ORCID Profile
0000-0003-3989-8893
Current Organisations
Newcastle University
,
University of Oxford
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Publisher: Oxford University Press (OUP)
Date: 22-03-2012
DOI: 10.1002/STEM.1037
Abstract: Recent successes in the stem cell field have identified some of the key chemical and biological cues which drive photoreceptor derivation from human embryonic stem cells (hESC) and human induced pluripotent stem cells (hiPSC) however, the efficiency of this process is variable. We have designed a three-step photoreceptor differentiation protocol combining previously published methods that direct the differentiation of hESC and hiPSC toward a retinal lineage, which we further modified with additional supplements selected on the basis of reports from the eye field and retinal development. We report that hESC and hiPSC differentiating under our regimen over a 60 day period sequentially acquire markers associated with neural, retinal field, retinal pigmented epithelium and photoreceptor cells, including mature photoreceptor markers OPN1SW and RHODOPSIN with a higher efficiency than previously reported. In addition, we report the ability of hESC and hiPSC cultures to generate neural and retinal phenotypes under minimal culture conditions, which may be linked to their ability to endogenously upregulate the expression of a range of factors important for retinal cell type specification. However, cultures that were differentiated with full supplementation under our photoreceptor-induction regimen achieve this within a significantly shorter time frame and show a substantial increase in the expression of photoreceptor-specific markers in comparison to cultures differentiated under minimal conditions. Interestingly, cultures supplemented only with B27 and/or N2 displayed comparable differentiation efficiency to those under full supplementation, indicating a key role for B27 and N2 during the differentiation process. Furthermore, our data highlight an important role for Dkk1 and Noggin in enhancing the differentiation of hESC and hiPSC toward retinal progenitor cells and photoreceptor precursors during the early stages of differentiation, while suggesting that further maturation of these cells into photoreceptors may not require additional factors and can ensue under minimal culture conditions. Disclosure of potential conflicts of interest is found at the end of this article.
Publisher: Elsevier BV
Date: 05-2021
Publisher: Oxford University Press (OUP)
Date: 03-2006
DOI: 10.1093/JXB/ERJ134
Abstract: Proteomic analysis of any biological system by two-dimensional gel electrophoresis (2-DE) requires high resolution and high reproducibility. The results presented here demonstrate the reproducible and accurate separation of rice (Oryza sativa L.) proteins using improved procedures for high resolution 2-DE, which were adapted for the separation of rice lamina proteins. Validation of this system was achieved by measuring the effects of s le preparation and biological variation on the coefficient of variation (CV) for replicate spots. The majority of experimental variation was shown to be introduced by the 2-DE technique (CV 0.26). Analysis of biological variation indicated that approximately 93-95% of spots were within a CV of 0.7. This provided a threshold value from which valid differences in expression between experimental groups could be screened. This system was then utilized for the proteomic analysis of short- and long-term salt-stress-responsive proteins in the rice leaf lamina. Analysis resulted in the separation of approximately 2500 protein species of which 32 were observed to be significantly regulated by salinity so far 11 of these proteins have been identified by tandem mass spectrometry. An increase in eight proteins, including RuBisCO activase and ferritin, occurred by 24 h of exposure to sodium chloride (50 mM) and continued to increase during the following 6 d. Only one protein, a putative phosphoglycerate kinase, was found to increase in expression within 24 h and did not increase over a longer period of exposure to salt. There were also proteins that showed no change 24 h after exposure to salt, but had increased (superoxide dismutase) or decreased (S-adenosyl-L-methionine synthetase) after 7 d salt treatment.
Publisher: Elsevier BV
Date: 11-2022
Publisher: Springer Science and Business Media LLC
Date: 17-08-2018
Publisher: National Institute for Health and Care Research
Date: 04-2021
DOI: 10.3310/EME08050
Abstract: Tuberculosis (TB) is a devastating disease for which new diagnostic tests are desperately needed. To validate promising new technologies [namely whole-blood transcriptomics, proteomics, flow cytometry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR)] and existing signatures for the detection of active TB in s les obtained from in iduals with suspected active TB. Four substudies, each of which used s les from the biobank collected as part of the interferon gamma release assay (IGRA) in the Diagnostic Evaluation of Active TB study, which was a prospective cohort of patients recruited with suspected TB. Secondary care. Adults aged ≥ 16 years presenting as inpatients or outpatients at 12 NHS hospital trusts in London, Slough, Oxford, Leicester and Birmingham, with suspected active TB. New tests using genome-wide gene expression microarray (transcriptomics), surface-enhanced laser desorption ionisation time-of-flight mass spectrometry/liquid chromatography–mass spectrometry (proteomics), flow cytometry or qRT-PCR. Area under the curve (AUC), sensitivity and specificity were calculated to determine diagnostic accuracy. Positive and negative predictive values were calculated in some cases. A decision tree model was developed to calculate the incremental costs and quality-adjusted life-years of changing from current practice to using the novels tests. The project, and four substudies that assessed the previously published signatures, measured each of the new technologies and performed a health economic analysis in which the best-performing tests were evaluated for cost-effectiveness. The diagnostic accuracy of the transcriptomic tests ranged from an AUC of 0.81 to 0.84 for detecting all TB in our cohort. The performance for detecting culture-confirmed TB or pulmonary TB was better than for highly probable TB or extrapulmonary tuberculosis (EPTB), but was not high enough to be clinically useful. None of the previously described serum proteomic signatures for active TB provided good diagnostic accuracy, nor did the candidate rule-out tests. Four out of six previously described cellular immune signatures provided a reasonable level of diagnostic accuracy (AUC = 0.78–0.92) for discriminating all TB from those with other disease and latent TB infection in human immunodeficiency virus-negative TB suspects. Two of these assays may be useful in the IGRA-positive population and can provide high positive predictive value. None of the new tests for TB can be considered cost-effective. The diagnostic performance of new tests among the HIV-positive population was either underpowered or not sufficiently achieved in each substudy. Overall, the diagnostic performance of all previously identified ‘signatures’ of TB was lower than previously reported. This probably reflects the nature of the cohort we used, which includes the harder to diagnose groups, such as culture-unconfirmed TB or EPTB, which were under-represented in previous cohorts. We are yet to achieve our secondary objective of deriving novel signatures of TB using our data sets. This was beyond the scope of this report. We recommend that future studies using these technologies target specific subtypes of TB, specifically those groups for which new diagnostic tests are required. This project was funded by the Efficacy and Mechanism Evaluation (EME) programme, a MRC and NIHR partnership.
Publisher: American Association for Cancer Research (AACR)
Date: 07-2014
DOI: 10.1158/1535-7163.MCT-13-0938
Abstract: Activating mutations in the MAPK pathway are prevalent drivers of several cancers. The chief consequence of these mutations is a hyperactive ERK1/2 MAPK able to promote cell proliferation, producing a critical hallmark of metastatic disease. The biochemistry of the ERK pathway is well characterized however, how the pathway achieves different outcomes in the face of genetic aberrations of cancer and subsequent treatment with chemical inhibitors is not clear. To investigate this, we used mass spectrometry to complete a global phosphoproteomic analysis of a BRAFV600E thyroid cancer cell line (SW1736) after treatment with the mutation-selective inhibitor vemurafenib (PLX4032) and MEK1/2 inhibitor selumetinib (AZD6244). We identified thousands of phosphorylation events orchestrated in BRAFV600E cells and performed kinase landscape analysis to identify putative kinases regulated in response to MAPK blockade. The abundance of phosphopeptides containing consensus motifs for acidophilic kinases increased after short-term inhibition with these compounds. We showed that coinhibition of the pleiotropic acidophilic protein kinase CK2 (CK2) and BRAFV600E synergistically reduced proliferation in patient-derived melanomas and thyroid cancer cells harboring the BRAF lesion. We investigated this mechanism and show a role for CK2 in controlling AKT activation that was not reliant on changes to PTEN or PDK1 phosphorylation. These findings highlight a role for CK2 blockade in potentiating the antiproliferative effects of BRAF and MEK inhibition in BRAF cancers. Mol Cancer Ther 13(7) 1894–906. ©2014 AACR.
Publisher: Frontiers Media SA
Date: 15-05-2015
Publisher: Cambridge University Press (CUP)
Date: 22-05-2014
DOI: 10.1017/S095252381400008X
Abstract: Blindness represents an increasing global problem with significant social and economic impact upon affected patients and society as a whole. In Europe, approximately one in 30 in iduals experience sight loss and 75% of those are unemployed, a social burden which is very likely to increase as the population of Europe ages. Diseases affecting the retina account for approximately 26% of blindness globally and 70% of blindness in the United Kingdom. To date, there are no treatments to restore lost retinal cells and improve visual function, highlighting an urgent need for new therapeutic approaches. A pioneering breakthrough has demonstrated the ability to generate synthetic retina from pluripotent stem cells under laboratory conditions, a finding with immense relevance for basic research, in vitro disease modeling, drug discovery, and cell replacement therapies. This review summarizes the current achievements in pluripotent stem cell differentiation toward retinal cells and highlights the steps that need to be completed in order to generate human synthetic retinae with high efficiency and reproducibly from patient-specific pluripotent stem cells.
Publisher: Oxford University Press (OUP)
Date: 13-05-2015
DOI: 10.1002/STEM.2023
Abstract: We and others have previously demonstrated that retinal cells can be derived from human embryonic stem cells (hESCs) and induced pluripotent stem cells under defined culture conditions. While both cell types can give rise to retinal derivatives in the absence of inductive cues, this requires extended culture periods and gives lower overall yield. Further understanding of this innate differentiation ability, the identification of key factors that drive the differentiation process, and the development of clinically compatible culture conditions to reproducibly generate functional neural retina is an important goal for clinical cell based therapies. We now report that insulin-like growth factor 1 (IGF-1) can orchestrate the formation of three-dimensional ocular-like structures from hESCs which, in addition to retinal pigmented epithelium and neural retina, also contain primitive lens and corneal-like structures. Inhibition of IGF-1 receptor signaling significantly reduces the formation of optic vesicle and optic cups, while exogenous IGF-1 treatment enhances the formation of correctly laminated retinal tissue composed of multiple retinal phenotypes that is reminiscent of the developing vertebrate retina. Most importantly, hESC-derived photoreceptors exhibit advanced maturation features such as the presence of primitive rod- and cone-like photoreceptor inner and outer segments and phototransduction-related functional responses as early as 6.5 weeks of differentiation, making these derivatives promising candidates for cell replacement studies and in vitro disease modeling. Stem Cells 2015 :2416–2430 Video Highlight: youtu.be/krihQeGS_zs
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Robert Parker.