A possible role of midbrain dopamine neurons in short- and long-term adaptation of saccades to position-reward mapping

Dopamine (DA) neurons respond to sensory stimuli that predict reward. To understand how DA neurons acquire such ability, we trained monkeys on a one-direction-rewarded version of memory-guided saccade task (1DR) only when we recorded from single DA neurons. In 1DR, position-reward mapping was changed across blocks of trials. In the early stage of training of 1DR, DA neurons responded to reward delivery; in the later stages, they responded predominantly to the visual cue that predicted reward or no reward (reward predictor) differentially. We found that such a shift of activity from reward to reward predictor also occurred within a block of trials after position-reward mapping was altered. A main effect of long-term training was to accelerate the within-block reward-to-predictor shift of DA neuronal responses. The within-block shift appeared first in the intermediate stage, but was slow, and DA neurons often responded to the cue that indicated reward in the preceding block. In the advanced stage, the reward-to-predictor shift occurred quickly such that the DA neurons' responses to visual cues faithfully matched the current position-reward mapping. Changes in the DA neuronal responses co-varied with the reward-predictive differentiation of saccade latency both in short-term (within-block) and long-term adaptation. DA neurons' response to the fixation point also underwent long-term changes until it occurred predominantly in the first trial within a block. This might trigger a switch between the learned sets. These results suggest that midbrain DA neurons play an essential role in adapting oculomotor behavior to frequent switches in position-reward mapping.     

Polyglutamine aggregates stimulate ER stress signals and caspase-12 activation

Accumulation of unfolded and malfolded proteins causes endoplasmic reticulum (ER) stress, stimulating unfolded protein response (UPR) and c-Jun N-terminal kinase (JNK) activation and activating caspase-12 located on the ER. Little is known about the relationship between the ER stress and polyglutamine [poly(Q)] aggregates. Poly(Q)72 repeats [poly(Q)(72)] induced the stimulation of ER stress signals such as JNK activation, upregulation of Grp78/Bip and caspase-12 activation in C2C5 cells. We prepared antiserum against the cleavage site of mouse caspase-12 at D(318) (anti-m12D318), and showed that poly(Q)(72) with perinuclear aggregates, cytoplasmic inclusions and nuclear inclusions stimulated JNK activation and anti-m12D318 immunoreactivity, but poly(Q)(72) with dispersed aggregates and small nuclear aggregates showed a significantly less effect. Poly(Q)(72) and poly(Q)(11) dispersed in cytoplasm did not. Anti-m12D318-positive cells showed apoptotic features. Unlike anti-m8D387 immunoreactivity, the anti-m12D318 immunoreactivity was not coaggregated with poly(Q). Ac-IETD-fmk (caspase-8 inhibitor) and Ac-DEVD-CHO (caspase-3 inhibitor) did not prevent the anti-m12D318 immunoreactivity induced by poly(Q)(72) aggregates. Anti-m12D318 immunoreactivity was detected in caspase-8(-/-) and caspase-3(-/-) mouse embryonic fibroblasts expressing poly(Q)(72) aggregates. Thus, caspase-12 was activated by poly(Q)(72) aggregates via a pathway independent of caspase-8 and caspase-3 activation, and caspase-12 activation was closely associated with poly(Q) aggregate-mediated cell death. Stimulation of ER stress signals may be involved in the pathogenesis of neurodegenerative disorders with poly(Q) expansion.     

Reward-predicting activity of dopamine and caudate neurons--a possible mechanism of motivational control of saccadic eye movement

Recent studies have suggested that the basal ganglia are related to motivational control of behavior. To study how motivational signals modulate motor signals in the basal ganglia, we examined activity of midbrain dopamine (DA) neurons and caudate (CD) projection neurons while monkeys were performing a one-direction-rewarded version (1DR) of memory-guided saccade task. The cue stimulus indicated the goal position for an upcoming saccade and the presence or absence of reward after the trial. Among four monkeys we studied, three were sensitive to reward such that saccade velocity was significantly higher in the rewarded trials than in the nonrewarded trials; one monkey was insensitive to reward. In the reward-sensitive monkeys, both DA and CD neurons responded differentially to reward-indicating and no-reward-indicating cues. Thus DA neurons responded with excitation to a reward-indicating cue and with inhibition to a no-reward-indicating cue. A group of CD neurons responded to the cue in their response fields (mostly contralateral) and the cue response was usually enhanced when it indicated reward. In the reward-insensitive monkey, DA neurons showed no response to the cue, while the cue responses of CD neurons were not modulated by reward. Many CD neurons in the reward-sensitive monkeys, but not the reward-insensitive monkey, showed precue activity. These results suggest that DA neurons, with their connection to CD neurons, modulate the spatially selective signals in CD neurons in the reward-predicting manner and CD neurons in turn modulate saccade parameters with their polysynaptic connections to the oculomotor brain stem.     

Early-life educational attainment,APOE ε4 alleles,and incident dementia risk in late life

GeroScience - We examined the interactions between educational attainment and genetic susceptibility on dementia risk among adults over 60 years old. A total of 174,161 participants were...     

Analysis of daily energy,protein, fat,and carbohydrate intake in citrin-deficient patients: Towards prevention of adult-onset type II citrullinemia

Patients with citrin deficiency during the adaptation/compensation period exhibit diverse clinical features and have characteristic diet of high protein, high fat, and low carbohydrate. Japanese cuisine typically contains high carbohydrate but evaluation of diet of citrin-deficient patients in 2008 showed a low energy intake and a protein:fat:carbohydrate (PFC) ratio of 19:44:37, which indicates low carbohydrate consumption rate. These findings prompted the need for diet intervention to prevent the adult onset of type II citrullinemia (CTLN2). Since the publication of the report about 10 years ago, patients are generally advised to eat what they wish under active dietary consultation and intervention. In this study, citrin-deficient patients and control subjects living in the same household provided answers to a questionnaire, filled-up a maximum 6-day food diary, and supplied physical data and information on medications if any. To study the effects of the current diet, the survey collected data from 62 patients and 45 controls comparing daily intakes of energy, protein, fat, and carbohydrate. Food analysis showed that patient's energy intake was 115% compared to the Japanese standard. The confidence interval of the PFC ratio of patients was 20–22:47–51:28–32, indicating higher protein, higher fat and lower carbohydrate relative to previous reports. The mean PFC ratio of female patients (22:53:25) was significantly different from that of male patients (20:46:34), which may explain the lower frequency of CTLN2 in females. Comparison of the present data to those published 10 years ago, energy, protein, and fat intakes were significantly higher but the amount of carbohydrate consumption remained the same. Regardless of age, most patients (except for adolescents) consumed 100–200 g/day of carbohydrates, which met the estimated average requirement of 100 g/day for healthy individuals. Finally, patients were generally not overweight and some CTLN2 patients were underweight although their energy intake was higher compared with the control subjects. We speculate that high-energy of a low carbohydrate diet under dietary intervention may help citrin-deficient patients attain normal growth and prevent the onset of CTLN2.     

Homozygous deletion of DIS3L2 exon 9 due to non-allelic homologous recombination between LINE-1s in a Japanese patient with Perlman syndrome

Perlman syndrome is a rare, autosomal recessive overgrowth disorder. Recently, the deletion of exon 9 and other mutations of the DIS3L2 gene have been reported in patients; however, the mechanism behind this deletion is still unknown. We report the homozygous deletion of exon 9 of DIS3L2 in a Japanese patient with Perlman syndrome. We identified the deletion junction, and implicate a non-allelic homologous recombination (NAHR) between two LINE-1 (L1) elements as the causative mechanism. Furthermore, the deletion junctions were different between the paternal and maternal mutant alleles, suggesting the occurrence of two independent NAHR events in the ancestors of each parent. The data suggest that the region around exon 9 might be a hot spot of L1-mediated NAHR.     

Predictors for typical asthma onset from cough variant asthma.

Cough variant asthma is recognized to be a precursor of asthma or preasthmatic state because nearly 30% patients with cough variant asthma develop typical asthma within several years. However, predictors for risk of typical asthma onset from cough variant asthma are unknown. Forty-one patients with cough variant asthma (median age 50 years, 13 men and 28 women), who had undertaken spirometry, bronchial reversibility test, methacholine provocation test, measurements of peripheral blood eosinophil count, serum total IgE, and specific IgE to common allergens, and induced sputum eosinophil count at presentation, were followed up with special emphasis on typical asthma onset during 1 year or more (median 4 years, range 1-12.4). Long-term inhaled corticosteroids (ICS) were taken in 27 patients. Univariate and multivariate logistic analyses were performed to determine the predictors for typical asthma onset. Asthma onset was recognized in 7 patients. Bronchial hyperresponsiveness, peripheral blood eosinophil count, and no use of ICS were significant predictors for the typical asthma onset by univariate analysis. However, only bronchial hyperresponsiveness was the significant predictor when multivariate analysis was used (adjusted OR 0.028, 95% CI 0.001-0.783, p = 0.0355). Bronchial hyperresponsiveness may be the most important predictor for risk of typical asthma onset from cough variant asthma.