Visualizing the structure of RNA-seq expression data using grade of membership models.
Grade of membership models, also known as "admixture models", "topic models" or "Latent Dirichlet Allocation", are a generalization of cluster models that allow each sample to have membership in multiple clusters. These models are widely used in population genetics to model admixed individuals who have ancestry from multiple "populations", and in natural language processing to model documents having words from multiple "topics". Here we illustrate the potential for these models to cluster samples of RNA-seq gene expression data, measured on either bulk samples or single cells. We also provide methods to help interpret the clusters, by identifying genes that are distinctively expressed in each cluster. By applying these methods to several example RNA-seq applications we demonstrate their utility in identifying and summarizing structure and heterogeneity. Applied to data from the GTEx project on 53 human tissues, the approach highlights similarities among biologically-related tissues and identifies distinctively-expressed genes that recapitulate known biology. Applied to single-cell expression data from mouse preimplantation embryos, the approach highlights both discrete and continuous variation through early embryonic development stages, and highlights genes involved in a variety of relevant processes-from germ cell development, through compaction and morula formation, to the formation of inner cell mass and trophoblast at the blastocyst stage. The methods are implemented in the Bioconductor package CountClust.
Department of Statistics, University of Chicago, Chicago, Illinois, United States of America.
Kushal K
http://orcid.org/0000-0002-3520-2345
KK
Dey
Department of Human Genetics, University of Chicago, Chicago, Illinois, United States of America.
Chiaowen Joyce
http://orcid.org/0000-0001-8961-7522
CJ
Hsiao
Department of Statistics, University of Chicago, Chicago, Illinois, United States of America.|Department of Human Genetics, University of Chicago, Chicago, Illinois, United States of America.
Matthew
M
Stephens
D000465:Algorithms; D000818:Animals; D001755:Blastocyst / Q000378:metabolism; D001921:Brain / Q000378:metabolism; D016000:Cluster Analysis; D019295:Computational Biology / Q000379:methods*; D020869:Gene Expression Profiling / Q000379:methods*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D051379:Mice; D012313:RNA / Q000235:genetics* / Q000378:metabolism; D015203:Reproducibility of Results; D017423:Sequence Analysis, RNA; D059467:Transcriptome / Q000235:genetics
D012313:RNA