Related Experiment Videos
Determination of the functionality of common APOA5 polymorphisms
Philippa J Talmud1, Jutta Palmen, Wendy Putt
1Division of Cardiovascular Genetics, Department of Medicine, Royal Free and University College Medical School, 5 University Street, London WC1E 6JF, United Kingdom. p.talmud@ucl.ac.uk
The Journal of Biological Chemistry
|June 9, 2005
Summary
Common APOA5 variants influence triglyceride levels, but individual single nucleotide polymorphisms (SNPs) within APOA5*2 do not directly explain this association. The effect may stem from SNP interactions or linkage disequilibrium with APOC3 variants.
Area of Science:
- Genetics and Molecular Biology
- Cardiovascular Disease Risk Factors
Background:
- Common variants in the APOA5 gene are consistently linked to variations in plasma triglyceride (TG) levels.
- These variants form distinct haplotypes, including APOA5*1, APOA5*2, and APOA5*3, each characterized by specific single nucleotide polymorphisms (SNPs).
Purpose of the Study:
- To investigate the functional impact of individual SNPs within the APOA5*2 haplotype on triglyceride levels.
- To determine if specific genetic variations in APOA5 directly contribute to altered TG concentrations.
Main Methods:
- Molecular modeling of the apoAV signal peptide (SP) to predict translocation efficiency.
- Functional assays using reporter gene constructs (SP-SEAP, luciferase) in HepG2 and Huh7 cells.
- In vitro transcription/translation and primer extension inhibition assays to assess translation efficiency.
Main Results:
- Molecular modeling predicted, and experimental data confirmed, reduced translocation for the Trp-19 SP compared to Ser-19 SP.
- Individual SNPs within APOA5*2 (-1131T-->C, -3A-->G, 1891T-->C) did not significantly alter reporter gene expression or translation efficiency.
- A 50% reduction in secreted SP-SEAP fusion protein was observed for the Trp-19 variant.
Conclusions:
- The association of APOA5*2 SNPs with plasma TG levels is not explained by the independent functional effects of these individual SNPs.
- Cooperativity between SNPs within the APOA5*2 haplotype cannot be ruled out.
- The observed association may be due to strong linkage disequilibrium with functional variants in the nearby APOC3 gene.