Ever wonder why Elizabeth Taylor had such compelling eyes? It turns out that she probably carried a mutation for doubled eyelashes, also known as distichiasis. [article]
The FOX (forkhead box) family of genes codes for a type of protein known as a transcription factor. This type of protein turns on and off genes during development as well as during cellular replication. Some of the FOX genes are important for longevity (article on longevity genes and FOXO3A).
The FOXC2 gene turns genes on and off during prenatal development. Specifically, it is required during the development of the kidneys and early development of the heart. It is also important for the development of the valves in the lymphatic system [ref]
So what do the lymphatic valves and heart development have to do with double eyelashes? Well, a mutation in the FOXC2 gene not only causes double lashes but also causes a predisposition to lymphedema (swelling of the arms and legs) and an increased risk of congestive heart failure. This mutation can also cause droopy eyelids and yellowish nails. It is amazing what these transcription factors can do when they turn on or off genes during development.
Genetic variants in FOXC2:
Check your genetic data for rs121909106 (23andme i5002816 v4; AncestryDNA):