Nucleosome landscape reflects phenotypic differences in Trypanosoma cruzi life forms

Area of Science:

• Epigenetics
• Molecular Biology
• Parasitology

Background:

• Trypanosoma cruzi exhibits distinct life forms with varying transcriptional activity and nuclear architecture.
• Epigenetic modifications, including histone posttranslational modifications, are implicated in these life form transitions.
• Understanding chromatin dynamics is crucial for deciphering parasite development and infectivity.

Purpose of the Study:

• To investigate genome-wide nucleosome positioning and occupancy differences between replicative (epimastigotes) and nonreplicative (cellular trypomastigotes) Trypanosoma cruzi life forms.
• To explore the role of chromatin architecture in regulating gene expression and phenotypic changes during T. cruzi life cycle progression.
• To identify epigenetic regulatory mechanisms associated with infective-stage and virulence factors.

Main Methods:

• Genome-wide high-resolution nucleosome mapping was performed on two T. cruzi life forms.
• A computational pipeline was developed to compare nucleosome positioning and occupancy data.
• Statistical analyses were used to identify differential nucleosome occupancy and its association with gene expression and functional categories.

Main Results:

• Over 125,000 nucleosomes were mapped, with approximately 20% showing differences between life forms.
• Nonreplicative forms displayed less dynamic nucleosomes, correlating with lower transcription and DNA replication arrest.
• Dynamic nucleosomes were enriched in regulatory regions, virulence factors, and genes involved in nuclear division, translation, and metabolism.
• Nucleosome depletion at 5' splice sites correlated with gene expression levels, suggesting a role in trans-splicing efficiency.

Conclusions:

• Chromatin architecture, specifically nucleosome positioning and occupancy, significantly differs between T. cruzi life forms.
• These epigenetic variations reflect phenotypic plasticity and are linked to differential gene expression and virulence.
• Nucleosome dynamics play a critical role in regulating T. cruzi life cycle transitions and infectivity, even without canonical transcriptional control.