Project description:Introns are universally present in the nuclear genomes of eukaryotes. The budding yeast, an otherwise intron-poor species, preserves two sets of ribosomal protein (RP) genes differing primarily in their introns. Despite recent findings on the role of RP introns under stress and starvation, understanding the contribution of introns to ribosome regulation remains challenging. Here, combining isogrowth profiling with single-cell protein measurements, we found that introns can mediate inducible phenotypic heterogeneity conferring a clear fitness advantage. Osmotic stress leads to bimodal expression of the small ribosomal subunit protein Rps22B, mediated by an intron in the 5′ untranslated region of its transcript. The two resulting yeast subpopulations differ in their ability to cope with starvation. Low Rps22B protein levels resulted in prolonged survival under sustained starvation, while high Rps22B levels enabled cells to grow faster after transient starvation. Further, yeast growing at high sugar concentrations – similar to those in ripe grapes – exhibit bimodal Rps22B expression when approaching stationary phase. Differential intron-mediated regulation of RP genes thus provides a way to diversify the population when starvation looms in natural environments. Our findings reveal a new role for introns in inducing phenotypic heterogeneity in changing environments and suggest that duplicated RP genes in yeast contribute to resolving the evolutionary conflict between precise expression control and environmental responsiveness.
Project description:This is a non-linear mathematical model of cancer immunosurveillance that takes into account intratumoral phenotypic heterogeneity, such as differential expression of cell surface receptors and growth factors, according to cell-mediated immune responses. The model describes phenomena that have also been observed in vivo, such as tumor dormancy, cancer immunoediting, and a strong sensitivity to initial conditions.
Project description:Osteosarcoma is the most common bone sarcoma in children and young adults. While chemotherapy is universally delivered, benefit from chemotherapy is limited to roughly half of localized patients. Increasingly, intratumoral heterogeneity is being appreciated as a source of therapeutic resistance. In this study we developed and evaluated an in vitro model of osteosarcoma heterogeneity, characterizing phenotype (growth in varying environments, sensitivity to chemotherapy) and genotype. We present the genotypic and phenotypic characterization of an osteosarcoma cell line panel with a focus on coculture of the most phenotypically divergent cell lines, 143B and SAOS2. The extent of phenotypic heterogeneity can be altered with relatively modest environmental (pH, glutamine) or chemical perturbations. We demonstrate that in nutrient rich in vitro culture conditions 143B outcompetes SAOS2, but with selection pressure from nutrient variations or conventional chemotherapy, SAOS2 growth can be favored in spheroids. Importantly, perturbations that affect the faster growing cell line have only a modest effect on final spheroid size when the simplest heterogeneity state (a two-cell line coculture) is evaluated, and thus the only evaluated therapies to eliminate the spheroids were by switching therapies from a first strike to a second strike. This extensively characterized, widely available system can be modeled and scaled to allow for improved strategies to anticipate resistance in osteosarcoma due to phenotypic heterogeneity.
Project description:Quantification of within patient Staphylococcus aureus phenotypic heterogeneity as a proxy for presence of persisters across clinical presentations
Project description:Background: Oral squamous cell carcinoma (OSCC) is a major world health problem with over 400,000 new cases diagnosed annually. Despite advances in surgery and chemo-radiotherapy, the 5 year survival has remained roughly constant at approximately 50% for several decades. The disease is characterized by both clinical and genetic heterogeneity, so elucidating the molecular basis of this heterogeneity would have significant clinical implications. It is well recognized that OSCCs from Asia that are associated with betel quid chewing are phenotypically distinct from those from the West that are predominantly caused by smoking/drinking, but the genetic basis of these differences are largely unknown. The aim of this study is to examine the most related genetic factors, carcinogenic related pathways, and molecular processes that might be responsible for the phenotypic heterogeneity of OSCC between UK and Sri Lankan population groups. Methods: We have compared the gene expression profiles of OSCCs and normal oral mucosal tissues from both Sri Lankan and UK individuals using Affymetrix gene expression arrays. Results: The gene expression profiles of UK and Sri Lankan OSCC are similar in many respects to other oral cancer expression profiles reported in the literature and were mainly similar to each other. However, genes involved in tumor invasion, metastasis and recurrence were more obviously associated with UK tumors as opposed to those from Sri Lanka. Interestingly, Ingenuity Pathway Analysis (IPA) revealed a highly activated cell-mediated immune response in both Sri Lankan normal and tumor samples relative to UK cohorts, which may, in part, explain the less aggressive behavior of these betel quid-induced OSCCs. Conclusion: The development of OSCCs in both UK and Sri Lankan populations appears largely mediated by similar biological pathways despite the differences related to race, ethnicity, lifestyle, and/or exposure to environmental carcinogens. However, IPA revealed a highly activated M-bM-^@M-^\Cell-mediated Immune ResponseM-bM-^@M-^] in Sri Lankan normal and tumor samples relative to UK cohorts. It seems likely, therefore, that any future attempts to personalize treatment for OSCC patients will need to be different in Western and Asian countries to reflect differences in gene expression and the immune status of the patients. All biopsy specimens of OSCC and normal oral mucosa were harvested with appropriate ethical approval and informed consent of individual patients (LREC 0769). Identical protocols for tissue collection and processing were used in both countries. OSCC samples were obtained from sequential incident cases treated by a single consultant surgeon from 2001 to 2004 at University Hospital of Birmingham, NHS Foundation Trust, Birmingham, UK, and Kandy General Hospital, Kandy, Sri Lanka. A total of 21 UK and 27 Sri Lankan samples yielded RNA of sufficient quality and quantity for microarray analysis. In addition, 8 normal oral mucosa specimens (five samples from UK & three samples from Sri Lankan population) were also profiled. All normal samples were from non-smokers, who did not chew betel quid and did not consume in excess of the national recommended weekly gender allowance of alcohol. Normal samples were taken from individuals with no history of cancer and had no first degree relatives with a history of cancer.