Dioxin and AHR impairs mesoderm gene expression and cardiac differentiation in human embryonic stem cells

Area of Science:

• Developmental toxicology
• Cardiovascular research
• Stem cell biology

Background:

• Dioxins are potent toxicants linked to heart defects.
• Mechanisms of dioxin developmental toxicity remain unclear.
• Species-specific responses suggest complex interactions.

Purpose of the Study:

• Investigate dioxin's impact on human cardiac development using embryonic stem cells (ESCs).
• Determine the susceptible window and dosage for 2,3,7,8‑tetrachlorodibenzo‑p‑dioxin (TCDD) toxicity.
• Elucidate the role of the aryl hydrocarbon receptor (AHR) in TCDD-induced cardiac developmental issues.

Main Methods:

• Utilized a human ESC cardiomyocyte differentiation model.
• Treated ESCs with TCDD at various developmental stages.
• Performed RNA-sequencing to identify differentially expressed genes.
• Conducted chromatin immunoprecipitation sequencing (ChIP-seq) to map AHR binding sites.

Main Results:

• TCDD exposure at the ESC stage inhibited cardiomyocyte differentiation.
• Aryl hydrocarbon receptor (AHR) activation mediated TCDD's inhibitory effects.
• TCDD promoted AHR binding and repressed key mesoderm genes essential for cardiac development.
• Identified specific genes and genomic regions affected by TCDD and AHR.

Conclusions:

• Dioxin impairs human embryonic cardiac differentiation through AHR-mediated repression of mesoderm genes.
• This study demonstrates dioxin's toxicity in human embryonic development.
• Highlights the utility of ESC models for studying developmental toxicology and dioxin's novel regulatory mechanisms.