Genetic causes of bone tumours discovered in 1,000-year-old Irish skeletons

Irish scientists have established the genetic causes of bone tumours in 1,000-year-old skeletons discovered in a “lost” graveyard Co Donegal.

They have shown two men buried in the medieval graveyard had a genetic condition called multiple osteochondromas, which causes benign bone tumours.

The skeletons were found in a graveyard at Ballyhanna, where the remains of some 1,300 children, women and men were found during construction of the N15 Bundoran-Ballyshannon bypass.

A major advance in modern medicine has been the ability to sequence a patient’s genetic make-up – known as a genome – to find the precise cause of a genetic condition. But until now this type of comprehensive search had not been done on the DNA of ancient individuals.

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It was made possible by sequencing the genetic make-up and identifying disease causing mutations in the bone samples. Details of the genomic analysis by teams at Trinity College Dublin and Queen’s University Belfast were published on Monday.

The land at Ballyhanna would have been owned by the church at the time of the burials and the Gaelic medieval population would have included tenant farmers, labourers, merchants, artisans, clergy and the very poor. Those buried showed high rates of skeletal indicators of stress and ill health and infectious diseases such as tuberculosis.

Life was particularly challenging for two men whose bones showed multiple tumours resulting from a genetic disease called multiple osteochondromas, according to lead researcher Iseult Jackson of TCD School of Genetics and Microbiology. This condition is rare, can be extremely painful and can lead to limb deformity, reduced stature, nerve compression and malignancy in about 5 per cent of cases.

The researchers analysed genome sequences from the two affected skeletons and identified mutations in a gene called EXT1, which is involved in the disease in modern patients. The mutations found were different in the two individuals; one has been identified in some patients today but the other has not previously been seen in sequencing data. Though the disease is genetic, the two individuals were not related.

This study in the European Journal of Human Genetics represents the first time a new disease mutation has been discovered in ancient genomic data, Ms Jackson confirmed.

The disease only occurs in 1 in 50,000 people and when it is found within a modern locality the affected people tend to be related. “Here it is surprising that the same rare condition occurred twice in the same parish but resulted from two different mutations. In this case, the lightning of genetic tragedy struck twice,” she added.

“The application of ancient DNA analysis to the people of Ballyhanna has enabled us to build upon earlier osteoarchaeological research,” she noted.

“We made several assumptions about these two men when we first realised that they both had suffered from multiple osteochondromas,” explained Prof Eileen Murphy of QUB. “We assumed they were contemporary but radiocarbon dating showed they were separated by several hundred years. We also assumed they were related but the new [ancient] DNA analysis has demonstrated that this is not the case.”

Discovery of mutations that cause serious diseases through application of “whole genome sequencing” has been a key medical breakthrough in recent years, said Prof Dan Bradley from Trinity’s School of Genetics and Microbiology. “The study demonstrates the important contribution that ancient DNA analysis on people from the past can make to understanding conditions that still affect people today.”