γ-Secretase cleavage of the Alzheimer risk factor TREM2 is determined by its intrinsic structural dynamics.

Sequence variants of the microglial expressed TREM2 (triggering receptor expressed on myeloid cells 2) are a major risk factor for late onset Alzheimer's disease. TREM2 requires a stable interaction with DAP12 in the membrane to initiate signaling, which is terminated by TREM2 ectodomain shedding and subsequent intramembrane cleavage by γ-secretase. To understand the structural basis for the specificity of the intramembrane cleavage event, we determined the solution structure of the TREM2 transmembrane helix (TMH). Caused by the presence of a charged amino acid in the membrane region, the TREM2-TMH adopts a kinked structure with increased flexibility. Charge removal leads to TMH stabilization and reduced dynamics, similar to its structure in complex with DAP12. Strikingly, these dynamical features match with the site of the initial γ-secretase cleavage event. These data suggest an unprecedented cleavage mechanism by γ-secretase where flexible TMH regions act as key determinants of substrate cleavage specificity.

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.

Inhibition of mitochondrial fusion by α-synuclein is rescued by PINK1, Parkin and DJ-1.

Aggregation of α-synuclein (αS) is involved in the pathogenesis of Parkinson's disease (PD) and a variety of related neurodegenerative disorders. The physiological function of αS is largely unknown. We demonstrate with in vitro vesicle fusion experiments that αS has an inhibitory function on membrane fusion. Upon increased expression in cultured cells and in Caenorhabditis elegans, αS binds to mitochondria and leads to mitochondrial fragmentation. In C. elegans age-dependent fragmentation of mitochondria is enhanced and shifted to an earlier time point upon expression of exogenous αS. In contrast, siRNA-mediated downregulation of αS results in elongated mitochondria in cell culture. αS can act independently of mitochondrial fusion and fission proteins in shifting the dynamic morphologic equilibrium of mitochondria towards reduced fusion. Upon cellular fusion, αS prevents fusion of differently labelled mitochondrial populations. Thus, αS inhibits fusion due to its unique membrane interaction. Finally, mitochondrial fragmentation induced by expression of αS is rescued by coexpression of PINK1, parkin or DJ-1 but not the PD-associated mutations PINK1 G309D and parkin Δ1-79 or by DJ-1 C106A.

United States Government-Supported Family Planning and Reproductive Health Outreach in the Democratic Republic of the Congo: Lessons Learned and Recommendations.

Background: In response to limited contraception availability and a lack of knowledge about family planning (FP) in the Democratic Republic of the Congo (DRC), the United States Agency for International Development (USAID) Integrated Health Program (IHP) in the DRC has been providing FP services, including outreach programs in the DRC. Our study aims to assess the FP outreach program by understanding the participants' perception of the campaign, its impact on their behavior, and their feedback regarding the campaign. Additionally, we draw insights from lessons learned and provide recommendations. Methods: Between July and August 2022, we conducted 47 in-person participant interviews with women of reproductive age who used the outreach services provided by USAID IHP. Participants were randomly selected from Sud-Kivu, Kasai-Oriental, Haut-Katanga, and Tanganyika provinces. Consent and confidentiality were assured, and responses were recorded and transcribed in a Word document. We used Excel for data coding and analysis. Results: The campaign reached 95.7% of women interviewed; however, some participants could not recall specific message details. Most respondents (89.3%) reported that the campaign motivated them to make FP decisions and change their behaviors. While 14.8% of women reported making FP decisions independently, 85.1% reported making the decision jointly with their partners. Our analysis resulted in three emerging themes: 1) Increased FP outreach and improved perception of FP, 2) Improved perceived behavioral changes due to FP outreach, and 3) The need for program improvement by including men and providing additional information about possible FP side effects. Implications: Our study provides insights into how women receive information and whether they find it useful and share it with other women in their community. In particular, women's feedback about the FP outreach program and our recommendations can inform future policies and interventions.

PET imaging of microglia in Alzheimer's disease using copper-64 labeled TREM2 antibodies.

Triggering receptor expressed on myeloid cells 2 (TREM2) plays an essential role in microglia activation and is being investigated as a potential therapeutic target for modulation of microglia in several neurological diseases. In this study, we present the development and preclinical evaluation of 64Cu-labeled antibody-based PET radiotracers as tools for non-invasive assessment of TREM2 expression. Furthermore, we tested the potential of an antibody transport vehicle (ATV) that binds human transferrin receptor to facilitate transcytosis of TREM2 antibody-based radiotracers to the CNS and improve target engagement. Methods: A TREM2 antibody with an engineered transport vehicle (ATV:4D9) and without (4D9) were covalently modified with pNCS-benzyl-NODAGA and labeled with copper-64. Potency, stability, and specificity were assessed in vitro followed by in vivo PET imaging at the early 2 h, intermediate 20 h, and late imaging time points 40 h post-injection using a human transferrin receptor (hTfR) expressing model for amyloidogenesis (5xFAD;TfRmu/hu) or wild-type mice (WT;TfRmu/hu), and hTfR negative controls. Organs of interest were isolated to determine biodistribution by ex vivo autoradiography. Cell sorting after in vivo tracer injection was used to demonstrate cellular specificity for microglia and to validate TREM2 PET results in an independent mouse model for amyloidogenesis (AppSAA;TfRmu/hu). For translation to human imaging, a human TREM2 antibody (14D3) was radiolabeled and used for in vitro autoradiography on human brain sections. Results: The 64Cu-labeled antibodies were obtained in high radiochemical purity (RCP), radiochemical yield (RCY), and specific activity. Antibody modification did not impact TREM2 binding. ATV:4D9 binding proved to be specific, and the tracer stability was maintained over 48 h. The uptake of [64Cu]Cu-NODAGA-ATV:4D9 in the brains of hTfR expressing mice was up to 4.6-fold higher than [64Cu]Cu-NODAGA-4D9 in mice without hTfR. TREM2 PET revealed elevated uptake in the cortex of 5xFAD mice compared to wild-type, which was validated by autoradiography. PET-to-biodistribution correlation revealed that elevated radiotracer uptake in brains of 5xFAD;TfRmu/hu mice was driven by microglia-rich cortical and hippocampal brain regions. Radiolabeled ATV:4D9 was selectively enriched in microglia and cellular uptake explained PET signal enhancement in AppSAA;TfRmu/hu mice. Human autoradiography showed elevated TREM2 tracer binding in the cortex of patients with Alzheimer's disease. Conclusion: [64Cu]Cu-NODAGA-ATV:4D9 has potential for non-invasive assessment of TREM2 as a surrogate marker for microglia activation in vivo. ATV engineering for hTfR binding and transcytosis overcomes the blood-brain barrier restriction for antibody-based PET radiotracers. TREM2 PET might be a versatile tool for many applications beyond Alzheimer's disease, such as glioma and chronic inflammatory diseases.

Loss of parkin or PINK1 function increases Drp1-dependent mitochondrial fragmentation.

Loss-of-function mutations in the parkin gene (PARK2) and PINK1 gene (PARK6) are associated with autosomal recessive parkinsonism. PINK1 deficiency was recently linked to mitochondrial pathology in human cells and Drosophila melanogaster, which can be rescued by parkin, suggesting that both genes play a role in maintaining mitochondrial integrity. Here we demonstrate that an acute down-regulation of parkin in human SH-SY5Y cells severely affects mitochondrial morphology and function, a phenotype comparable with that induced by PINK1 deficiency. Alterations in both mitochondrial morphology and ATP production caused by either parkin or PINK1 loss of function could be rescued by the mitochondrial fusion proteins Mfn2 and OPA1 or by a dominant negative mutant of the fission protein Drp1. Both parkin and PINK1 were able to suppress mitochondrial fragmentation induced by Drp1. Moreover, in Drp1-deficient cells the parkin/PINK1 knockdown phenotype did not occur, indicating that mitochondrial alterations observed in parkin- or PINK1-deficient cells are associated with an increase in mitochondrial fission. Notably, mitochondrial fragmentation is an early phenomenon upon PINK1/parkin silencing that also occurs in primary mouse neurons and Drosophila S2 cells. We propose that the discrepant findings in adult flies can be explained by the time of phenotype analysis and suggest that in mammals different strategies may have evolved to cope with dysfunctional mitochondria.

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.

The Trem2 R47H Alzheimer's risk variant impairs splicing and reduces Trem2 mRNA and protein in mice but not in humans.

BACKGROUND: The R47H variant of the Triggering Receptor Expressed on Myeloid cells 2 (TREM2) significantly increases the risk for late onset Alzheimer's disease. Mouse models accurately reproducing phenotypes observed in Alzheimer' disease patients carrying the R47H coding variant are required to understand the TREM2 related dysfunctions responsible for the enhanced risk for late onset Alzheimer's disease. METHODS: A CRISPR/Cas9-assisted gene targeting strategy was used to generate Trem2 R47H knock-in mice. Trem2 mRNA and protein levels as well as Trem2 splicing patterns were assessed in these mice, in iPSC-derived human microglia-like cells, and in human brains from Alzheimer's patients carrying the TREM2 R47H risk factor. RESULTS: Two independent Trem2 R47H knock-in mouse models show reduced Trem2 mRNA and protein production. In both mouse models Trem2 haploinsufficiency was due to atypical splicing of mouse Trem2 R47H, which introduced a premature stop codon. Cellular splicing assays using minigene constructs demonstrate that the R47H variant induced abnormal splicing only occurs in mice but not in humans. TREM2 mRNA levels and splicing patterns were both normal in iPSC-derived human microglia-like cells and patient brains with the TREM2 R47H variant. CONCLUSIONS: The Trem2 R47H variant activates a cryptic splice site that generates miss-spliced transcripts leading to Trem2 haploinsufficiency only in mice but not in humans. Since Trem2 R47H related phenotypes are mouse specific and do not occur in humans, humanized TREM2 R47H knock-in mice should be generated to study the cellular consequences caused by the human TREM2 R47H coding variant. Currently described phenotypes of Trem2 R47H knock-in mice can therefore not be translated to humans.

An economic model to reduce the cost of chemotherapy for gynecologic cancer.

OBJECTIVE: Chemotherapy with innovative state-of-the-art medicine at university level can be very costly. Reimbursement until 2002 was at a flat rate, often not even covering the costs of the pharmaceutical substances. To avoid debt a more cost-effective chemotherapy management system had to be found. MATERIALS AND METHODS: From this background, an economic model with four steps was developed: 1. Analysis of current financial situation; 2. Precalculation of chemotherapy costs; 3. Assignment to an individual cost-covering reimbursement pathway; and 4. Postcalculation for cost efficiency and elimination of potential mistakes. RESULTS: After successful implementation of this model we were able to reach cost effectiveness for our chemo unit within 12 months and pay back previous debts and were even able to employ new medical staff. CONCLUSION: With this model we are now able to perform chemotherapy cost effectively at a university level without reducing standard of care.

A multilocus technique for risk evaluation of patients with neuroblastoma.

PURPOSE: Precise and comprehensive analysis of neuroblastoma genetics is essential for accurate risk evaluation and only pangenomic/multilocus approaches fulfill the present-day requirements. We present the establishment and validation of the PCR-based multiplex ligation-dependent probe amplification (MLPA) technique for neuroblastoma. EXPERIMENTAL DESIGN: A neuroblastoma-specific MLPA kit was designed by the SIOP Europe Neuroblastoma Biology Committee in cooperation with MRC-Holland. The contained target sequences cover 19 chromosomal arms and reference loci. Validation was performed by single locus and pangenomic techniques (n = 174). Dilution experiments for determination of minimal tumor cell percentage were performed and testing of reproducibility was checked by interlaboratory testing (n = 15). Further 156 neuroblastomas were used for establishing the amplification cutoff level. RESULTS: The MLPA technique was tested in 310 neuroblastomas and 8 neuroblastoma cell lines (including validation and amplification cutoff level testing). Intertechnique validation showed a high concordance rate (99.5%). Interlaboratory MLPA testing (κ = 0.95, P < 0.01) revealed 7 discrepant of 1,490 results (0.5%). Validation by pangenomic techniques showed a single discordance of 190 consensus results (0.5%). The test results led to formulation of interpretation standards and to a kit revision. The minimal tumor cell percentage was fixed at 60%. CONCLUSIONS: The recently designed neuroblastoma-specific MLPA kit covers all chromosomal regions demanded by the International Neuroblastoma Risk Group for therapy stratification and includes all hitherto described genetic loci of prognostic interest for future studies and can be modified or extended at any time. Moreover, the technique is cost effective, reliable, and robust with a high interlaboratory and intertechnique concordance.