Molecular and Clinical Studies in 138 Japanese Patients with Silver-Russell Syndrome

Background

Recent studies have revealed relative frequency and characteristic phenotype of two major causative factors for Silver-Russell syndrome (SRS), i.e. epimutation of the H19-differentially methylated region (DMR) and uniparental maternal disomy 7 (upd(7)mat), as well as multilocus methylation abnormalities and positive correlation between methylation index and body and placental sizes in H19-DMR epimutation. Furthermore, rare genomic alterations have been found in a few of patients with idiopathic SRS. Here, we performed molecular and clinical findings in 138 Japanese SRS patients, and examined these matters.

Methodology/Principal Findings

We identified H19-DMR epimutation in cases 1–43 (group 1), upd(7)mat in cases 44–52 (group 2), and neither H19-DMR epimutation nor upd(7)mat in cases 53–138 (group 3). Multilocus analysis revealed hyper- or hypomethylated DMRs in 2.4% of examined DMRs in group 1; in particular, an extremely hypomethylated ARHI-DMR was identified in case 13. Oligonucleotide array comparative genomic hybridization identified a ∼3.86 Mb deletion at chromosome 17q24 in case 73. Epigenotype-phenotype analysis revealed that group 1 had more reduced birth length and weight, more preserved birth occipitofrontal circumference (OFC), more frequent body asymmetry and brachydactyly, and less frequent speech delay than group 2. The degree of placental hypoplasia was similar between the two groups. In group 1, the methylation index for the H19-DMR was positively correlated with birth length and weight, present height and weight, and placental weight, but with neither birth nor present OFC.

Conclusions/Significance

The results are grossly consistent with the previously reported data, although the frequency of epimutations is lower in the Japanese SRS patients than in the Western European SRS patients. Furthermore, the results provide useful information regarding placental hypoplasia in SRS, clinical phenotypes of the hypomethylated ARHI-DMR, and underlying causative factors for idiopathic SRS.     

Identification and biochemical characterization of the SLC9A7 interactome

Organellar and cytosolic pH homeostasis is central to most cellular processes, including vesicular trafficking, post-translational modification/processing of proteins, and receptor-ligand interactions. SLC9A7 (NHE7) was identified as a unique (Na⁺, K⁺)/H⁺ exchanger that dynamically cycles between the trans-Golgi network (TGN), endosomes and the plasma membrane. Here we have used mass spectrometry to explore the affinity-captured interactome of NHE7, leading to the identification of cytoskeletal proteins, cell adhesion molecules, membrane transporters, and signaling molecules. Among these binding proteins, calcium-calmodulin, but not apo-calmodulin, binds to NHE7 and regulates the organellar transporter activity. Vimentin was co-immunoprecipitated with endogenous NHE7 protein in human breast cancer MDA-MB-231 cells. A sizable population of NHE7 relocalized to focal complexes in migrating cells and showed colocalization with vimentin and actin in focal complexes. Among the NHE7-binding proteins identified, CD44, a cell surface glycoprotein receptor for hyaluronate and other ligands, showed regulated interaction with NHE7. Pretreatment of the cells with phorbol ester facilitated the NHE7-CD44 interaction and the lipid raft association of CD44. When lipid rafts were chemically disrupted, the NHE7-CD44 interaction was markedly reduced. These results suggest potential dual roles of NHE7 in intracellular compartments and subdomains of cell-surface membranes.     

Parasitic chytrids could promote copepod survival by mediating material transfer from inedible diatoms

Diatoms form large spring blooms in lakes and oceans, providing fuel for higher trophic levels at the start of the growing season. Some of the diatom blooms, however, are not grazed by filter-feeding zooplankton like Daphnia due to their large size. Several of these large diatoms are susceptible to chytrid infections. Zoospores of chytrids appeared to be excellent food for Daphnia, both in terms of size, shape, and quality (PUFAs and cholesterol). Thus, zoospores of chytrids can bridge the gap between inedible diatoms and Daphnia. In order to examine the effects of diatoms and chytrids on the survival of copepods, we performed one grazing and one survival experiment. The grazing experiment revealed that the diatom, Asterionella formosa, was not grazed by the copepod, Eudiaptomus gracilis, even after being infected by the chytrid Zygorhizidium planktonicum. However, carbon and nitrogen concentrations were significantly reduced by E. gracilis only when A. formosa was infected by Z. planktonicum, indicating that the chytrids might facilitate material transfer from inedible diatoms to the copepods. The survival experiment revealed that E. gracilis lived shorter with A. formosa than with the cryptophyta Cryptomonas pyrenoidifera. However, the survival of E. gracilis increased significantly in the treatment where A. formosa cells were infected by Z. planktonicum. Since E. gracilis could not graze A. formosa cells due to their large colonial forms, E. gracilis may acquire nutrients by grazing on the zoospores, and were so able to survive in the presence of the A. formosa. This provides new insights into the role of parasitic fungi in aquatic food webs, where chytrids may improve copepod survival during diatom blooms.     

Absence of Heterozygosity Due to Template Switching during Replicative Rearrangements

We investigated complex genomic rearrangements (CGRs) consisting of triplication copy-number variants (CNVs) that were accompanied by extended regions of copy-number-neutral absence of heterozygosity (AOH) in subjects with multiple congenital abnormalities. Molecular analyses provided observational evidence that in humans, post-zygotically generated CGRs can lead to regional uniparental disomy (UPD) due to template switches between homologs versus sister chromatids by using microhomology to prime DNA replication—a prediction of the replicative repair model, MMBIR. Our findings suggest that replication-based mechanisms might underlie the formation of diverse types of genomic alterations (CGRs and AOH) implicated in constitutional disorders.     

Angiotensin II-induced reduction in exercise capacity is associated with increased oxidative stress in skeletal muscle

Angiotensin II (ANG II)-induced oxidative stress has been known to be involved in the pathogenesis of cardiovascular diseases. We have reported that the oxidative stress in skeletal muscle can limit exercise capacity in mice (16). We thus hypothesized that ANG II could impair the skeletal muscle energy metabolism and limit exercise capacity via enhancing oxidative stress. ANG II (50 ng·kg(-1)·min(-1)) or vehicle was infused into male C57BL/6J mice for 7 days via subcutaneously implanted osmotic minipumps. ANG II did not alter body weight, skeletal muscle weight, blood pressure, cardiac structure, or function. Mice were treadmill tested, and expired gases were analyzed. The work to exhaustion (vertical distance × body weight) and peak oxygen uptake were significantly decreased in ANG II compared with vehicle. In mitochondria isolated from skeletal muscle, ADP-dependent respiration was comparable between ANG II and vehicle, but ADP-independent respiration was significantly increased in ANG II. Furthermore, complex I and III activities were decreased in ANG II. NAD(P)H oxidase activity and superoxide production by lucigenin chemiluminescence were significantly increased in skeletal muscle from ANG II mice. Treatment of ANG II mice with apocynin (10 mmol/l in drinking water), an inhibitor of NAD(P)H oxidase activation, completely inhibited NAD(P)H oxidase activity and improved exercise capacity, mitochondrial respiration, and complex activities in skeletal muscle. ANG II-induced oxidative stress can impair mitochondrial respiration in skeletal muscle and limit exercise capacity.     

Characteristic differences among osteogenic cell populations of rat bone marrow stromal cells isolated from untreated, hemolyzed or Ficoll-treated marrow

Background aimsAlthough bone marrow (BM) stromal cells (SC; BMSC) isolated from adherent cultures of untreated BM are known to contain both committed and uncommitted osteogenic cells, it remains unknown whether BMSC isolated either by hemolysis or Ficoll centrifugation also contain both of these populations.MethodsDifferences in the osteogenic cell populations of rat BMSC isolated from untreated, hemolyzed or Ficoll-treated BM were analyzed by in vivo transplantation, flow cytometry, alkaline phosphatase (ALP) assay, real-time polymerase chain reaction (PCR) and alizarin red staining.ResultsTransplantation of non-cultured samples indicated that the Ficolled BMSC contained the lowest number of committed osteogenic cells. Flow cytometric analysis of cultured, non-induced samples showed that the percentage of ALP-positive cells was significantly lower in Ficolled BMSC. Quantitative ALP assays confirmed that the lowest ALP activity was in the Ficolled BMSC. Hemolyzed BMSC also contained lower numbers of committed osteogenic cells than untreated BMSC, but still more than Ficolled BMSC. Interestingly, the Ficolled BMSC showed the greatest levels of osteogenic ability when cultured in osteogenic induction medium.ConclusionsThese findings suggest that, although Ficolled BMSC rarely contain committed osteogenic cells, they are able to show comparable or even greater levels of osteogenic ability after induction, possibly because they contain a greater proportion of uncommitted stem cells. In contrast, induction is optional but recommended for both untreated and hemolyzed BMSC before use, because both these groups contain both committed and uncommitted osteogenic cells. These findings are of significant importance when isolating BMSC for use in bone tissue engineering.     

Culture system for embryos of blue-breasted quail from the blastoderm stage to hatching.

The blue-breasted quail (Coturnix chinensis), the smallest species in the order Galliforms, is a candidate model animal for avian developmental engineering because it is precocious and prolific. This species requires 17 days to hatch and 8 to 9 weeks to mature to an adult body weight of about 50 g, whereas the Japanese quail (Coturnix japonica) requires 16 days to hatch and 6 to 8 weeks to mature to an adult body weight of 100 to 150 g. The early embryo is the most challenging embryonic stage in terms of culture and manipulation for avian biotechnology. We have evaluated various conditions for the culture of blue-breasted quail embryos from the blastoderm stage to hatching. A hatchability rate of 26% (10/39) is among the best of the various culture conditions examined in the present study and the embryo culture system should facilitate advances in avian biotechnology.     

GS143, an IkappaB ubiquitination inhibitor, inhibits allergic airway inflammation in mice

Asthma is characterized by airway inflammation with intense eosinophil infiltration and mucus hyper-production, in which antigen-specific Th2 cells play critical roles. Nuclear factor-κB (NF-κB) pathway has been demonstrated to be essential for the production of Th2 cytokines and chemokines in the airways in murine asthma models. In the present study, we examined the effect of GS143, a novel small-molecule inhibitor of IκB ubiquitination, on antigen-induced airway inflammation and Th2 cytokine production in mice. Intranasal administration of GS143 prior to antigen challenge suppressed antigen-induced NF-κB activation in the lung of sensitized mice. Intranasal administration of GS143 also inhibited antigen-induced eosinophil and lymphocyte recruitment into the airways as well as the expression of Th2 cytokines and eotaxin in the airways. Moreover, GS143 inhibited antigen-induced differentiation of Th2 cells but not of Th1 cells in vitro. Taken together, these results suggest that IκB ubiquitination inhibitor may have therapeutic potential against asthma.