Plasma MIA, CRP, and Albumin Predict Cognitive Decline in Parkinson's Disease.

OBJECTIVE: Using a multi-cohort, discovery-replication-validation design, we sought new plasma biomarkers that predict which individuals with Parkinson's disease (PD) will experience cognitive decline. METHODS: In 108 discovery cohort PD individuals and 83 replication cohort PD individuals, we measured 940 plasma proteins on an aptamer-based platform. Using proteins associated with subsequent cognitive decline in both cohorts, we trained a logistic regression model to predict which patients with PD showed fast (> = 1 point drop/year on Montreal Cognitive Assessment [MoCA]) versus slow (< 1 point drop/year on MoCA) cognitive decline in the discovery cohort, testing it in the replication cohort. We developed alternate assays for the top 3 proteins and confirmed their ability to predict cognitive decline - defined by change in MoCA or development of incident mild cognitive impairment (MCI) or dementia - in a validation cohort of 118 individuals with PD. We investigated the top plasma biomarker for causal influence by Mendelian randomization (MR). RESULTS: A model with only 3 proteins (melanoma inhibitory activity protein [MIA], C-reactive protein [CRP], and albumin) separated fast versus slow cognitive decline subgroups with an area under the curve (AUC) of 0.80 in the validation cohort. The individuals with PD in the validation cohort in the top quartile of risk for cognitive decline based on this model were 4.4 times more likely to develop incident MCI or dementia than those in the lowest quartile. Genotypes at MIA single nucleotide polymorphism (SNP) rs2233154 associated with MIA levels and cognitive decline, providing evidence for MIA's causal influence. CONCLUSIONS: An easily obtained plasma-based predictor identifies individuals with PD at risk for cognitive decline. MIA may participate causally in development of cognitive decline. ANN NEUROL 2022;92:255-269.

TMEM106B modifies TDP-43 pathology in human ALS brain and cell-based models of TDP-43 proteinopathy.

The neurodegenerative diseases amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with TAR DNA-binding protein-43 (TDP-43) inclusions (FTLD-TDP) share the neuropathological hallmark of aggregates of TDP-43. However, factors governing the severity and regional distribution of TDP-43 pathology, which may account for the divergent clinical presentations of ALS and FTLD-TDP, are not well understood. Here, we investigated the influence of genotypes at TMEM106B, a locus associated with risk for FTLD-TDP, and hexanucleotide repeat expansions in C9orf72, a known genetic cause for both ALS and FTLD-TDP, on global TDP-43 pathology and regional distribution of TDP-43 pathology in 899 postmortem cases from a spectrum of neurodegenerative diseases. We found that, among the 110 ALS cases, minor (C)-allele homozygotes at the TMEM106B locus sentinel SNP rs1990622 had more TDP-43 pathology globally, as well as in select brain regions. C9orf72 expansions similarly associated with greater TDP-43 pathology in ALS. However, adjusting for C9orf72 expansion status did not affect the relationship between TMEM106B genotype and TDP-43 pathology. To elucidate the direction of causality for this association, we directly manipulated TMEM106B levels in an inducible cell system that expresses mislocalized TDP-43 protein. We found that partial knockdown of TMEM106B, to levels similar to what would be expected in rs1990622 C allele carriers, led to development of more TDP-43 cytoplasmic aggregates, which were more insoluble, in this system. Taken together, our results support a causal role for TMEM106B in modifying the development of TDP-43 proteinopathy.

A Dementia-Associated Risk Variant near TMEM106B Alters Chromatin Architecture and Gene Expression.

Neurodegenerative diseases pose an extraordinary threat to the world's aging population, yet no disease-modifying therapies are available. Although genome-wide association studies (GWASs) have identified hundreds of risk loci for neurodegeneration, the mechanisms by which these loci influence disease risk are largely unknown. Here, we investigated the association between common genetic variants at the 7p21 locus and risk of the neurodegenerative disease frontotemporal lobar degeneration. We showed that variants associated with disease risk correlate with increased expression of the 7p21 gene TMEM106B and no other genes; co-localization analyses implicated a common causal variant underlying both association with disease and association with TMEM106B expression in lymphoblastoid cell lines and human brain. Furthermore, increases in the amount of TMEM106B resulted in increases in abnormal lysosomal phenotypes and cell toxicity in both immortalized cell lines and neurons. We then combined fine-mapping, bioinformatics, and bench-based approaches to functionally characterize all candidate causal variants at this locus. This approach identified a noncoding variant, rs1990620, that differentially recruits CTCF in lymphoblastoid cell lines and human brain to influence CTCF-mediated long-range chromatin-looping interactions between multiple cis-regulatory elements, including the TMEM106B promoter. Our findings thus provide an in-depth analysis of the 7p21 locus linked by GWASs to frontotemporal lobar degeneration, nominating a causal variant and causal mechanism for allele-specific expression and disease association at this locus. Finally, we show that genetic variants associated with risk of neurodegenerative diseases beyond frontotemporal lobar degeneration are enriched in CTCF-binding sites found in brain-relevant tissues, implicating CTCF-mediated gene regulation in risk of neurodegeneration more generally.

Increased expression of the frontotemporal dementia risk factor TMEM106B causes C9orf72-dependent alterations in lysosomes.

Frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) is an important cause of dementia in individuals under age 65. Common variants in the TMEM106B gene were previously discovered by genome-wide association to confer genetic risk for FTLD-TDP (p = 1 × 10-11, OR = 1.6). Furthermore, TMEM106B may act as a genetic modifier affecting age at onset and age at death in the Mendelian subgoup of FTLD-TDP due to expansions of the C9orf72 gene. Evidence suggests that TMEM106B variants increase risk for developing FTLD-TDP by increasing expression of Transmembrane Protein 106B (TMEM106B), a lysosomal protein. To further understand the functional role of TMEM106B in disease pathogenesis, we investigated the cell biological effects of increased TMEM106B expression. Here, we report that increased TMEM106B expression results in the appearance of a vacuolar phenotype in multiple cell types, including neurons. Concomitant with the development of this vacuolar phenotype, cells over-expressing TMEM106B exhibit impaired lysosomal acidification and degradative function, as well as increased cytotoxicity. We further identify a potential lysosomal sorting motif for TMEM106B and demonstrate that abrogation of sorting to lysosomes rescues TMEM106B-induced defects. Finally, we show that TMEM106B-induced defects are dependent on the presence of C9orf72, as knockdown of C9orf72 also rescues these defects. In sum, our results suggest that TMEM106B exerts its effects on FTLD-TDP disease risk through alterations in lysosomal pathways. Furthermore, TMEM106B and C9orf72 may interact in FTLD-TDP pathophysiology.

Redox signalling directly regulates TDP-43 via cysteine oxidation and disulphide cross-linking.

TDP-43 is the major disease protein in ubiquitin-positive inclusions of amyotrophic lateral sclerosis and frontotemporal lobar degeneration (FTLD) characterized by TDP-43 pathology (FTLD-TDP). Accumulation of insoluble TDP-43 aggregates could impair normal TDP-43 functions and initiate disease progression. Thus, it is critical to define the signalling mechanisms regulating TDP-43 since this could open up new avenues for therapeutic interventions. Here, we have identified a redox-mediated signalling mechanism directly regulating TDP-43. Using in vitro and cell-based studies, we demonstrate that oxidative stress promotes TDP-43 cross-linking via cysteine oxidation and disulphide bond formation leading to decreased TDP-43 solubility. Biochemical analysis identified several cysteine residues located within and adjacent to the second RNA-recognition motif that contribute to both intra- and inter-molecular interactions, supporting TDP-43 as a target of redox signalling. Moreover, increased levels of cross-linked TDP-43 species are found in FTLD-TDP brains, indicating that aberrant TDP-43 cross-linking is a prominent pathological feature of this disease. Thus, TDP-43 is dynamically regulated by a redox regulatory switch that links oxidative stress to the modulation of TDP-43 and its downstream targets.

Lower plasma apolipoprotein A1 levels are found in Parkinson's disease and associate with apolipoprotein A1 genotype.

The discovery of novel plasma-based biomarkers could lead to new approaches in the treatment of Parkinson's disease (PD). Here, we explore the role of plasma apolipoprotein A1 (ApoA1) as a risk marker for PD and evaluate the influence of APOA1 promoter variation on plasma ApoA1 levels. Plasma ApoA1 and the single-nucleotide polymorphism, rs670, were assayed in a discovery cohort (cohort 1) of 301 PD patients, 80 normal controls (NCs), and 165 subjects with other neurodegenerative diseases, as well as a cohort (cohort 2) of 158 PD patients from a second clinical site. Additionally, rs670 was genotyped in a third cohort of 1,494 PD and 925 NC subjects from both clinical sites. Compared to both normal and disease controls, PD patients have lower plasma ApoA1 (P < 0.001 for both comparisons). Moreover, in PD patients, plasma ApoA1 levels are correlated with genotype at the APOA1 promoter polymorphism, rs670. Specifically, lower plasma ApoA1 levels were found in rs670 major allele (G) homozygotes in both cohort 1 (P = 0.009) and in a replication cohort (cohort 2; n = 158 PD patients; P = 0.024). Finally, evaluating rs670 genotype frequencies in 1,930 PD cases versus 997 NCs, the rs670 GG genotype shows a trend toward association (odds ratio: 1.1; P = 0.10) with PD. Our results are compatible with a model whereby circulating ApoA1 levels may be useful in risk-stratifying subjects for the development of PD, with higher ApoA1 levels suggesting relative protection. Future studies evaluating modulation of ApoA1 as a novel therapeutic strategy in PD are warranted. © 2014 International Parkinson and Movement Disorder Society.

Myeloid cell-derived hypoxia-inducible factor attenuates inflammation in unilateral ureteral obstruction-induced kidney injury.

Renal fibrosis and inflammation are associated with hypoxia, and tissue pO(2) plays a central role in modulating the progression of chronic kidney disease. Key mediators of cellular adaptation to hypoxia are hypoxia-inducible factor (HIF)-1 and -2. In the kidney, they are expressed in a cell type-specific manner; to what degree activation of each homolog modulates renal fibrogenesis and inflammation has not been established. To address this issue, we used Cre-loxP recombination to activate or to delete both Hif-1 and Hif-2 either globally or cell type specifically in myeloid cells. Global activation of Hif suppressed inflammation and fibrogenesis in mice subjected to unilateral ureteral obstruction, whereas activation of Hif in myeloid cells suppressed inflammation only. Suppression of inflammatory cell infiltration was associated with downregulation of CC chemokine receptors in renal macrophages. Conversely, global deletion or myeloid-specific inactivation of Hif promoted inflammation. Furthermore, prolonged hypoxia suppressed the expression of multiple inflammatory molecules in noninjured kidneys. Collectively, we provide experimental evidence that hypoxia and/or myeloid cell-specific HIF activation attenuates renal inflammation associated with chronic kidney injury.

TMEM106B, the risk gene for frontotemporal dementia, is regulated by the microRNA-132/212 cluster and affects progranulin pathways.

Frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) is a fatal neurodegenerative disease with no available treatments. Mutations in the progranulin gene (GRN) causing impaired production or secretion of progranulin are a common Mendelian cause of FTLD-TDP; additionally, common variants at chromosome 7p21 in the uncharacterized gene TMEM106B were recently linked by genome-wide association to FTLD-TDP with and without GRN mutations. Here we show that TMEM106B is neuronally expressed in postmortem human brain tissue, and that expression levels are increased in FTLD-TDP brain. Furthermore, using an unbiased, microarray-based screen of >800 microRNAs (miRs), we identify microRNA-132 as the top microRNA differentiating FTLD-TDP and control brains, with <50% normal expression levels of three members of the microRNA-132 cluster (microRNA-132, microRNA-132*, and microRNA-212) in disease. Computational analyses, corroborated empirically, demonstrate that the top mRNA target of both microRNA-132 and microRNA-212 is TMEM106B; both microRNAs repress TMEM106B expression through shared microRNA-132/212 binding sites in the TMEM106B 3'UTR. Increasing TMEM106B expression to model disease results in enlargement and poor acidification of endo-lysosomes, as well as impairment of mannose-6-phosphate-receptor trafficking. Finally, endogenous neuronal TMEM106B colocalizes with progranulin in late endo-lysosomes, and TMEM106B overexpression increases intracellular levels of progranulin. Thus, TMEM106B is an FTLD-TDP risk gene, with microRNA-132/212 depression as an event which can lead to aberrant overexpression of TMEM106B, which in turn alters progranulin pathways. Evidence for this pathogenic cascade includes the striking convergence of two independent, genomic-scale screens on a microRNA:mRNA regulatory pair. Our findings open novel directions for elucidating miR-based therapies in FTLD-TDP.

Testing for Allele-specific Expression from Human Brain Samples.

Many single nucleotide polymorphisms (SNPs) identified by genome-wide association studies exert their effects on disease risk as expression quantitative trait loci (eQTL) via allele-specific expression (ASE). While databases for probing eQTLs in tissues from normal individuals exist, one may wish to ascertain eQTLs or ASE in specific tissues or disease-states not characterized in these databases. Here, we present a protocol to assess ASE of two possible target genes (GPNMB and KLHL7) of a known genome-wide association study (GWAS) Parkinson's disease (PD) risk locus in postmortem human brain tissue from PD and neurologically normal individuals. This was done using a sequence of RNA isolation, cDNA library generation, enrichment for transcripts of interest using customizable cDNA capture probes, paired-end RNA sequencing, and subsequent analysis. This method provides increased sensitivity relative to traditional bulk RNAseq-based and a blueprint that can be extended to the study of other genes, tissues, and disease states. Key features • Analysis of GPNMB allele-specific expression (ASE) in brain lysates from cognitively normal controls (NC) and Parkinson's disease (PD) individuals. • Builds on the ASE protocol of Mayba et al. (2014) and extends application from cells to human tissue. • Increased sensitivity by enrichment for desired transcript via RNA CaptureSeq (Mercer et al., 2014). • Optimized for human brain lysates from cingulate gyrus, caudate nucleus, and cerebellum.

Hepatic HIF-2 regulates erythropoietic responses to hypoxia in renal anemia.

The kidney is the main physiologic source of erythropoietin (EPO) in the adult and responds to decreases in tissue oxygenation with increased EPO production. Although studies in mice with liver-specific or global gene inactivation have shown that hypoxia-inducible factor 2 (Hif-2) plays a major role in the regulation of Epo during infancy and in the adult, respectively, the contribution of renal HIF-2 signaling to systemic EPO homeostasis and the role of extrarenal HIF-2 in erythropoiesis, in the absence of kidney EPO, have not been examined directly. Here, we used Cre-loxP recombination to ablate Hif-2α in the kidney, whereas Hif-2-mediated hypoxia responses in the liver and other Epo-producing tissues remained intact. We found that the hypoxic induction of renal Epo is completely Hif-2 dependent and that, in the absence of renal Hif-2, hepatic Hif-2 takes over as the main regulator of serum Epo levels. Furthermore, we provide evidence that hepatocyte-derived Hif-2 is involved in the regulation of iron metabolism genes, supporting a role for HIF-2 in the coordination of EPO synthesis with iron homeostasis.

GPNMB confers risk for Parkinson's disease through interaction with α-synuclein.

Many risk loci for Parkinson's disease (PD) have been identified by genome-wide association studies (GWASs), but target genes and mechanisms remain largely unknown. We linked the GWAS-derived chromosome 7 locus (sentinel single-nucleotide polymorphism rs199347) to GPNMB through colocalization analyses of expression quantitative trait locus and PD risk signals, confirmed by allele-specific expression studies in the human brain. In cells, glycoprotein nonmetastatic melanoma protein B (GPNMB) coimmunoprecipitated and colocalized with α-synuclein (aSyn). In induced pluripotent stem cell-derived neurons, loss of GPNMB resulted in loss of ability to internalize aSyn fibrils and develop aSyn pathology. In 731 PD and 59 control biosamples, GPNMB was elevated in PD plasma, associating with disease severity. Thus, GPNMB represents a PD risk gene with potential for biomarker development and therapeutic targeting.

Hypoxia-inducible factor-2 (HIF-2) regulates hepatic erythropoietin in vivo.

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-1alpha and/or Hif-2alpha (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-1alpha. Here we show that conditional inactivation of Hif-2alpha in pVHL-deficient mice suppressed hepatic Epo and the development of polycythemia. Furthermore, we found that physiological Epo expression in infant livers required Hif-2alpha but not Hif-1alpha and that the hypoxic induction of liver Epo in anemic adults was Hif-2alpha dependent. Since other Hif target genes such phosphoglycerate kinase 1 (Pgk) were Hif-1alpha 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.

Brain progranulin expression in GRN-associated frontotemporal lobar degeneration.

Frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP) is characterized by progressive decline in behavior, executive function, and language. Progranulin (GRN) gene mutations are pathogenic for FTLD-TDP, and GRN transcript haploinsufficiency is the proposed disease mechanism. However, the evidence for this hypothesis comes mainly from blood-derived cells; we measured progranulin expression in brain. We characterized mRNA and protein levels of progranulin from four brain regions (frontal cortex, temporal cortex, occipital cortex, and cerebellum) in FTLD-TDP patients with and without GRN mutations, as well as neurologically normal individuals. Moreover, we performed immunohistochemistry to evaluate the degree of TDP-43 pathology and microglial infiltration present in these groups. In most brain regions, patients with GRN mutations showed mRNA levels comparable to normal controls and to FTLD-TDP without GRN mutations. However, GRN transcript levels in a brain region severely affected by disease (frontal cortex) were increased in mutation-bearing patients. When compared with normal individuals, GRN mutation-bearing cases had a significant reduction in the amount of progranulin protein in the cerebellum and occipital cortex, but not in the frontal and temporal cortices. In GRN mutant cases, GRN mRNA originated from the normal allele, and moderate microglial infiltration was observed. In conclusion, GRN mutation carriers have increased levels of mRNA transcript from the normal allele in brain, and proliferation of microglia likely increases progranulin levels in affected regions of the FTLD-TDP brain, and whether or not these findings underlie the accumulation of TDP-43 pathology in FTLD-TDP linked to GRN mutations remains to be determined.

Author Correction: Aberrant activation of non-coding RNA targets of transcriptional elongation complexes contributes to TDP-43 toxicity.

The original version of this Article contained an error in the author affiliations. The affiliation of Alice Chen-Plotkin with the Department of Neurology, Perelman School of Medicine, Philadelphia, PA, 19104 USA was inadvertently omitted. This has now been corrected in both the PDF and HTML versions of the Article.

Aberrant activation of non-coding RNA targets of transcriptional elongation complexes contributes to TDP-43 toxicity.

TDP-43 is the major disease protein associated with amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration with ubiquitinated inclusions (FTLD-TDP). Here we identify the transcriptional elongation factor Ell-a shared component of little elongation complex (LEC) and super elongation complex (SEC)-as a strong modifier of TDP-43-mediated neurodegeneration. Our data indicate select targets of LEC and SEC become upregulated in the fly ALS/FTLD-TDP model. Among them, U12 snRNA and a stress-induced long non-coding RNA Hsrω, functionally contribute to TDP-43-mediated degeneration. We extend the findings of Hsrω, which we identify as a chromosomal target of TDP-43, to show that the human orthologue Sat III is elevated in a human cellular disease model and FTLD-TDP patient tissue. We further demonstrate an interaction between TDP-43 and human ELL2 by co-immunoprecipitation from human cells. These findings reveal important roles of Ell-complexes LEC and SEC in TDP-43-associated toxicity, providing potential therapeutic insight for TDP-43-associated neurodegeneration.

Molecular evidence for increased expression of genes related to immune and chaperone function in the prefrontal cortex in schizophrenia.

BACKGROUND: Schizophrenia is characterized by complex gene expression changes. The transcriptome alterations in the prefrontal cortex have been the subject of several recent postmortem studies that yielded both convergent and divergent findings. METHODS: To increase measurement precision, we used a custom-designed DNA microarray platform with long oligonucleotides and multiple probes with replicates. The platform was designed to assess the expression of > 1800 genes specifically chosen because of their hypothesized roles in the pathophysiology of schizophrenia. The gene expression differences in dorsolateral prefrontal cortex samples from 14 matched pairs of schizophrenia and control subjects were analyzed with two technical replicates and four data mining approaches. RESULTS: In addition to replicating many expression changes in synaptic, oligodendrocyte, and signal transduction genes, we uncovered and validated a robust immune/chaperone transcript upregulation in the schizophrenia samples. CONCLUSIONS: We speculate that the overexpression of SERPINA3, IFITM1, IFITM2, IFITM3, CHI3L1, MT2A, CD14, HSPB1, HSPA1B, and HSPA1A in schizophrenia subjects represents a long-lasting and correlated signature of an early environmental insult during development that actively contributes to the pathophysiology of prefrontal dysfunction.

Presenilin-1-dependent transcriptome changes.

Familial forms of Alzheimer's disease (FADs) are caused by the expression of mutant presenilin 1 (PS1) or presenilin 2. Using DNA microarrays, we explored the brain transcription profiles of mice with conditional knock-out of PS1 (cKO PS1) in the forebrain. In parallel, we performed a transcription profiling of the hippocampus and frontal cortex of the FAD-linked DeltaE9 mutant transgenic (TG) mice and matched controls [TG mice expressing wild-type human PS1 (hPS1)]. When the TG and cKO datasets were cross-compared, the majority of the 30 common expression alterations were in opposite direction, suggesting that the FAD-linked PS1 variant produces transcriptome changes primarily by gain of aberrant function. Our microarray studies also revealed an unanticipated inverse correlation of transcript levels between the brains of mice that coexpress DeltaE9 hPS1+ amyloid precursor protein (APP)695 Swe and DeltaE9 hPS1 single transgenic mice. The opposite directionality of these changes in transcript levels must be a function of APP and/or APP derivatives.

Plasma EGF and cognitive decline in Parkinson's disease and Alzheimer's disease.

OBJECTIVE: Cognitive decline occurs in multiple neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson's disease (PD). Shared underlying mechanisms may exist and manifest as shared biomarker signatures. Previously, we nominated plasma epidermal growth factor (EGF) as a biomarker predicting cognitive decline in patients with established PD. Here, we investigate EGF as a predictive biomarker in prodromal PD, as well as AD. METHODS: A cohort of PD patients (n = 236) was recruited to replicate our finding that low baseline EGF levels predict future cognitive decline. Additionally, plasma EGF and cognitive outcome measures were obtained from individuals with normal cognition (NC, n = 58), amnestic mild cognitive impairment (AD-MCI, n = 396), and Alzheimer's disease (AD, n = 112) in the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort to investigate whether low EGF levels correlate with cognitive status and outcome in AD-MCI and AD. Third, plasma EGF and cognitive measures were evaluated in the high-risk asymptomatic Parkinson's Associated Risk Study (PARS) cohort (n = 165) to investigate the association of EGF and cognitive performance in a PD prodromal context. RESULTS: In both PD and AD-MCI, low baseline plasma EGF predicted poorer long-term cognitive outcomes. In asymptomatic individuals at highest risk for developing PD from the PARS cohort, low baseline plasma EGF associated with poorer performance in the visuospatial domain but not in other cognitive domains. INTERPRETATION: Low plasma EGF at baseline predicts cognitive decline in both AD and PD. Evidence for this signal may exist in prodromal stages of both diseases.

Dysregulation of the ALS-associated gene TDP-43 leads to neuronal death and degeneration in mice.

Amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD) are characterized by cytoplasmic protein aggregates in the brain and spinal cord that include TAR-DNA binding protein 43 (TDP-43). TDP-43 is normally localized in the nucleus with roles in the regulation of gene expression, and pathological cytoplasmic aggregates are associated with depletion of nuclear protein. Here, we generated transgenic mice expressing human TDP-43 with a defective nuclear localization signal in the forebrain (hTDP-43-ΔNLS), and compared them with mice expressing WT hTDP-43 (hTDP-43-WT) to determine the effects of mislocalized cytoplasmic TDP-43 on neuronal viability. Expression of either hTDP-43-ΔNLS or hTDP-43-WT led to neuron loss in selectively vulnerable forebrain regions, corticospinal tract degeneration, and motor spasticity recapitulating key aspects of FTLD and primary lateral sclerosis. Only rare cytoplasmic phosphorylated and ubiquitinated TDP-43 inclusions were seen in hTDP-43-ΔNLS mice, suggesting that cytoplasmic inclusions were not required to induce neuronal death. Instead, neurodegeneration in hTDP-43 and hTDP-43-ΔNLS-expressing neurons was accompanied by a dramatic downregulation of the endogenous mouse TDP-43. Moreover, mice expressing hTDP-43-ΔNLS exhibited profound changes in gene expression in cortical neurons. Our data suggest that perturbation of endogenous nuclear TDP-43 results in loss of normal TDP-43 function(s) and gene regulatory pathways, culminating in degeneration of selectively vulnerable affected neurons.

Hypoxia-inducible factor 2 regulates hepatic lipid metabolism.

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 beta-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.