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

## TL;DR

This study shows that the DHX8 gene is crucial for larval development in silkworms, as its disruption causes severe growth defects and early death.

## Contribution

The study provides the first functional analysis of BmDHX8 in silkworms, linking RNA splicing to lipid and nutrient signaling during development.

## Key findings

- Disruption of BmDHX8 causes dwarfism and early death in silkworm larvae.
- Loss of BmDHX8 leads to RNA splicing errors and altered lipid and mTOR signaling.
- BmDHX8 knockout results in systemic developmental defects and metabolic dysregulation.

## Abstract

The spliceosome, an essential macromolecular complex in eukaryotic cells, catalyzes both constitutive and alternative splicing of intron-containing pre-mRNAs to generate mature transcripts for protein synthesis. As a key component of the spliceosome, DEAH-box helicase 8 (DHX8) is essential for efficient splicing of the pre-mRNA and thereby underpins multiple biological processes. In this study, we explored the role of Bombyx mori DHX8 (BmDHX8) in silkworm development through CRISPR-Cas9-mediated knockout. Disruption of BmDHX8 led to severe developmental defects, including dwarfism and early death of silkworm larvae. Further study suggested these phenotypes were associated with RNA splicing errors that altered lipid and nutrient signaling readouts. Our findings thus indicate that BmDHX8 functions as a regulator linking RNA processing to nutrient homeostasis during silkworm larval development.

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.