Familial hypercholesterolemia class II low-density lipoprotein receptor response to statin treatment

Area of Science:

• Genetics and Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Familial hypercholesterolemia (FH) is primarily caused by mutations in the low-density lipoprotein receptor (LDLR).
• Class II LDLR mutations lead to protein misfolding and retention in the endoplasmic reticulum (ER).
• Previous models using overexpression of class II LDLR mutants showed ER accumulation and unfolded protein response (UPR) activation.

Purpose of the Study:

• To develop and characterize a cellular model of FH class II using CRISPR-corrected induced pluripotent stem cells (iPSCs).
• To investigate the effects of statins on mutant LDLRs in iPSCs and derived hepatocyte-like cells (HLCs).
• To compare the cellular response to statins in this model versus traditional overexpression models.

Main Methods:

• Generation of iPSCs with class II LDLR mutations and CRISPR-mediated correction.
• Differentiation of iPSCs into HLCs.
• Treatment of cells with statins and tunicamycin.
• Analysis of LDLR protein levels and UPR markers (Grp78/HSPA5, spliced XBP1).
• Culture in lipoprotein-deficient serum (LPDS) medium.

Main Results:

• iPSCs and HLCs successfully replicated misfolded LDLR accumulation and restoration of function in corrected cells.
• Statins induced immature LDLR accumulation, which was resolved by CRISPR correction.
• Unlike overexpression models, statin-treated cells did not induce common UPR markers (Grp78, XBP1(S)), even in LPDS medium.
• Cells responded to tunicamycin with UPR induction, confirming cellular UPR capacity.

Conclusions:

• The developed iPSC model accurately recapitulates mutant and corrected class II LDLR function.
• Statin-induced LDLR biology in this model differs from overexpression systems.
• Overexpression models may not fully predict the in vivo effects of statins on class II LDLR protein biology.