Progressing super-enhancer landscape during mammary differentiation controls tissue-specific gene regulation

Area of Science:

• Molecular Biology
• Developmental Biology
• Genomics

Background:

• Mammary gland milk production relies on STAT5-driven super-enhancers during pregnancy.
• Lactation demands progressive mammary cell differentiation to meet increasing milk needs.
• The evolving enhancer landscape during lactation remains poorly understood.

Purpose of the Study:

• To investigate how hormonal exposure during lactation shapes the mammary enhancer landscape.
• To understand the impact of this evolving landscape on mammary cell biology and differentiation.
• To explore the functional plasticity of enhancers within the Wap super-enhancer during lactation.

Main Methods:

• Chromatin immunoprecipitation sequencing (ChIP-seq) to analyze transcription factor occupancy.
• Mouse genetics to study enhancer function through combinatorial deletions.
• Assessment of enhancer specificity in globally permissive chromatin.

Main Results:

• Transcription factor occupancy at mammary enhancers changes with advancing differentiation during lactation.
• Individual enhancers within the Wap super-enhancer exhibit evolving functions throughout lactation.
• A pregnancy-specific seed enhancer is dispensable during lactation, demonstrating compensatory flexibility.
• Structurally similar enhancers show differentiation-specific compensatory activities.

Conclusions:

• The mammary enhancer landscape is progressive and dynamic during lactation.
• Structurally equivalent enhancers possess unique, differentiation-specific functions.
• The Wap super-enhancer maintains mammary specificity independent of global chromatin context.