KIF6 Genotyping Assay

Clinical Background of KIF6

Standard risk factors for cardiovascular disease (e.g., age, gender, smoking status, diabetes and lipid levels) do not identify all people at risk for primary or recurrent disease. There is an important role for emerging risk factors, such as genetic variants that underlie a person’s risk for cardiovascular disease (CVD).^1-3 A variant in a member of the kinesin family of proteins (encoded by KIF6) has been associated with a 50% increased risk for coronary heart disease in six prospective studies of approximately 50,000 people.^4-7 This kinesin polymorphism also impacts response to treatment; carriers of the KIF6 risk variant (60% of the population) have significant event reduction of fatal or nonfatal coronary events from statin therapy.

Noncarriers of the KIF6 risk variant (40% of the population) did not receive significant reduction of coronary events during statin therapy. Thus, in addition to any indicated statin therapy, healthcare providers may consider other interventions for noncarriers.^4,8,9

Biology of the KIF6 Gene

KIF6 encodes a kinesin, a class of motor proteins involved in the intracellular transport along microtubules; the cargos transported include membrane organelles, protein complexes, and mRNAs.^10,11 Kinesins consist of a conserved motor domain that propels the kinesin along microtubules in an ATP dependent manner and a nonconserved tail domain that binds to its cargo.

The tail domains contain coiled-coil structures that facilitate protein-protein interactions,¹² and the KIF6 Trp719Arg polymorphism is located in this tail domain.  Thus, this non-conservative amino acid change that replaces a non-polar residue with a basic residue, might affect the cargo binding of the kinesin encoded by KIF6.

Several kinesins have been implicated in the pathogenesis of chronic diseases, such as neurodegenerative diseases, type 2 diabetes and Alzheimer’s Disease;¹³ however, the role of KIF6 and the Trp719Arg single-nucleotide polymorphism (SNP) in cardiovascular disease remains to be elucidated.

Provided courtesy of Professor Steven M Block

Summary and Explanation of the Test

The KIF6 Genotyping Assay is used to genotype the normal (Trp719) and the variant (Trp719Arg) allele in the KIF6 gene using purified human genomic DNA obtained from whole blood. Genomic DNA is prepared by the ABBOTT® m2000sp™ sample preparation system or by other methods suitable to prepare genomic DNA. The purified DNA is amplified using KIF6 specific primers and allele-specific probes.

Real-time detection of the KIF6 alleles during amplification is performed using the ABBOTT m2000rt™ thermal cycler for monitoring the fluorescence produced after each cycle of the PCR. After the PCR is completed, the m2000rt analysis software with the KIF6 application, calculates the cycle threshold (Ct) for the two KIF6 alleles and then calculates the delta Ct, which is the difference in Ct values generated by the VIC® and FAM™ probes. Based on this difference, the three genotypes are determined: homozygous (Trp/Trp) for the non-risk allele, and heterozygous (Trp/Arg), or homozygous (Arg/Arg) for the risk allele. A heterozygous positive control must be included with each assay run.

m2000 Workflow

References

1. Gibbons, G. H., et al. Genetic Markers: Progress and Potential for Cardiovascular Disease. Circulation 2004;109: IV47-58.
2. Lusis, A. J., et al. Genetic Basis of Atherosclerosis: Part II: Clinical Implications. Circulation 2004;110:2066-71.
3. Cohen, J. C. Genetic Approaches to Coronary Heart Disease. J Am Coll Cardiol 304. 2006; 48:A10-4.
4. Iakoubova, O. A., et al. Association of the Trp719Arg Polymorphism in Kinesin-like Protein 6 with Myocardial Infarction and Coronary Heart Disease in 2 Prospective Trials: The CARE and the WOSCOPS Trials. J Am Coll Cardiol 2008; 51(4):435-443.
5. Shiffman, D., et al. Association of Gene Variants with Incident Myocardial Infarction in the Cardiovascular Health Study. Atheroscler Thromb Vasc Biol 30. 2008;28:173-179.
6. Shiffman, D., et al. A Kinesin Family Member 6 (KIF6) Variant is Associated with Coronary Heart Disease in the Women’s Health Study. J Am Coll Cardiol 2008; 51(4):444-448.
7. Morrison, A. C., et al. Prediction of Coronary Heart Disease Risk using a Genetic Risk Score: The Atherosclerosis Risk in Communities Study. Am J Epidemiol 2007; Advance Access published April 18, 2007: doi:10.1093/aje/kwm 060.
8. Iakoubova, O. A., et al. Polymorphism in KIF6 Gene and Benefit From Statins After Acute Coronary Syndromes: Results From the PROVE IT-TIMI 22 Study. J Am Coll Cardiol 2008;51(4):449-455.
9. Iakoubova, O. A., et al. KIF6 Trp719Arg Polymorphism and the Effect of Statin Therapy in Elderly Patients: Results from the PROSPER Study. Eur J Cardiovasc Prev Rehabil 20 April 2010; doi:10.1097/    HJR.0b013e328336a0dd    .
10. Hirokawa,N.  Kinesin and Dynein Superfamily Proteins and the Mechanism of Organelle Transport. Science 1998; 279:519-26.
11. Miki,H.,etal..All Kinesin Superfamily Protein, KIF, Genes in Mouse and Human. Proc Natl Acad Sci USA 2001; 98: 7004-11.
12. Seiler,S.,et al. Cargo Binding and Regulatory Sites in theTail of Fungal Conventional Kinesin. Nat Cell Biol 2000; 2:333-8.
13. Seog, D.H.,et al. Molecular Motor Proteins of the Kinesin Superfamily Proteins (KIFs): Structure, Cargo and Disease.  J Korean Med Sci 2004;19:1-7