Deterministic Whole-Genome Amplification of Single Cells

Simultaneous Isolation and Amplification of mRNA and Genomic DNA of a Single Cell

Many biological or pathological processes are driven by cells difficult to identify or isolate, i.e., rare cells. Very often, these cells have elusive biology. Therefore, their detailed characterization is of utmost importance. There are many approaches that allow analysis of few or even many targets within one class of biomacromolecules/analytes (e.g., DNA, RNA, proteins, etc.) in single cells. However, due to rarity of the cells of interest, there is a great need to comprehensively analyze multiple analytes within these cells, in other words to perform multi-omics analysis. In this chapter, I describe a method to isolate, separate, and amplify total mRNA and genomic DNA of a single cells, using whole transcriptome (WTA) and whole genome amplification (WGA). These WTA and WGA products enable simultaneous analysis of transcriptome and genome of a single cell using various downstream high-throughput approaches.

Target Cell Pre-enrichment and Whole Genome Amplification for Single Cell Downstream Characterization

Rare target cells can be isolated from a high background of non-target cells using antibodies specific for surface proteins of target cells. A recently developed method uses a medical wire functionalized with anti-epithelial cell adhesion molecule (EpCAM) antibodies for in vivo isolation of circulating tumor cells (CTCs)1. A patient-matched cohort in non-metastatic prostate cancer showed that the in vivo isolation technique resulted in a higher percentage of patients positive for CTCs as well as higher CTC counts as compared to the current gold standard in CTC enumeration. As cells cannot be recovered from current medical devices, a new functionalized wire (referred to as Device) was manufactured allowing capture and subsequent detachment of cells by enzymatic treatment. Cells are allowed to attach to the Device, visualized on a microscope and detached using enzymatic treatment. Recovered cells are cytocentrifuged onto membrane-coated slides and harvested individually by means of laser microdissection or micromanipulation. Single-cell samples are then subjected to single-cell whole genome amplification allowing multiple downstream analysis including screening and target-specific approaches. The procedure of isolation and recovery yields high quality DNA from single cells and does not impair subsequent whole genome amplification (WGA). A single cell's amplified DNA can be forwarded to screening and/or targeted analysis such as array comparative genome hybridization (array-CGH) or sequencing. The device allows ex vivo isolation from artificial rare cell samples (i.e. 500 target cells spiked into 5 mL of peripheral blood). Whereas detachment rates of cells are acceptable (50 - 90%), the recovery rate of detached cells onto slides spans a wide range dependent on the cell line used (<10 - >50%) and needs some further attention. This device is not cleared for the use in patients.