Pathways linking aging and atheroprotection in Mif-deficient atherosclerotic mice.

Atherosclerosis is a chronic inflammatory condition of our arteries and the main underlying pathology of myocardial infarction and stroke. The pathogenesis is age-dependent, but the links between disease progression, age, and atherogenic cytokines and chemokines are incompletely understood. Here, we studied the chemokine-like inflammatory cytokine macrophage migration inhibitory factor (MIF) in atherogenic Apoe-/- mice across different stages of aging and cholesterol-rich high-fat diet (HFD). MIF promotes atherosclerosis by mediating leukocyte recruitment, lesional inflammation, and suppressing atheroprotective B cells. However, links between MIF and advanced atherosclerosis across aging have not been systematically explored. We compared effects of global Mif-gene deficiency in 30-, 42-, and 48-week-old Apoe-/- mice on HFD for 24, 36, or 42 weeks, respectively, and in 52-week-old mice on a 6-week HFD. Mif-deficient mice exhibited reduced atherosclerotic lesions in the 30/24- and 42/36-week-old groups, but atheroprotection, which in the applied Apoe-/- model was limited to lesions in the brachiocephalic artery and abdominal aorta, was not detected in the 48/42- and 52/6-week-old groups. This suggested that atheroprotection afforded by global Mif-gene deletion differs across aging stages and atherogenic diet duration. To characterize this phenotype and study the underlying mechanisms, we determined immune cells in the periphery and vascular lesions, obtained a multiplex cytokine/chemokine profile, and compared the transcriptome between the age-related phenotypes. We found that Mif deficiency promotes lesional macrophage and T-cell counts in younger but not aged mice, with subgroup analysis pointing toward a role for Trem2+ macrophages. The transcriptomic analysis identified pronounced MIF- and aging-dependent changes in pathways predominantly related to lipid synthesis and metabolism, lipid storage, and brown fat cell differentiation, as well as immunity, and atherosclerosis-relevant enriched genes such as Plin1, Ldlr, Cpne7, or Il34, hinting toward effects on lesional lipids, foamy macrophages, and immune cells. Moreover, Mif-deficient aged mice exhibited a distinct plasma cytokine/chemokine signature consistent with the notion that mediators known to drive inflamm'aging are either not downregulated or even upregulated in Mif-deficient aged mice compared with the corresponding younger ones. Lastly, Mif deficiency favored formation of lymphocyte-rich peri-adventitial leukocyte clusters. While the causative contributions of these mechanistic pillars and their interplay will be subject to future scrutiny, our study suggests that atheroprotection due to global Mif-gene deficiency in atherogenic Apoe-/- mice is reduced upon advanced aging and identifies previously unrecognized cellular and molecular targets that could explain this phenotype shift. These observations enhance our understanding of inflamm'aging and MIF pathways in atherosclerosis and may have implications for translational MIF-directed strategies.

Depletion and activation of microglia impact metabolic connectivity of the mouse brain.

AIM: We aimed to investigate the impact of microglial activity and microglial FDG uptake on metabolic connectivity, since microglial activation states determine FDG-PET alterations. Metabolic connectivity refers to a concept of interacting metabolic brain regions and receives growing interest in approaching complex cerebral metabolic networks in neurodegenerative diseases. However, underlying sources of metabolic connectivity remain to be elucidated. MATERIALS AND METHODS: We analyzed metabolic networks measured by interregional correlation coefficients (ICCs) of FDG-PET scans in WT mice and in mice with mutations in progranulin (Grn) or triggering receptor expressed on myeloid cells 2 (Trem2) knockouts (-/-) as well as in double mutant Grn-/-/Trem2-/- mice. We selected those rodent models as they represent opposite microglial signatures with disease associated microglia in Grn-/- mice and microglia locked in a homeostatic state in Trem2-/- mice; however, both resulting in lower glucose uptake of the brain. The direct influence of microglia on metabolic networks was further determined by microglia depletion using a CSF1R inhibitor in WT mice at two different ages. Within maps of global mean scaled regional FDG uptake, 24 pre-established volumes of interest were applied and assigned to either cortical or subcortical networks. ICCs of all region pairs were calculated and z-transformed prior to group comparisons. FDG uptake of neurons, microglia, and astrocytes was determined in Grn-/- and WT mice via assessment of single cell tracer uptake (scRadiotracing). RESULTS: Microglia depletion by CSF1R inhibition resulted in a strong decrease of metabolic connectivity defined by decrease of mean cortical ICCs in WT mice at both ages studied (6-7 m; p = 0.0148, 9-10 m; p = 0.0191), when compared to vehicle-treated age-matched WT mice. Grn-/-, Trem2-/- and Grn-/-/Trem2-/- mice all displayed reduced FDG-PET signals when compared to WT mice. However, when analyzing metabolic networks, a distinct increase of ICCs was observed in Grn-/- mice when compared to WT mice in cortical (p < 0.0001) and hippocampal (p < 0.0001) networks. In contrast, Trem2-/- mice did not show significant alterations in metabolic connectivity when compared to WT. Furthermore, the increased metabolic connectivity in Grn-/- mice was completely suppressed in Grn-/-/Trem2-/- mice. Grn-/- mice exhibited a severe loss of neuronal FDG uptake (- 61%, p < 0.0001) which shifted allocation of cellular brain FDG uptake to microglia (42% in Grn-/- vs. 22% in WT). CONCLUSIONS: Presence, absence, and activation of microglia have a strong impact on metabolic connectivity of the mouse brain. Enhanced metabolic connectivity is associated with increased microglial FDG allocation.

Loss of TMEM106B potentiates lysosomal and FTLD-like pathology in progranulin-deficient mice.

Single nucleotide polymorphisms (SNPs) in TMEM106B encoding the lysosomal type II transmembrane protein 106B increase the risk for frontotemporal lobar degeneration (FTLD) of GRN (progranulin gene) mutation carriers. Currently, it is unclear if progranulin (PGRN) and TMEM106B are synergistically linked and if a gain or a loss of function of TMEM106B is responsible for the increased disease risk of patients with GRN haploinsufficiency. We therefore compare behavioral abnormalities, gene expression patterns, lysosomal activity, and TDP-43 pathology in single and double knockout animals. Grn-/- /Tmem106b-/- mice show a strongly reduced life span and massive motor deficits. Gene expression analysis reveals an upregulation of molecular signature characteristic for disease-associated microglia and autophagy. Dysregulation of maturation of lysosomal proteins as well as an accumulation of ubiquitinated proteins and widespread p62 deposition suggest that proteostasis is impaired. Moreover, while single Grn-/- knockouts only occasionally show TDP-43 pathology, the double knockout mice exhibit deposition of phosphorylated TDP-43. Thus, a loss of function of TMEM106B may enhance the risk for GRN-associated FTLD by reduced protein turnover in the lysosomal/autophagic system.

Poly-glycine-alanine exacerbates C9orf72 repeat expansion-mediated DNA damage via sequestration of phosphorylated ATM and loss of nuclear hnRNPA3.

Repeat expansion in C9orf72 causes amyotrophic lateral sclerosis and frontotemporal lobar degeneration. Expanded sense and antisense repeat RNA transcripts in C9orf72 are translated into five dipeptide-repeat proteins (DPRs) in an AUG-independent manner. We previously identified the heterogeneous ribonucleoprotein (hnRNP) A3 as an interactor of the sense repeat RNA that reduces its translation into DPRs. Furthermore, we found that hnRNPA3 is depleted from the nucleus and partially mislocalized to cytoplasmic poly-GA inclusions in C9orf72 patients, suggesting that poly-GA sequesters hnRNPA3 within the cytoplasm. We now demonstrate that hnRNPA3 also binds to the antisense repeat RNA. Both DPR production and deposition from sense and antisense RNA repeats are increased upon hnRNPA3 reduction. All DPRs induced DNA double strand breaks (DSB), which was further enhanced upon reduction of hnRNPA3. Poly-glycine-arginine and poly-proline-arginine increased foci formed by phosphorylated Ataxia Telangiectasia Mutated (pATM), a major sensor of DSBs, whereas poly-glycine-alanine (poly-GA) evoked a reduction of pATM foci. In dentate gyri of C9orf72 patients, lower nuclear hnRNPA3 levels were associated with increased DNA damage. Moreover, enhanced poly-GA deposition correlated with reduced pATM foci. Since cytoplasmic pATM deposits partially colocalized with poly-GA deposits, these results suggest that poly-GA, the most frequent DPR observed in C9orf72 patients, differentially causes DNA damage and that poly-GA selectively sequesters pATM in the cytoplasm inhibiting its recruitment to sites of DNA damage. Thus, mislocalization of nuclear hnRNPA3 caused by poly-GA leads to increased poly-GA production, which partially depletes pATM, and consequently enhances DSB.

Best fitting tumor growth models of the von Bertalanffy-PütterType.

BACKGROUND: Longitudinal studies of tumor volume have used certain named mathematical growth models. The Bertalanffy-Pütter differential equation unifies them: It uses five parameters, amongst them two exponents related to tumor metabolism and morphology. Each exponent-pair defines a unique three-parameter model of the Bertalanffy-Pütter type, and the above-mentioned named models correspond to specific exponent-pairs. Amongst these models we seek the best fitting one. METHOD: The best fitting model curve within the Bertalanffy-Pütter class minimizes the sum of squared errors (SSE). We investigate also near-optimal model curves; their SSE is at most a certain percentage (e.g. 1%) larger than the minimal SSE. Models with near-optimal curves are visualized by the region of their near-optimal exponent pairs. While there is barely a visible difference concerning the goodness of fit between the best fitting and the near-optimal model curves, there are differences in the prognosis, whence the near-optimal models are used to assess the uncertainty of extrapolation. RESULTS: For data about the growth of an untreated tumor we found the best fitting growth model which reduced SSE by about 30% compared to the hitherto best fit. In order to analyze the uncertainty of prognosis, we repeated the search for the optimal and near-optimal exponent-pairs for the initial segments of the data (meaning the subset of the data for the first n days) and compared the prognosis based on these models with the actual data (i.e. the data for the remaining days). The optimal exponent-pairs and the regions of near-optimal exponent-pairs depended on how many data-points were used. Further, the regions of near-optimal exponent-pairs were larger for the first initial segments, where fewer data were used. CONCLUSION: While for each near optimal exponent-pair its best fitting model curve remained close to the fitted data points, the prognosis using these model curves differed widely for the remaining data, whence e.g. the best fitting model for the first 65 days of growth was not capable to inform about tumor size for the remaining 49 days. For the present data, prognosis appeared to be feasible for a time span of ten days, at most.

TREM2 deficiency impairs chemotaxis and microglial responses to neuronal injury.

Sequence variations in the triggering receptor expressed on myeloid cells 2 (TREM2) have been linked to an increased risk for neurodegenerative disorders such as Alzheimer's disease and frontotemporal lobar degeneration. In the brain, TREM2 is predominantly expressed in microglia. Several disease-associated TREM2 variants result in a loss of function by reducing microglial phagocytosis, impairing lipid sensing, preventing binding of lipoproteins and affecting shielding of amyloid plaques. We here investigate the consequences of TREM2 loss of function on the microglia transcriptome. Among the differentially expressed messenger RNAs in wild-type and Trem2-/- microglia, gene clusters are identified which represent gene functions in chemotaxis, migration and mobility. Functional analyses confirm that loss of TREM2 impairs appropriate microglial responses to injury and signals that normally evoke chemotaxis on multiple levels. In an ex vivo organotypic brain slice assay, absence of TREM2 reduces the distance migrated by microglia. Moreover, migration towards defined chemo-attractants is reduced upon ablation of TREM2 and can be rescued by TREM2 re-expression. In vivo, microglia lacking TREM2 migrate less towards injected apoptotic neurons, and outgrowth of microglial processes towards sites of laser-induced focal CNS damage in the somatosensory cortex is slowed. The apparent lack of chemotactic stimulation upon depletion of TREM2 is consistent with a stable expression profile of genes characterizing the homoeostatic signature of microglia.

Peripheral expression of brain-penetrant progranulin rescues pathologies in mouse models of frontotemporal lobar degeneration.

Progranulin (PGRN) haploinsufficiency is a major risk factor for frontotemporal lobar degeneration with TAR DNA-binding protein 43 (TDP-43) pathology (FTLD-GRN). Multiple therapeutic strategies are in clinical development to restore PGRN in the CNS, including gene therapy. However, a limitation of current gene therapy approaches aimed to alleviate FTLD-associated pathologies may be their inefficient brain exposure and biodistribution. We therefore developed an adeno-associated virus (AAV) targeting the liver (L) to achieve sustained peripheral expression of a transferrin receptor (TfR) binding, brain-penetrant (b) PGRN variant [AAV(L):bPGRN] in two mouse models of FTLD-GRN, namely, Grn knockout and GrnxTmem106b double knockout mice. This therapeutic strategy avoids potential safety and biodistribution issues of CNS-administered AAVs and maintains sustained concentrations of PGRN in the brain after a single dose. AAV(L):bPGRN treatment reduced several FTLD-GRN-associated pathologies including severe motor function deficits, aberrant TDP-43 phosphorylation, dysfunctional protein degradation, lipid metabolism, gliosis, and neurodegeneration in the brain. The potential translatability of our findings was tested in an in vitro model using cocultured human induced pluripotent stem cell (hiPSC)-derived microglia lacking PGRN and TMEM106B and wild-type hiPSC-derived neurons. As in mice, aberrant TDP-43, lysosomal dysfunction, and neuronal loss were ameliorated after treatment with exogenous TfR-binding protein transport vehicle fused to PGRN (PTV:PGRN). Together, our studies suggest that peripherally administered brain-penetrant PGRN replacement strategies ameliorate FTLD-GRN relevant phenotypes including TDP-43 pathology, neurodegeneration, and behavioral deficits. Our data provide preclinical proof of concept for the use of this AAV platform for treatment of FTLD-GRN and potentially other CNS disorders.

The FTLD Risk Factor TMEM106B Regulates the Transport of Lysosomes at the Axon Initial Segment of Motoneurons.

Genetic variations in TMEM106B, coding for a lysosomal membrane protein, affect frontotemporal lobar degeneration (FTLD) in GRN- (coding for progranulin) and C9orf72-expansion carriers and might play a role in aging. To determine the physiological function of TMEM106B, we generated TMEM106B-deficient mice. These mice develop proximal axonal swellings caused by drastically enlarged LAMP1-positive vacuoles, increased retrograde axonal transport of lysosomes, and accumulation of lipofuscin and autophagosomes. Giant vacuoles specifically accumulate at the distal end and within the axon initial segment, but not in peripheral nerves or at axon terminals, resulting in an impaired facial-nerve-dependent motor performance. These data implicate TMEM106B in mediating the axonal transport of LAMP1-positive organelles in motoneurons and axonal sorting at the initial segment. Our data provide mechanistic insight into how TMEM106B affects lysosomal proteolysis and degradative capacity in neurons.

Enhancing protective microglial activities with a dual function TREM2 antibody to the stalk region.

Triggering receptor expressed on myeloid cells 2 (TREM2) is essential for the transition of homeostatic microglia to a disease-associated microglial state. To enhance TREM2 activity, we sought to selectively increase the full-length protein on the cell surface via reducing its proteolytic shedding by A Disintegrin And Metalloproteinase (i.e., α-secretase) 10/17. We screened a panel of monoclonal antibodies against TREM2, with the aim to selectively compete for α-secretase-mediated shedding. Monoclonal antibody 4D9, which has a stalk region epitope close to the cleavage site, demonstrated dual mechanisms of action by stabilizing TREM2 on the cell surface and reducing its shedding, and concomitantly activating phospho-SYK signaling. 4D9 stimulated survival of macrophages and increased microglial uptake of myelin debris and amyloid ß-peptide in vitro. In vivo target engagement was demonstrated in cerebrospinal fluid, where nearly all soluble TREM2 was 4D9-bound. Moreover, in a mouse model for Alzheimer's disease-related pathology, 4D9 reduced amyloidogenesis, enhanced microglial TREM2 expression, and reduced a homeostatic marker, suggesting a protective function by driving microglia toward a disease-associated state.

Best-fitting growth curves of the von Bertalanffy-Pütter type.

INTRODUCTION: A large body of literature aims at identifying growth models that fit best to given mass-at-age data. The von Bertalanffy-Pütter differential equation is a unifying framework for the study of growth models. PROBLEM: The most common growth models used in poultry science literature fit into this framework, as these models correspond to different exponent-pairs (e.g., Brody, Gompertz, logistic, Richards, and von Bertalanffy models). Here, we search for the optimal exponent-pairs (a and b) amongst all possible exponent-pairs and expect a significantly better fit of the growth curve to concrete mass-at-age data. METHOD: Data fitting becomes more difficult, as there is a large region of nearly optimal exponent-pairs. We therefore develop a fully automated optimization method, with computation time of about 1 to 2 wk per data-set. For the proof of principle, we applied it to literature data about 217 male meat-type chickens, Athens Canadian Random Bred, that were reared under controlled conditions and weighed 28 times during a time span of 170 D. RESULTS: We compared 2 methods of data fitting, least squares using the sum of squared errors (SSE), which is common in literature, and a variant using the sum of squared log-errors SSElog. For these data, the optimal exponent-pairs were (0.43, 4.06) for SSE = 2,208.6 (31% improvement over literature values for the residual standard deviation) and (0.89, 0.93) for SSElog = 0.04599. Both optimal exponents were clearly distinct from the exponent-pairs of the common models in literature. This finding was reinforced by considering the region of nearly optimal exponents. DISCUSSION: We explain, why we recommend using SSElog for data fitting and we discuss prognosis, where data from the first 8 wk of growth would not be enough.

Comparing growth patterns of three species: Similarities and differences.

Quantitative studies of the growth of dinosaurs have made comparisons with modern animals possible. Therefore, it is meaningful to ask, if extinct dinosaurs grew faster than modern animals, e.g. birds (modern dinosaurs) and reptiles. However, past studies relied on only a few growth models. If these models were false, what about the conclusions? This paper fits growth data to a more comprehensive class of models, defined by the von Bertalanffy-Pütter (BP) differential equation. Applied to data about Tenontosaurus tilletti, Alligator mississippiensis and the Athens Canadian Random Bred strain of Gallus gallus domesticus the best fitting growth curves did barely differ, if they were rescaled for size and lifespan. A difference could be discerned, if time was rescaled for the age at the inception point (maximal growth) or if the percentual growth was compared.

Opposite microglial activation stages upon loss of PGRN or TREM2 result in reduced cerebral glucose metabolism.

Microglia adopt numerous fates with homeostatic microglia (HM) and a microglial neurodegenerative phenotype (MGnD) representing two opposite ends. A number of variants in genes selectively expressed in microglia are associated with an increased risk for neurodegenerative diseases such as Alzheimer's disease (AD) and frontotemporal lobar degeneration (FTLD). Among these genes are progranulin (GRN) and the triggering receptor expressed on myeloid cells 2 (TREM2). Both cause neurodegeneration by mechanisms involving loss of function. We have now isolated microglia from Grn-/- mice and compared their transcriptomes to those of Trem2-/-mice Surprisingly, while loss of Trem2 enhances the expression of genes associated with a homeostatic state, microglia derived from Grn-/- mice showed a reciprocal activation of the MGnD molecular signature and suppression of gene characteristic for HM The opposite mRNA expression profiles are associated with divergent functional phenotypes. Although loss of TREM2 and progranulin resulted in opposite activation states and functional phenotypes of microglia, FDG (fluoro-2-deoxy-d-glucose)-µPET of brain revealed reduced glucose metabolism in both conditions, suggesting that opposite microglial phenotypes result in similar wide spread brain dysfunction.

Early lysosomal maturation deficits in microglia triggers enhanced lysosomal activity in other brain cells of progranulin knockout mice.

BACKGROUND: Heterozygous loss-of-function mutations in the progranulin gene (GRN) lead to frontotemporal lobar degeneration (FTLD) while the complete loss of progranulin (PGRN) function results in neuronal ceroid lipofuscinosis (NCL), a lysosomal storage disease. Thus the growth factor-like protein PGRN may play an important role in lysosomal degradation. In line with a potential lysosomal function, PGRN is partially localized and processed in lysosomes. In the central nervous system (CNS), PGRN is like other lysosomal proteins highly expressed in microglia, further supporting an important role in protein degradation. We have previously reported that cathepsin (Cat) D is elevated in GRN-associated FTLD patients and Grn knockout mice. However, the primary mechanism that causes impaired protein degradation and elevated CatD levels upon PGRN deficiency in NCL and FTLD remains unclear. METHODS: mRNA expression analysis of selected lysosomal hydrolases, lysosomal membrane proteins and autophagy-related genes was performed by NanoString nCounter panel. Protein expression, maturation and in vitro activity of Cat D, B and L in mouse embryonic fibroblasts (MEF) and brains of Grn knockout mice were investigated. To selectively characterize microglial and non-microglial brain cells, an acutely isolated microglia fraction using MACS microbeads (Miltenyi Biotec) conjugated with CD11b antibody and a microglia-depleted fraction were analyzed for protein expression and maturation of selected cathepsins. RESULTS: We demonstrate that loss of PGRN results in enhanced expression, maturation and in vitro activity of Cat D, B and L in mouse embryonic fibroblasts and brain extracts of aged Grn knockout mice. Consistent with an overall enhanced expression and activity of lysosomal proteases in brain of Grn knockout mice, we observed an age-dependent transcriptional upregulation of certain lysosomal proteases. Thus, lysosomal dysfunction is not reflected by transcriptional downregulation of lysosomal proteases but rather by the upregulation of certain lysosomal proteases in an age-dependent manner. Surprisingly, cell specific analyses identified early lysosomal deficits in microglia before enhanced cathepsin levels could be detected in other brain cells, suggesting different functional consequences on lysosomal homeostasis in microglia and other brain cells upon lack of PGRN. CONCLUSIONS: The present study uncovers early and selective lysosomal dysfunctions in Grn knockout microglia/macrophages. Dysregulated lysosomal homeostasis in microglia might trigger compensatory lysosomal changes in other brain cells.

Optimal and near-optimal exponent-pairs for the Bertalanffy-Pütter growth model.

The Bertalanffy-Pütter growth model describes mass m at age t by means of the differential equation dm/dt = p * m a  - q * mb . The special case using the von Bertalanffy exponent-pair a = 2/3 and b = 1 is most common (it corresponds to the von Bertalanffy growth function VBGF for length in fishery literature). Fitting VBGF to size-at-age data requires the optimization of three model parameters (the constants p, q, and an initial value for the differential equation). For the general Bertalanffy-Pütter model, two more model parameters are optimized (the pair a < b of non-negative exponents). While this reduces bias in growth estimates, it increases model complexity and more advanced optimization methods are needed, such as the Nelder-Mead amoeba method, interior point methods, or simulated annealing. Is the improved performance worth these efforts? For the case, where the exponent b = 1 remains fixed, it is known that for most fish data any exponent a < 1 could be used to model growth without affecting the fit to the data significantly (when the other parameters were optimized). We hypothesized that the optimization of both exponents would result in a significantly better fit of the optimal growth function to the data and we tested this conjecture for a data set (20,166 fish) about the mass-growth of Walleye (Sander vitreus), a fish from Lake Erie, USA. To this end, we assessed the fit on a grid of 14,281 exponent-pairs (a, b) and identified the best fitting model curve on the boundary a = b of the grid (a = b = 0.686); it corresponds to the generalized Gompertz equation dm/dt = p * ma  - q * ln(m) * ma . Using the Akaike information criterion for model selection, the answer to the conjecture was no: The von Bertalanffy exponent-pair model (but not the logistic model) remained parsimonious. However, the bias reduction attained by the optimal exponent-pair may be worth the tradeoff with complexity in some situations where predictive power is solely preferred. Therefore, we recommend the use of the Bertalanffy-Pütter model (and of its limit case, the generalized Gompertz model) in natural resources management (such as in fishery stock assessments), as it relies on careful quantitative assessments to recommend policies for sustainable resource usage.

On the exponent in the Von Bertalanffy growth model.

Von Bertalanffy proposed the differential equation m'(t) = p × m(t) a  - q × m(t) for the description of the mass growth of animals as a function m(t) of time t. He suggested that the solution using the metabolic scaling exponent a = 2/3 (Von Bertalanffy growth function VBGF) would be universal for vertebrates. Several authors questioned universality, as for certain species other models would provide a better fit. This paper reconsiders this question. Based on 60 data sets from literature (37 about fish and 23 about non-fish species) it optimizes the model parameters, in particular the exponent 0 ≤ a < 1, so that the model curve achieves the best fit to the data. The main observation of the paper is the large variability in the exponent, which can vary over a very large range without affecting the fit to the data significantly, when the other parameters are also optimized. The paper explains this by differences in the data quality: variability is low for data from highly controlled experiments and high for natural data. Other deficiencies were biologically meaningless optimal parameter values or optimal parameter values attained on the boundary of the parameter region (indicating the possible need for a different model). Only 11 of the 60 data sets were free of such deficiencies and for them no universal exponent could be discerned.

Calcium Carbide: A Unique Reagent for Organic Synthesis and Nanotechnology.

Acetylene, HC≡CH, is one of the primary building blocks in synthetic organic and industrial chemistry. Several highly valuable processes have been developed based on this simplest alkyne and the development of acetylene chemistry has had a paramount impact on chemical science over the last few decades. However, in spite of numerous useful possible reactions, the application of gaseous acetylene in everyday research practice is rather limited. Moreover, the practical implementation of high-pressure acetylene chemistry can be very challenging, owing to the risk of explosion and the requirement for complex equipment; special safety precautions need to be taken to store and handle acetylene under high pressure, which limit its routine use in a standard laboratory setup. Amazingly, recent studies have revealed that calcium carbide, CaC2 , can be used as an easy-to-handle and efficient source of acetylene for in situ chemical transformations. Thus, calcium carbide is a stable and inexpensive acetylene precursor that is available on the ton scale and it can be handled with standard laboratory equipment. The application of calcium carbide in organic synthesis will bring a new dimension to the powerful acetylene chemistry.

TREM2 deficiency reduces the efficacy of immunotherapeutic amyloid clearance.

Immunotherapeutic approaches are currently the most advanced treatments for Alzheimer's disease (AD). Antibodies against amyloid ß-peptide (Aß) bind to amyloid plaques and induce their clearance by microglia via Fc receptor-mediated phagocytosis. Dysfunctions of microglia may play a pivotal role in AD pathogenesis and could result in reduced efficacy of antibody-mediated Aß clearance. Recently, heterozygous mutations in the triggering receptor expressed on myeloid cells 2 (TREM2), a microglial gene involved in phagocytosis, were genetically linked to late onset AD Loss of TREM2 reduces the ability of microglia to engulf Aß. We have now investigated whether loss of TREM2 affects the efficacy of immunotherapeutic approaches. We show that anti-Aß antibodies stimulate Aß uptake and amyloid plaque clearance in a dose-dependent manner in the presence or absence of TREM2. However, TREM2-deficient N9 microglial cell lines, macrophages as well as primary microglia showed significantly reduced uptake of antibody-bound Aß and as a consequence reduced clearance of amyloid plaques. Titration experiments revealed that reduced efficacy of amyloid plaque clearance by Trem2 knockout cells can be compensated by elevating the concentration of therapeutic antibodies.