Biology subjects

Martin, D.

Publications and source records attributed to Martin, D..

7 recordsLinked to original sources

bioRxiv2018

Stromal fibroblast activation and inflammation in frozen shoulder

IntroductionFrozen shoulder is a common, fibro-proliferative disease characterised by the insidious onset of pain and progressively restricted range of shoulder movement. Despite the prevalence of this disease, there is limited understanding of the molecular mechanisms underpinning the pathogenesis of this debilitating disease. Previous studies have identified increased myofibroblast differentiation and proliferation, immune cell influx and dysregulated cytokine production. We hypothesised that subpopulations within the stromal compartment may take on an activated phenotype, thus initiating the inflammatory processes observed in frozen shoulder. Therefore, we sought to evaluate the presence and possible pathogenic role of known stromal activation proteins in Frozen shoulder,\n\nMethodsShoulder capsule samples were collected from 10 patients with idiopathic frozen shoulder and 10 patients undergoing shoulder stabilisation surgery. Stromal activation marker expression (CD248, CD146, VCAM and PDPN, FAP) was quantified using immunohistochemistry. Control and diseased fibroblasts were cultured for in vitro studies from capsule biopsies from instability and frozen shoulder surgeries, respectively. The inflammatory profile and effects of IL-1{beta} upon diseased and control fibroblasts was assessed using ELISA, immunohistochemistry and qPCR.\n\nResultsImmunohistochemistry demonstrated increased expression of stromal activation markers CD248, CD146, VCAM and PDPN in the frozen shoulder group compared with control (p < 0.05). Fibroblasts cultured from diseased capsule produced elevated levels of inflammatory protein (IL-6, IL-8 & CCL-20) in comparison to control fibroblasts. Exposing control fibroblasts to an inflammatory stimuli, (IL-1{beta}) significantly increased stromal activation marker transcript and protein expression (CD248, PDPN and VCAM).\n\nConclusionsThese results show that stromal fibroblasts have an activated phenotype in frozen shoulder and this is associated with inflammatory cytokine dysregulation. Furthermore, it supports the hypothesis that activated stromal fibroblasts may be involved in regulating the inflammatory and fibrotic processes involved in this disease.

immunology↗

bioRxiv2018

Evolutionary analysis of base-pairing interactions in DNA and RNA secondary structures

Pairs of nucleotides within biologically functional nucleic acid secondary structures often exhibit evidence of coevolution that is consistent with the maintenance of canonical base-pairing. MESSI is a sequence evolution model that infers substitution rates associated with base-paired sites in alignments of DNA or RNA sequences. MESSI can estimate these whilst simultaneously accounting for the uncertainty associated with an unknown RNA or DNA secondary structure shared across an alignment of sequences. Moreover, the unknown structure can be predicted, or a base-pairing probability matrix calculated. MESSI optionally leverages CUDA GPU parallelism to accelerate inference. MESSI was used to infer coevolution rates associated with GC, AU (AT in DNA), GU (GT in DNA) pairs in non-coding RNA alignments, and single-stranded RNA and DNA virus alignments. Inferred rates of GU pair coevolution were found to be higher at base-paired sites in single-stranded RNA viruses and non-coding RNAs than those of GT pairs in single-stranded DNA viruses, suggesting that GT pairs do not stabilise DNA secondary structures to the same extent as GU pairs in RNA. The relative coevolution rates associated with GC, AU, and GU pairs were largely consistent with their relative chemical base-pairing stabilities (GC base-pairs being more stable than AU base-pairs, and AU base-pairs being more stable than GU base-pairs). Additionally, MESSI estimates the degrees of coevolution at individual base-paired sites in an alignment. These estimates were computed for a SHAPE-MaP-determined HIV-1 NL4-3 RNA secondary structure and two corresponding alignments. MESSIs estimates of coevolution were significantly more strongly correlated with experimentally-determined SHAPE-MaP pairing scores as compared to three non-evolutionary measures of base-pairing covariation. Finally, to assist researchers in prioritising substructures with potential biological functionality, MESSI automatically identifies substructures and ranks them by degrees of coevolution at base-paired sites within them. Such a ranking was created for an HIV-1 subtype B alignment, revealing an excess of top-ranking substructures that have been previously identified in the literature as having structure-related functional importance, and a number of top-ranking structures that have not yet been characterised.

molecular biology↗

bioRxiv2018

Dual role of Bnl/Fgf signaling in proliferation and endoreplication of Drosophila trachealadult progenitor cells

AbstractAdult progenitor cells activation is a key event in the formation of adult organs during development. The initiation of proliferation of these progenitor cells requires specific temporal signals, mostly of them still unknown. In Drosophila, formation of adult tracheal system depends on the activation of tracheal adult progenitors (tracheoblasts) of Tr4 and Tr5 tracheal metamers specific spiracular branches (SB) during the last larval stage. The mitotic activity of these tracheoblasts generate a pool of tracheal differentiated cells that migrate during pupal development along the larval trachea by the activation of the Branchless (Bnl)/Fibroblast growth factor (FGF) signaling to form the abdominal adult tracheal system. In here, we found that, in addition to migration, Bnl/FGF signaling, mediated by the transcription factor Pointed, is also required for adult progenitor cell proliferation in the SBs. Moreover, we found that tracheoblast proliferation in Tr4 and Tr5 SBs relies on the specific expression of the FGF ligand Bnl in their nearby transverse connective branches. Finally, we also show that, in absence of the transcription factor Cut (Ct), Bnl/FGF signaling induces endoreplication of differentiated tracheoblast daughter cells by in part promoting Fizzy-related (Fzr) expression. Altogether, our results suggest a dual role of Bnl/FGF signaling in tracheal adult progenitors, inducing both proliferation and endoreplication of tracheoblasts in late larval development, depending on the presence or absence of the transcription factor ct, respectively.\n\nAuthor summaryThe generation of adult organs and tissue renewal are complex processes that depend on the proliferation and posterior differentiation of undifferentiated progenitor cells in a temporal coordinated manner. Although many signals that regulate the activity of progenitor cells have been identified, the characterization of the mechanisms underlying the temporal and spatial control of such events remain unknown. The tracheal system of Drosophila, the respiratory organ, forms during embryogenesis and it is remodeled during metamorphosis from quiescent adult progenitor cells that proliferate. We have discovered that this proliferation depends on the activation of the FGF signaling as mutations that either inactivate or over-activate the pathway blocks cell division or induced over-proliferation of progenitor cells, respectively. Interestingly, we have found that the same signaling pathway also controls tracheal progenitor cells differentiation by promoting endoreplication. We found that this dual role of FGF signaling in adult progenitor cells, depends on the presence or absence of the transcription factor Cut. Altogether, our results, reveal the mechanism that control the division and differentiation of progenitor cells and open the possibility that analogous signaling pathway may play a similar role in vertebrate stem cell regulation and tumor growth.

developmental biology↗

bioRxiv2018

Cbs overdosage is necessary and sufficient to induce cognitive phenotypes in mouse models of Down syndrome and interacts genetically with Dyrk1a

Identifying dosage sensitive genes is a key to understand the mechanisms underlying intellectual disability in Down syndrome (DS). The Dp(17Abcg1-Cbs)1Yah DS mouse model (Dp1Yah) show cognitive phenotype and needs to be investigated to identify the main genetic driver. Here, we report that, in the Dp1Yah mice, 3 copies of the Cystathionine-beta-synthase gene (Cbs) are necessary to observe a deficit in the novel object recognition (NOR) paradigm. Moreover, the overexpression of Cbs alone is sufficient to induce NOR deficit. Accordingly targeting the overexpression of human CBS, specifically in Camk2a-expressing neurons, leads to impaired objects discrimination. Altogether this shows that Cbs overdosage is involved in DS learning and memory phenotypes. In order to go further, we identified compounds that interfere with the phenotypical consequence of CBS overdosage in yeast. Pharmacological intervention in the Tg(CBS) with one selected compound restored memory in the novel object recognition. In addition, using a genetic approach, we demonstrated an epistatic interaction between Cbs and Dyrk1a, another human chromosome 21 gene encoding the dual-specificity tyrosine phosphorylation-regulated kinase 1a and an already known target for DS therapeutic intervention. Further analysis using proteomic approaches highlighted several pathways, including synaptic transmission, cell projection morphogenesis, and actin cytoskeleton, that are affected by DYRK1A and CBS overexpression. Overall we demonstrated that CBS overdosage underpins the DS-related recognition memory deficit and that both CBS and DYRK1A interact to control accurate memory processes in DS. In addition, our study establishes CBS as an intervention point for treating intellectual deficiencies linked to DS.\n\nSIGNIFICANT STATEMENTHere, we investigated a region homologous to Hsa21 and located on mouse chromosome 17. We demonstrated using three independent genetic approaches that the overdosage of the Cystathionine-beta-synthase gene (Cbs) gene, encoded in the segment, is necessary and sufficient to induce deficit in novel object recognition (NR).\n\nIn addition, we identified compounds that interfere with the phenotypical consequence of CBS overdosage in yeast and in mouse transgenic lines. Then we analyzed the relation between Cbs overdosage and the consequence of DYRK1a overexpression, a main driver of another region homologous to Hsa21 and we demonstrated that an epistatic interaction exist between Cbs and Dyrk1a affecting different pathways, including synaptic transmission, cell projection morphogenesis, and actin cytoskeleton.

genetics↗

bioRxiv2017

Effects of tDCS Dosage on Working Memory in Healthy Participants

BackgroundTranscranial direct current stimulation (tDCS) has been found to improve working memory (WM) performance in healthy participants following a single session. However, results are mixed and the overall effect size is small. Interpretation of these results is confounded by heterogeneous study designs, including differences in tDCS dose (current intensity) and sham conditions used.\n\nAimsWe systematically investigated the effect of tDCS dose on working memory using behavioural and neurophysiological outcomes.\n\nMethodsIn a single-blind parallel group design, 100 participants were randomised across five groups to receive 15 minutes of bifrontal tDCS at different current intensities (2mA, 1mA, and three sham tDCS conditions at 0.034mA, 0.016mA, or 0mA). EEG activity was acquired while participants performed a WM task prior to, during, and following tDCS. Response time, accuracy and an event-related EEG component (P3) were evaluated.\n\nResultsWe found no significant differences in response time or performance accuracy between current intensities. The P3 amplitude was significantly lower in the 0mA condition compared to the 0.034mA, 1mA and 2mA tDCS conditions. Changes in WM accuracy were moderately correlated with changes in the P3 amplitude following tDCS compared to baseline levels (r = 0.34).\n\nConclusionsWorking memory was not significantly altered by tDCS, regardless of dose. The P3 amplitude showed that stimulation at 1mA, 2mA and a sham condition (0.034mA) had biological effects, with the largest effect size for 1mA stimulation. These findings indicate higher sensitivity of neurophysiological outcomes to tDCS and suggests that sham stimulation previously considered inactive may alter neuronal function.

neuroscience↗

bioRxiv2017

Serology reflects a decline in the prevalence of trachoma in two regions of The Gambia

Trachoma is caused by Chlamydia trachomatis (Ct). It is targeted for global elimination as a public health problem. In 2014, a population-based cross-sectional study was performed in two previously trachoma-endemic areas of The Gambia. Participants of all ages from Lower River Region (LRR) (N = 1028) and Upper River Region (URR) (N = 840) underwent examination for trachoma and had blood collected for detection of antibodies against the Ct antigen Pgp3, by ELISA. Overall, 30 (1.6%) individuals had active trachoma; the prevalence in children aged 1-9 years was 3.4% (25/742) with no statistically significant difference in prevalence between the regions. There was a significant difference in overall seroprevalence by region: 26.2% in LRR and 17.1% in URR (p<0.0001). In children 1-9 years old, seroprevalence was 4.4% in LRR and 3.9% in URR. Reversible catalytic models using information on age-specific seroprevalence demonstrated a decrease in the transmission of Ct infection in both regions, possibly reflecting the impact of improved access to water, health and sanitation as well as mass drug administration campaigns. Serological testing for antibodies to Ct antigens is potentially useful for trachoma programmes, but consideration should be given to the coendemicity of sexually transmitted Ct infections.

epidemiology↗

bioRxiv2017

Age-specific prevalence of anti-Pgp3 antibodies and severe conjunctival scarring in the Solomon Islands

BackgroundTrachomatous trichiasis (TT) and ocular Chlamydia trachomatis (Ct) infection in the Solomon Islands are scarce, whereas trachomatous inflammation-follicular (TF) is prevalent.\n\nMethodsWe enrolled 1511 people aged [≥]1 year from randomly selected households in 13 villages in which >10% of the population had TF prior to a single round of azithromycin MDA undertaken six months previously. Blood was collected from people of all ages to be screened for anti-Pgp3 antibodies. Photographs were collected from people of all ages for analysis of scarring severity.\n\nResultsConjunctival scars were visible in 13.1% of photographs. Mild (p<0.0001) but not severe (p=0.149) scars increased in prevalence with age. Anti-Pgp3 antibody seroprevalence was 18% in 1-9 year olds, increased sharply around the age of sexual debut, and reached 69% in those over 25 years. Anti-Pgp3 seropositivity did not increase significantly between the ages of 1-9 years, and was not associated with scarring in children (p=0.472) or TF in children (p=0.581).\n\nConclusionsSigns of trachoma are common in the Solomon Islands but occur frequently in individuals who have no serological evidence of prior ocular infection with Ct. WHO recommendations for directing MDA provision based on signs alone may not be suitable in this context.

epidemiology↗