Possible involvement of zinc transporter ZIP13 in myogenic differentiation

Ehlers-Danlos syndrome spondylodysplastic type 3 (EDSSPD3, OMIM 612350) is an inherited recessive connective tissue disorder that is caused by loss of function of SLC39A13/ZIP13, a zinc transporter belonging to the Slc39a/ZIP family. We previously reported that patients with EDSSPD3 harboring a homozygous loss of function mutation (c.221G > A, p.G64D) in ZIP13 exon 2 (ZIP13G64D) suffer from impaired development of bone and connective tissues, and muscular hypotonia. However, whether ZIP13 participates in the early differentiation of these cell types remains unclear. In the present study, we investigated the role of ZIP13 in myogenic differentiation using a murine myoblast cell line (C2C12) as well as patient-derived induced pluripotent stem cells (iPSCs). We found that ZIP13 gene expression was upregulated by myogenic stimulation in C2C12 cells, and its knockdown disrupted myotubular differentiation. Myocytes differentiated from iPSCs derived from patients with EDSSPD3 (EDSSPD3-iPSCs) also exhibited incomplete myogenic differentiation. Such phenotypic abnormalities of EDSSPD3-iPSC-derived myocytes were corrected by genomic editing of the pathogenic ZIP13G64D mutation. Collectively, our findings suggest the possible involvement of ZIP13 in myogenic differentiation, and that EDSSPD3-iPSCs established herein may be a promising tool to study the molecular basis underlying the clinical features caused by loss of ZIP13 function.

Mathematical Models of the Effect of Glucagon on Glycemia in Individuals With Type 2 Diabetes Treated With Dapagliflozin

Context

Sodium-glucose cotransporter 2 (SGLT2) inhibitors lower blood glucose levels by promoting urinary glucose excretion, but their overall effects on hormonal and metabolic status remain unclear.

Objective

We here investigated the roles of insulin and glucagon in the regulation of glycemia in individuals treated with an SGLT2 inhibitor using mathematical model analysis.

Methods

Hyperinsulinemic-euglycemic clamp and oral glucose tolerance tests were performed in 68 individuals with type 2 diabetes treated with the SGLT2 inhibitor dapagliflozin. Data previously obtained from such tests in 120 subjects with various levels of glucose tolerance and not treated with an SGLT2 inhibitor were examined as a control. Mathematical models of the feedback loops connecting glucose and insulin (GI model) or glucose, insulin, and glucagon (GIG model) were generated.

Results

Analysis with the GI model revealed that the disposition index/clearance, which is defined as the product of insulin sensitivity and insulin secretion divided by the square of insulin clearance and represents the glucose-handling ability of insulin, was significantly correlated with glycemia in subjects not taking an SGLT2 inhibitor but not in those taking dapagliflozin. Analysis with the GIG model revealed that a metric defined as the product of glucagon sensitivity and glucagon secretion divided by glucagon clearance (designated production index/clearance) was significantly correlated with blood glucose level in subjects treated with dapagliflozin.

Conclusion

Treatment with an SGLT2 inhibitor alters the relation between insulin effect and blood glucose concentration, and glucagon effect may account for variation in glycemia among individuals treated with such drugs.

Local field potential responses associated with perceptual filling-in at blind spot in macaque primary visual cortex

To understand the neural mechanisms of perceptual filling-in at the blind spot (BS), we analyzed neural activity in the region representing the visual field corresponding to the BS (BS region) in the primary visual cortex (V1) of the macaque monkey. We inserted a linear array electrode into the BS region or surrounding region and recorded the multiunit activities (MUAs) and local field potential (LFP). We examined the responses of MUAs and LFP to a large visual stimulus that entirely covered the BS (surface stimuli) while the monkey performed a visual fixation task in either the monocular condition without receiving direct retinal input or the binocular condition receiving retinal information. We observed clear MUA responses in the deep layers within the BS region under monocular conditions, confirming previous reports that V1 neurons in the BS region are activated when perceptual filling-in occurs. Current source density analysis using LFP showed that MUA responses were mainly observed in layer 5. Although LFP responses were generally stronger in the binocular condition than in the monocular condition, a notable exception was observed in the BS region. LFP responses in the low-beta band in the superficial layers were stronger in the monocular condition than in the binocular condition. These results suggest that low-beta activity in the superficial layer is related to the occurrence of perceptual filling-in in the BS. The origin of this activity is considered to be feedback signals from the extrastriate areas to the V1.NEW & NOTEWORTHY Two characteristic activities were induced in the blind spot (BS) region in response to the stimulus, causing perceptual filling-in: 1) beta-band LFP responses in the superficial layers and 2) neuronal responses in the deep layers, mainly in layer 5. These data suggest that the feedback signal from the extrastriate areas to the BS region in V1 is involved in perceptual filling-in.

Theoretical study to gain fundamental insight into reaction mechanism of N-S acyl transfer of N-sulfanylethylanilide-based protein labeling reagent on protein surface

Elucidation of protein function is one of the central issues in the field of life sciences. To study the function of proteins not in isolation, but in a cell or its lysate, thus, it is necessary to selectively label the target protein in a mixture. Affinity labeling is one of several widely used methods for selective labeling; however, this method has the disadvantage that the labeling reagent is always activated, albeit weakly. Therefore, fine-tuning of the reactivity and/or reaction conditions is generally required for successful target-selective labeling. We previously developed a new affinity labeling reagent with N-sulfanylethylanilide (SEAlide) as a key reactive unit. It was designed based on the following hypotheses. SEAlide is less reactive and does not label in the absence of a target protein. Upon target binding, amino acid side-chain functional groups on the target surface convert SEAlide into a thioester form via N-S acyl transfer, allowing the target to be labeled. However, no evidence has been obtained so far to directly prove the hypothesis. In this study, we examine whether amino acid side-chain functional groups can activate SEAlide from the viewpoint of theoretical chemistry. The theoretical studies show that the activation free energy and enthalpy of the acyl transfer of SEAlide are reduced in the presence of methylammonium, which is a model for the protonated side chain of Lys, and acetate, which is a model for the deprotonated side chain of Asp/Glu. It suggests that Lys and Asp/Glu side chains could potentially stabilize the activation transition states to accelerate the thioester formation. Furthermore, the significant decrease in the activation enthalpy indicates that the contribution of entropy to the transition state is large. This result supports the original hypothesis that the SEAlide-based labeling reagent is efficiently activated by binding to the target protein.

Estimating gene-level false discovery probability improves eQTL statistical fine-mapping precision

Statistical fine-mapping prioritizes putative causal variants from a large number of candidate variants, and is widely used in expression quantitative loci (eQTLs) studies. In eQTL fine-mapping, the existence of causal variants for gene expression is not guaranteed, since the genetic heritability of gene expression explained by nearby (cis-) variants is limited. Here we introduce a refined fine-mapping algorithm, named Knockoff-Finemap combination (KFc). KFc estimates the probability that the causal variant(s) exist in the cis-window of a gene through construction of knockoff genotypes (i.e. a set of synthetic genotypes that resembles the original genotypes), and uses it to adjust the posterior inclusion probabilities (PIPs). Utilizing simulated gene expression data, we show that KFc results in calibrated PIP distribution with improved precision. When applied to gene expression data of 465 genotyped samples from the Japan COVID-19 Task Force (JCTF), KFc resulted in significant enrichment of a functional score as well as reporter assay hits in the top PIP bins. When combined with functional priors derived from an external fine-mapping study (GTEx), KFc resulted in a significantly higher proportion of hematopoietic trait putative causal variants in the top PIP bins. Our work presents improvements in the precision of a major fine-mapping algorithm.

DNA hypomethylation characterizes genes encoding tissue-dominant functional proteins in liver and skeletal muscle

Each tissue has a dominant set of functional proteins required to mediate tissue-specific functions. Epigenetic modifications, transcription, and translational efficiency control tissue-dominant protein production. However, the coordination of these regulatory mechanisms to achieve such tissue-specific protein production remains unclear. Here, we analyzed the DNA methylome, transcriptome, and proteome in mouse liver and skeletal muscle. We found that DNA hypomethylation at promoter regions is globally associated with liver-dominant or skeletal muscle-dominant functional protein production within each tissue, as well as with genes encoding proteins involved in ubiquitous functions in both tissues. Thus, genes encoding liver-dominant proteins, such as those involved in glycolysis or gluconeogenesis, the urea cycle, complement and coagulation systems, enzymes of tryptophan metabolism, and cytochrome P450-related metabolism, were hypomethylated in the liver, whereas those encoding-skeletal muscle-dominant proteins, such as those involved in sarcomere organization, were hypomethylated in the skeletal muscle. Thus, DNA hypomethylation characterizes genes encoding tissue-dominant functional proteins.

Distinct functions between ferrous and ferric iron in lung cancer cell growth

Accumulating evidence suggests an association between iron metabolism and lung cancer progression. In biological systems, iron is present in either reduced (Fe2+ ; ferrous) or oxidized (Fe3+ ; ferric) states. However, ferrous and ferric iron exhibit distinct chemical and biological properties, the role of ferrous and ferric iron in lung cancer cell growth has not been clearly distinguished. In this study, we manipulated the balance between cellular ferrous and ferric iron status by inducing gene mutations involving the FBXL5-IRP2 axis, a ubiquitin-dependent regulatory system for cellular iron homeostasis, and determined its effects on lung cancer cell growth. FBXL5 depletion (ferrous iron accumulation) was found to suppress lung cancer cell growth, whereas IRP2 depletion (ferric iron accumulation) did not suppress such growth, suggesting that ferrous iron but not ferric iron plays a suppressive role in cell growth. Mechanistically, the depletion of FBXL5 impaired the degradation of the cyclin-dependent kinase inhibitor, p27, resulting in a delay in the cell cycle at the G1/S phase. FBXL5 depletion in lung cancer cells also improved the survival of tumor-bearing mice. Overall, this study highlights the important function of ferrous iron in cell cycle progression and lung cancer cell growth.

Conditional blastocyst complementation of a defective Foxa2 lineage efficiently promotes the generation of the whole lung

Millions suffer from incurable lung diseases, and the donor lung shortage hampers organ transplants. Generating the whole organ in conjunction with the thymus is a significant milestone for organ transplantation because the thymus is the central organ to educate immune cells. Using lineage-tracing mice and human pluripotent stem cell (PSC)-derived lung-directed differentiation, we revealed that gastrulating Foxa2 lineage contributed to both lung mesenchyme and epithelium formation. Interestingly, Foxa2 lineage-derived cells in the lung mesenchyme progressively increased and occupied more than half of the mesenchyme niche, including endothelial cells, during lung development. Foxa2 promoter-driven, conditional Fgfr2 gene depletion caused the lung and thymus agenesis phenotype in mice. Wild-type donor mouse PSCs injected into their blastocysts rescued this phenotype by complementing the Fgfr2-defective niche in the lung epithelium and mesenchyme and thymic epithelium. Donor cell is shown to replace the entire lung epithelial and robust mesenchymal niche during lung development, efficiently complementing the nearly entire lung niche. Importantly, those mice survived until adulthood with normal lung function. These results suggest that our Foxa2 lineage-based model is unique for the progressive mobilization of donor cells into both epithelial and mesenchymal lung niches and thymus generation, which can provide critical insights into studying lung transplantation post-transplantation shortly.

Discovery of a cystathionine γ-lyase (CSE) selective inhibitor targeting active-site pyridoxal 5'-phosphate (PLP) via Schiff base formation

D,L-Propargylglycine (PAG) has been widely used as a selective inhibitor to investigate the biological functions of cystathionine γ-lyase (CSE), which catalyzes the formation of reactive sulfur species (RSS). However, PAG also inhibits other PLP (pyridoxal-5'-phosphate)-dependent enzymes such as methionine γ-lyase (MGL) and L-alanine transaminase (ALT), so highly selective CSE inhibitors are still required. Here, we performed high-throughput screening (HTS) of a large chemical library and identified oxamic hydrazide 1 as a potent inhibitor of CSE (IC50 = 13 ± 1 μM (mean ± S.E.)) with high selectivity over other PLP-dependent enzymes and RSS-generating enzymes. Inhibitor 1 inhibited the enzymatic activity of human CSE in living cells, indicating that it is sufficiently membrane-permeable. X-Ray crystal structure analysis of the complex of rat CSE (rCSE) with 1 revealed that 1 forms a Schiff base linkage with the cofactor PLP in the active site of rCSE. PLP in the active site may be a promising target for development of selective inhibitors of PLP-dependent enzymes, including RSS-generating enzymes such as cystathionine β-synthase (CBS) and cysteinyl-tRNA synthetase 2 (CARS2), which have unique substrate binding pocket structures.

Cooperative DNA-binding activities of Chp2 are critical for its function in heterochromatin assembly

Heterochromatin protein 1 (HP1) is an evolutionarily conserved protein that plays a critical role in heterochromatin assembly. HP1 proteins share a basic structure consisting of an N-terminal chromodomain (CD) and a C-terminal chromoshadow domain (CSD) linked by a disordered hinge region. The CD recognizes histone H3 lysine 9 methylation, a hallmark of heterochromatin, while the CSD forms a dimer to recruit other chromosomal proteins. HP1 proteins have been shown to bind DNA or RNA primarily through the hinge region. However, how DNA or RNA binding contributes to their function remains elusive. Here, we focus on Chp2, one of the two HP1 proteins in fission yeast, and investigate how Chp2's DNA-binding ability contributes to its function. Similar to other HP1 proteins, the Chp2 hinge exhibits clear DNA-binding activity. Interestingly, the Chp2 CSD also shows robust DNA-binding activity. Mutational analysis revealed that basic residues in the Chp2 hinge and at the N-terminus of the CSD are essential for DNA binding, and the combined amino acid substitutions of these residues alter Chp2 stability, impair Chp2 heterochromatin localization and lead to a silencing defect. These results demonstrate that the cooperative DNA-binding activities of Chp2 play an important role in heterochromatin assembly in fission yeast.

Structural insights into endothelin receptor signalling

Endothelins and their receptors, type A (ETA) and type B (ETB), modulate vital cellular processes, including growth, survival, invasion and angiogenesis, through multiple G proteins. This review highlights the structural determinations of these receptors by X-ray crystallography and cryo-electron microscopy, and their activation mechanisms by endothelins. Explorations of the conformational changes upon receptor activation have provided insights into the unique G-protein coupling feature of the endothelin receptors. The review further delves into the binding modes of the clinical antagonist and the inverse agonists. These findings significantly contribute to understanding the mechanism of G-protein activation and have potential implications for drug development, particularly in the context of vasodilatory antagonists and agonists targeting the endothelin receptors.

Identification of In-Droplet Multicellular Communities by Light-Induced Combinatorial DNA Barcoding

A microdroplet co-culture system is useful for the parallel assessment of numerous possible cell-cell interactions by generating isolated subcommunities from a pool of heterogeneous cells. However, the integration of single-cell sequencing into such analysis has been limited due to the lack of effective molecular identifiers for each in-droplet subcommunity. Herein, we present a strategy for generating in-droplet subcommunity identifiers using DNA-functionalized microparticles encapsulated within microdroplets. These microparticles serve as initial information carriers, where their combinations act as distinct identifiers for in-droplet subcommunity. Upon optical trigger, DNA barcoding molecules encoding the microparticle information are once released in the microdroplets and then tag cell membranes. The tagged DNA molecules then serve as a second information carrier readable by single-cell sequencing to reconstitute the community in silico in the single-cell RNA sequencing data space.

A fungal sesquiterpene biosynthesis gene cluster critical for mutualist-pathogen transition in Colletotrichum tofieldiae

Plant-associated fungi show diverse lifestyles from pathogenic to mutualistic to the host; however, the principles and mechanisms through which they shift the lifestyles require elucidation. The root fungus Colletotrichum tofieldiae (Ct) promotes Arabidopsis thaliana growth under phosphate limiting conditions. Here we describe a Ct strain, designated Ct3, that severely inhibits plant growth. Ct3 pathogenesis occurs through activation of host abscisic acid pathways via a fungal secondary metabolism gene cluster related to the biosynthesis of sesquiterpene metabolites, including botrydial. Cluster activation during root infection suppresses host nutrient uptake-related genes and changes mineral contents, suggesting a role in manipulating host nutrition state. Conversely, disruption or environmental suppression of the cluster renders Ct3 beneficial for plant growth, in a manner dependent on host phosphate starvation response regulators. Our findings indicate that a fungal metabolism cluster provides a means by which infectious fungi modulate lifestyles along the parasitic-mutualistic continuum in fluctuating environments.

Generation and mutational analysis of a transgenic murine model of the human MAF mutation

Aymé-Gripp syndrome is an autosomal dominant multisystem disorder. The major clinical features of this syndrome include congenital cataracts, sensorineural hearing loss, intellectual disability, and a distinctive flat facial appearance. MAF has been identified as a causative gene of the syndrome, and heterozygous variants owing to impairment in glycogen synthase kinase 3 (GSK3)-mediated MAF phosphorylation shows related disorders. However, the underlying mechanisms of these types of disorders in affected individuals remain poorly understood. To explore the underlying mechanisms and discover new phenotypes, a murine model with a Maf mutation on a GSK3 phosphorylation motif, p.Thr58Ile, was generated using CRISPR-Cas9 gene editing. This is a homologous mutation to that in human patients. Our murine model exhibited similar phenotypes to those in humans, such as lens abnormalities, short stature, growth retardation, and abnormal skull morphology. The murine model showed decreased brain volume and malocclusion. Considering the sequencing and genotyping data, our models were successfully generated for the first time (to the best of our knowledge). Therefore, this study offers new and unique functional insights into human and murine MAF and novel clinical values of MAF pathogenic variants associated with changes in the functions of several organs based on a viable murine model.

Features extracted using tensor decomposition reflect the biological features of the temporal patterns of human blood multimodal metabolome

High-throughput omics technologies have enabled the profiling of entire biological systems. For the biological interpretation of such omics data, two analyses, hypothesis- and data-driven analyses including tensor decomposition, have been used. Both analyses have their own advantages and disadvantages and are mutually complementary; however, a direct comparison of these two analyses for omics data is poorly examined.We applied tensor decomposition (TD) to a dataset representing changes in the concentrations of 562 blood molecules at 14 time points in 20 healthy human subjects after ingestion of 75 g oral glucose. We characterized each molecule by individual dependence (constant or variable) and time dependence (later peak or early peak). Three of the four features extracted by TD were characterized by our previous hypothesis-driven study, indicating that TD can extract some of the same features obtained by hypothesis-driven analysis in a non-biased manner. In contrast to the years taken for our previous hypothesis-driven analysis, the data-driven analysis in this study took days, indicating that TD can extract biological features in a non-biased manner without the time-consuming process of hypothesis generation.

Cullin 3 mutant causing familial hyperkalemic hypertension lacks normal activity in the kidney

Mutations in the ubiquitin ligase scaffold protein cullin 3 (CUL3) cause the disease familial hyperkalemic hypertension (FHHt). We recently reported that in the kidney, aberrant mutant CUL3 (CUL3-Δ9) activity lowers the abundance of CUL3-Δ9 and Kelch-like 3, the CUL3 substrate adaptor for with-no-lysine kinase 4 (WNK4) and that this is mechanistically important. However, whether CUL3-Δ9 exerts additional effects on other targets that may alter renal function is unclear. Here, we sought to determine 1) whether CUL3-Δ9 expression can rescue the phenotype of renal tubule-specific Cul3 knockout mice, and 2) whether CUL3-Δ9 expression affects other CUL3 substrates. Using an inducible renal tubule-specific system, we studied two CUL3-Δ9-expressing mouse models: Cul3 knockout (Cul3-/-/Δ9) and Cul3 heterozygous background (Cul3+/-/Δ9, FHHt model). The effects of CUL3-Δ9 in these mice were compared with Cul3-/- and Cul3+/- mice. Similar to Cul3-/- mice, Cul3-/-/Δ9 mice displayed polyuria with loss of aquaporin 2 and collecting duct injury; proximal tubule injury also occurred. CUL3-Δ9 did not promote degradation of two CUL3 targets that accumulate in the Cul3-/- kidney: high-molecular-weight (HMW) cyclin E and NAD(P)H:quinone oxidoreductase 1 (NQO1) [a surrogate for the CUL3-Kelch-like ECH-associated protein 1 (KEAP1) substrate nuclear factor erythroid-2-related factor 2]. Since CUL3-Δ9 expression cannot rescue the Cul3-/- phenotype, our data suggest that CUL3-Δ9 cannot normally function in ubiquitin ligase complexes. In Cul3+/-/Δ9 mice, KEAP1 abundance did not differ but NQO1 abundance was higher, suggesting adaptor sequestration by CUL3-Δ9 in vivo. Together, our results provide evidence that in the kidney, CUL3-Δ9 completely lacks normal activity and can trap CUL3 substrate adaptors in inactive complexes.NEW & NOTEWORTHY CUL3 mutation (CUL3-Δ9) causes familial hyperkalemic hypertension (FHHt) by reducing adaptor KLHL3, impairing substrate WNK4 degradation. Whether CUL3-Δ9 affects other targets in kidneys remains unclear. We found that CUL3-Δ9 cannot degrade two CUL3 targets, cyclin E and nuclear factor erythroid-2-related factor 2 (NRF2; using a surrogate marker NQO1), or rescue injury or polyuria caused by Cul3 disruption. In an FHHt model, CUL3-Δ9 impaired NRF2 degradation without reduction of its adaptor KEAP1. Our data provide additional insights into CUL3-Δ9 function in the kidney.

Structure of the human galanin receptor 2 bound to galanin and Gq reveals the basis of ligand specificity and how binding affects the G-protein interface

Galanin is a neuropeptide expressed in the central and peripheral nervous systems, where it regulates various processes including neuroendocrine release, cognition, and nerve regeneration. Three G-protein coupled receptors (GPCRs) for galanin have been discovered, which is the focus of efforts to treat diseases including Alzheimer’s disease, anxiety, and addiction. To understand the basis of the ligand preferences of the receptors and to assist structure-based drug design, we used cryo-electron microscopy (cryo-EM) to solve the molecular structure of GALR2 bound to galanin and a cognate heterotrimeric G-protein, providing a molecular view of the neuropeptide binding site. Mutant proteins were assayed to help reveal the basis of ligand specificity, and structural comparison between the activated GALR2 and inactive hβ2AR was used to relate galanin binding to the movements of transmembrane (TM) helices and the G-protein interface.

Sp7 Action in the Skeleton: Its Mode of Action, Functions, and Relevance to Skeletal Diseases

Osteoblast differentiation is a tightly regulated process in which key transcription factors (TFs) and their target genes constitute gene regulatory networks (GRNs) under the control of osteogenic signaling pathways. Among these TFs, Sp7 works as an osteoblast determinant critical for osteoblast differentiation. Following the identification of Sp7 and a large number of its functional studies, recent genome-scale analyses have made a major contribution to the identification of a "non-canonical" mode of Sp7 action as well as "canonical" ones. The analyses have not only confirmed known Sp7 targets but have also uncovered its additional targets and upstream factors. In addition, biochemical analyses have demonstrated that Sp7 actions are regulated by chemical modifications and protein-protein interaction with other transcriptional regulators. Sp7 is also involved in chondrocyte differentiation and osteocyte biology as well as postnatal bone metabolism. The critical role of SP7 in the skeleton is supported by its relevance to human skeletal diseases. This review aims to overview the Sp7 actions in skeletal development and maintenance, particularly focusing on recent advances in our understanding of how Sp7 functions in the skeleton under physiological and pathological conditions.

A novel model of ischemia in rats with middle cerebral artery occlusion using a microcatheter and zirconia ball under fluoroscopy

The failure of neuroprotective treatment-related clinical trials may be partially caused by unestablished animal models. Existing animal models are less likely to provide occlusion confined to the middle cerebral artery (MCA), making transarterial intervention difficult. We aimed to develop a novel focal stroke model using a microcatheter and zirconium dioxide that is non-magnetic under fluoroscopic guidance, which can monitor MCA occlusion and can improve hemorrhagic complications. Using male Sprague Dawley rats (n = 10), a microcatheter was navigated from the caudal ventral artery to the left internal carotid artery using an X-ray fluoroscopy to establish local occlusion. All rat cerebral angiographies were successful. No rats had hemorrhagic complications. Eight (80%) rats underwent occlusion of the MCA bifurcation by zirconium dioxide. Accidentally, the left posterior cerebral artery was failure embolized in 2 rats (20%). The median operating time was 8 min. All rats of occlusion MCA revealed an incomplete hemiparesis on the right side with neurological deficit score ranging from 1 to 3 (median 1, interquartile range 1-3) at 24 h after the induction of ischemia. Moreover, 2% 2,3,5-triphenyl tetrazolium chloride staining showed that the median infarct volume (mm3) was 280 (interquartile range 267-333) 24 h after the left MCA bifurcation occlusion. We present a novel rat model for focal stroke using a microcatheter and zirconium dioxide which does not affect the MRI. The model is predictable which is well confined within the territory supplied by the MCA, and reproducibility of this model is 80%. Fluoroscopy was able to identify which the MCA occlusion and model success while creating the model. It permitted exclusion of animals with complications from the experiment.

Metabolic fingerprints of fear memory consolidation during sleep

Metabolites underlying brain function and pathology are not as well understood as genes. Here, we applied a novel metabolomics approach to further understand the mechanisms of memory processing in sleep. As hippocampal dentate gyrus neurons are known to consolidate contextual fear memory, we analyzed real-time changes in metabolites in the dentate gyrus in different sleep-wake states in mice. Throughout the study, we consistently detected more than > 200 metabolites. Metabolite profiles changed dramactically upon sleep-wake state transitions, leading to a clear separation of phenotypes between wakefulness and sleep. By contrast, contextual fear memory consolidation induced less obvious metabolite phenotypes. However, changes in purine metabolites were observed upon both sleep-wake state transitions and contextual fear memory consolidation. Dietary supplementation of certain purine metabolites impaired correlations between conditioned fear responses before and after memory consolidation. These results point toward the importance of purine metabolism in fear memory processing during sleep.

Native adiponectin in serum binds to mammalian cells expressing T-cadherin, but not AdipoRs or calreticulin

Adiponectin is an adipocyte-derived atypically abundant circulating factor that protects various organs and tissues through its receptors, AdipoRs, calreticulin, and T-cadherin. To identify the major binding partner of circulating native adiponectin, we expressed these receptors on the surface of HEK293 cells. Adiponectin, either that in mouse or human serum, purified from serum, or produced by mammalian cells, bound to cells expressing T-cadherin, but not to those expressing AdipoR1 or calreticulin. The stable introduction of T-cadherin and AdipoR1 into CHO cells resulted in the cell surface localization of these receptors. Native adiponectin in serum bound to cells expressing T-cadherin, not to those expressing AdipoR1. The knockdown of T-cadherin, but not AdipoRs resulted in the significant attenuation of native adiponectin binding to C2C12 myotubes. Therefore, native adiponectin binding depended on the amount of T-cadherin expressed in HEK293 cells, CHO cells, and C2C12 myotubes. Collectively, our mammalian cell-based studies suggest that T-cadherin is the major binding partner of native adiponectin in serum.

Three-dimensional evaluation of murine ovarian follicles using a modified CUBIC tissue clearing method

BACKGROUND

Recently, we demonstrated the three-dimensional (3D) localization of murine trophoblast giant cells in the pregnant uterus using a modified Clear Unobstructed Brain Imaging Cocktails and Computational analysis (CUBIC) tissue-clearing method and hybrid construct consisting of the cytomegalovirus enhancer fused to the chicken beta-actin promoter (CAG) conjugated enhanced green fluorescent protein (EGFP) transgenic mice. In this study, we applied this method to obtain a transparent whole-image of the ovary and observed the 3D localization of individual oocytes in the developing follicles.

METHODS

Ovarian samples were obtained from EGFP transgenic mice and subjected to nuclear staining with propidium iodide (PI) and CUBIC treatment. The detection of double fluorescence signals (green and red) and subsequent reconstruction of 3D images of the whole ovary were performed by light-sheet microscopy and computer programs, respectively.

RESULTS

The ovary became transparent using the CUBIC method and each nucleus of the follicle component cells was uniformly fluoro-stained by PI perfusion. In contrast, EGFP signals were strong in oocytes, whereas those of surrounding granulosa cells were faint. These signal differences in EGFP expression among oocytes, granulosa cells, and theca-interstitial cells produce well-contrasted images of the growing follicles, providing clear information of the 3D localization of individual oocytes.

CONCLUSION

These results indicate that this procedure is one of the effective approaches to analyze the 3D structure of follicles in the whole ovary.

Role of GABA in the regulation of the central circadian clock of the suprachiasmatic nucleus

In mammals, circadian rhythms, such as sleep/wake cycles, are regulated by the central circadian clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN consists of thousands of individual neurons, which exhibit circadian rhythms. They synchronize with each other and produce robust and stable oscillations. Although several neurotransmitters are expressed in the SCN, almost all SCN neurons are γ-amino butyric acid (GABA)-ergic. Several studies have attempted to understand the roles of GABA in the SCN; however, precise mechanisms of the action of GABA in the SCN are still unclear. GABA exhibits excitatory and/or inhibitory characteristics depending on the circadian phase or region in the SCN. It can both synchronize and destabilize cellular circadian rhythms in individual SCN cells. Differing environmental light conditions, such as a long photoperiod, result in the decoupling of circadian oscillators of the dorsal and ventral SCN. This is due to high intracellular chloride concentrations in the dorsal SCN. Because mice with functional GABA deficiency, such as vesicular GABA transporter- and glutamate decarboxylase-deficient mice, are neonatal lethal, research has been limited to pharmacological approaches. Furthermore, different recording methods have been used to understand the roles of GABA in the SCN. The excitability of GABAergic neurons also changes during the postnatal period. Although there are technical difficulties in understanding the functions of GABA in the SCN, technical developments may help uncover new roles of GABA in circadian physiology and behavior.

Hippocampal calpain is required for the consolidation and reconsolidation but not extinction of contextual fear memory

Memory consolidation, reconsolidation, and extinction have been shown to share similar molecular signatures, including new gene expression. Calpain is a Ca2+-dependent protease that exerts its effects through the proteolytic cleavage of target proteins. Neuron-specific conditional deletions of calpain 1 and 2 impair long-term potentiation in the hippocampus and spatial learning. Moreover, recent studies have suggested distinct roles of calpain 1 and 2 in synaptic plasticity. However, the role of hippocampal calpain in memory processes, especially memory consolidation, reconsolidation, and extinction, is still unclear. In the current study, we demonstrated the critical roles of hippocampal calpain in the consolidation, reconsolidation, and extinction of contextual fear memory in mice. We examined the effects of pharmacological inhibition of calpain in the hippocampus on these memory processes, using the N-Acetyl-Leu-Leu-norleucinal (ALLN; calpain 1 and 2 inhibitor). Microinfusion of ALLN into the dorsal hippocampus impaired long-term memory (24 h memory) without affecting short-term memory (2 h memory). Similarly, this pharmacological blockade of calpain in the dorsal hippocampus also disrupted reactivated memory but did not affect memory extinction. Importantly, the systemic administration of ALLN inhibited the induction of c-fos in the hippocampus, which is observed when memory is consolidated. Our observations showed that hippocampal calpain is required for the consolidation and reconsolidation of contextual fear memory. Further, the results suggested that calpain contributes to the regulation of new gene expression that is necessary for these memory processes as a regulator of Ca2+-signal transduction pathway.

Usefulness of DNA Methylation Levels in COASY and SPINT1 Gene Promoter Regions as Biomarkers in Diagnosis of Alzheimer's Disease and Amnestic Mild Cognitive Impairment

In order to conduct early therapeutic interventions for Alzheimer's disease (AD), convenient, early diagnosis markers are required. We previously reported that changes in DNA methylation levels were associated with amnestic mild cognitive impairment (aMCI) and AD. As the results suggested changes in DNA methylation levels in the COASY and SPINT1 gene promoter regions, in the present study we examined DNA methylation in these regions in normal controls (NCs, n = 30), aMCI subjects (n = 28) and AD subjects (n = 30) using methylation-sensitive high resolution melting (MS-HRM) analysis. The results indicated that DNA methylation in the two regions was significantly increased in AD and aMCI as compared to NCs (P < 0.0001, P < 0.0001, ANOVA). Further analysis suggested that DNA methylation in the COASY gene promoter region in particular could be a high sensitivity, high specificity diagnosis biomarker (COASY: sensitivity 96.6%, specificity 96.7%; SPINT1: sensitivity 63.8%, specificity 83.3%). DNA methylation in the COASY promoter region was associated with CDR Scale Sum of Boxes (CDR-SB), an indicator of dementia severity. In the SPINT1 promoter region, DNA methylation was negatively associated with age in NCs and elevated in aMCI and AD subjects positive for antibodies to Herpes simplex virus type 1 (HSV-1). These findings suggested that changes in DNA methylation in the COASY and SPINT1 promoter regions are influenced by various factors. In conclusion, DNA methylation levels in the COASY and SPINT1 promoter regions were considered to potentially be a convenient and useful biomarker for diagnosis of AD and aMCI.

The relationship between widespread changes in gravity and cerebral blood flow

OBJECTIVES

We investigated the dose-effect relationship between wide changes in gravity from 0 to 2.0 Gz (Δ0.5 Gz) and cerebral blood flow (CBF), to test our hypothesis that CBF has a linear relationship with levels of gravity.

SUBJECTS AND METHODS

Ten healthy seated men were exposed to 0, 0.5, 1.0, 1.5, and 2.0 Gz for 21 min, by using a tilt chair and a short-arm human centrifuge. Steady-state CBF velocity (CBFV) in the middle cerebral artery by transcranial Doppler ultrasonography, mean arterial pressure (MAP) at the heart level (MAPHeart), heart rate, stroke volume, cardiac output and respiratory conditions were obtained for the last 6 min at each gravity level. Then, MAP in the middle cerebral artery (MAPMCA), reflecting cerebral perfusion pressure, was estimated.

RESULTS

Steady-state CBFV decreased stepwise from 0.5 to 2.0 Gz. Steady-state heart rate, stroke volume, estimated MAPMCA and end-tidal carbon dioxide pressure (ETCO2) also changed stepwise from hypogravity to hypergravity. On the other hand, steady-state MAPHeart and cardiac output did not change significantly. Steady-state CBFV positively and linearly correlated with estimated MAPMCA and ETCO2 in most subjects.

CONCLUSION

The present study demonstrated stepwise gravity-induced changes in steady-state CBFV from 0.5 to 2.0 Gz despite unchanged steady-state MAPHeart. The combined effects of reduced MAPMCA and ETCO2 likely led to stepwise decreases in CBFV. We caution that a mild increase in gravity from 0 to 2.0 Gz reduces CBF, even if arterial blood pressure at the heart level is maintained.