Embryonic neocortical development depends on balanced production of progenitors and neurons. Genetic mutations disrupting progenitor mitosis frequently impair neurogenesis; however, the link between ...altered mitosis and cell fate remains poorly understood. Here we demonstrate that prolonged mitosis of radial glial progenitors directly alters neuronal fate specification and progeny viability. Live imaging of progenitors from a neurogenesis mutant, Magoh+/−, reveals that mitotic delay significantly correlates with preferential production of neurons instead of progenitors, as well as apoptotic progeny. Independently, two pharmacological approaches reveal a causal relationship between mitotic delay and progeny fate. As mitotic duration increases, progenitors produce substantially more apoptotic progeny or neurons. We show that apoptosis, but not differentiation, is p53 dependent, demonstrating that these are distinct outcomes of mitotic delay. Together our findings reveal that prolonged mitosis is sufficient to alter fates of radial glia progeny and define a new paradigm to understand how mitosis perturbations underlie brain size disorders such as microcephaly.
•Mitotically delayed Magoh+/− radial glia directly produce altered progeny•Pharmacological prolonging of mitosis recapitulates Magoh+/− progenitor phenotypes•Prolonged progenitor mitosis causes increased neurogenic and apoptotic divisions•Apoptosis and differentiation are mutually exclusive outcomes of mitotic delay
Pilaz et al. use live imaging and genetic and pharmacological approaches to demonstrate a causal relationship between prolonged mitosis of neural progenitors and fate specification in the developing brain. Their study has implications for understanding neurodevelopmental disorders such as microcephaly.
Ganglion cells (GCs) are fundamental to retinal neural circuitry, processing photoreceptor signals for transmission to the brain via their axons. However, much remains unknown about their role in ...vision and their vulnerability to disease leading to blindness. A major bottleneck has been our inability to observe GCs and their degeneration in the living human eye. Despite two decades of development of optical technologies to image cells in the living human retina, GCs remain elusive due to their high optical translucency. Failure of conventional imaging—using predominately singly scattered light—to reveal GCs has led to a focus on multiply-scattered, fluorescence, two-photon, and phase imaging techniques to enhance GC contrast. Here, we show that singly scattered light actually carries substantial information that reveals GC somas, axons, and other retinal neurons and permits their quantitative analysis. We perform morphometry on GC layer somas, including projection of GCs onto photoreceptors and identification of the primary GC subtypes, even beneath nerve fibers. We obtained singly scattered images by: (i) marrying adaptive optics to optical coherence tomography to avoid optical blurring of the eye; (ii) performing 3D subcellular image registration to avoid motion blur; and (iii) using organelle motility inside somas as an intrinsic contrast agent. Moreover, through-focus imaging offers the potential to spatially map individual GCs to underlying amacrine, bipolar, horizontal, photoreceptor, and retinal pigment epithelium cells, thus exposing the anatomical substrate for neural processing of visual information. This imaging modality is also a tool for improving clinical diagnosis and assessing treatment of retinal disease.
Recently discovered relationships between the gastrointestinal microbiome and the brain have implications for psychiatric disorders, including major depressive disorder (MDD). Bacterial ...transplantation from MDD patients to rodents produces depression-like behaviors. In humans, case-control studies have examined the gut microbiome in healthy and affected individuals. We systematically reviewed existing studies comparing gut microbial composition in MDD and healthy volunteers.
A PubMed literature search combined the terms "depression," "depressive disorder," "stool," "fecal," "gut," and "microbiome" to identify human case-control studies that investigated relationships between MDD and microbiota quantified from stool. We evaluated the resulting studies, focusing on bacterial taxa that were different between MDD and healthy controls.
Six eligible studies were found in which 50 taxa exhibited differences (
< 0.05) between patients with MDD and controls. Patient characteristics and methodologies varied widely between studies. Five phyla-
, and
-were represented; however, divergent results occurred across studies for all phyla. The largest number of differentiating taxa were within phylum
, in which nine families and 12 genera differentiated the diagnostic groups. The majority of these families and genera were found to be statistically different between the two groups in two identified studies. Family
differentiated the diagnostic groups in four studies (with an even split in directionality). Across all five phyla, nine genera were higher in MDD (
, and
), six were lower (
, and
), and six were divergent (
, and
). We highlight mechanisms and products of bacterial metabolism as they may relate to the etiology of depression.
No consensus has emerged from existing human studies of depression and gut microbiome concerning which bacterial taxa are most relevant to depression. This may in part be due to differences in study design. Given that bacterial functions are conserved across taxonomic groups, we propose that studying microbial functioning may be more productive than a purely taxonomic approach to understanding the gut microbiome in depression.
The quantum spin properties of nitrogen-vacancy defects in diamond enable diverse applications in quantum computing and communications
. However, fluorescent nanodiamonds also have attractive ...properties for in vitro biosensing, including brightness
, low cost
and selective manipulation of their emission
. Nanoparticle-based biosensors are essential for the early detection of disease, but they often lack the required sensitivity. Here we investigate fluorescent nanodiamonds as an ultrasensitive label for in vitro diagnostics, using a microwave field to modulate emission intensity
and frequency-domain analysis
to separate the signal from background autofluorescence
, which typically limits sensitivity. Focusing on the widely used, low-cost lateral flow format as an exemplar, we achieve a detection limit of 8.2 × 10
molar for a biotin-avidin model, 10
times more sensitive than that obtained using gold nanoparticles. Single-copy detection of HIV-1 RNA can be achieved with the addition of a 10-minute isothermal amplification step, and is further demonstrated using a clinical plasma sample with an extraction step. This ultrasensitive quantum diagnostics platform is applicable to numerous diagnostic test formats and diseases, and has the potential to transform early diagnosis of disease for the benefit of patients and populations.
Oxidized low-density lipoprotein (OxLDL), which contains hundreds of different oxidized lipid molecules, is a hallmark of hyperlipidemia and atherosclerosis. The same oxidized lipids found in OxLDL ...are also formed in apoptotic cells, and are present in tissues as well as in the circulation under pathological conditions. In many disease contexts, oxidized lipids constitute damage signals, or patterns, that activate pattern-recognition receptors (PRRs) and significantly contribute to inflammation. Here, we review recent discoveries and emerging trends in the field of oxidized lipids and the regulation of inflammation, focusing on oxidation products of polyunsaturated fatty acids esterified into cholesteryl esters (CEs) and phospholipids (PLs). We also highlight context-dependent activation and biased agonism of Toll-like receptor-4 (TLR4) and the NLRP3 inflammasome, among other signaling pathways activated by oxidized lipids.
This study sought to assess, for the first time, the relationship between serum concentrations of the soluble interleukin-1 receptor family member ST2 (sST2) and serial change in left ventricular ...(LV) function after acute myocardial infarction (AMI).
Serum sST2 levels are elevated early after AMI and are associated with lower pre-discharge LV ejection fraction and adverse cardiovascular outcomes.
The sST2 levels were measured in 100 patients (mean age 58.9 +/- 12.0 years; 77% male), admitted with AMI with resultant LV systolic dysfunction, at baseline and at 12 and 24 weeks. Patients underwent cardiac magnetic resonance imaging and measurement of N-terminal pro-brain natriuretic peptide, norepinephrine, and aldosterone at each time point.
Median sST2 decreased from 263.3 pg/ml at baseline to 140.0 pg/ml at 24 weeks (p < 0.001). Serum sST2 correlated significantly with LV ejection fraction at baseline (r = -0.30, p = 0.002) and 24 weeks (r = -0.23, p = 0.026); change in sST2 correlated with change in LV end-diastolic volume index (r = -0.24, p = 0.023). Level of sST2 was positively associated with infarct volume index at baseline (r = 0.26, p = 0.005) and 24 weeks (r = 0.22, p = 0.037), and with change in infarct volume index (r = -0.28, p = 0.001). Level of sST2 was significantly higher in patients with greater infarct transmurality and endocardial extent, and in the presence of microvascular obstruction. Level of sST2 correlated significantly with norepinephrine and aldosterone, but not with N-terminal pro-brain natriuretic peptide.
Measurement of sST2 early after AMI assists in the prediction of medium-term LV functional recovery. Novel relationships were observed between sST2, infarct magnitude/evolution, and aldosterone. Serum sST2 may be of pathophysiological importance in ventricular and infarct remodeling after AMI. (Effects of Eplerenone on Left Ventricular Remodelling Following Heart Attack; NCT00132093).
The giant tsunami that swept the Pacific from Alaska to Antarctica in 1946 was generated along one of three Alaska Trench instrumentally recorded aftershock areas following great and giant ...earthquakes. Aftershock areas were investigated during the past decade with multibeam bathymetry, ocean bottom seismograph wide‐angle seismic, reprocessed legacy, and new seismic reflection images. Summarized and updated here are previous papers and additional data. Tectonic structures collocated with aftershock area boundaries indicate possible lengths of rupture in future great earthquakes. NE aftershock area boundaries relate to subducted lower plate structures whereas the SW zone upper plate retains Beringian structural relicts. The lower to middle slope transition separating a stronger continental framework rock from a weaker accreted prism occurs along splay fault zones previously interpreted as backstops in seismic images. Damage zones along splay faults are generally 1‐km‐wide dipping typically 21°. Splays form slip paths from the plate interface to the seafloor much shorter than the 3–4° dipping plate interface beneath the frontal prism. Associated seafloor vent structures indicate overpressured fluids at depth. Splay fault dip and its rigid hanging wall impart greater seafloor uplift than the accreted prism per unit of slip making them effective tsunami generators. Backstop splay fault zones (BSFZs) run along the entire Alaska Trench. Beneath the frontal prism, active bend faults add rugosity to the plate interface and km high relief is commonly imaged in reprocessed legacy and new seismic data. The 1946 Unimak great (M8.6) earthquake epicenter is located near the BSFZ.
Plain Language Summary
Along the Alaska Trench lower slope, a tectonic boundary termed a backstop was recognized in seismic reflection images ∼40 years ago. Backstops are envisioned as mechanical boundaries along which weak sediment accreted against a buttress of stronger more rigid rock. Upper parts are seismically imaged but deeper parts are hidden by the overprint of multiple reflections and are not resolved convincingly in two‐dimensional seismic reflection data. Legacy (1970–1990) seismic data were reprocessed with later more developed software and combined with high‐resolution bathymetry. The combined data reveal that backstops are splay fault zones, similar to those off Nankai, Japan resolved in three‐dimensional data. Models indicate that splay faults may generate giant tsunamis like the 1946 Pacific‐wide tsunami that traveled from Alaska to Antarctica. The diversion of earthquake slipup splay faults could be helped locally by a rough interface separating oceanic from continental plates. Beneath the accreted prism, plate interface roughness was resolved with modern software. Splay faults run along the entire Alaskan margin and add a feature to consideration of trans‐oceanic tsunamis reaching American west coasts and Hawaii.
Key Points
Alaska convergent margin backstops are splay fault zones between the accreted prism and the continental margin framework
These splay faults continue along the entire Alaska margin and occur at or near the updip end of the seismogenic zone
The tsunami potential of backstop splay fault zones adds to considerations of tsunami hazards along the U.S. west coast
Recognition and repair of damaged replication forks are essential to maintain genome stability and are coordinated by the combined action of the Fanconi anemia and homologous recombination pathways. ...These pathways are vital to protect stalled replication forks from uncontrolled nucleolytic activity, which otherwise causes irreparable genomic damage. Here, we identify BOD1L as a component of this fork protection pathway, which safeguards genome stability after replication stress. Loss of BOD1L confers exquisite cellular sensitivity to replication stress and uncontrolled resection of damaged replication forks, due to a failure to stabilize RAD51 at these forks. Blocking DNA2-dependent resection, or downregulation of the helicases BLM and FBH1, suppresses both catastrophic fork processing and the accumulation of chromosomal damage in BOD1L-deficient cells. Thus, our work implicates BOD1L as a critical regulator of genome integrity that restrains nucleolytic degradation of damaged replication forks.
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•BOD1L protects against severe genome instability caused by replication stress•BOD1L acts in the FA pathway downstream of FANCD2/BRCA2•BOD1L maintains fork stability by stabilizing RAD51 nucleofilaments•Loss of BOD1L allows DNA2-dependent over-resection of damaged forks
Higgs et al. identify BOD1L as a factor essential to maintain genomic integrity by stabilizing RAD51 at sites of replication damage. Loss of BOD1L allows destabilization of RAD51 by the BLM/FBH1 helicases, causing replication fork over-resection and catastrophic genome instability.
Age-associated epigenetic changes are implicated in aging. Notably, age-associated DNA methylation changes comprise a so-called aging "clock", a robust biomarker of aging. However, while genetic, ...dietary and drug interventions can extend lifespan, their impact on the epigenome is uncharacterised. To fill this knowledge gap, we defined age-associated DNA methylation changes at the whole-genome, single-nucleotide level in mouse liver and tested the impact of longevity-promoting interventions, specifically the Ames dwarf Prop1
mutation, calorie restriction and rapamycin.
In wild-type mice fed an unsupplemented ad libitum diet, age-associated hypomethylation was enriched at super-enhancers in highly expressed genes critical for liver function. Genes harbouring hypomethylated enhancers were enriched for genes that change expression with age. Hypermethylation was enriched at CpG islands marked with bivalent activating and repressing histone modifications and resembled hypermethylation in liver cancer. Age-associated methylation changes are suppressed in Ames dwarf and calorie restricted mice and more selectively and less specifically in rapamycin treated mice.
Age-associated hypo- and hypermethylation events occur at distinct regulatory features of the genome. Distinct longevity-promoting interventions, specifically genetic, dietary and drug interventions, suppress some age-associated methylation changes, consistent with the idea that these interventions exert their beneficial effects, in part, by modulation of the epigenome. This study is a foundation to understand the epigenetic contribution to healthy aging and longevity and the molecular basis of the DNA methylation clock.
Recently gold nanoparticles (Au NPs) have shown promising biological and military applications due to their unique electronic and optical properties. However, little is known about their ...biocompatibility in the event that they come into contact with a biological system. In the present study, we have investigated whether modulating the surface charge of 1.5 nm Au NPs induced changes in cellular morphology, mitochondrial function, mitochondrial membrane potential (MMP), intracellular calcium levels, DNA damage-related gene expression, and of p53 and caspase-3 expression levels after exposure in a human keratinocyte cell line (HaCaT). The evaluation of three different Au NPs (positively charged, neutral, and negatively charged) showed that cell morphology was disrupted by all three NPs and that they demonstrated a dose-dependent toxicity; the charged Au NPs displayed toxicity as low as 10 µg ml(-1) and the neutral at 25 µg ml(-1). Furthermore, there was significant mitochondrial stress (decreases in MMP and intracellular Ca2+ levels) following exposure to the charged Au NPs, but not the neutral Au NPs. In addition to the differences observed in the MMP and Ca2+ levels, up or down regulation of DNA damage related gene expression suggested a differential cell death mechanism based on whether or not the Au NPs were charged or neutral. Additionally, increased nuclear localization of p53 and caspase-3 expression was observed in cells exposed to the charged Au NPs, while the neutral Au NPs caused an increase in both nuclear and cytoplasmic p53 expression. In conclusion, these results indicate that surface charge is a major determinant of how Au NPs impact cellular processes, with the charged NPs inducing cell death through apoptosis and neutral NPs leading to necrosis.
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