Identification of Protein-RNA Interactions in Mouse Testis Tissue Using fRIP

During development, cells must quickly switch from one cell state to the next to execute precise and timely differentiation. One method to ensure fast transitions in cell states is by controlling gene expression at the post-transcriptional level through action of RNA-binding proteins on mRNAs. The ability to accurately identify the RNA targets of RNA-binding proteins at specific stages is key to understanding the functional role of RNA-binding proteins during development. Here we describe an adapted formaldehyde RNA immunoprecipitation (fRIP) protocol to identify the in vivo RNA targets of a cytoplasmic RNA-binding protein, YTHDC2, from testis, during the first wave of spermatogenesis, at the stage when germ cells are shutting off the proliferative program and initiating terminal differentiation ( Bailey et al., 2017 ). This protocol enables quick and efficient identification of endogenous RNAs bound to an RNA-binding protein, and facilitates the monitoring of stage-specific changes during development.