induce necroptosis in hepatocytes. We confirmed that a critical activator of necroptosis, RIPK3, was epigenetically silenced in mouse and human primary hepatocytes and rendered them unable to undergo necroptosis.We have provided compelling evidence that necroptosis is disabled in hepatocytes during homeostasis and in the pathological conditions tested in this study.
Molecular Neuropsychiatry
Hu X,. Rocco BR, Fee C, Sibille E.
PMID: - | DOI: 10.1159/000495840
Converging evidence suggests that deficits in somatostatin (SST)-expressing neuron signaling contributes to major depressive disorder. Preclinical studies show that enhancing this signaling, specifically at α5 subunit-containing γ-aminobutyric acid subtype A receptors (α5-GABAARs), provides a potential means to overcome low SST neuron function. The cortical microcircuit comprises multiple subtypes of inhibitory γ-aminobutyric acid (GABA) neurons and excitatory pyramidal cells (PYCs). In this study, multilabel fluorescence in situ hybridization was used to characterize α5-GABAAR gene expression in PYCs and three GABAergic neuron subgroups – vasoactive intestinal peptide (VIP)-, SST-, and parvalbumin (PV)-expressing cells – in the human and mouse frontal cortex. Across species, we found the majority of gene expression in PYCs (human: 39.7%; mouse: 54.14%), less abundant expression in PV neurons (human: 20%; mouse: 16.33%), and no expression in VIP neurons (0%). Only human SST cells expressed GABRA5, albeit at low levels (human: 8.3%; mouse: 0%). Together, this localization suggests potential roles for α5-GABAARs within the cortical microcircuit: (1) regulators of PYCs, (2) regulators of PV cell activity across species, and (3) sparse regulators of SST cell inhibition in humans. These results will advance our ability to predict the effects of pharmacological agents targeting α5-GABAARs, which have shown therapeutic potential in preclinical animal models.
Kumar, S;Budhathoki, S;Oliveira, CB;Kahle, AD;Calhan, OY;Lukens, JR;Deppmann, CD;
PMID: 36602874 | DOI: 10.1172/jci.insight.157433
The molecular mediators of cell death and inflammation in Alzheimer's disease (AD) have yet to be fully elucidated. Caspase-8 is a critical regulator of several cell death and inflammatory pathways; however, its role in AD pathogenesis has not yet been examined in detail. In the absence of Caspase-8, mice are embryonic lethal due to excessive RIPK3-dependent necroptosis. Compound RIPK3 and Caspase-8 mutants rescue embryonic lethality, which we leveraged to examine the roles of these pathways in an amyloid beta (Aβ)-mediated mouse model of AD. We find that combined deletion of Caspase-8 and RIPK3, but not RIPK3 alone, leads to diminished Aβ deposition and microgliosis in the 5xFAD mouse model of AD. Despite its well-known role in cell death, Caspase-8 does not appear to impact cell loss in the 5xFAD model. In contrast, we found that Caspase-8 is a critical regulator of Aβ-driven inflammasome gene expression and IL-1β release. Interestingly, loss of RIPK3 had only a modest effect on disease progression suggesting that inhibition of necroptosis or RIPK3-mediated cytokine pathways are not critical during mid stages of Aβ amyloidosis. These findings suggest that therapeutics targeting Caspase-8 may represent a novel strategy to limit Aꞵ amyloidosis and neuroinflammation in AD.
Gunduz-Cinar O, Brockway E, Lederle L, Wilcox T, Halladay LR, Ding Y, Oh H, Busch EF, Kaugars K, Flynn S, Limoges A, Bukalo O, MacPherson KP, Masneuf S, Pinard C, Sibille E, Chesler EJ, Holmes A.
PMID: 29311651 | DOI: 10.1038/s41380-017-0003-3
Recent years have seen advances in our understanding of the neural circuits associated with trauma-related disorders, and the development of relevant assays for these behaviors in rodents. Although inherited factors are known to influence individual differences in risk for these disorders, it has been difficult to identify specific genes that moderate circuit functions to affect trauma-related behaviors. Here, we exploited robust inbred mouse strain differences in Pavlovian fear extinction to uncover quantitative trait loci (QTL) associated with this trait. We found these strain differences to be resistant to developmental cross-fostering and associated with anatomical variation in basolateral amygdala (BLA) perineuronal nets, which are developmentally implicated in extinction. Next, by profiling extinction-driven BLA expression of QTL-linked genes, we nominated Ppid (peptidylprolyl isomerase D, a member of the tetratricopeptide repeat (TPR) protein family) as an extinction-related candidate gene. We then showed that Ppid was enriched in excitatory and inhibitory BLA neuronal populations, but at lower levels in the extinction-impaired mouse strain. Using a virus-based approach to directly regulate Ppid function, we demonstrated that downregulating BLA-Ppid impaired extinction, while upregulating BLA-Ppid facilitated extinction and altered in vivo neuronal extinction encoding. Next, we showed that Ppid colocalized with the glucocorticoid receptor (GR) in BLA neurons and found that the extinction-facilitating effects of Ppid upregulation were blocked by a GR antagonist. Collectively, our results identify Ppid as a novel gene involved in regulating extinction via functional actions in the BLA, with possible implications for understanding genetic and pathophysiological mechanisms underlying risk for trauma-related disorders.
Acta neuropathologica communications
Davis, SE;Cook, AK;Hall, JA;Voskobiynyk, Y;Carullo, NV;Boyle, NR;Hakim, AR;Anderson, KM;Hobdy, KP;Pugh, DA;Murchison, CF;McMeekin, LJ;Simmons, M;Margolies, KA;Cowell, RM;Nana, AL;Spina, S;Grinberg, LT;Miller, BL;Seeley, WW;Arrant, AE;
PMID: 37118844 | DOI: 10.1186/s40478-023-01571-4
Loss of function progranulin (GRN) mutations are a major autosomal dominant cause of frontotemporal dementia (FTD). Patients with FTD due to GRN mutations (FTD-GRN) develop frontotemporal lobar degeneration with TDP-43 pathology type A (FTLD-TDP type A) and exhibit elevated levels of lysosomal proteins and storage material in frontal cortex, perhaps indicating lysosomal dysfunction as a mechanism of disease. To investigate whether patients with sporadic FTLD exhibit similar signs of lysosomal dysfunction, we compared lysosomal protein levels, transcript levels, and storage material in patients with FTD-GRN or sporadic FTLD-TDP type A. We analyzed samples from frontal cortex, a degenerated brain region, and occipital cortex, a relatively spared brain region. In frontal cortex, patients with sporadic FTLD-TDP type A exhibited similar increases in lysosomal protein levels, transcript levels, and storage material as patients with FTD-GRN. In occipital cortex of both patient groups, most lysosomal measures did not differ from controls. Frontal cortex from a transgenic mouse model of TDP-opathy had similar increases in cathepsin D and lysosomal storage material, showing that TDP-opathy and neurodegeneration can drive these changes independently of progranulin. To investigate these changes in additional FTLD subtypes, we analyzed frontal cortical samples from patients with sporadic FTLD-TDP type C or Pick's disease, an FTLD-tau subtype. All sporadic FTLD groups had similar increases in cathepsin D activity, lysosomal membrane proteins, and storage material as FTD-GRN patients. However, patients with FTLD-TDP type C or Pick's disease did not have similar increases in lysosomal transcripts as patients with FTD-GRN or sporadic FTLD-TDP type A. Based on these data, accumulation of lysosomal proteins and storage material may be a common aspect of end-stage FTLD. However, the unique changes in gene expression in patients with FTD-GRN or sporadic FTLD-TDP type A may indicate distinct underlying lysosomal changes among FTLD subtypes.
Ziminski J, Hessler S, Margetts-Smith G, Sieburg MC, Crombag HS, Koya E.
PMID: 28213443 | DOI: 10.1523/JNEUROSCI.3766-16.2017
Cues that predict the availability of food rewards influence motivational states and elicit food-seeking behaviors. If a cue no longer predicts food availability, animals may adapt accordingly by inhibiting food seeking responses. Sparsely activated sets of neurons, coined neuronal ensembles, have been shown to encode the strength of reward-cue associations. While alterations in intrinsic excitability have been shown to underlie many learning and memory processes, little is known about these properties specifically on cue-activated neuronal ensembles. We examined the activation patterns of cue-activated orbitofrontal cortex (OFC) and nucleus accumbens (NAc) shell ensembles using wild-type and Fos-GFP mice following appetitive conditioning with sucrose and extinction learning. We also investigated the neuronal excitability of recently activated, GFP+ neurons in these brain areas using whole-cell electrophysiology in brain slices. Exposure to a sucrose cue elicited activation of neurons in both the NAc shell and OFC. In the NAc shell, but not the OFC, these activated GFP+ neurons were more excitable than surrounding GFP- neurons. Following extinction, the number of neurons activated in both areas was reduced and activated ensembles in neither area exhibited altered excitability. These data suggest that learning-induced alterations in the intrinsic excitability of neuronal ensembles is regulated dynamically across different brain areas. Furthermore, we show that changes in associative strength modulate the excitability profile of activated ensembles in the NAc shell.SIGNIFICANCE STATEMENTSparsely distributed sets of neurons called 'neuronal ensembles' encode learned associations about food and cues predictive of its availability. Widespread changes in neuronal excitability have been observed in limbic brain areas after associative learning, but little is known about the excitability changes that occur specifically on neuronal ensembles that encode appetitive associations. Here we reveal that sucrose cue exposure recruited a more excitable ensemble in the nucleus accumbens, but not orbitofrontal cortex compared to their surrounding neurons. This excitability difference was not observed when the cue's salience was diminished following extinction learning. These novel data provide evidence that the intrinsic excitability of appetitive memory-encoding ensembles is differentially regulated across brain areas and dynamically adapts to changes in associative strength.
Englund, J;Haikonen, J;Shteinikov, V;Amarilla, SP;Atanasova, T;Shintyapina, A;Ryazantseva, M;Partanen, J;Voikar, V;Lauri, SE;
PMID: 34663781 | DOI: 10.1038/s41398-021-01654-7
Early life stress (ELS) is a well-characterized risk factor for mood and anxiety disorders. GABAergic microcircuits in the amygdala are critically implicated in anxiety; however, whether their function is altered after ELS is not known. Here we identify a novel mechanism by which kainate receptors (KARs) modulate feedforward inhibition in the lateral amygdala (LA) and show that this mechanism is downregulated after ELS induced by maternal separation (MS). Specifically, we show that in control rats but not after MS, endogenous activity of GluK1 subunit containing KARs disinhibit LA principal neurons during activation of cortical afferents. GluK1 antagonism attenuated excitability of parvalbumin (PV)-expressing interneurons, resulting in loss of PV-dependent inhibitory control and an increase in firing of somatostatin-expressing interneurons. Inactivation of Grik1 expression locally in the adult amygdala reduced ongoing GABAergic transmission and was sufficient to produce a mild anxiety-like behavioral phenotype. Interestingly, MS and GluK1-dependent phenotypes showed similar gender specificity, being detectable in male but not female rodents. Our data identify a novel KAR-dependent mechanism for cell-type and projection-specific functional modulation of the LA GABAergic microcircuit and suggest that the loss of GluK1 KAR function contributes to anxiogenesis after ELS.
