Updated project metadata. We have identified eukaryotic translation initiation factor 4E family member 1B (Eif4e1b) as a regulator of maternal RNA translation, whose maternal deletion leads to 2-cell arrest phenotype in mouse embryos. eIF4E1b protein binds mRNA selectively in oocytes and controls their translation in early embryos. eIF4E1b expresses specifically in mouse ovary and we have generated a knock-in mouse line in which HA tag is conjugated to the C terminus of eIF4E1b. We aim to identify eIF4E1b co-factors using mass spectrometry after anit-HA immunoprecipitation (IP) using mouse ovaries.