Functional study of m6A methyltransferase METTL16 in drosophila development

To further determine the function of dMETTL16, we used the CRISPR/Cas9 system to construct dMETTL16 mutations and discovered that mutants are semilethal at the larval stage while surviving adults are female sterile. More interestingly, a 50% reduction of U6 gene dosage leads to complete lethality of dMETTL16 mutants at the larval stage suggesting that loss of U6 function is one of the primary defects in the mutants. Using a novel antibody-based in vitro methylation assay, we proved that U6 is a substrate of dMETTL16.

To determine whether the phenotypes depend on m6A methylase activity, we constructed point mutations of the active site of dMETTL16, and discovered that ovarian development was restored while maternal lethality ensures. These results suggest that dMETTL16 has important functions that are independent of its methyltransferase activity. Our study establishes Drosophila as a genetically tractable model for the study of dMETTL16’s function and can be explored to uncover additional dMETTL16 m6A targets.