Unveiling the Role of the Most Impactful Cardiovascular Risk Locus through Haplotype Editing

Area of Science:

• Genetics
• Cardiovascular Biology
• Stem Cell Biology

Background:

• The 9p21.3 locus is a major genetic risk factor for coronary artery disease (CAD), particularly in non-African populations.
• This risk is associated with a non-coding DNA segment (haplotype) of approximately 60 kb, whose function remains unclear.
• Understanding the mechanism by which this locus influences CAD is crucial for developing targeted therapies.

Purpose of the Study:

• To investigate the functional role of the 9p21.3 risk haplotype in vascular smooth muscle cells (VSMCs).
• To elucidate the cellular and molecular mechanisms underlying the association between the 9p21.3 locus and coronary artery disease.
• To establish a cellular model for functional annotation of the human genome.

Main Methods:

• Generation of induced pluripotent stem cells (iPSCs) from individuals with and without the 9p21.3 CAD risk haplotype.
• Genome editing to delete the risk haplotype in iPSCs.
• Differentiation of iPSCs into vascular smooth muscle cells (VSMCs).
• Transcriptional profiling and functional assays (adhesion, contraction, proliferation) of VSMCs.

Main Results:

• VSMCs derived from the risk haplotype exhibited widespread alterations in transcriptional networks, impacting known CAD risk genes and pathways.
• These risk VSMCs displayed aberrant adhesion, contraction, and proliferation.
• Deletion of the risk haplotype restored VSMC stability, while expression of the long non-coding RNA ANRIL induced risk phenotypes in non-risk VSMCs.

Conclusions:

• The 9p21.3 risk haplotype predisposes VSMCs to a cell state associated with CAD phenotypes.
• This study identifies novel VSMC-based gene networks involved in CAD risk.
• Haplotype-edited iPSCs serve as a valuable tool for functional genomic annotation and understanding complex disease genetics.