VEGFA's distal enhancer regulates its alternative splicing in CML

Area of Science:

• Molecular Biology
• Cancer Genomics
• Gene Regulation

Background:

• Enhancer demethylation in leukemia can cause gene overexpression, promoting cancer.
• Vascular Endothelial Growth Factor A (VEGFA) is implicated in cancer progression through alternative splicing.
• The VEGFA +157 enhancer is demethylated in chronic myeloid leukemia (CML).

Purpose of the Study:

• To investigate if the VEGFA +157 enhancer regulates VEGFA alternative splicing in CML.
• To explore the mechanism by which enhancer activity influences VEGFA splicing.
• To determine the role of CCNT2 in enhancer-mediated splicing regulation.

Main Methods:

• Site-directed mutagenesis of the VEGFA +157 enhancer.
• Chromatin activator tethering assays.
• Analysis of VEGFA splicing patterns and eRNA expression in CML patients.
• CCNT2 binding assays and knockdown experiments.

Main Results:

• Mutating the VEGFA +157 enhancer led to exclusion of exons 6a and 7.
• Activating the enhancer promoted inclusion of exons 6a and 7.
• CML patients showed high +157 eRNA expression and inclusion of VEGFA exons 6a and 7.
• CCNT2 binds the VEGFA promoter and enhancer, and its silencing caused exon exclusion by slowing RNAPII elongation.

Conclusions:

• The VEGFA +157 enhancer regulates VEGFA alternative splicing by modulating RNAPII elongation rate via CCNT2.
• This study reveals a novel mechanism linking enhancer activity to alternative splicing of its target gene.
• Findings provide insights into CML pathogenesis and potential therapeutic targets.