Biology subjects

Rain, J.-C.

Publications and source records attributed to Rain, J.-C..

5 recordsLinked to original sources

bioRxiv2023

Strategy of selection and optimization of single domain antibodies targeting the PHF6 linear peptide within the Tau intrinsically disordered protein

The use of VHHs (Variable domain of the Heavy-chain of the Heavy-chain-only antibodies) as disease-modifying biomolecules in neurodegenerative disorders holds promises including to target aggregation-sensitive proteins. Exploitation of their clinical values dependents however on the capacity to deliver VHHs with optimal physico-chemical properties for their specific context of use. We described previously a VHH with high therapeutic potential in a family of neurodegenerative diseases called tauopathies. The activity of this promising parent VHH named Z70 relies on its binding within the central region of the Tau protein. Accordingly, we carried out random mutagenesis followed by yeast two-hybrid screening to obtain optimized variants. The VHHs selected from this initial screen targeted the same epitope as VHH Z70 as shown using nuclear magnetic resonance spectroscopy and had indeed improved binding affinities according to dissociation constant values obtained by surface plasmon resonance spectroscopy. The improved affinities can be partially rationalized based on three-dimensional structures of three complexes consisting of an optimized VHH and a peptide containing the Tau epitope. Interestingly, the ability of the VHH variants to inhibit Tau aggregation and seeding could not be predicted from their affinity alone. We indeed showed that the in vitro and in cellulo VHH stabilities are other limiting key factors to their efficacy. Our results demonstrate that only a complete pipeline of experiments, here described, permits a rational selection of optimized VHH variants, resulting in our capacity to propose two VHH variants derived from the parent Z70 for their next development steps.

biochemistry↗

bioRxiv2022

AUTS2 gene dosage affects synaptic AMPA receptors via a local dendritic spine AUTS2-TTC3-AKT-mTORC1 signaling dysfunction

The Human 1.2-Mb AUTS2 locus on chromosome 7q11.22 encodes a 1259-aa full-length protein, and a 711-aa C-terminal isoform. Functions of these AUTS2 proteins are only partly known. The major traits found in patients displaying AUTS2 locus mutations are Intellectual Disabilities, microcephaly attention deficit hyperactivity disorder (ADHD) (54%), and autistic traits. Furthermore, AUTS2 common variants were recently found associated to alcohol consumption and dyslexia using GWAS approaches. Auts2 localizes mainly in cell nuclei. We evidenced by super-resolution that Auts2 is present in dendritic spines. Auts2 interacts with Ttc3, the Akt2 E3 ligase, and negatively regulates Akt2 ubiquitination. Auts2 haploinsufficiency affects Akt/mTorc1 pathway with a decrease in AMPA and NMDA receptor subunits and in synaptic currents. Akt2 injection in postsynaptic neurons is sufficient to reverse changes in synaptic currents generated by Auts2 haploinsufficiency. Using chromosome engineering based on targeted meiotic recombination, we generated two mouse models with Auts2 locus deletion and duplication. Deleted Auts2 locus mice display stereotypies (rearing), perseveration and abnormal recognition memory. Duplicated Auts2 locus mice display similar perseveration and abnormal recognition memory but also a decrease in cued and contextual fear memory. Gene dosage induce changes in brain sub-region neuronal networks. In the thalamo-lateral amygdala pathway linked to cued fear memory, we found synaptic impairments linked to AMPA receptors, with a specific decrease in pAKT/total AKT ratio in duplicated Auts2 mice. Altogether, our study thereby provides a novel mechanistic and potentially therapeutic understanding of synaptic AKT/mTORC1 deregulated signaling and its related behavioral and cognitive phenotypes.

neuroscience↗

bioRxiv2021

Inhibition of Tau seeding by targeting Tau nucleation core within neurons with a single domain antibody fragment

Tau proteins aggregate into filaments in brain cells in Alzheimers disease and related disorders referred to as tauopathies. Here, we used fragments of camelid heavy-chain-only antibodies (VHHs or single domain antibody fragments) targeting Tau as immuno-modulators of its pathologic seeding. A VHH issued from the screen against Tau of a synthetic phage-display library of humanized VHHs was selected for its capacity to bind Tau microtubule-binding domain, composing the core of Tau fibrils. This lead VHH was optimized to improve its biochemical properties and to act in the intracellular compartment, resulting in VHH Z70. VHH Z70 was more efficient than the lead to inhibit in vitro Tau aggregation in heparin-induced assays. Expression of VHH Z70 in a cellular model of Tau seeding also decreased the fluorescence-reported aggregation. Finally, intracellular expression of VHH Z70 in the brain of an established tauopathy mouse seeding model demonstrated its capacity to mitigate accumulation of pathological Tau. VHH Z70, by targeting Tau inside brain neurons, where most of the pathological Tau resides, provides a new tool to explore the optimal strategies of immunotherapy in tauopathies.

biochemistry↗

bioRxiv2019

Chr21 protein-protein interactions: enrichment in products involved in intellectual disabilities, autism and Late Onset Alzheimer Disease

Intellectual disability (ID) found in Down syndrome (DS), which is characterized by an extra copy of 234 genes on Chr21 is poorly understood. We first used two DS mouse models that either display an extra copy of the Dyrk1A gene or of the mouse Chr16 syntenic region. Exome sequencing of transcripts deregulated in embryonic hippocampus uncovers enrichment in genes involved in chromatin and synapse respectively. Using large-scale yeast two-hybrid screen (154 distinct screens) of human brain library containing at least 107 independent fragments, we identified 3,636 novel protein-protein interactions with an enrichment of direct interactors of both Chromosome 21(Hsa21) baits and rebounds in ID-related genes. Using proximity ligation assays, we identified that Hsa21-encoded proteins are located at the dendritic spine postsynaptic density in a protein network located at the dendritic spine post synapse. We located Hsa21 DYRK1A and DSCAM that confers a [~] 20-fold increase in Autism Spectrum Disorders (ASDs), in this postsynaptic network. We found that a DSCAM intracellular domain binds either DYRK1A or DLGs that are multimeric scaffolds for the clustering of receptors, ion channels, and associated signaling proteins. The DYRK1A-DSCAM interaction is conserved from drosophila to humans. The identified postsynaptic.network is enriched in ARC-related synaptic plasticity, ASDs and Late-Onset Alzheimer Disease. Altogether, these results emphasize links between DS and brain diseases with complex genetics.

neuroscience↗

bioRxiv2018

BIN1 genetic risk factor for Alzheimer is sufficient to induce early structural tract alterations in entorhinal cortex-dentate gyrus pathway and related hippocampal multi-scale impairments

Genetic factors are known to contribute to Late Onset Alzheimers disease (LOAD) but their contribution to pathophysiology, specially to prodomic phases accessible to therapeutic approaches are far to be understood. To translate genetic risk of Alzheimers disease (AD) into mechanistic insight, we generated transgenic mouse lines that express a [~]195 kbp human BAC that includes only BIN1, a gene associated to LOAD. This model gives a modest BIN1 overexpression, dependent of the number of BAC copies. At 6 months of age, we detected impaired entorhinal cortex (EC)-hippocampal pathways with specific impairments in EC-dentate gyrus synaptic long-term potentiation, dendritic spines of granular cells and recognition episodic memory. Structural changes were quantified using MRI. Their whole-brain functional impact were analyzed using resting state fMRI with a hypoconnectivity centered on entorhinal cortex. These early phenotype defects independent of any changes in A-beta can be instrumental in the search for new AD drug targets.

neuroscience↗