In subjects with schizophrenia, impairments in working memory are associated with dysfunction of the dorsolateral prefrontal cortex (DLPFC). This dysfunction appears to be due, at least in part, to abnormalities in c-aminobutyric acid (GABA)-mediated inhibitory circuitry. To test the hypothesis that altered GABA-mediated circuitry in the DLPFC of subjects with schizophrenia reflects expression changes of genes that encode selective presynaptic and postsynaptic components of GABA neurotransmission, we conducted a systematic expression analysis of GABA-related transcripts in the DLPFC of 14 pairs of schizophrenia and age-, sex-and post-mortem interval-matched control subjects using a customized DNA microarray with enhanced sensitivity and specificity. Subjects with schizophrenia exhibited expression deficits in GABA-related transcripts encoding (1) presynaptic regulators of GABA neurotransmission (67 kDa isoform of glutamic acid decarboxylase (GAD 67 ) and GABA transporter 1), (2) neuropeptides (somatostatin (SST), neuropeptide Y (NPY) and cholecystokinin (CCK)) and (3) GABA A receptor subunits (a1, a4, b3, c2 and d). Real-time qPCR and/or in situ hybridization confirmed the deficits for six representative transcripts tested in the same pairs and in an extended cohort, respectively. In contrast, GAD 67 , SST and a1 subunit mRNA levels, as assessed by in situ hybridization, were not altered in the DLPFC of monkeys chronically exposed to antipsychotic medications. These findings suggest that schizophrenia is associated with alterations in inhibitory inputs from SST/NPY-containing and CCKcontaining subpopulations of GABA neurons and in the signaling via certain GABA A receptors that mediate synaptic (phasic) or extrasynaptic (tonic) inhibition. In concert with previous findings, these data suggest that working memory dysfunction in schizophrenia is mediated by altered GABA neurotransmission in certain DLPFC microcircuits.

IntroductionFrontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) are characterized by the presence of ubiquitin-positive inclusions (1). These inclusions are found in the brain and spinal cord of ALS patients as well as in patients with a major subtype of FTLD designated FTLD-TDP because these inclusions were shown to be comprised of the TAR-DNA binding protein 43 (TDP-43) (2). Since (a) cognitive abnormalities or dementia consistent with FTLD are increasingly recognized in ALS patients, (b) some FTLD patients develop MND, and (c) cytoplasmic TDP-43 aggregates are found in the brain and spinal cord of both ALS and FTLD-TDP patients, TDP-43 pathology appears to define a single neurodegenerative disorder (TDP-43 proteinopathy) with a spectrum of clinical manifestations (3-5). The importance of TDP-43 in the pathogenesis of these diseases is supported by the presence of autosomal dominant mutations in the TARDBP gene associated with ALS and FTLD (6).Human TDP-43 (hTDP-43) is a highly conserved and ubiquitously expressed 414-amino acid nuclear protein that binds to both DNA and RNA (7,8). TDP-43 is implicated in repression of gene transcription, regulation of exon splicing, and nuclear body functions (for a summary see recent reviews, refs. 4 and 6). Pathological TDP-43 can be abnormally cleaved, phosphorylated, and ubiquitinated, and most TDP-43 aggregates are mislocalized outside the nucleus within the cytoplasm or neurites (2). Interestingly,

Erythropoiesis is critically dependent on erythropoietin (EPO), a glycoprotein hormone that is regulated by hypoxia-inducible factor (HIF). Hepatocytes are the primary source of extrarenal EPO in the adult and express HIF-1 and HIF-2, whose roles in the hypoxic induction of EPO remain controversial. In order to define the role of HIF-1 and HIF-2 in the regulation of hepatic EPO expression, we have generated mice with conditional inactivation of Hif-1α and/or Hif-2α (Epas1) in hepatocytes. We have previously shown that inactivation of the von Hippel-Lindau tumor suppressor pVHL, which targets both HIFs for proteasomal degradation, results in increased hepatic Epo production and polycythemia independent of Hif-1α. Here we show that conditional inactivation of Hif-2α in pVHL-deficient mice suppressed hepatic Epo and the development of polycythemia. Furthermore, we found that physiological Epo expression in infant livers required Hif-2α but not Hif-1α and that the hypoxic induction of liver Epo in anemic adults was Hif-2α dependent. Since other Hif target genes such phosphoglycerate kinase 1 (Pgk) were Hif-1α dependent, we provide genetic evidence that HIF-1 and HIF-2 have distinct roles in the regulation of hypoxia-inducible genes and that EPO is preferentially regulated by HIF-2 in the liver.

The disease protein in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) and amyotrophic lateral sclerosis (ALS) was identified recently as the TDP-43 (TAR DNA-binding protein 43), thereby providing a molecular link between these two disorders. In FTLD-U and ALS, TDP-43 is redistributed from its normal nuclear localization to form cytoplasmic insoluble aggregates. Moreover, pathological TDP-43 is abnormally ubiquitinated, hyperphosphorylated, and N-terminally cleaved to generate C-terminal fragments (CTFs). However, the specific cleavage site ( 4 with ubiquitin-positive, tau-negative inclusions (FTLD-U) with or without motor neuron disease as well as sporadic and the majority of familial amyotrophic lateral sclerosis (ALS) cases (1, 2). Human TDP-43 is encoded by the TARDBP gene on chromosome 1. It is a 414-amino acid nuclear protein with two highly conserved RNA recognition motifs (RRM1 and RRM2) and a C-terminal tail with a typical glycine-rich region that mediates protein-protein interactions, including interactions with other heterogeneous ribonucleoprotein (hnRNP) family members such as hnRNP A1, A2/B1, and A3 (3). Thus, TDP-43 is a ubiquitously expressed RNA/DNA-binding protein that also interacts with other nuclear proteins such as splicing factors. As such, TDP-43 is implicated in repression of gene transcription, regulation of exon splicing, and the functions of nuclear bodies (4 -9).Pathological TDP-43 accumulates as insoluble aggregates in the central nervous system neurons and glia of patients with FTLD-U and ALS (1). Moreover, FTLD-U patients can develop ALS, and ALS patients often suffer from a dementia consistent with FTLD-U (10). We therefore proposed that these diseases are part of a clinicopathological spectrum of the same neurodegenerative process collectively referred to as TDP-43 proteinopathy (1, 2). TDP-43 inclusions are present as cytoplasmic, neuritic, or nuclear inclusions, and affected neurons show a dramatic depletion of normal nuclear 11,12). To mimic this nuclear clearance and to model the sequestration of endogenous TDP-43 into cytoplasmic aggregates, we overexpressed TDP-43 with mutated nuclear localization signals (⌬NLS-TDP-43) in cultured cells that showed a reduction in endogenous nuclear TDP-43 and accumulations of insoluble cytoplasmic aggregates (13). Moreover, overexpression of

In mammals, the liver integrates nutrient uptake and delivery of carbohydrates and lipids to peripheral tissues to control overall energy balance. Hepatocytes maintain metabolic homeostasis by coordinating gene expression programs in response to dietary and systemic signals. Hepatic tissue oxygenation is an important systemic signal that contributes to normal hepatocyte function as well as disease. Hypoxia-inducible factors 1 and 2 (HIF-1 and HIF-2, respectively) are oxygen-sensitive heterodimeric transcription factors, which act as key mediators of cellular adaptation to low oxygen. Previously, we have shown that HIF-2 plays an important role in both physiologic and pathophysiologic processes in the liver. HIF-2 is essential for normal fetal EPO production and erythropoiesis, while constitutive HIF-2 activity in the adult results in polycythemia and vascular tumorigenesis. Here we report a novel role for HIF-2 in regulating hepatic lipid metabolism. We found that constitutive activation of HIF-2 in the adult results in the development of severe hepatic steatosis associated with impaired fatty acid ␤-oxidation, decreased lipogenic gene expression, and increased lipid storage capacity. These findings demonstrate that HIF-2 functions as an important regulator of hepatic lipid metabolism and identify HIF-2 as a potential target for the treatment of fatty liver disease.The liver plays a central role in maintaining overall organism energy balance by controlling carbohydrate and lipid metabolism. Hepatocytes coordinate these processes by regulating gene expression programs in response to dietary signals from the portal vein and systemic signals from the hepatic artery. Oxygen is an important systemic signal that modulates metabolic activities and disease in the liver. Under physiologic conditions, an oxygen gradient is established in the liver such that the partial pressure of oxygen in periportal blood is 60 to 65 mm Hg and in the perivenous blood is 30 to 35 mm Hg (17). This oxygen gradient is important for the zonation of metabolic activity in the liver. Because oxygen is an essential electron acceptor for oxidative metabolism, hepatocytes that perform glucose or fatty acid oxidation are located in the aerobic periportal zone, whereas oxygen-independent metabolic functions such as glucose uptake, glycolysis, and fatty acid synthesis are predominately performed by perivenous hepatocytes (16). Patients who experience perivenous hypoxia as a result of heart failure, obstructive sleep apnea, or excessive alcohol use can develop chronic liver injury characterized by steatosis and inflammation (17). Therefore, it is critical that oxygen-signaling pathways in hepatocytes are appropriately integrated into adaptive and/or maladaptive liver injury responses.Hypoxia-inducible transcription factors (HIFs) are important components of the cellular oxygen-signaling pathway. In response to low oxygen tensions, HIFs facilitate both oxygen delivery and adaptation to oxygen deprivation by regulating the expression of genes that are i...