Dopamine precursor depletion improves punishment prediction during reversal learning in healthy females but not males

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TNPO2 variants associate with human developmental delays, neurologic deficits, and dysmorphic features and alter TNPO2 activity in Drosophila

Transportin-2 (TNPO2) mediates multiple pathways including non-classical nucleocytoplasmic shuttling of >60 cargoes, such as developmental and neuronal proteins. We identified 15 individuals carrying de novo coding variants in TNPO2 who presented with global developmental delay (GDD), dysmorphic features, ophthalmologic abnormalities, and neurological features. To assess the nature of these variants, functional studies were performed in Drosophila. We found that fly dTnpo (orthologous to TNPO2) is expressed in a subset of neurons. dTnpo is critical for neuronal maintenance and function as downregulating dTnpo in mature neurons using RNAi disrupts neuronal activity and survival. Altering the activity and expression of dTnpo using mutant alleles or RNAi causes developmental defects, including eye and wing deformities and lethality. These effects are dosage dependent as more severe phenotypes are associated with stronger dTnpo loss. Interestingly, similar phenotypes are observed with dTnpo upregulation and ectopic expression of TNPO2, showing that loss and gain of Transportin activity causes developmental defects. Further, proband-associated variants can cause more or less severe developmental abnormalities compared to wild-type TNPO2 when ectopically expressed. The impact of the variants tested seems to correlate with their position within the protein. Specifically, those that fall within the RAN binding domain cause more severe toxicity and those in the acidic loop are less toxic. Variants within the cargo binding domain show tissue-dependent effects. In summary, dTnpo is an essential gene in flies during development and in neurons. Further, proband-associated de novo variants within TNPO2 disrupt the function of the encoded protein. Hence, TNPO2 variants are causative for neurodevelopmental abnormalities

Reliance on habits at the expense of goal-directed control following dopamine precursor depletion

Rationale Dopamine is well known to play an important role in learning and motivation. Recent animal studies have implicated dopamine in the reinforcement of stimulus-response habits, as well as in flexible, goal-directed action. However, the role of dopamine in human action control is still not well understood. Objectives We present the first investigation of the effect of reducing dopamine function in healthy volunteers on the balance between habitual and goal-directed action control. Methods The dietary intervention of acute dietary phenylalanine and tyrosine depletion (APTD) was adopted to study the effects of reduced global dopamine function on action control. Participants were randomly assigned to either the APTD or placebo group (ns = 14) to allow for a between-subjects comparison of performance on a novel three-stage experimental paradigm. In the initial learning phase, participants learned to respond to different stimuli in order to gain rewarding outcomes. Subsequently, an outcome-devaluation test and a slips-of-action test were conducted to assess whether participants were able to flexibly adjust their behaviour to changes in the desirability of the outcomes. Results APTD did not prevent stimulus-response learning, nor did we find evidence for impaired response-outcome learning in the subsequent outcome-devaluation test. However, when goal-directed and habitual systems competed for control in the slips-of-action test, APTD tipped the balance towards habitual control. These findings were restricted to female volunteers. Conclusions We provide direct evidence that the balance between goal-directed and habitual control in humans is dopamine dependent. The results are discussed in light of gender differences in dopamine function and psychopathologies

Biomarker candidates of neurodegeneration in Parkinson’s disease for the evaluation of disease-modifying therapeutics

Reliable biomarkers that can be used for early diagnosis and tracking disease progression are the cornerstone of the development of disease-modifying treatments for Parkinson’s disease (PD). The German Society of Experimental and Clinical Neurotherapeutics (GESENT) has convened a Working Group to review the current status of proposed biomarkers of neurodegeneration according to the following criteria and to develop a consensus statement on biomarker candidates for evaluation of disease-modifying therapeutics in PD. The criteria proposed are that the biomarker should be linked to fundamental features of PD neuropathology and mechanisms underlying neurodegeneration in PD, should be correlated to disease progression assessed by clinical rating scales, should monitor the actual disease status, should be pre-clinically validated, and confirmed by at least two independent studies conducted by qualified investigators with the results published in peer-reviewed journals. To date, available data have not yet revealed one reliable biomarker to detect early neurodegeneration in PD and to detect and monitor effects of drug candidates on the disease process, but some promising biomarker candidates, such as antibodies against neuromelanin, pathological forms of α-synuclein, DJ-1, and patterns of gene expression, metabolomic and protein profiling exist. Almost all of the biomarker candidates were not investigated in relation to effects of treatment, validated in experimental models of PD and confirmed in independent studies

Mitochondrial superclusters influence age of onset of Parkinson’s disease in a gender specific manner in the Cypriot population: A case-control study

Despite evidence supporting an involvement of mitochondrial dysfunction in the pathogenesis of some neurodegenerative disorders, there are inconsistent findings concerning mitochondrial haplogroups and their association to neurodegenerative disorders, including idiopathic Parkinson's disease (PD).To test this hypothesis for the Greek-Cypriot population, a cohort of 230 PD patients and 457 healthy matched controls were recruited. Mitochondrial haplogroup distributions for cases and controls were determined. Association tests were carried out between mitochondrial haplogroups and PD.Mitochondrial haplogroup U was associated with a reduced PD risk in the Cypriot population. After pooling mitochondrial haplogroups together into haplogroup clusters and superclusters, association tests demonstrated a significantly protective effect of mitochondrial haplogroup cluster N (xR) and supercluster LMN for PD risk only in females. In addition, for female PD cases belonging to UKJT and R (xH, xUKJT) haplogroup, the odds of having a later age of onset of PD were 13 and 15 times respectively higher than the odds for female cases with an H haplogroup.Statistically significant associations regarding PD risk and PD age of onset were mostly detected for females thus suggesting that gender is a risk modifier between mitochondrial haplogroups and PD status / PD age of onset. The biological mechanisms behind this gender specificity remain to be determined

Transcription factors C/EBP-alpha and HNF-1 alpha are associated with decreased expression of liver-specific genes in sepsis

Previous studies have demonstrated sepsis-specific changes in the transcription of key hepatic genes. However, the role of hepatic transcription factors in sepsis-associated organ dysfunction has not been well established. We hypothesize that the binding activities of C/EBPalpha and beta, HNF-1alpha, and HNF-3 transiently decrease during mild sepsis but persistently decrease after fulminant sepsis, and that the decrease in this binding activity correlates in time and severity with previously described decreases in the transcription of key hepatic genes. Male C57/BL6 mice had nonlethal sepsis induced by cecal ligation and single puncture (CLP) and fulminant sepsis via cecal ligation and double puncture (2CLP). Sham-operated and unoperated animals served as controls. Transcription factor binding activity was assessed with electrophoretic mobility shift assays. C/EBP-alpha and HNF-1alpha binding activity decreased transiently after CLP and persistently after 2CLP. Binding activity of both C/EBP-beta and HNF-3 were unchanged. The decrease in C/EBP-a and HNF-1alpha binding activities correlated in time and magnitude with the decreased hepatic gene transcription previously observed in sepsis. Furthermore, the loss of activity after 2CLP correlated in time with outcome. Sepsis decreases DNA binding activities of C/EBPalpha and HNF-1alpha, two key hepatocyte transcription factors, in a time course consistent with down-regulation of their target hepatic genes. Therefore, alterations in transcription factor binding are likely important in the transcriptional modulation that is characteristic of hepatic dysfunction in sepsis

Photic reflex myoclonus: a neurophysiological study in progressive myoclonus epilepsies

PURPOSE: To investigate the neurophysiological features of photic reflex myoclonus (PRM) in patients with progressive myoclonus epilepsies (PMEs) of different types (Unverricht-Lundborg disease, Lafora's disease, cryptogenic). METHODS: All patients underwent computerized video-polygraphic recordings, collecting electromyographic (EMG) activity from several cranial and limb muscles. PRM was elicited by intermittent photic stimulation (IPS). RESULTS: IPS could evoke PRM with a 1:1 relation at frequencies up to 12 Hz. Back-average of the EEG, triggered from the onset of PRM at the upper limbs, showed a contralateral positive-negative transient in central region, preceded by approximately 10 ms by a similar, ipsilateral occipital wave. When IPS induced bilateral jerking, a time lag of approximately 10 ms between the homologous muscles of the two sides was observed, paralleled by a similar delay between the associated contralateral EEG transients in the two central regions, suggesting spread of cortical myoclonic activity from one hemisphere to the other via transcallosal fibers. PRM propagated in different cranial and limb muscles according to a rostrocaudal pattern, with latencies compatible with a transmission along fast-conducting corticospinal motor pathways. CONCLUSIONS: In our PME patients, PRM presented uniform neurophysiological features, indicating the participation of both occipital and motor cortices, with bilateral spread presumably mediated by transcallosal connections and propagation down the spinal cord via fast-conducting corticospinal pathways