Nature Middle East | House of Wisdom

One thousand and one tales of genetic disorders in Arabs

This is a guest post from Ghazi O. Tadmouri,  assistant director of the Centre for Arab Genomic Studies, Dubai, United Arab Emirates.

In April 2003, scientists announced the completion of a high-quality sequence of the entire human genome, including data on 23,000 genes.  Nine years later, nearly 14,000 genes have been identified and the functions of only a few have been determined. While none of the Arab States contributed to the Human Genome Project at that time, today they are partners in gene annotation and human genome variation collection efforts through detailed analysis of the phenotypic and genotypic aspects of genetic disorders described in the region. Over the last 13 months, three major conferences that took place in the region emphasized this role, including the co-organization of the Human Genome Meeting 2011 with the 4th Pan Arab Human Genetics Conference in Dubai in March 2011, the International Conference on Consanguinity in Muscat in March 2012, and the 4th International Conference of Medical Genetics in Kuwait in April 2012.

A quick overview of the studies presented in these events strongly reflects a remarkable heterogeneity of genetic disorders recognized in Arab populations. The Catalogue of Transmission Genetics in Arabs (CTGA) database, maintained by the Centre for Arab Genomic Studies, Dubai, represents the most comprehensive knowledge base in this regard. The latest release of the database indicates the presence of at least 1,000 genetic disorders in Arab states, including 550 in Gulf Cooperation Council (GCC) countries alone. Yet, unlike many world populations, more than two-third of the genetic disorders in Arabs are autosomal recessive. This is probably a result of the widespread practice of consanguineous marriages, with rates ranging between 25-60% in many communities.

While some regard consanguinity as an undesired choice, scientists comprehend its potential in helping them to delineate the causative gene mutation of many genetic disorders. Whether genes linked to these disorders turn out to be novel or known ones, associated mutations always reveal an explosion of unprecedented human genome sequence variability. Based on the out-of-Africa model to describe the origin and early dispersal of anatomically modern humans, population geneticists strongly believe that the Arab world regions were the second oldest inhabited area by modern humans. This extended history is considered as the mother of all human genome variability in the Arab World.

While the CTGA Database catalogues variability in some 400 genes described in Arabs, this collection is far from complete as genome research is not equally practiced among Arab scientific centers. This issue implies a more interesting twist since geneticists indicate that more than 250 disorders have not been uncovered at all at the genetic level. The availability of associated gene knowledge will certainly have favorable implications on urgent needs of the region, including genetic counseling, proper diagnosis, prognosis, and appropriate management of patients with genetic disorders.  Yet, this situation offers a golden opportunity for Arab scientists to step into the ‘omics’ era by coordinating a long-awaiting Arab Human Variome Project.


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