mRNA 3′ uridylation and poly(A) tail length sculpt the mammalian maternal transcriptome

A fundamental principle in biology is that the program for early development is established during oogenesis in the form of the maternal transcriptome1,2. How the maternal transcriptome acquires the appropriate content and dosage of transcripts is not fully understood. Here we show that TUT4/7-mediated mRNA 3′ terminal uridylation sculpts the mouse maternal transcriptome by eliminating transcripts during oocyte growth. TUT4/7-mediated uridylation is essential for both oocyte maturation and fertility. In comparison to somatic cells, the oocyte transcriptome displays shorter poly(A) tail length and a high relative proportion of terminal oligo-uridylation. TUT4/7 deletion leads to the accumulation of a cohort of transcripts with a high frequency of very short poly(A) tails and a loss of 3′ oligo-uridylation. In contrast, TUT4/7-deficiency does not alter gene expression in a variety of somatic cells. In summary, we show essential and specific functions for poly(A) tail length and 3′ terminal uridylation in sculpting a functional maternal transcriptome.