The widespread influence of ZSWIM8 on microRNAs during mouse embryonic development

Abstract MicroRNAs (miRNAs) pair to sites in mRNAs to direct the degradation of these RNA transcripts. Conversely, certain RNA transcripts can direct the degradation of particular miRNAs. This target-directed miRNA degradation (TDMD) requires the ZSWIM8 E3 ubiquitin ligase. Here, we report the function of ZSWIM8 in the mouse embryo. Zswim8 −/− embryos were smaller than their littermates and died near the time of birth. This highly penetrant perinatal lethality was apparently caused by a lung sacculation defect attributed to failed maturation of alveolar epithelial cells. Some mutant individuals also had heart ventricular septal defects. These developmental abnormalities were accompanied by aberrant accumulation of >50 miRNAs observed across 12 tissues, which often led to enhanced repression of their mRNA targets. These ZSWIM8-sensitive miRNAs were preferentially produced from genomic miRNA clusters, and in some cases, ZSWIM8 caused a switch in the dominant strand that accumulated from a miRNA hairpin—observations suggesting that TDMD provides a mechanism to uncouple co-produced miRNAs from each other. Overall, our findings indicate that the regulatory influence of TDMD in mammalian biology is widespread and posit the existence of many yet-unidentified transcripts that trigger miRNA degradation.