Mapping the Qatari genome points way to prevention of inherited diseases

Manama: A Weill Cornell Medical College study that analysed the DNA of Qatar’s native population has discovered genetic variations that could help doctors target interventions to reduce the prevalence of a variety of debilitating hereditary disorders.

Researchers at Weill Cornell Medical College in Qatar (WCMC-Q) and Weill Cornell Medical College New York (WCMC-NY), working with colleagues from Cornell University in Ithaca and Hamad Medical Corporation, identified 37 genetic variants in 33 genes known to play causal roles in 36 diseases, including cystic fibrosis, sickle cell anaemia and muscular dystrophy.

The study points the way to more comprehensive screening for a host of inherited diseases, which could significantly reduce their incidence, the college said in a press release.

The project, entitled Exome Sequencing Identifies Potential Risks Variants for Mendelian Disorders at High Prevalence in Qatar, sequenced the DNA of 100 Qatari nationals representing the three major ethnic subgroups of the country — the Bedouin, people of Persian-South Asian descent, and people of African descent. By analysing the individuals’ exomes — important sections of the DNA containing the code translated into proteins — and comparing them with the genetic data of the participants in the worldwide 1000 Genomes Project (1000G), the researchers were able to identify the variations that cause disease among the Qatari population.

All of the conditions targeted in the study were so-called ‘Mendelian diseases’, in reference to diseases caused by a single mutated gene. They are also known as monogenic disorders.

Dr Khalid Fakhro, Postdoctoral Associate in Genetic Medicine at WCMC-Q, and Dr Juan L. Rodriguez-Flores of WCMC-NY, were co-lead principal investigators on the study, part of a group of research projects investigating the Qatari genome led by Dr Ronald Crystal, Chairman of Genetic Medicine at Weill Cornell Medical College in New York.

“There are about 3.2 billion letters that comprise the human genome and about two per cent of those letters code for the actual proteins,” Crystal said. “This two per cent is found in regions called exomes. A Mendelian or monogenic disease is caused by a change in a single letter out of the 3.2 billion. The reason this is relevant for Qatar is that the structure of the society encourages a high degree of consanguineous marriage [marriages to relatives], so the frequency of these monogenic diseases is quite high,” he said.

Pre-marital counselling and screening is one method of decreasing the likelihood of children being born with monogenic diseases. Parents undergo screening to see if either or both carry genetic variations that cause disease before having children. The individuals that carry the disorder do not necessarily have the conditions themselves, but may carry them on recessive genes.

“Disorders are present in all populations around the world, so it is not the case that Qatar is different. Qatar is only different in that its variations and the frequency with which they occur are unique to its population. By finding out what these variations are and taking appropriate action we can save people from the trauma of some very unpleasant disorders,” Crystal said.

Currently, premarital counselling in Qatar screens for four genetic variations out of the 37 identified by the study.

Incorporating the newly discovered variations into the screening process could have a significant impact.

Crystal explained the possible practical applications of the study.

“With more comprehensive screening, people will be able to make more informed choices about whether they feel it is safe to have children together,” he said.