Genetic analysis reveals hidden ancestral links in motor neuron disease and dementia

Researchers at the Macquarie University Brain Institute and Clinic identified hundreds of previously unrecognized family connections among people with frontotemporal dementia (FTD) and motor neuron disease (MND).

The team analyzed the DNA of 3,524 individuals from Australia, New Zealand, and the United Kingdom to find relatives ranging from siblings to third cousins. The researchers used cryptic relatedness analysis to uncover these links. Dr.

Lyndal Henden noted that these connections are often hard to see in adult-onset diseases because many people carry a genetic variant without showing symptoms. This makes traditional family histories incomplete. By identifying these hidden relatives, the team can group people into genetic families to better track down the causes of these diseases. The study identified 793 related pairs and discovered that more than 30% of the relationships were previously unknown.

These findings allowed the team to build 73 new DNA-based family trees for people whose diseases had no known genetic explanation. Professor Kelly Williams stated that this allows researchers to compare affected relatives and prioritize specific regions of DNA inherited from a common ancestor. The analysis also revealed founder networks where people carry the same genetic changes because they inherited them from a shared distant ancestor.

The researchers found that many people clinically labeled with sporadic disease actually shared genetic links with others. Among those with FTD, almost 16% were genetically related to another person in the study, while 5.5% of those with ALS showed similar links.