Can HMGCR rs3846662 affect HMG-CoA reductase splicing and statin response?

The HMGCR rs3846662 variant is a key genetic modifier of lipid metabolism, directly linking the post-transcriptional splicing of the rate-limiting cholesterol enzyme to clinical statin response and cellular feedback.

Mechanistic pathways

• Splicing Regulation: The intronic rs3846662 variant acts as a functional splicing quantitative trait locus (sQTL) by modulating the binding affinity of the splicing repressor hnRNP A1 to HMGCR pre-mRNA.
• Isoform Expression: Strengthening this binding promotes the skipping of exon 13, yielding a truncated transcript (HMGCR13⁻) that lacks 53 amino acids within the catalytic and statin-binding domain, leaving the resulting enzyme catalytically inactive.

Cellular feedback and statin response

• Feedback Modulation: Alternative splicing of HMGCR serves as an endogenous feedback mechanism. Intracellular sterol loading shifts splicing toward the inactive HMGCR13⁻ isoform to suppress biosynthetic flux, whereas rs3846662 dictates the baseline sensitivity of this homeostatic loop.
• Clinical Efficacy: Because the HMGCR13⁻ isoform lacks a functional drug-binding pocket, cells expressing it are highly resistant to statin inhibition.
• Clinical Trial Evidence: In the CAP and PRINCE trials, rs3846662 (primarily within the H7 haplotype) was associated with attenuated low-density lipoprotein cholesterol (LDL-C) reduction during simvastatin and pravastatin therapy, explaining 6% to 15% of response variation. However, this effect is cohort- and drug-dependent; large-scale GWAS of rosuvastatin in the JUPITER trial did not identify rs3846662 as a primary determinant of response.

Bottom line

• The HMGCR rs3846662 variant alters hnRNP A1-mediated splicing to produce a statin-resistant, inactive enzyme isoform, serving as a moderate pharmacogenetic modifier of statin efficacy by reshaping endogenous cholesterol feedback sensitivity.