Drosophila Modulo is essential for transposon silencing and developmental robustness

Area of Science:

• Epigenetics
• Developmental Biology
• Genomics

Background:

• Germline transposable element (TE) silencing is essential for genome integrity and developmental robustness.
• The Piwi-interacting RNA (piRNA) pathway, involving Piwi, Aubergine (Aub), and Argonaute 3 (Ago3), is the primary mechanism for TE silencing in the germline.
• Piwi mediates transcriptional silencing via H3K9me3, while Aub and Ago3 handle post-transcriptional silencing.

Purpose of the Study:

• To investigate the role of the Drosophila Modulo protein, a homolog of mammalian Nucleolin, in TE silencing and developmental robustness.
• To elucidate Modulo's interaction with the piRNA pathway and its contribution to epigenetic regulation.

Main Methods:

• Assessed Modulo's interaction with Piwi and its effect on H3K9me3 enrichment at TE sites.
• Examined the impact of Modulo deficiency on Piwi-interacting protein Panoramix's targeting of transposon RNAs.
• Evaluated the consequences of maternal Modulo function on offspring developmental robustness and TE activation.

Main Results:

• Modulo is crucial for H3K9me3 enrichment at TEs, interacting with Piwi downstream of nuclear entry.
• Loss of Modulo function impairs Panoramix's ability to target transposon RNAs.
• Maternal Modulo deficiency compromises offspring developmental robustness and increases ectopic eye outgrowths induced by Kr[If-1].

Conclusions:

• Modulo is an essential epigenetic regulator in the maternal germline, critical for piRNA pathway-mediated TE silencing.
• Maternal Modulo function ensures developmental robustness by inhibiting TE activation and transcriptome variability.
• Modulo plays a key role in safeguarding genome integrity and promoting normal development across generations.