A transcription factor atlas of stem cell fate in planarians

Whole-body regeneration requires the ability to produce the full repertoire of adult cell types. The planarian Schmidtea mediterranea contains over 125 cell types, which can be regenerated from a stem cell population called neoblasts. Neoblast fate choice can be regulated by the expression of fate-specific transcription factors (FSTFs). How fate choices are made and distributed across neoblasts versus their post-mitotic progeny remains unclear. We used single-cell RNA sequencing to systematically map fate choices made in S/G2/M neoblasts and, separately, in their post-mitotic progeny that serve as progenitors for all adult cell types. We defined transcription factor expression signatures associated with all detected fates, identifying numerous new progenitor classes and FSTFs that regulate them. Our work generates an atlas of stem cell fates with associated transcription factor signatures for most cell types in a complete adult organism.

Neurotensin orchestrates valence assignment in the amygdala

The ability to associate temporally segregated information and assign positive or negative valence to environmental cues is paramount for survival. Studies have shown that different projections from the basolateral amygdala (BLA) are potentiated following reward or punishment learning1-7. However, we do not yet understand how valence-specific information is routed to the BLA neurons with the appropriate downstream projections, nor do we understand how to reconcile the sub-second timescales of synaptic plasticity8-11 with the longer timescales separating the predictive cues from their outcomes. Here we demonstrate that neurotensin (NT)-expressing neurons in the paraventricular nucleus of the thalamus (PVT) projecting to the BLA (PVT-BLA:NT) mediate valence assignment by exerting NT concentration-dependent modulation in BLA during associative learning. We found that optogenetic activation of the PVT-BLA:NT projection promotes reward learning, whereas PVT-BLA projection-specific knockout of the NT gene (Nts) augments punishment learning. Using genetically encoded calcium and NT sensors, we further revealed that both calcium dynamics within the PVT-BLA:NT projection and NT concentrations in the BLA are enhanced after reward learning and reduced after punishment learning. Finally, we showed that CRISPR-mediated knockout of the Nts gene in the PVT-BLA pathway blunts BLA neural dynamics and attenuates the preference for active behavioural strategies to reward and punishment predictive cues. In sum, we have identified NT as a neuropeptide that signals valence in the BLA, and showed that NT is a critical neuromodulator that orchestrates positive and negative valence assignment in amygdala neurons by extending valence-specific plasticity to behaviourally relevant timescales.

Satb2 neurons in the parabrachial nucleus mediate taste perception

The neural circuitry mediating taste has been mapped out from the periphery to the cortex, but genetic identity of taste-responsive neurons has remained elusive. Here, we describe a population of neurons in the gustatory region of the parabrachial nucleus that express the transcription factor Satb2 and project to taste-associated regions, including the gustatory thalamus and insular cortex. Using calcium imaging in awake, freely licking mice, we show that Satb2 neurons respond to the five basic taste modalities. Optogenetic activation of these neurons enhances taste preferences, whereas chronic inactivation decreases the magnitude of taste preferences in both brief- and long-access taste tests. Simultaneous inactivation of Satb2 and calcitonin gene-related peptide neurons in the PBN abolishes responses to aversive tastes. These data suggest that taste information in the parabrachial nucleus is conveyed by multiple populations of neurons, including both Satb2 and calcitonin gene-related peptide neurons.

Satb2 neurons in the parabrachial nucleus mediate taste perception

The neural circuitry mediating taste has been mapped out from the periphery to the cortex, but genetic identity of taste-responsive neurons has remained elusive. Here, we describe a population of neurons in the gustatory region of the parabrachial nucleus that express the transcription factor Satb2 and project to taste-associated regions, including the gustatory thalamus and insular cortex. Using calcium imaging in awake, freely licking mice, we show that Satb2 neurons respond to the five basic taste modalities. Optogenetic activation of these neurons enhances taste preferences, whereas chronic inactivation decreases the magnitude of taste preferences in both brief- and long-access taste tests. Simultaneous inactivation of Satb2 and calcitonin gene-related peptide neurons in the PBN abolishes responses to aversive tastes. These data suggest that taste information in the parabrachial nucleus is conveyed by multiple populations of neurons, including both Satb2 and calcitonin gene-related peptide neurons.

Hippocampal neural activity reflects the economy of choices during goal-directed navigation

Distinguishing spatial contexts is likely essential for the well-known role of the hippocampus in episodic memory. We studied whether types of hippocampal neural organization thought to underlie context discrimination are impacted by learned economic considerations of choice behavior. Hippocampal place cells and theta activity were recorded as rats performed a maze-based probability discounting task that involved choosing between a small certain reward or a large probabilistic reward. Different spatial distributions of place fields were observed in response to changes in probability, the outcome of the rats' choice, and whether or not rats were free to make that choice. The degree to which the reward location was represented by place cells scaled with the expected probability of rewards. Theta power increased around the goal location also in proportion to the expected probability of signaled rewards. Furthermore, theta power dynamically varied as specific econometric information was obtained "on the fly" during task performance. Such an economic perspective of memory processing by hippocampal place cells expands our view of the nature of context memories retrieved by hippocampus during adaptive navigation.

Mortality from diabetes in Nauru. Results of 4-yr follow-up

A population survey in 1982 confirmed that Nauruan adults suffer from an extremely high prevalence (24%) of non-insulin-dependent diabetes mellitus. A follow-up study of the survey subjects was conducted in 1986. The aim was to assess the burden of diabetes to Nauruans in terms of premature mortality. Age-adjusted mortality rates for diabetic subjects were significantly increased when compared with normal subjects (relative risks for 4-yr mortality were 4.53 in men, P less than .01, and 3.96 in women, P less than .05). Although there was an excess number of deaths among diabetic subjects compared with normal subjects and subjects with impaired glucose tolerance, there was no significant association between cause of death and diabetes.

Plasma insulin response among Nauruans. Prediction of deterioration in glucose tolerance over 6 yr

A longitudinal study of 266 randomly selected nondiabetic Nauruans [215 with normal tolerance and 51 with impaired glucose tolerance (IGT)] over 6 yr showed that deterioration in glucose tolerance status had occurred in 61 subjects. Of the subjects with initially normal tolerance, 34 (16%) progressed to IGT and 14 (6.5%) progressed to diabetes. Thirteen of the subjects with IGT (25%) progressed to diabetes. Subjects were examined in 1975 through 1976, and follow-up examinations were performed in 1982. After age, a high 2-h plasma insulin response to a glucose load was the factor most predictive of progression from normal tolerance to both diabetes (P less than .001) and IGT (P less than .01). Both a high 2-h glucose level and greater obesity independently predicted progression from IGT, and a diminished 2-h insulin response just failed to significantly improve the model (P less than .06). The negative parameter of the insulin response associated with deterioration from IGT differed significantly (P less than .01) from the positive-parameter estimate of the response associated with progression to diabetes from normal tolerance (P less than .01), implying a qualitative difference between these nondiabetic subgroups. The use of a glucose-insulin interaction term to predict progression to diabetes for all nondiabetic subjects confirmed this difference; this term's addition improved the model (P less than .01), and progression to diabetes was associated with a high insulin response for 2-h glucose less than 7.8 mM but a low response for 2-h glucose greater than 7.8 mM.

Obesity, hypertension, carbohydrate disorders and the risk of chronic diseases. Is there any epidemiological evidence for integrated prevention programmes?

The major cause of coronary heart disease, hypertension, non-insulin-dependent diabetes and obesity in adults in developed countries appears to be the result of risk factors that are introduced by way of their life-styles. Many developing countries are also noting increases in morbidity and mortality from these diseases. There is increasing evidence of common risk factors in the aetiology of these chronic disorders and two or more of these diseases may coexist in the same subjects. This evidence provides a strong rationale for a community-based, integrated approach to the primary prevention of such non-communicable diseases by the reduction of the level of risk factors. This may be achieved by community-based programmes which stress the importance of a healthy life-style, such as the practice of good nutrition, weight reduction in the obese, increased physical activity, the avoidance of stress and a reduction in alcohol and cigarette consumption.

The association of non-insulin-dependent diabetes with parity and still-birth occurrence amongst five Pacific populations

Previous reports have shown the prevalence of non-insulin-dependent diabetes to be high amongst several populations living in the South and Central Pacific region, and a number of factors including a sedentary life-style, urban residence, obesity and genetic factors have been implicated in its aetiology. Amongst some populations increasing parity has been shown to be associated with abnormal glucose tolerance, but the cross-sectional data available did not suggest any such association amongst the five Pacific Island populations surveyed. Still-birth rates are high amongst all these populations, particularly so amongst the older women, and several methods of analysis suggest that abnormal glucose tolerance is associated with a significantly increased risk of still-birth. This association appears more marked amongst younger women in all populations, with the overall relative risk of a still-birth occurrence for diabetic women aged less than 45 years being 2.6 (95% confidence interval being 1.4-4.8), and for women aged less than 45 years with impaired glucose tolerance being 2.2 (95% confidence interval being 1.3-3.7). As many of the women diabetic at the time of surveys would not have been during their pregnancies, these risk estimates are probably underestimates. Longitudinal studies may suggest even higher figures. Nonetheless the results of these surveys suggest that the high prevalence of abnormal glucose tolerance in these populations may be at least partly responsible for their high levels of still-birth occurrence.

The low prevalence of hypertension in Falkland Islands men

A morbidity survey in the Falkland Islands, conducted in 1979, showed that Falkland Islands men had a lower prevalence of hypertension than their counterparts in the United Kingdon. Such a difference was not found in women.As a migrant population, Falkland Islanders are unusual in that they moved from a developed society to a more traditional setting. In men, but not in women, the change in environment led to a greater proportion of the population engaging in a high level of habitual physical activity and to a low prevalence of obesity.These findings (based on ICD codes rather than BP measurements) are consistent with the hypothesis that such a change in lifestyle may have resulted in the lower population prevalence of hypertension observed in the morbidity survey, and the implications could be important for public health.

The Falkland Islands morbidity survey

A 12-month retrospective morbidity survey of the Falkland Islands in 1979 is described. A larger proportion of the population appear to have sought medical attention in this time than would be expected on the basis of comparable British figures. In general, cause-specific morbidity was similar in the two countries, although there were several discrepancies identified which may have been of environmental origin. The low prevalence of essential hypertension in males was particularly notable.

Variations in the lung size of children in Papua New Guinea: genetic and environmental factors

In Papua New Guinea, rural village children of both sexes living in the highlands (1500--2000 m) were found to have mean values of forced vital capacity 27 per cent greater than children at sea level. Urban children with an apparently lower level of habitual activity had a lung size similar to that of rural children living at the same altitude. In a number of healthy children of coastal parents reared in the highlands and of highland parents reared on the coast, the size of the lung was, in general, appropriate for the altitude rather than for the parentage. These findings suggest that the highland--coastal difference is probably environmental rather than genetic in origin.

Kuru

Theis report discusses problems involved in the diagnosis of kuru. The gentic and epidemiological pattern is also reviewed. This reveals a continuing overall reduction in kuru incidence with the disappearance of juvenile cases and increasing age of male kuru patients a reduction in the age of female cases. The significance of these trends in relation to the transmission of kuru is discussed.

Kuru. Epidemiological developments

Important changes have occurred in the epidemiology of kuru since the last review in 1970. There has been a continued decline in the annual incidence, particularly in females. There is a change in the average age of onset in both sexes, and cases are no longer seen in children and adolescents. Alteration in the geographical distribution has resulted in kuru now being confined almost wholly to the South Fore region.