3,235 research outputs found
Joint Modeling and Registration of Cell Populations in Cohorts of High-Dimensional Flow Cytometric Data
In systems biomedicine, an experimenter encounters different potential
sources of variation in data such as individual samples, multiple experimental
conditions, and multi-variable network-level responses. In multiparametric
cytometry, which is often used for analyzing patient samples, such issues are
critical. While computational methods can identify cell populations in
individual samples, without the ability to automatically match them across
samples, it is difficult to compare and characterize the populations in typical
experiments, such as those responding to various stimulations or distinctive of
particular patients or time-points, especially when there are many samples.
Joint Clustering and Matching (JCM) is a multi-level framework for simultaneous
modeling and registration of populations across a cohort. JCM models every
population with a robust multivariate probability distribution. Simultaneously,
JCM fits a random-effects model to construct an overall batch template -- used
for registering populations across samples, and classifying new samples. By
tackling systems-level variation, JCM supports practical biomedical
applications involving large cohorts
Merging Mixture Components for Cell Population Identification in Flow Cytometry
We present a framework for the identification of cell subpopulations in
flow cytometry data based on merging mixture components using the
flowClust methodology. We show that the cluster merging algorithm
under our framework improves model fit and provides a better
estimate of the number of distinct cell subpopulations than
either Gaussian mixture models or flowClust, especially for
complicated flow cytometry data distributions. Our framework
allows the automated selection of the number of distinct cell
subpopulations and we are able to identify cases where the
algorithm fails, thus making it suitable for application in a high
throughput FCM analysis pipeline. Furthermore, we demonstrate a
method for summarizing complex merged cell subpopulations in a
simple manner that integrates with the existing flowClust
framework and enables downstream data analysis. We demonstrate the
performance of our framework on simulated and real FCM data. The
software is available in the flowMerge package through the
Bioconductor project
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Identifying and quantifying heterogeneity in high content analysis: Application of heterogeneity indices to drug discovery
One of the greatest challenges in biomedical research, drug discovery and diagnostics is understanding how seemingly identical cells can respond differently to perturbagens including drugs for disease treatment. Although heterogeneity has become an accepted characteristic of a population of cells, in drug discovery it is not routinely evaluated or reported. The standard practice for cell-based, high content assays has been to assume a normal distribution and to report a well-to-well average value with a standard deviation. To address this important issue we sought to define a method that could be readily implemented to identify, quantify and characterize heterogeneity in cellular and small organism assays to guide decisions during drug discovery and experimental cell/tissue profiling. Our study revealed that heterogeneity can be effectively identified and quantified with three indices that indicate diversity, non-normality and percent outliers. The indices were evaluated using the induction and inhibition of STAT3 activation in five cell lines where the systems response including sample preparation and instrument performance were well characterized and controlled. These heterogeneity indices provide a standardized method that can easily be integrated into small and large scale screening or profiling projects to guide interpretation of the biology, as well as the development of therapeutics and diagnostics. Understanding the heterogeneity in the response to perturbagens will become a critical factor in designing strategies for the development of therapeutics including targeted polypharmacology. © 2014 Gough et al
MCA: Multiresolution Correlation Analysis, a graphical tool for subpopulation identification in single-cell gene expression data
Background: Biological data often originate from samples containing mixtures
of subpopulations, corresponding e.g. to distinct cellular phenotypes. However,
identification of distinct subpopulations may be difficult if biological
measurements yield distributions that are not easily separable. Results: We
present Multiresolution Correlation Analysis (MCA), a method for visually
identifying subpopulations based on the local pairwise correlation between
covariates, without needing to define an a priori interaction scale. We
demonstrate that MCA facilitates the identification of differentially regulated
subpopulations in simulated data from a small gene regulatory network, followed
by application to previously published single-cell qPCR data from mouse
embryonic stem cells. We show that MCA recovers previously identified
subpopulations, provides additional insight into the underlying correlation
structure, reveals potentially spurious compartmentalizations, and provides
insight into novel subpopulations. Conclusions: MCA is a useful method for the
identification of subpopulations in low-dimensional expression data, as
emerging from qPCR or FACS measurements. With MCA it is possible to investigate
the robustness of covariate correlations with respect subpopulations,
graphically identify outliers, and identify factors contributing to
differential regulation between pairs of covariates. MCA thus provides a
framework for investigation of expression correlations for genes of interests
and biological hypothesis generation.Comment: BioVis 2014 conferenc
Different approaches for assessing sperm function
Different approaches can be used to assess sperm function in different conditions, i.e. sperm storage, freezing-thawing or activation by induction of capacitation and acrosome reaction. In this review we will focus on the assays routinely performed in our laboratories, giving a literature support to critically analyse different approaches. In fact, researchers usually tend to look for the \u201cone shot\u201c parameter that could explain itself a specific process; it is our conviction that a multiparametric approach is still more valid, as some changes in sperm function are very complex and could be explained only by operating in different ways. Sperm motility, the most evident sperm characteristic, should be assessed by computer-aided sperm analysers that permit an objective evaluation of the motility and its kinematic parameters. Commercial and open source instruments are available and could be profitably used together with specific statistical approaches. The use of microscopy, and particularly fluorescent microscopy, could be a very useful tool to assess different parameters in sperm cells both by fluorophores that give indication of a determined function, and by immunolocalization of proteins, that permits the discover of new features or to explain particular sperm functions. The same substrates could be used also in flow cytometry: the difference is that it permits to study wider sperm populations (and their sub-population distribution). Flow cytometry is undergoing a very wide use in spermatology and technical and experimental rigor is needed to obtain reliable results. Metabolic assessment of sperm features, particularly energetic supply, ATP formation and other enzyme activities, could represent a very important challenge to acquire new information and complete/integrate those derived from other techniques. Finally, functional assays such as oocyte binding and in vitro fertilization, represent a very strong tool to assess sperm function in vitro, as they could evidence the functional intactness of some pathways
Testing for differential abundance in mass cytometry data.
When comparing biological conditions using mass cytometry data, a key challenge is to identify cellular populations that change in abundance. Here, we present a computational strategy for detecting 'differentially abundant' populations by assigning cells to hyperspheres, testing for significant differences between conditions and controlling the spatial false discovery rate. Our method (http://bioconductor.org/packages/cydar) outperforms other approaches in simulations and finds novel patterns of differential abundance in real data.This work was supported by Cancer Research UK (core funding to J.C.M., award no. A17197), the University of Cambridge and Hutchison Whampoa Limited. J.C.M. was also supported by core funding from EMBL
Microglial subtypes: diversity within the microglial community
Microglia are brain-resident macrophages forming the first active immune barrier in the central nervous system. They fulfill multiple functions across development and adulthood and under disease conditions. Current understanding revolves around microglia acquiring distinct phenotypes upon exposure to extrinsic cues in their environment. However, emerging evidence suggests that microglia display differences in their functions that are not exclusively driven by their milieu, rather by the unique properties these cells possess. This microglial intrinsic heterogeneity has been largely overlooked, favoring the prevailing view that microglia are a single-cell type endowed with spectacular plasticity, allowing them to acquire multiple phenotypes and thereby fulfill their numerous functions in health and disease. Here, we review the evidence that microglia might form a community of cells in which each member (or "subtype") displays intrinsic properties and performs unique functions. Distinctive features and functional implications of several microglial subtypes are considered, across contexts of health and disease. Finally, we suggest that microglial subtype categorization shall be based on function and we propose ways for studying them. Hence, we advocate that plasticity (reaction states) and diversity (subtypes) should both be considered when studying the multitasking microglia.España, Ministerio de Ciencia, Innovación y Universidades FEDER y UE RTI2018-098645-B-10
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