RESUMO
The RNA-binding protein TDP-43, associated to amyotrophic lateral sclerosis and frontotemporal dementia, regulates the alternative splicing of several genes, including the skipping of TNIK exon 15. TNIK, a genetic risk factor for schizophrenia and causative for intellectual disability, encodes for a Ser/Thr kinase regulating negatively F-actin dynamics. Here we show that in the human adult nervous system TNIK exon 15 is mostly included compared to the other tissues and that, during neuronal differentiation of human induced pluripotent stem cells and of human neuroblastoma cells, TNIK exon 15 inclusion increases independently of TDP-43 protein content. By studying the possible molecular interplay of TDP-43 with brain-specific splicing factors, we found that the neuronal NOVA-1 protein competitively inhibits both TDP-43 and hnRNPA2/B1 skipping activity on TNIK by means of a RNA-dependent interaction and that this competitive mechanism is common to other TDP-43 RNA targets. We also show that the TNIK protein isoforms including/excluding exon 15 differently regulate cell spreading in non-neuronal cells and neuritogenesis in primary cortical neurons. Our data suggest a complex regulation between the ubiquitous TDP-43 and the neuron-specific NOVA-1 splicing factors in the brain that may help better understand the pathobiology of both neurodegenerative diseases and schizophrenia.
Assuntos
Proteínas de Ligação a DNA/genética , Proteínas Serina-Treonina Quinases/genética , Proteínas de Ligação a RNA/genética , Esquizofrenia/genética , Processamento Alternativo/genética , Linhagem Celular , Proteínas de Ligação a DNA/química , Éxons/genética , Humanos , Antígeno Neuro-Oncológico Ventral , Neurônios/metabolismo , Neurônios/patologia , Isoformas de Proteínas/química , Isoformas de Proteínas/genética , Proteínas Serina-Treonina Quinases/química , RNA Mensageiro/genética , Proteínas de Ligação a RNA/química , Esquizofrenia/patologiaRESUMO
BACKGROUND AND OBJECTIVE: Counterfactual thinking (CFT) refers to the generation of mental simulations of alternatives to past events, actions and outcomes. CFT is a pervasive cognitive feature in every-day life and is closely related to decision-making, planning and problem-solving - all of which are cognitive processes linked to unimpaired frontal lobe functioning. Huntington's Disease (HD) is a neurodegenerative disorder characterised by motor, behavioral and cognitive dysfunctions. Because an impairment in frontal and executive functions has been described in HD, we hypothesised that HD patients may have a CFT impairment. METHODS: Tests of spontaneous counterfactual thoughts and counterfactual-derived inferences were administered to 24 symptomatic HD patients and 24 age- and sex-matched healthy subjects. RESULTS: Our results show a significant impairment in the spontaneous generation of CFT and low performance on the Counterfactual Inference Test (CIT) in HD patients. Low performance on the spontaneous CFT test significantly correlates with impaired attention abilities, verbal fluency and frontal lobe efficiency, as measured by Trail Making Test - Part A, Phonemic Verbal Fluency Test and FAB. CONCLUSIONS: Spontaneous CFT and the use of this type of reasoning are impaired in HD patients. This deficit may be related to frontal lobe dysfunction, which is a hallmark of HD. Because CFT has a pervasive role in patients' daily lives regarding their planning, decision making and problem solving skills, cognitive rehabilitation may improve HD patients' ability to analyse current behaviors and future actions.
