Chr21 protein–protein interactions: enrichment in proteins involved in intellectual disability, autism, and late-onset Alzheimer’s disease

Down syndrome (DS) is caused by human chromosome 21 (HSA21) trisomy. It is characterized by a poorly understood intellectual disability (ID). We studied two mouse models of DS, one with an extra copy of the Dyrk1A gene (189N3) and the other with an extra copy of the mouse Chr16 syntenic region (Dp(16)1Yey). RNA-seq analysis of the transcripts deregulated in the embryonic hippocampus revealed an enrichment in genes associated with chromatin for the 189N3 model, and synapses for the Dp(16)1Yey model. A large-scale yeast two-hybrid screen (82 different screens, including 72 HSA21 baits and 10 rebounds) of a human brain library containing at least 107 independent fragments identified 1,949 novel protein–protein interactions. The direct interactors of HSA21 baits and rebounds were significantly enriched in ID-related genes (P-value < 2.29 × 10−8). Proximity ligation assays showed that some of the proteins encoded by HSA21 were located at the dendritic spine postsynaptic density, in a protein network at the dendritic spine postsynapse. We located HSA21 DYRK1A and DSCAM, mutations of which increase the risk of autism spectrum disorder (ASD) 20-fold, in this postsynaptic network. We found that an intracellular domain of DSCAM bound either DLGs, which are multimeric scaffolds comprising receptors, ion channels and associated signaling proteins, or DYRK1A. The DYRK1A-DSCAM interaction domain is conserved in Drosophila and humans. The postsynaptic network was found to be enriched in proteins associated with ARC-related synaptic plasticity, ASD, and late-onset Alzheimer’s disease. These results highlight links between DS and brain diseases with a complex genetic basis

Analyse d’un nouveau modèle transgénique murin d’Alzheimer à début tardif basé sur la surexpression de BIN1 et induisant des endophénotypes précliniques de la maladie

Late-onset Alzheimer’s Disease (LOAD) is the most common form of dementia and one of the most challenging disease of modern society. Although familial Alzheimer’s Disease (FAD) only account for 2% of the cases, research on the molecular basis of this pathology has mostly been performed on animal models of FAD. The first objective of this doctoral thesis was to identify new pathways involved in LOAD physiopathology. New synaptic partners of BIN1, the second most associated locus with LOAD after APOE, have been characterized. The second objective of this thesis was to study a new mouse model of LOAD, after APOE models: a mouse mimicking the overexpression of BIN1 found in patients. Together, the results place BIN1 in a synaptic interactome involved in the regulation of two major hallmarks of LOAD: dendritic spine morphology and amyloid β peptide regulation. They also link BIN1 with an alteration of the Lateral Entorhinal Cortex, which is the first brain structure affected in patients. Altogether, this doctoral thesis gives new insights on molecular pathways involved in early pathologic features of LOAD, at early presymptomatic stages of the disease, attainable by new therapeutic strategies.La Maladie d’Alzheimer Sporadique (MAS) est à ce jour la cause majoritaire de démence à travers le monde. Cette pathologie est aujourd’hui une question de santé publique avec des conséquences économiques et sociales du fait du vieillissement de la population et du coût de la prise en charge des patients. Les études visant à élucider les mécanismes moléculaires de cette maladie se basent pourtant majoritairement sur des modèles animaux de la forme familiale, qui ne représente que 2% des cas de Maladie d’Alzheimer. La première partie de cette thèse de doctorat a eu pour objectif d’explorer de nouvelles voies de signalisation neuronales pouvant être impliquées dans la MAS. Elle a permis l’identification de nouveaux partenaires synaptiques de la protéine BIN1, dont le gène représente le second locus de susceptibilité pour la MAS après APOE. Dans un second temps, les travaux de cette thèse ont consisté en la caractérisation d’un nouveau modèle murin de cette maladie, après les modèles APOE : une souris mimant la surexpression du gène BIN1 mise en évidence chez les patients. Il a été possible d’inclure la protéine BIN1 dans un interactome synaptique impliqué dans la régulation de deux marqueurs majeurs de la physiopathologie de la MAS : la morphologie des épines dendritiques et la régulation du peptide amyloïde β, et de les relier à une atteinte du cortex entorhinal latéral, la première structure impactée chez les patients. Au total, cette thèse a permis de mettre en évidence des voies de signalisation impliquées dans les phases pré-symptomatiques de la maladie. Ces voies de signalisation sont des cibles thérapeutiques potentielles pour le traitement de la Maladie d’Alzheimer Sporadique

Analysis of a new transgenic murine Alzheimer model

La Maladie d’Alzheimer Sporadique (MAS) est à ce jour la cause majoritaire de démence à travers le monde. Cette pathologie est aujourd’hui une question de santé publique avec des conséquences économiques et sociales du fait du vieillissement de la population et du coût de la prise en charge des patients. Les études visant à élucider les mécanismes moléculaires de cette maladie se basent pourtant majoritairement sur des modèles animaux de la forme familiale, qui ne représente que 2% des cas de Maladie d’Alzheimer. La première partie de cette thèse de doctorat a eu pour objectif d’explorer de nouvelles voies de signalisation neuronales pouvant être impliquées dans la MAS. Elle a permis l’identification de nouveaux partenaires synaptiques de la protéine BIN1, dont le gène représente le second locus de susceptibilité pour la MAS après APOE. Dans un second temps, les travaux de cette thèse ont consisté en la caractérisation d’un nouveau modèle murin de cette maladie, après les modèles APOE : une souris mimant la surexpression du gène BIN1 mise en évidence chez les patients. Il a été possible d’inclure la protéine BIN1 dans un interactome synaptique impliqué dans la régulation de deux marqueurs majeurs de la physiopathologie de la MAS : la morphologie des épines dendritiques et la régulation du peptide amyloïde β, et de les relier à une atteinte du cortex entorhinal latéral, la première structure impactée chez les patients. Au total, cette thèse a permis de mettre en évidence des voies de signalisation impliquées dans les phases pré-symptomatiques de la maladie. Ces voies de signalisation sont des cibles thérapeutiques potentielles pour le traitement de la Maladie d’Alzheimer Sporadique.Late-onset Alzheimer’s Disease (LOAD) is the most common form of dementia and one of the most challenging disease of modern society. Although familial Alzheimer’s Disease (FAD) only account for 2% of the cases, research on the molecular basis of this pathology has mostly been performed on animal models of FAD. The first objective of this doctoral thesis was to identify new pathways involved in LOAD physiopathology. New synaptic partners of BIN1, the second most associated locus with LOAD after APOE, have been characterized. The second objective of this thesis was to study a new mouse model of LOAD, after APOE models: a mouse mimicking the overexpression of BIN1 found in patients. Together, the results place BIN1 in a synaptic interactome involved in the regulation of two major hallmarks of LOAD: dendritic spine morphology and amyloid β peptide regulation. They also link BIN1 with an alteration of the Lateral Entorhinal Cortex, which is the first brain structure affected in patients. Altogether, this doctoral thesis gives new insights on molecular pathways involved in early pathologic features of LOAD, at early presymptomatic stages of the disease, attainable by new therapeutic strategies

Chr21 protein-protein interactions: enrichment in proteins involved in intellectual disability, autism, and late-onset Alzheimer&apos;s disease

Down syndrome (DS) is caused by human chromosome 21 (HSA21) trisomy. It is characterized by a poorly understood intellectual disability (ID). We studied two mouse models of DS, one with an extra copy of the Dyrk1A gene (189N3) and the other with an extra copy of the mouse Chr16 syntenic region (Dp(16)1Yey). RNA-seq analysis of the transcripts deregulated in the embryonic hippocampus revealed an enrichment in genes associated with chromatin for the 189N3 model, and synapses for the Dp(16)1Yey model. A large-scale yeast two-hybrid screen (82 different screens, including 72 HSA21 baits and 10 rebounds) of a human brain library containing at least 107 independent fragments identified 1,949 novel protein-protein interactions. The direct interactors of HSA21 baits and rebounds were significantly enriched in ID-related genes (P-value < 2.29 x 10(-8)). Proximity ligation assays showed that some of the proteins encoded by HSA21 were located at the dendritic spine postsynaptic density, in a protein network at the dendritic spine postsynapse. We located HSA21 DYRK1A and DSCAM, mutations of which increase the risk of autism spectrum disorder (ASD) 20-fold, in this postsynaptic network. We found that an intracellular domain of DSCAM bound either DLGs, which are multimeric scaffolds comprising receptors, ion channels and associated signaling proteins, or DYRK1A. The DYRK1A-DSCAM interaction domain is conserved in Drosophila and humans. The postsynaptic network was found to be enriched in proteins associated with ARC-related synaptic plasticity, ASD, and late-onset Alzheimer&apos;s disease. These results highlight links between DS and brain diseases with a complex genetic basis.11Nsciescopu

Fluorescent nanodiamond tracking reveals intraneuronal transport abnormalities induced by brain-disease-related genetic risk factors

International audienceBrain diseases such as autism and Alzheimer's disease (each inflicting >1% of the world population) involve a large network of genes displaying subtle changes in their expression. Abnormalities in intraneuronal transport have been linked to genetic risk factors found in patients, suggesting the relevance of measuring this key biological process. However, current techniques are not sensitive enough to detect minor abnormalities. Here we report a sensitive method to measure the changes in intraneuronal transport induced by brain-disease-related genetic risk factors using fluorescent nanodiamonds (FNDs). We show that the high brightness, photostability and absence of cytotoxicity allow FNDs to be tracked inside the branches of dissociated neurons with a spatial resolution of 12 nm and a temporal resolution of 50 ms. As proof of principle, we applied the FND tracking assay on two transgenic mouse lines that mimic the slight changes in protein concentration (∼30%) found in the brains of patients. In both cases, we show that the FND assay is sufficiently sensitive to detect these changes