The H3.3K27M oncohistone antagonizes reprogramming in Drosophila

Area of Science:

• Developmental Biology
• Epigenetics
• Cancer Biology

Background:

• Development relies on precise gene activation and silencing.
• Mis-expression of master regulator transcription factors can redirect development and is linked to cancers.
• Chromatin-mediated gene silencing plays a critical role in maintaining developmental programs.

Purpose of the Study:

• To investigate the role of gene silencing in developmental reprogramming using a specific transcription factor.
• To determine if inhibiting histone H3K27 trimethylation affects the reprogramming of eye tissue to wing tissue.
• To explore the link between impaired silencing, transcription factor mis-expression, and abnormal cell growth.

Main Methods:

• Mis-expression of the wing-specific Vestigial (Vg) master regulator in developing eye tissue.
• Introduction of an H3.3K27M oncohistone mutation to inhibit histone H3K27 trimethylation.
• CUT&Tag chromatin profiling and transcriptome profiling of RNA Polymerase II.

Main Results:

• Oncohistone production blocked eye-to-wing reprogramming.
• H3K27 trimethylation was reduced in mutant tissues, indicating impaired silencing.
• Vg and H3.3K27M synergistically caused eye tissue overgrowth, implicating mis-regulated signaling factors.

Conclusions:

• Effective developmental reprogramming requires the silencing of previous developmental programs.
• Crippled gene silencing combined with transcription factor mis-expression can lead to growth dysregulation.
• This mechanism may explain the origins of cancers associated with oncohistones.