The Masc-PSI complex directly induces male-type doublesex splicing in silkworms

Area of Science:

• Genetics
• Molecular Biology
• Developmental Biology

Background:

• The WZ sex determination system is prevalent in various animals, notably lepidopteran insects.
• In silkworms (Bombyx mori), the Masculinizer (BmMasc) protein is crucial for male sex determination by initiating the production of the male-type Bombyx mori doublesex (BmdsxM).
• The precise molecular pathway linking BmMasc to BmdsxM production remains unelucidated.

Purpose of the Study:

• To investigate the molecular mechanism by which BmMasc mediates masculinization in Bombyx mori.
• To identify interacting partners of BmMasc involved in sex determination.
• To elucidate the role of Bombyx mori P-element somatic inhibitor (BmPSI) in BmMasc-dependent BmdsxM expression.

Main Methods:

• Co-immunoprecipitation to detect physical interactions between BmMasc and BmPSI.
• RNA interference (RNAi) via knockdown experiments to assess the necessity of BmPSI for BmMasc activity.
• RNA immunoprecipitation (RIP) to identify BmMasc-bound RNA targets.

Main Results:

• BmMasc physically interacts with the RNA-binding protein BmPSI.
• BmPSI is essential for the masculinizing function of BmMasc.
• The BmMasc-BmPSI complex binds to female-specific regions of Bmdsx pre-mRNA.
• This binding event induces exon skipping, leading to the production of BmdsxM.

Conclusions:

• The BmMasc-BmPSI protein complex plays a pivotal role in silkworm sex determination.
• This complex regulates Bmdsx alternative splicing by targeting specific pre-mRNA regions.
• The findings reveal a novel mechanism for sex determination in Bombyx mori, involving targeted pre-mRNA modification by a protein complex.