Authors: Ao M, Chavez MB, Chu EY, Hemstreet KC, Yin Y, Yadav MC, Millán JL, Fisher LW, Goldberg HA, Somerman MJ, Foster BL
Journal: Bone. 2017 Sep 1;105:134-147. doi: 10.1016/j.bone.2017.08.027. [Epub ahead of print]
Although acellular cementum is essential for tooth attachment, factors directing its development and regeneration remain poorly understood. Inorganic pyrophosphate (PPi), a mineralization inhibitor, is a key regulator of cementum formation: tissue-nonspecific alkaline phosphatase (Alpl/TNAP) null mice (increased PPi) feature deficient cementum, while progressive ankylosis protein (Ank/ANK) null mice (decreased PPi) feature increased cementum. Bone sialoprotein (Bsp/BSP) and osteopontin (Spp1/OPN) are multifunctional extracellular matrix components of cementum proposed to have direct and indirect effects on cell activities and mineralization. Studies on dentoalveolar development of Bsp knockout (Bsp-/-) mice revealed severely reduced acellular cementum, however underlying mechanisms remain unclear. The similarity in defective cementum phenotypes between Bsp-/- mice and Alpl-/- mice (the latter featuring elevated PPi and OPN), prompted us to examine whether BSP is operating by modulating PPi-associated genes. Genetic ablation of Bsp caused a 2-fold increase in circulating PPi, altered mRNA expression of Alpl, Spp1, and Ank, and increased OPN protein in the periodontia. Generation of a Bsp knock-out (KO) cementoblast cell line revealed significantly decreased mineralization capacity, 50% increased PPi in culture media, and increased Spp1 and Ank mRNA expression. While addition of 2μg/ml recombinant BSP altered Spp1, Ank, and Enpp1 expression in cementoblasts, changes resulting from this dose were not dependent on the integrin-binding RGD motif or MAPK/ERK signaling pathway. Decreasing PPi by genetic ablation of Ank on the Bsp-/- mouse background reestablished cementum formation, allowing >3-fold increased acellular cementum volume compared to wild-type (WT). However, deleting Ank did not fully compensate for the absence of BSP. Bsp-/-; Ank-/- double-deficient mice exhibited mean 20-27% reduced cementum thickness and volume compared to Ank-/- mice. From these data, we conclude that the perturbations in PPi metabolism are not solely driving the cementum pathology in Bsp-/- mice, and that PPi is more potent than BSP as a cementum regulator, as shown by the ability to override loss of BSP by lowering PPi. We propose that BSP and PPi work in concert to direct mineralization in cementum and likely other mineralized tissues.
Authors: Weng TY, Tsai SA, Su TP
Journal: J Biomed Sci. 2017 Sep 16;24(1):74. doi: 10.1186/s12929-017-0380-6.
The sigma-1 receptor (Sig-1R) is a chaperone that resides mainly at the mitochondrion-associated endoplasmic reticulum (ER) membrane (called the MAMs) and acts as a dynamic pluripotent modulator in living systems. At the MAM, the Sig-1R is known to play a role in regulating the Ca2+ signaling between ER and mitochondria and in maintaining the structural integrity of the MAM. The MAM serves as bridges between ER and mitochondria regulating multiple functions such as Ca2+ transfer, energy exchange, lipid synthesis and transports, and protein folding that are pivotal to cell survival and defense. Recently, emerging evidences indicate that the MAM is critical in maintaining neuronal homeostasis. Thus, given the specific localization of the Sig-1R at the MAM, we highlight and propose that the direct or indirect regulations of the Sig-1R on mitochondrial functions may relate to neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD) and amyotrophic lateral sclerosis (ALS). In addition, the promising use of Sig-1R ligands to rescue mitochondrial dysfunction-induced neurodegeneration is addressed.
Authors: Zhang F, Zhu G, Jacobson O, Liu Y, Chen K, Yu G, Ni Q, Fan J, Yang Z, Xu F, Fu X, Wang Z, Ma Y, Niu G, Zhao X, Chen X
Journal: ACS Nano. 2017 Sep 26;11(9):8838-8848. doi: 10.1021/acsnano.7b03003. Epub 2017 Sep 6.
We report a camptothecin (CPT) prodrug that was well formulated in solution and rapidly transformed into long-circulating nanocomplexes in vivo for highly efficient drug delivery and effective cancer therapy. Specifically, using a redox-responsive disulfide linker, CPT was conjugated with an albumin-binding Evans blue (EB) derivative; the resulting amphiphilic CPT-ss-EB prodrug self-assembled into nanostructures in aqueous solution, thus conferring high solubility and stability. By binding CPT-ss-EB to endogenous albumin, the 80 nm CPT-ss-EB nanoparticles rapidly transformed into 7 nm albumin/prodrug nanocomplexes. CPT-ss-EB was efficient at intracellular delivery into cancer cells, released intact CPT in a redox-responsive manner, and exhibited cytotoxicity as potent as CPT. In mice, the albumin/CPT-ss-EB nanocomplex exhibited remarkably long blood circulation (130-fold greater than CPT) and efficient tumor accumulation (30-fold of CPT), which consequently contributed to excellent therapeutic efficacy. Overall, this strategy of transformative nanomedicine is promising for efficient drug delivery.
Authors: Schellenberg MJ, Lieberman JA, Herrero-Ruiz A, Butler LR, Williams JG, Muñoz-Cabello AM, Mueller GA, London RE, Cortés-Ledesma F, Williams RS
Journal: Science. 2017 Sep 29;357(6358):1412-1416. doi: 10.1126/science.aam6468. Epub 2017 Sep 14.
Topoisomerase 2 (TOP2) DNA transactions proceed via formation of the TOP2 cleavage complex (TOP2cc), a covalent enzyme-DNA reaction intermediate that is vulnerable to trapping by potent anticancer TOP2 drugs. How genotoxic TOP2 DNA-protein cross-links are resolved is unclear. We found that the SUMO (small ubiquitin-related modifier) ligase ZATT (ZNF451) is a multifunctional DNA repair factor that controls cellular responses to TOP2 damage. ZATT binding to TOP2cc facilitates a proteasome-independent tyrosyl-DNA phosphodiesterase 2 (TDP2) hydrolase activity on stalled TOP2cc. The ZATT SUMO ligase activity further promotes TDP2 interactions with SUMOylated TOP2, regulating efficient TDP2 recruitment through a "split-SIM" SUMO2 engagement platform. These findings uncover a ZATT-TDP2-catalyzed and SUMO2-modulated pathway for direct resolution of TOP2cc.
Authors: Chattaraj P, Munjal T, Honda K, Rendtorff ND, Ratay JS, Muskett JA, Risso DS, Roux I, Gertz EM, Schäffer AA, Friedman TB, Morell RJ, Tranebjærg L, Griffith AJ
Journal: J Med Genet. 2017 Aug 5. pii: jmedgenet-2017-104721. doi: 10.1136/jmedgenet-2017-104721.
BACKGROUND: Enlargement of the vestibular aqueduct (EVA) is the most common radiological abnormality in children with sensorineural hearing loss. Mutations in coding regions and splice sites of the SLC26A4 gene are often detected in Caucasians with EVA. Approximately one-fourth of patients with EVA have two mutant alleles (M2), one-fourth have one mutant allele (M1) and one-half have no mutant alleles (M0). The M2 genotype is correlated with a more severe phenotype.
METHODS: We performed genotype-haplotype analysis and massively parallel sequencing of the SLC26A4 region in patients with M1 EVA and their families.
RESULTS: We identified a shared novel haplotype, termed CEVA (Caucasian EVA), composed of 12 uncommon variants upstream of SLC26A4. The presence of the CEVA haplotype on seven of ten 'mutation-negative' chromosomes in a National Institutes of Health M1 EVA discovery cohort and six of six mutation-negative chromosomes in a Danish M1 EVA replication cohort is higher than the observed prevalence of 28 of 1006 Caucasian control chromosomes (p<0.0001 for each EVA cohort). The corresponding heterozygous carrier rate is 28/503 (5.6%). The prevalence of CEVA (11 of 126) is also increased among M0 EVA chromosomes (p=0.0042).
CONCLUSIONS: The CEVA haplotype causally contributes to most cases of Caucasian M1 EVA and, possibly, some cases of M0 EVA. The CEVA haplotype of SLC26A4 defines the most common allele associated with hereditary hearing loss in Caucasians. The diagnostic yield and prognostic utility of sequence analysis of SLC26A4 exons and splice sites will be markedly increased by addition of testing for the CEVA haplotype.
Authors: Oh KS, Patel H, Gottschalk RA, Lee WS, Baek S, Fraser IDC, Hager GL, Sung MH
Journal: Immunity. 2017 Aug 15;47(2):298-309.e5. doi: 10.1016/j.immuni.2017.07.012. Epub 2017 Aug 8.
Despite the widespread use of glucocorticoids (GCs), their anti-inflammatory effects are not understood mechanistically. Numerous investigations have examined the effects of glucocorticoid receptor (GR) activation prior to inflammatory challenges. However, clinical situations are emulated by a GC intervention initiated in the midst of rampant inflammatory responses. To characterize the effects of a late GC treatment, we profiled macrophage transcriptional and chromatinscapes with Dexamethasone (Dex) treatment before or after stimulation by lipopolysaccharide (LPS). The late activation of GR had a similar gene-expression profile as from GR pre-activation, while ameliorating the disruption of metabolic genes. Chromatin occupancy of GR was not predictive of Dex-regulated gene expression, contradicting the "trans-repression by tethering" model. Rather, GR activation resulted in genome-wide blockade of NF-κB interaction with chromatin and directly induced inhibitors of NF-κB and AP-1. Our investigation using GC treatments with clinically relevant timing highlights mechanisms underlying GR actions for modulating the "inflamed epigenome."
Authors: Gomez JL, Bonaventura J, Lesniak W, Mathews WB, Sysa-Shah P, Rodriguez LA, Ellis RJ, Richie CT, Harvey BK, Dannals RF, Pomper MG, Bonci A, Michaelides M
Journal: Science. 2017 Aug 4;357(6350):503-507. doi: 10.1126/science.aan2475.
The chemogenetic technology DREADD (designer receptors exclusively activated by designer drugs) is widely used for remote manipulation of neuronal activity in freely moving animals. DREADD technology posits the use of "designer receptors," which are exclusively activated by the "designer drug" clozapine N-oxide (CNO). Nevertheless, the in vivo mechanism of action of CNO at DREADDs has never been confirmed. CNO does not enter the brain after systemic drug injections and shows low affinity for DREADDs. Clozapine, to which CNO rapidly converts in vivo, shows high DREADD affinity and potency. Upon systemic CNO injections, converted clozapine readily enters the brain and occupies central nervous system-expressed DREADDs, whereas systemic subthreshold clozapine injections induce preferential DREADD-mediated behaviors.
Authors: Khincha PP, Dagnall CL, Hicks B, Jones K, Aviv A, Kimura M, Katki H, Aubert G, Giri N, Alter BP, Savage SA, Gadalla SM
Journal: Int J Mol Sci. 2017 Aug 13;18(8). pii: E1765. doi: 10.3390/ijms18081765.
Several methods have been employed to measure telomere length (TL) in human studies. It has been difficult to directly compare the results from these studies because of differences in the laboratory techniques and output parameters. We compared TL measurements (TLMs) by the three most commonly used methods, quantitative polymerase chain reaction (qPCR), flow cytometry with fluorescence in situ hybridization (flow FISH) and Southern blot, in a cohort of patients with the telomere biology disorder dyskeratosis congenita (DC) and in their unaffected relatives (controls). We observed a strong correlation between the Southern blot average TL and the flow FISH total lymphocyte TL in both the DC patients and their unaffected relatives (R² of 0.68 and 0.73, respectively). The correlation between the qPCR average TL and that of the Southern blot method was modest (R² of 0.54 in DC patients and of 0.43 in unaffected relatives). Similar results were noted when comparing the qPCR average TL and the flow FISH total lymphocyte TL (R² of 0.49 in DC patients and of 0.42 in unaffected relatives). In conclusion, the strengths of the correlations between the three widely used TL assays (qPCR, flow FISH, and Southern blot) were significantly different. Careful consideration is warranted when selecting the method of TL measurement for research and for clinical studies.
Authors: Zhao F, Franco HL, Rodriguez KF, Brown PR, Tsai MJ, Tsai SY, Yao HH
Journal: Science. 2017 Aug 18;357(6352):717-720. doi: 10.1126/science.aai9136.
The sexual differentiation paradigm contends that the female pattern of the reproductive system is established by default because the male reproductive tracts (Wolffian ducts) in the female degenerate owing to a lack of androgen. Here, we discovered that female mouse embryos lacking Coup-tfII (chicken ovalbumin upstream promoter transcription factor II) in the Wolffian duct mesenchyme became intersex-possessing both female and male reproductive tracts. Retention of Wolffian ducts was not caused by ectopic androgen production or action. Instead, enhanced phosphorylated extracellular signal-regulated kinase signaling in Wolffian duct epithelium was responsible for the retention of male structures in an androgen-independent manner. We thus suggest that elimination of Wolffian ducts in female embryos is actively promoted by COUP-TFII, which suppresses a mesenchyme-epithelium cross-talk responsible for Wolffian duct maintenance.
Authors: Gianferante DM, Mirabello L, Savage SA
Journal: Nat Rev Endocrinol. 2017 Aug;13(8):480-491. doi: 10.1038/nrendo.2017.16. Epub 2017 Mar 24.
Clinical outcomes and treatment modalities for osteosarcoma, the most common primary cancer of bone, have changed very little over the past 30 years. The peak incidence of osteosarcoma occurs during the adolescent growth spurt, which suggests that bone growth and pubertal hormones are important in the aetiology of the disease. Tall stature, high birth weight and certain inherited cancer predisposition syndromes are well-described risk factors for osteosarcoma. Common genetic variants are also associated with osteosarcoma. The somatic genome of osteosarcoma is highly aneuploid, exhibits extensive intratumoural heterogeneity and has a higher mutation rate than most other paediatric cancers. Complex pathways related to bone growth and development and tumorigenesis are also important in osteosarcoma biology. In this Review, we discuss the contributions of germline and somatic genetics, tumour biology and animal models in improving our understanding of osteosarcoma aetiology, and their potential to identify novel therapeutic targets and thus improve the lives of patients with osteosarcoma.