Target-directed microRNA degradation broadly regulates microRNA expression and embryonic growth in mammals
MicroRNAs (miRNAs) are post-transcriptional regulators of gene expression that play critical roles in development and disease. Target-directed miRNA degradation (TDMD), a pathway in which miRNAs that bind to specialized targets with extensive complementarity are rapidly decayed, has emerged as a potent mechanism of controlling miRNA levels. Nevertheless, the biological role and scope of miRNA regulation by TDMD in mammals remains poorly understood. To address these questions, we generated mice with constitutional or conditional deletion of Zswim8, which encodes an essential TDMD factor. Loss of Zswim8 resulted in major developmental defects in heart and lung, growth restriction, and perinatal lethality. Small RNA sequencing of embryonic tissues revealed widespread miRNA regulation by TDMD. Deletion of two miRNAs, miR-322 and miR-503, rescued growth of Zswim8 null embryos, directly implicating the TDMD pathway as a key regulator of mammalian body size. These data reveal the broad landscape and developmental role of TDMD in mammals. Overall design: To investigate the landscape of target-directed microRNA degradation in mammals, we generated Zswim8 knockout mice using CRISPR/Cas9. We then performed small RNA sequencing on tissues from embryonic day 18.5 tissues. Tissues sequenced include brain, heart, kidney, liver, lung, intestines, skin, and stomach. Three biological replicates were used for both wildtype and Zswim8 knockout.