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Genetic mutation for mental retardation found in Amish community

18 March 2013
Appeared in BioNews 697

A genetic mutation linked to mental retardation has been identified in an Amish community in the USA. It is the first time that a mutation on the HERC2 gene has been associated with impaired mental development.

Researchers from the Bellvitge Institute for Biomedical Research (Idibell) and the University of Barcelona in Spain analysed genetic data from fifteen people of the Old Order Amish Community in Ohio, USA who presented conditions similar to those experienced by people with Angelman syndrome. The results showed a mutation in HERC2 gene that meant the protein it produces does not function correctly.

'In these communities there are high rates of inbreeding, making homozygous recessive diseases more frequent than in the general population', said Jose Luis Rosa from Idibell. 'We observed that there must be a common genetic cause'.

There are approximately 250,000 Amish living in the USA and Canada with the population estimated as doubling every twenty years or so. The Amish are a Christian community known for their simple living and plain dress, as well as their reluctance to adopt modern technology.

A tradition of marrying within the community has lead to a genetically similar population and, as a result, the incidence of genetic conditions in the Amish community is higher than in the wider population.

The researchers say the findings will not only be useful in investigating mental retardation in the Amish community, but also may benefit others affected by Angelman-like symptoms in providing a possible genetic explanation.

'Individuals from anywhere in the world that have similar symptoms to Angelman syndrome but do not have the genetic mutation associated with the disease and are diagnosed as Angelman-like, could have the same gene mutation in HERC 2 observed in Amish, which could provide an explanation for the disorder, and genetic counselling to their families', explained Rosa, adding that a possible human gene therapy for the condition is very far away.

The researchers had previously identified a link between a mutation in the HERC1 gene and brain degeneration in mice. 'Overall, these studies demonstrate an important role of HERC protein family in the pathogenesis of neuronal disorders', said Rosa.

The study was published in the Journal of Medical Genetics.

Amish Inbreeding Causes Genetic Mutation and Mental Retardation
International Business Times |  13 March 2013
Found in Amish a genetic mutation causing mental retardation very similar to Angelman syndrome
Bellvitge Institute for Biomedical Research (press release) |  12 March 2013
Mutation of HERC2 causes developmental delay with Angelman-like features
Journal of Medical Genetics |  14 December 2012
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