Altered splicing of Tau in DM1 is different from the foetal splicing process

AbstractAmong the different mechanisms underlying the etiopathogenesis of myotonic dystrophy type 1 (DM1), a backward reprogramming to a foetal splicing machinery is an interesting hypothesis. To address this possibility, Tau splicing, which is regulated during development and modified in DM1, was analyzed. Indeed, a preferential expression of the foetal Tau isoform, instead of the six normally found, is observed in adult DM1 brains. By using two cell lines, we show here that the cis-regulating elements necessary to generate the unique foetal Tau isoform are dispensable to reproduce the trans-dominant effect induced by DM1 mutation on Tau exon 2 inclusion. Our results suggest that the mis-splicing of Tau in DM1 is resulting from a disease-associated mechanism

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

L'utilisation d'un promoteur alternatif de MAPT génère de nouveaux transcrits ARNm plus courts dans le cerveau des malades d'Alzheimer et de paralysie supranucléaire progressive

International audienceAlternative promoter usage is an important mechanism for transcriptome diversity and the regulation of gene expression. Indeed, this alternative usage may influence tissue/subcellular specificity, protein translation and function of the proteins. The existence of an alternative promoter for MAPT gene was considered for a long time to explain differential tissue specificity and differential response to transcription and growth factors between mRNA transcripts. The alternative promoter usage could explain partly the different tau proteins expression patterns observed in tauopathies. Here, we report on our discovery of a functional alternative promoter for MAPT, located upstream of the gene's second exon (exon 1). By analyzing genome databases and brain tissue from control individuals and patients with Alzheimer's disease or progressive supranuclear palsy, we identified novel shorter transcripts derived from this alternative promoter. These transcripts are increased in patients' brain tissue as assessed by 5'RACE-PCR and qPCR. We suggest that these new MAPT isoforms can be translated into normal or amino-terminal-truncated tau proteins. We further suggest that activation of MAPT's alternative promoter under pathological conditions leads to the production of truncated proteins, changes in protein localization and function, and thus neurodegeneration

Neurogénétique des gènes humains des récepteurs de l'adénosine: structures génétiques et implication dans les maladies cérébrales

International audienceAdenosine 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

Adenosine receptors in Huntington's disease

Huntington's disease is a devastating hereditary neurodegenerative disorder caused by CAG mutation within the IT15 gene encoding Huntingtin protein. Even though mutant and normal Huntingtin are ubiquitously expressed, the degenerative processes primarily occur within the striatum and particularly hit the GABAergic enkephalin neuronal subpopulation of medium spiny neurons particularly enriched with adenosine A2ARs, suggesting that the latter might play a role in HD. In agreement, variants in the ADORA2A gene influence the age at onset in HD and A2AR dynamics is largely altered by mutated Huntingtin. Adenosine receptors are involved in a number of processes critical for neuronal function and homeostasis, such as modulation of synaptic activity and excitotoxicity, the control of neurotrophin levels and functions as well as the regulation of protein degradation mechanisms. In the present review, we critically reviewed the current knowledge involving adenosine receptors in HD and discussed whether they represent a suitable therapeutic target.SCOPUS: ch.binfo:eu-repo/semantics/publishe

RNF216 mutations as a novel cause of autosomal recessive Huntington-like disorder

Objective: To identify the genetic cause in 2 Belgian families with autosomal recessive Huntington-like disorder (HDL). Methods: Homozygosity mapping and whole-exome sequencing in a consanguineous family as well as Sanger sequencing of the candidate gene in an independent family with HDL followed by genotype-phenotype correlation studies. Results: We identified a homozygous mutation in the gene RNF216 p.(Gly456Glu) within a shared 4.8-Mb homozygous region at 7p22.3 in 2 affected siblings of a consanguineous HDL family. In an independent family, 2 siblings with HDL were compound heterozygous for mutations in RNF216 p.(Gln302*) and p.(Tyr539Cys). Chorea, behavioral problems, and severe dementia were the core clinical signs in all patients. Brain imaging consistently showed white matter lesions. Low gonadotropin serum levels and cerebellar atrophy could be demonstrated in the index family. Conclusions: Mutations in RNF216 have recently been found in families with Gordon Holmes syndrome, a condition defined by hypogonadotropic hypogonadism and cerebellar ataxia. The mode of inheritance was proposed to be oligogenic for most families. We describe novel RNF216 mutations causing an HDL phenotype with pure monogenic recessive inheritance. Subclinical serum evidence of hypogonadotropic hypogonadism links this disorder to Gordon Holmes syndrome. Our study thus challenges the oligogenic inheritance model and emphasizes chorea as an essential clinical feature in RNF216-mediated neurodegeneration

La protéine TMEM240, mutée dans la SCA21, est exprimée dans les cellules de Purkinje et ses terminaisons synaptiques: Localisation de TMEM240 dans le cervelet

International audienceA 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, post-synaptic fractionation, and confirmatory electron microscopy showed TMEM240 to be localized to the post-synaptic 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