Safety and feasibility of transcranial direct current stimulation (tDCS) combined with sensorimotor retraining in chronic low back pain: a protocol for a pilot randomised controlled trial.

INTRODUCTION: Chronic low back pain (LBP) is a common and costly health problem yet current treatments demonstrate at best, small effects. The concurrent application of treatments with synergistic clinical and mechanistic effects may improve outcomes in chronic LBP. This pilot trial aims to (1) determine the feasibility, safety and perceived patient response to a combined transcranial direct current stimulation (tDCS) and sensorimotor retraining intervention in chronic LBP and (2) provide data to support a sample size calculation for a fully powered trial should trends of effectiveness be present. METHODS AND ANALYSIS: A pilot randomised, assessor and participant-blind, sham-controlled trial will be conducted. Eighty participants with chronic LBP will be randomly allocated to receive either (1) active tDCS + sensorimotor retraining or (2) sham tDCS + sensorimotor retraining. tDCS (active or sham) will be applied to the primary motor cortex for 20 min immediately prior to 60 min of supervised sensorimotor retraining twice per week for 10 weeks. Participants in both groups will complete home exercises three times per week. Feasibility, safety, pain, disability and pain system function will be assessed immediately before and after the 10-week intervention. Analysis of feasibility and safety will be performed using descriptive statistics. Statistical analyses will be conducted based on intention-to-treat and per protocol and will be used to determine trends for effectiveness. ETHICS AND DISSEMINATION: Ethical approval has been gained from the institutional human research ethics committee (H10184). Written informed consent will be provided by all participants. Results from this pilot study will be submitted for publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ACTRN12616000624482.

BPTF Maintains Chromatin Accessibility and the Self-Renewal Capacity of Mammary Gland Stem Cells.

Chromatin remodeling is a key requirement for transcriptional control of cellular differentiation. However, the factors that alter chromatin architecture in mammary stem cells (MaSCs) are poorly understood. Here, we show that BPTF, the largest subunit of the NURF chromatin remodeling complex, is essential for MaSC self-renewal and differentiation of mammary epithelial cells (MECs). BPTF depletion arrests cells at a previously undefined stage of epithelial differentiation that is associated with an incapacity to achieve the luminal cell fate. Moreover, genome-wide analysis of DNA accessibility following genetic or chemical inhibition, suggests a role for BPTF in maintaining the open chromatin landscape at enhancers regions in MECs. Collectively, our study implicates BPTF in maintaining the unique epigenetic state of MaSCs.

Mutagenic Bypass of an Oxidized Abasic Lesion-Induced DNA Interstrand Cross-Link Analogue by Human Translesion Synthesis DNA Polymerases.

5'-(2-Phosphoryl-1,4-dioxobutane) (DOB) is an oxidized abasic site that is produced by several antitumor agents and γ-radiolysis. DOB reacts reversibly with a dA opposite the 3'-adjacent nucleotide to form DNA interstrand cross-links (ICLs), genotoxic DNA lesions that can block DNA replication and transcription. Translesion synthesis (TLS) is an important step in several ICL repair pathways to bypass unhooked intermediates generated by endonucleolytic incision. The instability of DOB-ICLs has made it difficult to learn about their TLS-mediated repair capability and mutagenic potential. We recently developed a method for chemically synthesizing oligonucleotides containing a modified DOB-ICL analogue. Herein, we examined the capabilities of several highly relevant eukaryotic TLS DNA polymerases (pols), including human pol η, pol κ, pol ι, pol ν, REV1, and yeast pol ζ, to bypass this DOB-ICL analogue. The prelesion, translesion, and postlesion replication efficiency and fidelity were examined. Pol η showed moderate bypass activity when encountering the DOB-ICL, giving major products one or two nucleotides beyond the cross-linked template nucleotide. In contrast, DNA synthesis by the other pols was stalled at the position before the cross-linked nucleotide. Steady-state kinetic data and liquid chromatography-mass spectrometry sequencing of primer extension products by pol η unambiguously revealed that pol η-mediated bypass is highly error-prone. Together, our study provides the first set of in vitro evidence that the DOB-ICL is a replication-blocking and highly miscoding lesion. Compared to several other TLS pols examined, pol η is likely to contribute to the TLS-mediated repair of the DOB-ICL in vivo.

Kinetic and structural mechanisms of (5'S)-8,5'-cyclo-2'-deoxyguanosine-induced dna replication stalling.

The (5'S)-8,5'-cyclo-2'-deoxyguanosine (S-cdG) lesion is produced from reactions of DNA with hydroxyl radicals generated from ionizing radiation or endogenous oxidative metabolisms. An elevated level of S-cdG has been detected in Xeroderma pigmentosum, Cockayne syndrome, breast cancer patients, and aged mice. S-dG blocks DNA replication and transcription in vitro and in human cells and produces mutant replication and transcription products in vitro and in vivo. Major cellular protection against S-dG includes nucleotide excision repair and translesion DNA synthesis. We used kinetic and crystallographic approaches to elucidate the molecular mechanisms of S-cdG-induced DNA replication stalling using model B-family Sulfolobus solfataricus P2 DNA polymerase B1 (Dpo1) and Y-family S. solfataricus P2 DNA polymerase IV (Dpo4). Dpo1 and Dpo4 inefficiently bypassed S-cdG with dCTP preferably incorporated and dTTP (for Dpo4) or dATP (for Dpo1) misincorporated. Pre-steady-state kinetics and crystallographic data mechanistically explained the low-efficiency bypass. For Dpo1, S-cdG attenuated Kd,dNTP,app and kpol. For Dpo4, the S-cdG-adducted duplex caused a 6-fold decrease in Dpo4:DNA binding affinity and significantly reduced the concentration of the productive Dpo4:DNA:dCTP complex. Consistent with the inefficient bypass, crystal structures of Dpo4:DNA(S-cdG):dCTP (error-free) and Dpo4:DNA(S-cdG):dTTP (error-prone) complexes were catalytically incompetent. In the Dpo4:DNA(S-cdG):dTTP structure, S-cdG induced a loop structure and caused an unusual 5'-template base clustering at the active site, providing the first structural evidence of the previously suggested template loop structure that can be induced by a cyclopurine lesion. Together, our results provided mechanistic insights into S-cdG-induced DNA replication stalling.

Deloading tape reduces muscle stress at rest and during contraction.

PURPOSE: Taping techniques that aim to protect and reduce stress on an injured tissue during rehabilitation are common in sport. Called deloading tape, the mechanism of action is hypothesized to involve effects ranging from direct mechanical deloading of the underlying soft tissues to psychological effects on confidence. There is no evidence that deloading tape has direct mechanical effects. This study used an elastographic technique (supersonic shear imaging) to test the hypothesis that deloading tape applied to the skin over the rectus femoris would reduce stress within the taped area of this muscle. METHODS: Thirteen healthy volunteers participated in this experiment. Muscle shear elastic modulus was compared between three treatments (no tape, deloading tape, and sham tape) in four conditions: three conditions without muscle contraction at different rectus femoris muscle-tendon unit lengths (moderately stretched, highly stretched, and shortened) and during submaximal isometric leg extension. RESULTS: Although there was no effect of treatment when the muscle was shortened (P = 0.99), the shear elastic modulus was significantly affected by treatment for the three other conditions (all P < 0.002). Muscle shear elastic modulus was significantly less during application of deloading tape than that during both the no tape and sham tape conditions (all P ≤ 0.001; e.g., vs no tape: moderately stretched, 8.4 ± 2.7 vs 6.7 ± 1.7 kPa; highly stretched, 25.2 ± 8.2 vs 14.4 ± 4.3 kPa; submaximal contraction, 21.3 ± 4.8 vs 14.2 ± 4.3 kPa). CONCLUSIONS: Through the use of elastography, this is the first study to support the hypothesis that deloading tape reduces stress in the underlying muscle region, thereby providing a biomechanical explanation for the effect observed during rehabilitation in clinical practice (reduce pain, restore function, and aid recovery). Further investigations are necessary to confirm these results in injured tissues.