Characterization of cellular enzymatic activity through functional single cell analysis using DropMap

Assuming normal distribution within cell populations has long been status quo in cellular research. With the fast development of techniques, numerous examples of heterogeneites within isogenic cultures have been unveiled, demonstrating the need of single cell analysis. Currently there are many widely used techniques for this, such as single cell RNA-sequencing, FACS and CyTOF, allowing high-troughput single-cell genotyping and medium to high troughput single cell phenotyping based on intracellular and cell surface proteins, but not secreted proteins. In this master’s thesis project the DropMap technology was utilized to develop high-throughput enzymatic activity assays on a single-cell level, revealing the heterogeneous nature of enzyme secretion and activation, even within cell lines. Around 1500 cells were screened in each assay with the microfluidic technique, providing a precise picture of the cell population and its heterogeneity. Within each assay interesting findings were discovered, such as subpopulations in shape of expression patterns, size and activity levels that could not have been detected in bulk measurements. The importance of activity measurements opposed to only secretion measurements was shown and described. The DropMap technology proved its usefulness both in terms of debug possibilities and explanations but above all its resolution and detailed output, providing a reliable platform for development of highly detailed enzymatic assays on a single cell level.