Finding the Missing Heritability

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The CoSAGE Project provides a unique and powerful opportunity to tackle the causes of common health problems.

There are three main challenges that impede our ability to identify the causes of common health problems…complexity, complexity, and complexity.  That is, common human health problems are caused by genetic, lifestyle, and environmental factors. And, within each of these areas, there may be dozens of factors that contribute to any health problem.  The amount that genetic factors contribute to a given disease is called heritability and can be estimated from twin studies.  For example, researchers have learned that most common diseases (e.g. diabetes, cancer, heart disease, dementia) that affect humans have high heritability. Recently, the great challenge facing human genetic research has been called “the case of missing heritability”. In the last 15 years, geneticists have become very skilled at 

identifying genetic factors with very strong effects and those genetic factors with very weak effects.  Despite these successes, much of the heritability remains unaccounted for in common diseases. For instance, geneticists have identified over 100 DNA variations that are associated with the risk for Type II diabetes, but all of these DNA variations, together, account for less than 20% of the heritability of Type II diabetes.

Where is the “missing heritability” in common diseases and how do we find it? No one knows for sure. However, the CoSAGE team believes that one approach to finding the “missing heritability” is to partner with a stable community over time, collecting and analyzing detailed health, lifestyle, and environmental data.  Because many of the residents of the CoSAGE partner community are descendants of the original immigrants that settled in mid-Michigan between 1836 and 1870, and because they have maintained extensive genealogic records, we will be able to further benefit from using both population and family-based strategies to tease apart the heritability of complex disease.