With the progress in our understanding of germ cell development, there is an emerging need to investigate the mechanisms of mRNA translation functioning in these cells. Indeed, posttranscriptional regulations of gene expression drive the most important transitions of the germ cell life cycle. Here we describe a strategy to measure mRNA translation in the oocyte, taking advantage of an approach originally developed to identify the transcriptome of a subgroup of cells in a complex cell mixture. This technique takes advantage of the "RiboTag" approach to express an HA-tag on the large ribosomal subunit of the ribosomes in the oocyte. Immunoprecipitation of the extracts followed by qPCR or RNAseq is used to identify mRNAs actively translated.

Meiotic progression requires exquisitely coordinated translation of maternal messenger (m)RNA that has accumulated during oocyte growth. A major regulator of this program is the cytoplasmic polyadenylation element binding protein 1 (CPEB1). However, the temporal pattern of translation at different meiotic stages indicates the function of additional RNA binding proteins (RBPs). Here, we report that deleted in azoospermia-like (DAZL) cooperates with CPEB1 to regulate maternal mRNA translation. Using a strategy that monitors ribosome loading onto endogenous mRNAs and a prototypic translation target, we show that ribosome loading is induced in a DAZL- and CPEB1-dependent manner, as the oocyte reenters meiosis. Depletion of the two RBPs from oocytes and mutagenesis of the 3' untranslated regions (UTRs) demonstrate that both RBPs interact with the Tex19.1 3' UTR and cooperate in translation activation of this mRNA. We observed a synergism between DAZL and cytoplasmic polyadenylation elements (CPEs) in the translation pattern of maternal mRNAs when using a genome-wide analysis. Mechanistically, the number of DAZL proteins loaded onto the mRNA and the characteristics of the CPE might define the degree of cooperation between the two RBPs in activating translation and meiotic progression.