Download or read book Multiplex Single-cell RNA Sequencing for Chemical Genomics and Spatial Transcriptomics written by Sanjay R. Srivatsan and published by . This book was released on 2021 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Each of us begins life as a single fertilized cell. Following a seemingly predetermined set of cell divisions, the single cell morphs into a rough mass, then a hollowed tube, and finally becomes a recognizable neonatal form. How the information contained within a single cell si- multaneously specifies an organism’s anatomy, the construction of its organs, and the ability to cogitate on this very question, remains one of biology’s open questions. Although centuries of careful experiments devoted to characterizing development have revealed many important genes and mechanisms, the results of these experiments span different model organisms, developmental stages, cell populations and measurement modalities. Integrating this knowledge base into coher- ent representation requires a cellular scaffold that charts an organism’s development over the axes of time and space. Preliminary unified representations of developing organisms (e.g. C. Elegans, Zebrafish and Mouse) have been created by large-scale single cell RNA sequencing (scRNA-seq) efforts. These efforts have characterized the set of intermediates through which differentiating cells transit and have profiled the large number of cell types present in a developing organism. Although scRNA-seq data have proven powerful in cataloging cellular states, they lack crucial context: i) the experimental context afforded by the comparison of multiple conditions (e.g. wild-type vs. perturbation) and ii) a cell’s spatial context, a crucial factor driving its behavior. To address these knowledge gaps, over the course of my PhD I have developed two scRNA-seq technologies: 1) sci- Plex, a generalizable strategy to label cell populations and 2) sci-Space, a methodology to record acell’s spatial position in conjunction with its single cell transcriptome. (1) First I developed the sci-Plex protocol, an inexpensive and efficient method to label single cells through the chemical fixation of unmodified single stranded oligos to nuclei prior to scRNA- seq library preparation. To demonstrate proof-of-concept of the sci-Plex protocol, I performed a high-throughput, high-content drug screen at single cell resolution in 3 cancer cell lines; effectively conducting 4,500 independent scRNA-seq experiments at once. The resulting dataset enabled characterization of a drug’s potency, class, mechanism of action, and the heterogeneity of cellular responses induced upon drug treatment. For example, our scRNA-seq data showed that histone deacetylase inhibitors likely lead to cell death by trapping valuable acetyl molecules on chromatin. (2) Next, I extended the application of the sci-Plex protocol and developed the sci-Space method to capture spatial information from sectioned tissue. The fast and scalable sci-Space method uses patterned oligonucleotide barcodes in a regular array such that each spot contains a unique set of sequences. Then, to mark each nucleus’ coordinates on the grid, the barcodes are stamped onto a tissue section prior to disaggregation and library preparation. To showcase the power of sci-Space, I collected a dataset comprising over 120,000 cells originating from 14 sections of a single E14 mouse embryo. The resulting data uncovers the genes that drive the devel- oping organism’s body plan and reveals a widespread migration signature within neurons that form the developing brain. These data also provide a quantitative assessment of how cell state relates to spatial position within the developing embryo. Specifically, our estimates indicate that 25% of the variance in gene expression observed is attributable to spatial position. It is my hope that this technology will power the generation of a unified scaffold of development akin to the reference genome. I believe that such a unified representation will be instrumental in amassing data, accel- erating discovery and facilitating translation through the training of machine learning models of cellular state.