[Show abstract][Hide abstract] ABSTRACT: Steroid hormones are crucial for many biological events in multicellular organisms. In insects, the principal steroid hormones are ecdysteroids, which play essential roles in regulating molting and metamorphosis. During larval and pupal development, ecdysteroids are synthesized in the prothoracic gland (PG) from dietary cholesterol via a series of hydroxylation and oxidation steps. The expression of all but one of the known ecdysteroid biosynthetic enzymes is restricted to the PG, but the transcriptional regulatory networks responsible for generating such exquisite tissue-specific regulation is only beginning to be elucidated. Here, we report identification and characterization of the C2H2-type zinc finger transcription factor Ouija board (Ouib) necessary for ecdysteroid production in the PG in the fruit fly Drosophila melanogaster. Expression of ouib is predominantly limited to the PG, and genetic null mutants of ouib result in larval developmental arrest that can be rescued by administrating an active ecdysteroid. Interestingly, ouib mutant animals exhibit a strong reduction in the expression of one ecdysteroid biosynthetic enzyme, spookier. Using a cell culture-based luciferase reporter assay, Ouib protein stimulates transcription of spok by binding to a specific ~15 bp response element in the spok PG enhancer element. Most remarkable, the developmental arrest phenotype of ouib mutants is rescued by over-expression of a functionally-equivalent paralog of spookier. These observations imply that the main biological function of Ouib is to specifically regulate spookier transcription during Drosophila development.
[Show abstract][Hide abstract] ABSTRACT: The development of vertebrate neurons requires a change in membrane phosphatidylcholine (PC) metabolism. Although PC hydrolysis is essential for enhanced axonal outgrowth mediated by phospholipase D (PLD), less is known about the determinants of PC metabolism on dendritic arborization. We show that protein arginine methyltransferase 8 (PRMT8) acts as a phospholipase that directly hydrolyzes PC, generating choline and phosphatidic acid. We found that PRMT8 knockout mice (prmt8 (-/-)) displayed abnormal motor behaviors, including hindlimb clasping and hyperactivity. Moreover, prmt8 (-/-) mice and TALEN-induced zebrafish prmt8 mutants and morphants showed abnormal phenotypes, including the development of dendritic trees in Purkinje cells and altered cerebellar structure. Choline and acetylcholine levels were significantly decreased, whereas PC levels were increased, in the cerebellum of prmt8 (-/-) mice. Our findings suggest that PRMT8 acts both as an arginine methyltransferase and as a PC-hydrolyzing PLD that is essential for proper neurological functions.
[Show abstract][Hide abstract] ABSTRACT: Protein arginine methyltransferase 1 (PRMT1) is involved in cell proliferation, DNA damage response, and transcriptional regulation.
While PRMT1 is extensively expressed in the central nervous system (CNS) at embryonic and perinatal stages, the physiological
role of PRMT1 was poorly understood. Here, to investigate the primary function of PRMT1 in the CNS, we generated CNS-specific
PRMT1 knockout mice by Cre-loxP system. These mice exhibited post-natal growth retardation with tremors and most of them died
in two weeks after birth. Brain histological analyses revealed the prominent cell reduction in the white matter tracts of
the mutant mice. Furthermore, ultrastructural analysis demonstrated that myelin sheath was almost completely ablated in the
CNS of these animals. In agreement with hypomyelination, we also observed that most major myelin proteins including MBP, CNPase,
and MAG were dramatically decreased, although neuronal and astrocytic markers were preserved in the brain of CNS-specific
PRMT1 knockout mice. These animals had reduced number of OLIG2+ oligodendrocyte lineage cells in the white matter. We found
that expressions of transcription factors essential for oligodendrocyte specification and further maturation were significantly
suppressed in the brain of the mutant mice. Our findings provide evidence that PRMT1 is required for CNS development, especially
for oligodendrocyte maturation processes.
Preview · Article · Dec 2015 · Journal of Biological Chemistry
[Show abstract][Hide abstract] ABSTRACT: Since serotonin, homocysteine and oxytocin are known to fluctuate during mammalian gestation, we screened amines altered in pregnant-associated hypertensive (PAH) mice by tagging their amino groups with 6-aminoquinoline carbamoyl (AQC) group in concert with ultra high-performance liquid chromatography (UPLC). Interestingly, a candidate amine significantly increased in PAH mice was recovered to the basal level, when treated with antihypertensive drugs. Mass spectrometric analyses indicated that the molecular mass of this amine was 61.2, which was identified as ethanolamine.
No preview · Article · Nov 2015 · Journal of chromatography. B, Analytical technologies in the biomedical and life sciences
[Show abstract][Hide abstract] ABSTRACT: Genomic imprinting is a major monoallelic gene expression regulatory mechanism in mammals, and depends on gamete-specific DNA methylation of specialized cis-regulatory elements called imprinting control regions (ICRs). Allele-specific DNA methylation of the ICRs is faithfully maintained at the imprinted loci throughout development, even in early embryos where genomes undergo extensive epigenetic reprogramming, including DNA demethylation, to acquire totipotency. We previously found that an ectopically introduced H19 ICR fragment in transgenic mice acquired paternal allele-specific methylation in the somatic cells of offspring, while it was not methylated in sperm, suggesting its gametic and postfertilization modifications are separable events. We hypothesized that this latter activity might contribute to maintenance of the methylation imprint in early embryos. Here we demonstrate that methylation of the paternally inherited transgenic H19 ICR commences soon after fertilization in a maternal Dnmt3a- and Dnmt3L-dependent manner. When its germline methylation was partially obstructed by insertion of insulator sequences, the endogenous, paternal H19 ICR also exhibited postfertilization methylation. Finally, we refined the responsible sequences for this activity in transgenic mice, and found that deletion of the 5' segment of the endogenous paternal H19 ICR decreased its methylation after fertilization, attenuated Igf2 gene expression. These results demonstrate that this segment of the H19 ICR is essential for its de novo post-fertilization DNA methylation, and that this activity contributes to the maintenance of imprinted methylation at the endogenous H19 ICR during early embryogenesis.
[Show abstract][Hide abstract] ABSTRACT: The renin-angiotensin system (RAS) plays a central role in blood pressure regulation. Although clinical and experimental studies have suggested that inhibition of RAS is associated with progression of anemia, little evidence is available to support this claim. Here we report that knockout mice that lack angiotensin II, including angiotensinogen and renin knockout mice, exhibit anemia. The anemia of angiotensinogen knockout mice was rescued by angiotensin II infusion, and rescue was completely blocked by simultaneous administration of AT1 receptor blocker. To genetically determine the responsible receptor subtype, we examined AT1a, AT1b, and AT2 knockout mice, but did not observe anemia in any of them. To investigate whether pharmacological AT1 receptor inhibition recapitulates the anemic phenotype, we administered AT1 receptor antagonist in hypotensive AT1a receptor knockout mice to inhibit the remaining AT1b receptor. In these animals, hematocrit levels barely decreased, but blood pressure further decreased to the level observed in angiotensinogen knockout mice. We then generated AT1a and AT1b double-knockout mice to completely ablate the AT1 receptors; the mice finally exhibited the anemic phenotype. These results provide clear evidence that although erythropoiesis and blood pressure are negatively controlled through the AT1 receptor inhibition in vivo, the pathways involved are complex and distinct, because erythropoiesis is more resistant to AT1 receptor inhibition than blood pressure control.
[Show abstract][Hide abstract] ABSTRACT: Intracapillary foam cell infiltration with podocyte alterations is a characteristic pathology of focal segmental glomerulosclerosis (FSGS). We investigated the possible role of podocyte injury in glomerular macrophage and foam cell infiltration in a podocyte-selective injury model (NEP25 mice) and hypercholesterolemic model [low-density lipoprotein receptor deficiency (LDLR(-/-)) mice] with doxorubicin-induced nephropathy. Acute podocyte selective injury alone failed to induce glomerular macrophages in the NEP25 mice. However, in the doxorubicin-treated hypercholesterolemic LDLR(-/-) mice, glomerular macrophages/foam cells significantly increased and were accompanied by lipid deposition and the formation and ingestion of oxidized phospholipids (oxPLs). Glomerular macrophages significantly correlated with the amount of glomerular oxPL. The NEP25/LDLR(-/-) mice exhibited severe hypercholesterolemia, glomerular lipid deposition, and renal dysfunction. Imaging mass spectrometry revealed that a major component of oxidized low-density lipoprotein, lysophosphatidylcholine 16:0 and 18:0, was present only in the glomeruli of NEP25/LDLR(-/-) mice. Lysophosphatidylcholine 16:0 stimulated mesangial cells and macrophages, and lysophosphatidylcholine 18:0 stimulated glomerular endothelial cells to express adhesion molecules and chemokines, promoting macrophage adhesion and migration in vitro. In human FSGS, glomerular macrophage-derived foam cells contained oxPLs accompanied by the expression of chemokines in the tuft. In conclusion, glomerular lipid modification represents a novel pathology by podocyte injury, promoting FSGS. Podocyte injury-driven lysophosphatidylcholine de novo accelerated glomerular macrophage-derived foam cell infiltration via lysophosphatidylcholine-mediated expression of adhesion molecules and chemokines in glomerular resident cells.
Full-text · Article · Jun 2015 · American Journal Of Pathology
[Show abstract][Hide abstract] ABSTRACT: Phospholipase D (PLD) catalyzes the hydrolysis of phosphatidylcholine (PC), the most abundant phospholipids of plasma membrane, resulting in the production of choline and phosphatidic acid (PA). Choline is a precursor of the neurotransmitter acetylcholine, whereas PA functions as an intracellular lipid mediator of diverse biological functions. For assessing PLD activity in vitro, PLD-derived choline has been often analyzed with radioactive or non-radioactive methods. In this study, we have developed a new method for detecting choline and PA with MALDI-QIT-TOF/MS by using 9-aminoacridine as a matrix. The standard calibration curves showed that choline and PA could be detected with linearity over the range from 0.05 and 1 pmol, respectively. Importantly, this method enables the concomitant detection of choline and PA as a reaction product of PC hydrolysis by PLD2 proteins. Thus, our simple and direct method would be useful to characterize the enzymatic properties of PLD, thereby providing insight into mechanisms of PLD activation.
No preview · Article · Jun 2014 · Bioscience Biotechnology and Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Abstract Renin is predominantly expressed in juxtaglomerular cells in the kidney and regulates blood pressure homeostasis. To examine possible in vivo functions of a mouse distal enhancer (mdE), we generated transgenic mice (TgM) carrying either wild-type or mdE-deficient renin BACs (bacterial artificial chromosome), integrated at the identical chromosomal site. In the kidneys of the TgM, the mdE contributed 80% to basal renin promoter activity. To test for possible physiological roles for the mdE, renin BAC transgenes were used to rescue the hypotensive renin-null mice. Interestingly, renal renin expression in the Tg(BAC):renin-null compound mice was indistinguishable between the wild-type and mutant BAC carriers. Surprisingly, however, the plasma renin activity and angiotensin I concentration in the mdE compound mutant mice were significantly lower than the same parameters in the control mice, and the mutants were consistently hypotensive, demonstrating that blood pressure homeostasis is regulated through transcriptional cis elements controlling renin activity.
No preview · Article · Apr 2014 · Journal of Receptor and Signal Transduction Research
[Show abstract][Hide abstract] ABSTRACT: Protein arginine methyltransferase 7 (PRMT7) is a member of a family of enzymes that catalyze the transfer of methyl groups from S-adenosyl-L-methionine to nitrogen atoms on arginine residues. Here, we describe the crystal structure of Caenorhabditis elegans PRMT7 in complex with its reaction product S-adenosyl-L-homocysteine. The structural data indicated that PRMT7 harbors two tandem repeated PRMT core domains that form a novel homodimer-like structure. S-adenosyl-L-homocysteine bound to the N-terminal catalytic site only; the C-terminal catalytic site is occupied by a loop that inhibits cofactor binding. Mutagenesis demonstrated that only the N-terminal catalytic site of PRMT7 is responsible for cofactor binding.
[Show abstract][Hide abstract] ABSTRACT: Abstract Context: There are few short-term mouse models of chronic obstructive pulmonary disease (COPD) mimicking the human disease. In addition, p38 is recently recognized as a target for the treatment of COPD. However, the precise mechanism how p38 contributes to the pathogenesis of COPD is still unknown. Objective: We attempted to create a new mouse model for COPD by intra-tracheal administration of a mixture of lipopolysaccharide (LPS) and cigarette smoke solution (CSS), and investigated the importance of the p38 mitogen-activated protein kinase (p38) pathway in the pathogenesis of COPD. Methods: Mice were administered LPS + CSS once a day on days 0-4 and 7-11. Thereafter, CSS alone was administered to mice once a day on days 14-18. On day 28, histopathological changes of the lung were evaluated, and bronchoalveolar lavage fluid (BALF) was subjected to western blot array for cytokines. Transgenic (TG) mice expressing a constitutive-active form of MKK6, a p38-specific activator in the lung, were subjected to our experimental protocol of COPD model. Results: LPS + CSS administration induced enlargement of alveolar air spaces and destruction of lung parenchyma. BALF analyses of the LPS + CSS group revealed an increase in expression levels of several cytokines involved in the pathogenesis of human COPD. These results suggest that our experimental protocol can induce COPD in mice. Likewise, histopathological findings of the lung and induction of cytokines in BALF from MKK6 c.a.-TG mice were more marked than those in WT mice. Conclusion: In a new experimental COPD mouse model, p38 accelerates the development of emphysema.
No preview · Article · Mar 2014 · Journal of Receptor and Signal Transduction Research
[Show abstract][Hide abstract] ABSTRACT: Agenesis of the corpus callosum (ACC) is a congenital abnormality of the brain structure. More than 60 genes are known to be involved in corpus callosum development. However, the molecular mechanisms underlying ACC are not fully understood. Previously, we produced a novel transgenic mouse strain, TAS, carrying genes of the tetracycline-inducible expression system that are not involved in brain development, and inherited ACC was observed in the brains of all homozygous TAS mice. Although ACC was probably induced by transgene insertion mutation, the causative gene and the molecular mechanism of its pathogenesis remain unclear. Here, we first performed interphase three-color fluorescence in situ hybridization (FISH) analysis to determine the genomic insertion site. Transgenes were inserted into chromosome 18 similar to 12.0 Mb from the centromere. Gene expression analysis and genomic PCR walking showed that the genomic region containing exon 4 of Cables1 was deleted by transgene insertion and the other exons of Cables1 were intact. The mutant allele was designated as Cables1(TAS). Interestingly, Cables1(TAS) mRNA consisted of exons 1-3 of Cables1 and part of the transgene that encoded a novel truncated Cables1 protein. Homozygous TAS mice exhibited mRNA expression of Cables1(TAS) in the fetal cerebrum, but not that of wild-type Cables1. To investigate whether a dominant negative effect of Cables1(TAS) or complete loss of function of Cables1 gives rise to ACC, we produced Cables1-null mutant mice. ACC was not observed in Cables1-null mutant mice, suggesting that a dominant negative effect of Cables1(TAS) impairs callosal formation. Moreover, ACC frequency in Cables1(+/TAS) mice was significantly lower than that in Cables1(-/TAS) mice, indicating that wild-type Cables1 interfered with the dominant negative effect of Cables1(TAS). This study indicated that truncated Cables1 causes ACC and wild-type Cables1 contributes to callosal formation.
No preview · Article · Dec 2013 · Laboratory Investigation
[Show abstract][Hide abstract] ABSTRACT: Angiotensin converting enzyme 2 (ACE2) is a negative regulator of the renin-angiotensin system (RAS), catalyzing the conversion of Angiotensin II to Angiotensin 1-7. Apelin is a second catalytic substrate for ACE2 and functions as an inotropic and cardioprotective peptide. While an antagonistic relationship between the RAS and apelin has been proposed, such functional interplay remains elusive. Here we found that ACE2 was downregulated in apelin-deficient mice. Pharmacological or genetic inhibition of angiotensin II type 1 receptor (AT1R) rescued the impaired contractility and hypertrophy of apelin mutant mice, which was accompanied by restored ACE2 levels. Importantly, treatment with angiotensin 1-7 rescued hypertrophy and heart dysfunctions of apelin-knockout mice. Moreover, apelin, via activation of its receptor, APJ, increased ACE2 promoter activity in vitro and upregulated ACE2 expression in failing hearts in vivo. Apelin treatment also increased cardiac contractility and ACE2 levels in AT1R-deficient mice. These data demonstrate that ACE2 couples the RAS to the apelin system, adding a conceptual framework for the apelin-ACE2-angiotensin 1-7 axis as a therapeutic target for cardiovascular diseases.
No preview · Article · Nov 2013 · The Journal of clinical investigation
[Show abstract][Hide abstract] ABSTRACT: Mono-allelic expression at the mouse IGF2/H19 locus is controlled by differential allelic DNA methylation of the imprinting control region (ICR). Because a randomly integrated H19 ICR fragment, when incorporated into the genome of transgenic mice (TgM), was allele-specifically methylated in somatic, but not in germ cells, it was suggested that allele-discriminating epigenetic signature, set within or somewhere outside of the Tg H19 ICR fragment in germ cells, was later translated into a differential DNA methylation pattern. To test if the chicken β-globin HS4 (cHS4) chromatin insulator might interfere with methylation imprinting establishment at the H19 ICR, we inserted the H19 ICR fragment, flanked by a set of floxed cHS4 core sequences, into a human β-globin locus YAC and generated TgM (insulated ICR' TgM). As controls, the cHS4 sequences were removed from one side (5'HS4-deleted ICR') or both sides (pseudo-WT ICR') of the insulated ICR' by in vivo cre-loxP recombination. The data show that while maternally inherited transgenic H19 ICR was not methylated in insulated ICR' TgM, it was significantly methylated upon paternal transmission, though the level was lower than in the pseudo-WT ICR' control. Because this reduced level of methylation was also observed in the 5'HS4-deleted ICR' TgM, we speculate that the phenotype is due to VEZF1-dependent demethylation activity, rather than the insulator function, borne in cHS4. Collectively, although we cannot rule out the possibility that cHS4 is incapable of blocking an allele-discriminating signal from outside of the transgene, the epigenetic signature appears to be marked intrinsically within the H19 ICR.
[Show abstract][Hide abstract] ABSTRACT: Lung surfactant is a complex mixture of lipids and proteins, which is secreted from the alveolar type II epithelial cell and coats the surface of alveoli as a thin layer. It plays a crucial role in the prevention of alveolar collapse through its ability to reduce surface tension. Under normal conditions, surfactant homeostasis is maintained by balancing its release and the uptake by the type II cell for recycling and the internalization by alveolar macrophages for degradation. Little is known about how the surfactant pool is monitored and regulated. Here we show, by an analysis of gene-targeted mice exhibiting massive accumulation of surfactant, that Ig-Hepta/GPR116, an orphan receptor, is expressed on the type II cell and sensing the amount of surfactant by monitoring one of its protein components, surfactant protein D, and its deletion results in a pulmonary alveolar proteinosis and emphysema-like pathology. By a coexpression experiment with Sp-D and the extracellular region of Ig-Hepta/GPR116 followed by immunoprecipitation, we identified Sp-D as the ligand of Ig-Hepta/GPR116. Analyses of surfactant metabolism in Ig-Hepta(+/+) and Ig-Hepta(-/-) mice by using radioactive tracers indicated that the Ig-Hepta/GPR116 signaling system exerts attenuating effects on (i) balanced synthesis of surfactant lipids and proteins and (ii) surfactant secretion, and (iii) a stimulating effect on recycling (uptake) in response to elevated levels of Sp-D in alveolar space.
[Show abstract][Hide abstract] ABSTRACT: Abnormal methylation at the maternally inherited H19 imprinted control region (H19 ICR) is one of the causative alterations leading to pathogenesis of Beckwith-Wiedemann syndrome (BWS). Recently, it was shown in human BWS patients, as well as mouse cell culture experiments, that Sox-Oct motifs (SOM) in the H19 ICR might play a role in protecting the maternal ICR from de novo DNA methylation. By grafting a mouse H19 ICR fragment into a human β-globin yeast artificial chromosome (YAC) followed by analysis in transgenic mice (TgM), we showed previously that the fragment carried sufficient information to establish and maintain differential methylation after fertilization. To examine possible functions of the SOM in the establishment and/or maintenance of differential methylation, two kinds of YAC-TgM were generated in this study. In the ΔSOM TgM, carrying the mouse H19 ICR bearing an SOM deletion, a maternally inherited transgenic ICR exhibited increased levels of methylation around the deletion site, in comparison to the wild-type control, after implantation. In the λ+CTCF+b (LCb) TgM, carrying a 2.3 kb λ DNA fragment supplemented with the fragment b including the SOM and four CTCF binding sites, maternally- and some of the paternally-inherited LCb fragments were significantly less methylated when compared with a control λ+CTCF fragment that was supplemented only with additional CTCF sites; the λ+CTCF was substantially methylated regardless of the parent of origin after implantation. These results demonstrated that the SOM in the maternal H19 ICR was required for maintaining surrounding sequences in the unmethylated state in vivo.
Preview · Article · Jul 2013 · Human Molecular Genetics
[Show abstract][Hide abstract] ABSTRACT: Renal dysfunction is accelerated by various factors such as hypertension, aging and diabetes. Glomerular hyper-filtration, considered one of the major risk factors leading to diabetic nephropathy, is often encountered in diabetic patients. However, the interrelationship of these risk factors during the course and development of renal dysfunction has not been fully elucidated. In this study, the effects of aging and uninephrectomy (UNx)-induced hyperfiltration on renal changes were investigated in Tsukuba hypertensive mice (THM) carrying both human renin and angiotensinogen genes. In THM, the urinary albumin/creatinine (Alb/Cr) ratio was elevated with age without a concomitant increase in the plasma Cr concentration. Moreover, the urinary neutrophil gelatinase-associated lipocalin/Cr (NGAL/Cr) ratio, the renal monocyte chemoattractant protein-1 (MCP-1) mRNA expression and the renal collagen type I α 2 (COL1A2) mRNA expression were also increased with age. Age-related albuminuria in THM is likely caused by renal tubular damage, enhanced inflammatory response and tubulointerstitial fibrosis. Furthermore, following UNx, the urinary Alb/Cr ratio and the plasma Cr concentration were increased in THM. The urinary NGAL/Cr ratio and the renal MCP-1 and COL1A2 mRNA expression were not affected by UNx. These results suggested that UNx-induced albuminuria in THM was caused by glomerular dysfunction, rather than renal tubular injury. In conclusion, this study demonstrated for the first time the effects of aging and UNx on renal changes in THM. These findings strongly reinforce the significance of applying a diversity of therapeutic approaches to the management of renal dysfunction.