DDX1 vesicles control calcium-dependent mitochondrial activity in mouse embryos.

Area of Science:

• Developmental Biology
• Cell Biology
• Molecular Genetics

Background:

• The DEAD box protein DDX1 is known for roles in RNA processing and DNA repair.
• DDX1 aggregates in the cytoplasm of early mouse embryos, and its absence causes developmental arrest.
• The precise function of DDX1 in early embryogenesis remains unclear.

Purpose of the Study:

• To elucidate the function of DDX1 in early mouse embryonic development.
• To characterize the novel DDX1-containing structures observed in early embryos.
• To investigate the role of these structures in calcium regulation and mitochondrial function.

Main Methods:

• Identification and characterization of DDX1-containing organelles using microscopy.
• Analysis of Ddx1 knockout mouse embryos to assess developmental phenotypes.
• Assessment of calcium distribution, mitochondrial membrane potential, and reactive oxygen species levels.
• RNA sequencing analysis of embryos with varying Ddx1 expression levels.

Main Results:

• A novel organelle, the Membrane Associated RNA-containing Vesicle (MARV), containing DDX1 and nucleic acids, was identified.
• DDX1 is essential for MARV formation, which exhibit ring-like structures in early embryos.
• Ddx1 knockout disrupts embryonic calcium distribution, increases mitochondrial activity and ROS, and leads to developmental arrest.
• Downregulation of developmental and mitochondrial RNAs correlates with low Ddx1 RNA levels.

Conclusions:

• DDX1 is crucial for the formation of MARVs, which regulate spatial calcium distribution in early embryos.
• MARVs play a vital role in calcium-controlled mitochondrial functions essential for embryonic development.
• Dysregulation of MARVs and calcium homeostasis contributes to developmental defects observed in Ddx1 knockout embryos.