The neuroepithelial basement membrane serves as a boundary and a substrate for neuron migration in the zebrafish hindbrain

<p>Abstract</p> <p>Background</p> <p>The facial branchiomotor neurons of cranial nerve VII undergo a stereotyped tangential migration in the zebrafish hindbrain that provides an ideal system for examining the complex interactions between neurons and their environment that result in directed migration. Several studies have shown the importance of the planar cell polarity pathway in facial branchiomotor neuron migration but the role of apical-basal polarity has not been determined. Here we examine the role of the PAR-aPKC complex in forming the basal structures that guide facial branchiomotor neurons on an appropriate migratory path.</p> <p>Results</p> <p>High resolution timelapse imaging reveals that facial branchiomotor neurons begin their migration by moving slowly ventrally and posteriorly with their centrosomes oriented medially and then, upon contact with the Laminin-containing basement membrane at the rhombomere 4-rhombomere 5 boundary, speed up and reorient their centrosomes on the anterior-posterior axis. Disruption of the PAR-aPKC complex members aPKCλ, aPKCζ, and Pard6gb results in an ectopic ventral migration in which facial branchiomotor neurons escape from the hindbrain through holes in the Laminin-containing basement membrane. Mosaic analysis reveals that the requirement for aPKC is cell-nonautonomous, indicating that it is likely required in the surrounding polarized neuroepithelium rather than in facial motor neurons themselves. Ventral facial motor neuron ectopia can be phenocopied by mutation of <it>lamininα1</it>, suggesting that it is defects in maintenance of the laminin-containing basement membrane that are the likely cause of ventral mismigration in aPKCλ+ζ double morphants.</p> <p>Conclusions</p> <p>Our results suggest that the laminin-containing ventral basement membrane, dependent on the activity of the PAR-aPKC complex in the hindbrain neuroepithelium, is both a substrate for migration and a boundary that constrains facial branchiomotor neurons to the appropriate migratory path.</p

Programmed hierarchical patterning of bacterial populations.

Modern genetic tools allow the dissection and emulation of fundamental mechanisms shaping morphogenesis in multicellular organisms. Several synthetic genetic circuits for control of multicellular patterning have been reported to date. However, hierarchical induction of gene expression domains has received little attention from synthetic biologists, despite its importance in biological self-organization. Here we report a synthetic genetic system implementing population-based AND-logic for programmed autonomous induction of bacterial gene expression domains. We develop a ratiometric assay for bacteriophage T7 RNA polymerase activity and use it to systematically characterize different intact and split enzyme variants. We then utilize the best-performing variant to build a three-color patterning system responsive to two different homoserine lactones. We validate the AND gate-like behavior of this system both in cell suspension and in surface culture. Finally, we use the synthetic circuit in a membrane-based spatial assay to demonstrate programmed hierarchical patterning of gene expression across bacterial populations

Variation in Individual Responses to Time-Restricted Feeding and Resistance Training

Time-restricted feeding (TRF) is a form of intermittent fasting which limits all caloric intake to a certain period of time each day in an attempt to reduce daily energy intake, promote weight loss, and improve health. Resistance training (RT) has been reported to increase muscular strength and improve body composition. Very limited information is available on the combination of TRF and RT. The purpose of this study was to examine the variation in individual body composition, dietary intake, and muscular performance responses to an 8-wk TRF and RT program. Healthy males (n = 20; age = 22 ± 3 y; BMI = 27 ± 6 kg/m2; % fat = 22 ± 6 % wt) were randomized to TRF + RT or RT alone for 8 wks. RT was performed 3 dys/wk and consisted of alternate workouts of upper and lower body using a resistance progression scheme. TRF limited energy intake to a 4-hr period on the 4 dys/wk when RT was not performed. Energy intake was not restricted in either group, and eating times were not specified in the RT alone group. Body composition, muscular performance, and dietary records were assessed at 0, 4, and 8 wks. Inter- and intra-individual variations in outcome measures were estimated by hierarchical linear growth modeling. The amount of variability attributable to characteristics between or within participants was evaluated from variance estimates. For TRF + RT, percent changes ranged from -5.5 to +2.6% for body weight, -22.1 to +9.4% for fat mass, -7.7 to +4.6% for lean body mass, +3.4 to +30.4% for bench press 1-RM, and +10.1 to +67.6% for leg press 1-RM. For RT alone, percent changes ranged from -6.6 to +2.1% for body weight, -14.4 to +12.6% for fat mass, -4.1 to +3.9% for lean body mass, +4.9 to +12.9% for bench press 1-RM, and +14.3 to +37.7% for leg press 1-RM. Percentages of total variability attributed to inter-individual factors ranged from 3.3 to 49.2% for dietary measures, 59.0 to 93.9% for muscular performance, and 97.0 to 99.6% for body composition. Remaining variability was attributed to intra-individual factors. Individual responses to the study interventions varied widely. Differences between individuals were an important source of variability, indicating participant samples should be homogenous and/or quite large to examine changes in body composition or muscular performance using nutrition and exercise interventions

Fibroblast growth factors 1 and 2 in cerebrospinal fluid are associated with HIV disease, methamphetamine use, and neurocognitive functioning.

BackgroundHuman immunodeficiency virus (HIV) and methamphetamine use commonly affect neurocognitive (NC) functioning. We evaluated the relationships between NC functioning and two fibroblast growth factors (FGFs) in volunteers who differed in HIV serostatus and methamphetamine dependence (MAD).MethodsA total of 100 volunteers were categorized into four groups based on HIV serostatus and MAD in the prior year. FGF-1 and FGF-2 were measured in cerebrospinal fluid by enzyme-linked immunosorbent assays along with two reference biomarkers (monocyte chemotactic protein [MCP]-1 and neopterin). Comprehensive NC testing was summarized by global and domain impairment ratings.ResultsSixty-three volunteers were HIV+ and 59 had a history of MAD. FGF-1, FGF-2, and both reference biomarkers differed by HIV and MAD status. For example, FGF-1 levels were lower in subjects who had either HIV or MAD than in HIV- and MAD- controls (P=0.003). Multivariable regression identified that global NC impairment was associated with an interaction between FGF-1 and FGF-2 (model R(2)=0.09, P=0.01): higher FGF-2 levels were only associated with neurocognitive impairment among subjects who had lower FGF-1 levels. Including other covariates in the model (including antidepressant use) strengthened the model (model R(2)=0.18, P=0.004) but did not weaken the association with FGF-1 and FGF-2. Lower FGF-1 levels were associated with impairment in five of seven cognitive domains, more than FGF-2, MCP-1, or neopterin.ConclusionThese findings provide in vivo support that HIV and MAD alter expression of FGFs, which may contribute to the NC abnormalities associated with these conditions. These cross-sectional findings cannot establish causality and the therapeutic benefits of recombinant FGF-1 need to be investigated

Turing Patterning in Stratified Domains

Reaction-diffusion processes across layered media arise in several scientific domains such as pattern-forming E. coli on agar substrates, epidermal-mesenchymal coupling in development, and symmetry-breaking in cell polarisation. We develop a modelling framework for bi-layer reaction-diffusion systems and relate it to a range of existing models. We derive conditions for diffusion-driven instability of a spatially homogeneous equilibrium analogous to the classical conditions for a Turing instability in the simplest nontrivial setting where one domain has a standard reaction-diffusion system, and the other permits only diffusion. Due to the transverse coupling between these two regions, standard techniques for computing eigenfunctions of the Laplacian cannot be applied, and so we propose an alternative method to compute the dispersion relation directly. We compare instability conditions with full numerical simulations to demonstrate impacts of the geometry and coupling parameters on patterning, and explore various experimentally-relevant asymptotic regimes. In the regime where the first domain is suitably thin, we recover a simple modulation of the standard Turing conditions, and find that often the broad impact of the diffusion-only domain is to reduce the ability of the system to form patterns. We also demonstrate complex impacts of this coupling on pattern formation. For instance, we exhibit non-monotonicity of pattern-forming instabilities with respect to geometric and coupling parameters, and highlight an instability from a nontrivial interaction between kinetics in one domain and diffusion in the other. These results are valuable for informing design choices in applications such as synthetic engineering of Turing patterns, but also for understanding the role of stratified media in modulating pattern-forming processes in developmental biology and beyond.Comment: 25 pages, 7 figure

Dietary fatty acids and mortality risk from heart disease in US adults: an analysis based on NHANES

We investigated the association of dietary intake of major types of fatty acids with heart disease mortality in a general adult cohort with or without a prior diagnosis of myocardial infarction (MI). This cohort study included US adults who attended the National Health and Nutrition Examination Surveys from 1988 to 2014. Heart disease mortality was ascertained by linkage to the National Death Index records through 31 December 2015. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) of fatty acid intake for heart disease mortality. This cohort included 45,820 adults among which 1,541 had a prior diagnosis of MI. Participants were followed up for 532,722 person-years (mean follow-up, 11.6 years), with 2,313 deaths recorded from heart disease being recorded. Intake of saturated (SFAs) and monounsaturated fatty acids (MUFAs) was associated with heart disease mortality after adjustment for all the tested confounders. In contrast, a 5% higher calorie intake from polyunsaturated fatty acids (PUFAs) was associated with a 9% (HR, 0.91; 95% CI 0.83–1.00; P = 0.048) lower multivariate-adjusted risk of heart disease mortality. Sub-analyses showed that this inverse association was present in those without a prior diagnosis of MI (HR,0.89; 95% CI 0.80–0.99) but not in those with the condition (HR, 0.94; 95% CI 0.75–1.16). The lack of association in the MI group could be due to a small sample size or severity and procedural complications (e.g., stenting and medication adherence) of the disease. Higher PUFA intake was associated with a favourable lipid profile. However, further adjustment for plasma lipids did not materially change the inverse association between PUFAs and heart disease mortality. Higher intake of PUFAs, but not SFAs and MUFAs, was associated with a lower adjusted risk of heart disease mortality in a large population of US adults supporting the need to increase dietary PUFA intake in the general public