An international team of scientists, led by Dr Jacques L. Michaud, have recently identified a genetic mutation that causes a form of mental deficiency.
Mental retardation affects 1 to 3% of children, and NSMD (non-syndromic mental deficiency) is the most common form of it. Until recently the understanding of the genetics behind NSMD was very limited. Last month, the team published on The New England Journal of Medicine claiming that they have found the genetic mutation that is a cause of NSMD.
Dr Michaud and his team examined the DNA of 94 patients with NSMD together with 142 patients with autism, 143 patients with schizophrenia and 190 healthy control subjects. They found 3 children with the same type of mutation (de novo protein-truncating mutation*) and all diagnosed with NSMD. The team also managed to identify the gene, SYNGAP1 gene, which, when mutated, will cause the truncation of SYNGAP1 proteins. This SYNGAP1 protein is involved in the function of the synapses, i.e. connections between brain cells. Truncated SYNGAP1 protein lacks domains that are important for synaptic plasticity (a characteristic which is required for learning and memory).
Earlier studies on mice suggest that the SYNGAP1 gene mutation causes impaired learning. This recent finding shown its connection to human genetics.
These findings can possibly lead to the creation of drugs that can improve cognitive processes in NSMD patients. Moreover, Dr Michaud said that this information can “help geneticist counsel parents” whose children have NSMD.
Mental retardation affects 1 to 3% of children, and NSMD (non-syndromic mental deficiency) is the most common form of it. Until recently the understanding of the genetics behind NSMD was very limited. Last month, the team published on The New England Journal of Medicine claiming that they have found the genetic mutation that is a cause of NSMD.Dr Michaud and his team examined the DNA of 94 patients with NSMD together with 142 patients with autism, 143 patients with schizophrenia and 190 healthy control subjects. They found 3 children with the same type of mutation (de novo protein-truncating mutation*) and all diagnosed with NSMD. The team also managed to identify the gene, SYNGAP1 gene, which, when mutated, will cause the truncation of SYNGAP1 proteins. This SYNGAP1 protein is involved in the function of the synapses, i.e. connections between brain cells. Truncated SYNGAP1 protein lacks domains that are important for synaptic plasticity (a characteristic which is required for learning and memory).
Earlier studies on mice suggest that the SYNGAP1 gene mutation causes impaired learning. This recent finding shown its connection to human genetics.
These findings can possibly lead to the creation of drugs that can improve cognitive processes in NSMD patients. Moreover, Dr Michaud said that this information can “help geneticist counsel parents” whose children have NSMD.
At the end of the journal article, the authors noted that “the disruption of a single SYNGAP1 allele** is sufficient to cause cognitive dysfunction in humans” which shows the importance of accuracy in genetics to students like us.
*de novo mutations are mutations that are present for the first time in one family member, i.e. not inherited from parents
**Allele is the variant forms of the same gene
Student #42006655
Reference:
Hamdan, F., Gauthier, J., Spiegelman, D., Noreau, A., Yang, Y., & Michaud, J., et al. (2009). Mutation in SYNGAP1 in Autosomal Nonsyndromic Mental Retardation. The New England Journal of Medicine, 360, 599-605.
Medical News Today, United States of America. (2009, February 5). Researchers Identify Gene Mutations That Affect Learning, Memory In Children. Retrieved March 20, 2009, from http://www.medicalnewstoday.com/articles/137968.php
The Canadian Press, Toronto, Canada. (2009, February 5). Gene mutation linked to common mental deficiency. Retrieved March 20, 2009, from http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/20090205/gene_mutation_090205/20090205?hub=Health
National Centre for Biotechnology Information, United States of America. (2009, March 8). SYNGAP1 synaptic Ras GTPase activating protein 1 homolog. Retrieved March 20, 2009, from http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=8831
National Library of Medicine, United States of America. (2009). De novo mutation. Retrieved March 20, 2009, from http://ghr.nlm.nih.gov/glossary=denovomutation
National Library of Medicine, United States of America. (2009). Allele. Retrieved March 20, 2009, from http://ghr.nlm.nih.gov/glossary=allele
A link to an online version of the journal is here: http://content.nejm.org/cgi/content/short/360/6/599
