Tau is a neuronal protein linked to pathologies called tauopathies, including Alzheimer's disease. In Alzheimer's disease, tau aggregates into filaments leading to the observation of intraneuronal fibrillary tangles. Molecular mechanisms resulting in tau aggregation and in tau pathology spreading through the brain regions are still not fully understood. New tools are thus needed to decipher tau pathways involved in the diseases. In this context, a family of novel single domain antibody fragments, or VHHs, directed against tau were generated and characterized. Among the selected VHHs obtained from screening of a synthetic library, a family of six VHHs shared the same CDR3 recognition loop and recognized the same epitope, located in the C-terminal domain of tau. Affinity parameters characterizing the tau/VHHs interaction were next evaluated using surface plasmon resonance spectroscopy. The equilibrium constants K D were in the micromolar range but despite conservation of the CDR3 loop sequence, a range of affinities was observed for this VHH family. One of these VHHs, named F8-2, was additionally shown to bind tau upon expression in a neuronal cell line model. Optimization of VHH F8-2 by yeast two-hybrid allowed the generation of an optimized VHH family characterized by lower K D than the F8-2 wild-type counterpart, and recognizing the same epitope. The optimized VHHs can also be used as antibodies for detecting tau in transgenic mice brain tissues. These results validate the use of these VHHs for in vitro studies, but also their potential for in-cell expression, and assays in mouse models, to explore the mechanisms underlying tau physiopathology.

No abstract

Authors' contributions:VH wrote the manuscript. CMD, MH, KC and BS revised the manuscript for intellectual content.LB provided intellectual input and editorial suggestions. Confirmation statement:All of the authors have reviewed and approved the manuscript prior to submission.We confirm that the manuscript has been submitted solely to this journal and is not published, in press, or submitted elsewhere. AbstractAdenosine receptors are G-protein-coupled receptors involved in a wide range of physiological and pathological phenomena in most mammalian systems. All four receptors are widely expressed in the central nervous system, where they modulate neurotransmitter release and neuronal plasticity. A large number of gene association studies have shown that common genetic variants of the adenosine receptors (encoded by the ADORA1, ADORA2A, ADORA2B and ADORA3 genes) have a neuroprotective or neurodegenerative role in neurologic/psychiatric diseases. New genetic studies of rare variants and few novel associations with depression or epilepsy subtypes have recently been reported. Here, we review the literature on the genetics of adenosine receptors in neurologic and/or psychiatric diseases in humans, and discuss perspectives for further genetic research. We also provide an update on the genetic structures of the four human adenosine receptor genes and their regulation -a topic that has not been extensively addressed. Our review emphasizes the importance of (i) better characterizing the genetics of adenosine receptor genes and (ii) understanding how these genes are regulated.

No abstract

Adult hippocampal neurogenesis (AHN) has been widely confirmed in mammalian brains. A growing body of evidence points to the fact that AHN sustains hippocampal-dependent functions such as learning and memory. Impaired AHN has been reported in post-mortem human brain hippocampus of Alzheimer's disease (AD) and is considered to contribute to defects in learning and memory. Neurofibrillary tangles (NFTs) and amyloid plaques are the two key neuropathological hallmarks of AD. NFTs are composed of abnormal tau proteins accumulating in many brain areas during the progression of the disease, including in the hippocampus. The physiological role of tau and impact of tau pathology on AHN is still poorly understood. Modifications in AHN have also been reported in some tau transgenic and tau-deleted mouse models. We present here a brief review of advances in the relationship between development of tau pathology and AHN in AD and what insights have been gained from studies in tau mouse models.

A variety of missense mutations and a stop mutation in the gene coding for transmembrane protein 240 (TMEM240) have been reported to be the causative mutations of spinocerebellar ataxia 21 (SCA21). We aimed to investigate the expression of TMEM240 protein in mouse brain at the tissue, cellular, and subcellular levels. Immunofluorescence labeling showed TMEM240 to be expressed in various areas of the brain, with the highest levels in the hippocampus, isocortex, and cerebellum. In the cerebellum, TMEM240 was detected in the deep nuclei and the cerebellar cortex. The protein was expressed in all three layers of the cortex and various cerebellar neurons. TMEM240 was localized to climbing, mossy, and parallel fiber afferents projecting to Purkinje cells, as shown by coimmunostaining with VGLUT1 and VGLUT2. Co-immunostaining with synaptophysin, postsynaptic fractionation, and confirmatory electron microscopy showed TMEM240 to be localized to the postsynaptic side of synapses near the Purkinje-cell soma. Similar results were obtained in human cerebellar sections. These data suggest that TMEM240 may be involved in the organization of the cerebellar network, particularly in synaptic inputs converging on Purkinje cells. This study is the first to describe TMEM240 expression in the normal mouse brain.