Isotyping the human TOMM40 variable-length polymorphism by gene amplification and restriction digest

Recent studies have shown that the translocase of outer mitochondrial membrane 40 homolog (TOMM40) contains a polymorphic poly-T variant, the long variant of which is associated with an increase in AD incidence among APOE 3 carriers. Current methods to isotype the poly-T region rely on long PCR, subcloning and sequencing to distinguish among the allelic variants. While such methods are extremely accurate as well as quantitative in determining the number of T residues in the poly-T region, the process can be cumbersome, time consuming and expensive to employ in routine laboratories. To this end, we have developed a quick and simple method to isotype the human TOMM40 variable length polymorphism using a PCR- and restriction digest-based approach, enabling rapid genotyping of TOMM40 variants.