Heritable diseases — say Huntington’s, sickle cell anemia, or cystic fibrosis — are typically thought of as the result of a certain mutation in one gene. But sometimes, variants of a few genes collectively cause what are called “oligogenic” diseases.
This, it turns out, is what happened to the Legkiy family. Tatiana; her older sister, Anna; and the lost fetus each received rare mutations in three genes from their parents — two from their father, one from their mother — that together triggered the heart issues. Having one of those genetic variants, or even two, wouldn’t have caused serious problems. But the subtle nudges from each of the variants scooched them past a threshold into having unhealthy hearts.
In 2014, while searching for disease-influencing variants of genes involved in the development of the heart, the team landed on three in the MKL2, MYH7, and NKX2-5.
“Each of these genes, their function is disrupted in a given number of cells, but each one only causes a slight level of disruption,” said Casey Gifford, a Gladstone scientist and the lead author of the paper.
But together, she added, the mutations are capable of causing serious congenital heart problems.
Read full, original post: A family’s medical mystery sheds light on the surprising ways disease-causing genes can be inherited