High-Throughput, Comprehensive Single-Cell Proteomic Analysis of Xenopus laevis Embryos at the 50-Cell Stage Using a Microplate- Based MICROFASP System

We report both the design of a high-throughput MICROFASP (a miniaturized filter aided sample preparation) system and its use for the comprehensive proteomic analysis of single blastomeres isolated from 50-cell stage Xenopus laevis embryos (similar to 200 ng of yolk-free protein/blastomere). A single run of the MICROFASP system was used to process 146 of these blastomeres in parallel. Three samples failed to generate signals presumably due to membrane clogging. Two cells were lost due to operator error. Of the surviving samples, 32 were analyzed using a Q Exactive HF mass spectrometer in survey experiments (data not included). The 109 remaining blastomeres were analyzed using a capillary LC-ESI-MS/MS system coupled to an Orbitrap Fusion Lumos mass spectrometer, which identified a total of 4189 protein groups and 40,998 unique peptides. On average, 3468 +/- 229 protein groups and 14,525 +/- 2437 unique peptides were identified from each blastomere, which is the highest throughput and deepest proteome coverage to date of single blastomeres at this stage of development. We also compared two dissociation buffers, Newport and calcium-magnesium-free (CMFM) buffers; the two buffers generated similar numbers of protein identifications (3615 total protein IDs from use of the Newport dissociation buffer and 3671 total protein IDs from use of the CMFM buffer).