Genetic mutation for mental retardation found in Amish community

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.