Paving the road to elaborate the genetics of intellectual disabilities. H. Najmabadi1, H. Hu2, Z. Fattahi1, S. Abedini1, M. Hosseini1, F. Larti1, R. Jazayeri1, M. Oladnabi1, M. Mohseni1, T. Wienker2, L. Musante2, K. Kahrizi1, H. H. Ropers2 1) Genetics Research Center, University of Social Welfare & Rehabilitation Sciences, Tehran, Iran; 2) Max Planck Institute for Molecular Genetics, Berlin, Germany.

   The complex human brain has been derived from very simple system and through evolution has adapted a role to an extremely powerful and capable part of our body to make us what we are. It is believed that more than fifty percent of our genes needed for its function. Failure of most of these genes could create catastrophic effects for the individual resulting in intellectual disability (ID). Many of these changes could be inherited while some could be de nova. Over eleven years ago we decided to structure a system to identify these genetic causes; A comprehensive approach. Many families from different ethnicities (Persian, Turk, Arab, Kurdish, and...) with complete clinical profile having two and more affected individuals were recruited. Karyotying, FMR1 testing, and families with ID and microcephaly were also checked for the mutation by linkage analysis and conventional sequencing. In the first few years of the study we indentified number of novel genesand later on in October 2011 we reported 50 novel ID genes using next generation sequencing. Since then additional 240 families with two and more affected have been investigated in our group. This work has been continuing last couple of years and here we are reporting additional 52 novel genes either causing syndromic or non-syndromic ID and many previously reported ID genes. In over 50% of thesefamilies the pathologicalchanges have been identified. In 19 families we could not conclude a single candidate gene because they had at least two candidate genes.Functional analyses have been conducted in many of these genes, and theresults showthe connection between these genes and the involved pathways in the human brain, as well as the role of these genes in brain size and its functions.These findings have contributed to improve the diagnosis of ID and understanding the human brain function.

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