The genes surrounding APOE on chromosome 19 can amplify or moderate the risk your APOE status already confers.
Neighboring genes share regulatory regions and functional relationships with APOE. The chr19 corridor analysis adds resolution to your baseline APOE picture.
The Biology
Chromosomes are not just collections of unrelated genes. Neighboring genes often have related functions, shared regulatory regions, and documented interactions. The stretch of chromosome 19 surrounding APOE contains variants with independent effects on Alzheimer's and cardiovascular risk. TOMM40 encodes a mitochondrial outer membrane translocase involved in protein import into the mitochondrial matrix. A cellular energy and protein homeostasis function with emerging relevance to neurodegeneration.
What Varia Analyzes
TOMM40 rs2075650 is in tight linkage disequilibrium with APOE4 and has been studied as an age-of-onset modifier. Carriers of the A allele, particularly in combination with APOE4, may experience earlier average age of Alzheimer's disease onset based on pharmacogenomics research. The dedicated APOC1 H2 haplotype analysis. Which operates through a distinct mechanism involving direct APOE4 expression amplification. Appears in Domain XII.
Why It Matters
The chromosome 19 corridor analysis adds resolution to the APOE picture. Two people with identical APOE4 status may have meaningfully different risk trajectories depending on the modifying variants they carry in this region. A TOMM40 A/A finding in an APOE4 carrier represents one of the more specific age-of-onset signals available from consumer genomic data.
Key sources
- Roses AD, et al. A TOMM40 variable-length polymorphism predicts the age of late-onset Alzheimer's disease. Pharmacogenomics J. 2010.
- Cruchaga C, et al. Association and expression analyses with single-nucleotide polymorphisms in TOMM40 in Alzheimer disease. Arch Neurol. 2011.
- Lambert JC, et al. Distortion of allelic equilibrium of the apolipoprotein C-I gene predisposes to late-onset Alzheimer's disease. Hum Mol Genet. 1997.