DHX8 Plays a Critical Role in Larval Development in Lepidopteran Bombyx mori.

DHX8 encodes a DEAH-box RNA helicase, an ATP-dependent enzyme that plays essential roles in RNA metabolism, including pre-mRNA splicing, transcription, and mRNA decay. Although DHX8 dysfunction has been linked with developmental abnormalities and disease pathogenesis in multiple model organisms, its biological functions in Lepidoptera, particularly in the silkworm Bombyx mori, remain unknown. To investigate the developmental role of B. mori DHX8 (BmDHX8), we generated knockout mutants using CRISPR-Cas9 genome editing. Genome sequencing confirmed frameshift mutations in the BmDHX8 locus. BmDHX8 mutants exhibited severe developmental defects such as dramatically reduced body size and premature lethality of silkworm larvae. Molecular characterization suggested systemic dysregulation, as evidenced by decreased triglyceride accumulation, impaired mTOR signaling activity, and increased aberrant splicing events. Therefore, these results indicate that loss of BmDHX8 is associated with aberrant splicing and alterations in lipid homeostasis and mTOR signaling pathways, potentially contributing to developmental defects. Taken together, our study offers an initial functional knockout analysis of BmDHX8 in regulating larval development in silkworms.