Endogenous Mouse Dicer Is an Exclusively Cytoplasmic Protein

Area of Science:

• Molecular Biology
• Genetics
• Cell Biology

Background:

• Dicer protein is crucial for microRNA and short-interfering RNA biogenesis.
• Previous studies suggested Dicer's involvement in nuclear processes like dsRNA clearance in human and mouse cell lines.

Purpose of the Study:

• To precisely determine the in vivo cellular localization of Dicer in mice.
• To investigate if Dicer's localization is conserved in mammals.
• To clarify Dicer's role in nuclear versus cytoplasmic functions.

Main Methods:

• Utilized an endogenously epitope-tagged Dicer knock-in mouse model.
• Performed biochemical fractionation and confocal immunofluorescence microscopy on primary mouse cells and tissues.
• Examined Dicer localization during mouse embryogenesis across all germ layers and extraembryonic tissues.

Main Results:

• Endogenous Dicer was found to be exclusively cytoplasmic in all examined primary mouse cell lines and adult tissues.
• No evidence of Dicer shuttling between the nucleus and cytoplasm was observed.
• FGF or DNA damage signaling did not induce Dicer nuclear translocation.
• Dicer remained strictly cytoplasmic during all stages of embryogenesis and in all embryonic tissues.

Conclusions:

• Dicer protein plays an exclusively cytoplasmic role in RNA biogenesis in vivo in mice.
• The data exclude a direct function for Dicer in nuclear RNA processing in the mouse.
• Dicer's cytoplasmic localization is a conserved feature in mammalian development and adult tissues.