Project description:We used single cell RNA sequencing to investigate the diversity of ILCs, NKs, and T cells in the human tonsil and the impact of freeze-thawing on their expression profile
Project description:RNA-Seq is ubiquitous, but depending on the study, sub-optimal sample handling may be required, resulting in repeated freeze-thaw cycles. However, little is known about how each cycle impacts downstream analyses, due to a lack of study and known limitations in common RNA quality metrics, e.g., RIN, at quantifying RNA degradation following repeated freeze-thaws. Here we quantify the impact of repeated freeze-thaw on the reliability of downstream RNA-Seq analysis. To do so, we developed a method to estimate the relative noise between technical replicates independently of RIN. Using this approach we inferred the effect of both RIN and the number of freeze-thaw cycles on sample noise. We find that RIN is unable to fully account for the change in sample noise due to freeze-thaw cycles. Additionally, freeze-thaw is detrimental to sample quality and differential expression (DE) reproducibility, approaching zero after three cycles for poly(A)-enriched samples, wherein the inherent 3’ bias in read coverage is more exacerbated by freeze-thaw cycles, while ribosome-depleted samples are less affected by freeze-thaws. The use of poly(A)-enrichment for RNA sequencing is pervasive in library preparation of frozen tissue, and thus, it is important during experimental design and data analysis to consider the impact of repeated freeze-thaw cycles on reproducibility.
Project description:In this study, we assess technical differences between commonly used single-cell RNA-Sequencing (scRNA-Seq) methods. We perform scRNA-seq on a homogenous population of mouse embryonic stem cells along with two kinds of control spike-in molecules to assess sensitivity and accuracy of these specific methods. In this dataset, we assess the RNA-degradation and decay rates by subjecting both spike-in molecules to range of repeated freezing and thawing (freeze-thaw) cycles. We manually add spike-in molecules across a 96-well plate (containing cells and reagents), perform Smart-Seq2 method manually and generate single-cell libraries using Nextera XT kit
Project description:Frozen dough baking is useful method in the modern bread-making industry. However, the fermentation activity of baker’s yeast dramatically decreased after thawing due to freeze injuries, because baker’s yeast cells contained in dough experience freeze injuries during freeze-thaw processes. Here, we performed genome-wide expression analysis to determine genetic response in baker’s yeasts under freeze-thaw condition using a DNA microarray analysis. Functional and clustering analyses in gene expression reveal that genes could be characterized by the term of freeze-thaw stress. Under short-term freeze stress (freeze treatment for 3 day), genes involved in ribosomal protein were up-regulated. Under long-term freeze stress (freeze treatment for longer than 7 day), genes involved in energy synthesis were up-regulated. In each phase, genes involved in protein damage, several stresses and trehalose and glycogen metabolism were also up-regulated. Through these freeze stress, yeast cells may improve reduced efficiency of translation and enhanced cell protection mechanism to survive under freeze stress condition. These regulations of these genes would be controlled by the cAMP-protein kinase A pathway. Keywords: baker’s yeast, freeze-thaw stress, gene expression, freezing period
2009-07-31 | GSE8673 | GEO
Project description:Co-occurrence networks for bacteria and fungi
Project description:Frozen dough baking is useful method in the modern bread-making industry. However, the fermentation activity of bakerâs yeast dramatically decreased after thawing due to freeze injuries, because bakerâs yeast cells contained in dough experience freeze injuries during freeze-thaw processes. Here, we performed genome-wide expression analysis to determine genetic response in bakerâs yeasts under freeze-thaw condition using a DNA microarray analysis. Functional and clustering analyses in gene expression reveal that genes could be characterized by the term of freeze-thaw stress. Under short-term freeze stress (freeze treatment for 3 day), genes involved in ribosomal protein were up-regulated. Under long-term freeze stress (freeze treatment for longer than 7 day), genes involved in energy synthesis were up-regulated. In each phase, genes involved in protein damage, several stresses and trehalose and glycogen metabolism were also up-regulated. Through these freeze stress, yeast cells may improve reduced efficiency of translation and enhanced cell protection mechanism to survive under freeze stress condition. These regulations of these genes would be controlled by the cAMP-protein kinase A pathway. Experiment Overall Design: All experiments were done in duplicate from two independent samples.
Project description:Mesenchymal stromal cells (MSC) are increasingly used as an investigative therapeutic product for immune disorders and degenerative disease. Typically, MSC are isolated from human tissue, expanded in culture and cryopreserved until usage. The safety and efficacy of MSC therapy will depend on the phenotypical and functional characteristics of MSC. The freeze-thawing procedure may change these characteristics. Furthermore, the microenvironment that the cells encounter after administration may impact the properties of MSC. It has been demonstrated that the large majority of MSC localize to the lungs after intravenous infusion, making this the site to study the effects of the in vivo milieu on administered MSC. In the present study we investigated the effect of freeze-thawing and of the mouse lung microenvironment on human adipose tissue-derived MSC. The effect of freeze-thawing on the whole genome expression profile of MSC was small and did not exceed inter-donor differences. There were no major changes in the expression of hemostatic regulators on transcriptional level, but significantly increased expression of procoagulant tissue factor on the surface of thawed adipose MSC, correlating with increased procoagulant activity of thawed cells after blood exposure in vitro and after infusion to mice. Exposure for 2h to the lung microenvironment had a major effect on MSC gene expression and affected several immunological and metabolic pathways. This indicates that MSC undergo functional changes shortly after infusion and this may influence the efficacy of MSC to modulate inflammatory responses. The results of this study demonstrate that MSC rapidly alter in response to the local milieu and that disease specific conditions may shape MSC after administration.
2016-02-01 | GSE76081 | GEO
Project description:Bacteria community responds to freeze-thaw cycles
Project description:In frozen dough baking technology, baker’s yeast Saccharomyces cerevisiae encounter freeze-thaw injury. After thawing, dramatically decrease in cell viability and fermentation activity is caused by freeze-thaw injury. The freezing period is critical factor in freeze-thaw injury, thus we focused and investigated time-dependent gene expression profiles in recovery process from freeze injury. First, changes in gene expression profiles in S. cerevisiae in recovery process from freeze-thaw injury were analyzed using a DNA microarray. The results showed the genes which were involved in homeostasis of metal ions were time-dependent up-regulated 2-fold or more in a series. Then we examined whether these genes were related to tolerance in freeze-thaw injury by using deletion strain. The results showed that deletion of MAC1, CTR1, and PCA1 genes which involved in copper ion transport exhibited freeze-thaw sensitivity in compared with wild type. These genes are involved in copper ion uptake to a cell under a copper deficiency condition or in copper ion homeostasis, suggesting that it may be related between freeze-thaw injury and copper ion transport. To determine the effect of supplementation of copper ion on cells after freeze-thaw treatment, cell viability, intracellular superoxide dismutase (SOD) activity, and intracellular levels of reactive oxygen species (ROS) were examined by various copper ion condition medium. The results showed that intracellular SOD activity was increased and intracellular levels of ROS were decreased by supplementation of copper ion, but there was no significant difference in cell viability. These results of the present study may suggest that copper ion concentration in yeast cell after freeze-thaw treatment is important to recovery from freeze-thaw injury due to redox control of intracellular levels of ROS, but copper ion did not directly affect cell viability.