RESEARCH ARTICLE Functional Proteomics Screen Enables Enrichment of Distinct Cell Types from

The current world-wide epidemic of diabetes has prompted attempts to generate new sources of insulin-producing cells for cell replacement therapy. An inherent challenge in many of these strategies is the lack of cell-surface markers permitting isolation and charac-terization of specific cell types from differentiating stem cell populations. Here we introduce an iterative proteomics procedure allowing tag-free isolation of cell types based on their function. Our method detects and associates specific cell-surface markers with particular cell functionality by coupling cell capture on antibody arrays with immunofluorescent label-ing. Using this approach in an iterative manner, we discovered marker combinations capa-ble of enriching for discrete pancreatic cell subtypes from human islets of Langerhans: insulin-producing beta cells (CD9high/CD56+), glucagon-producing alpha cells (CD9-/CD56+) and trypsin-producing acinar cells (CD9- /CD56-). This strategy may assist future beta cell research and the development of diagnostic tools for diabetes. It can also be ap-plied more generally for function-based purification of desired cell types from other limited and heterogeneous biological samples