Dr. Adams
01-11-2008, 12:12 PM
"Novel microdeletions and reciprocal microduplications in chromosome 16 were found in about 1% of autism cases, and a common variant in a gene on chromosome 7 was found to increase the risk of autism, in 2 recent studies.
The genetics of autism . . . are basically puzzles with many pieces, and this is 1 of those pieces, but there are many more that need to be found" to provide insight into the disease mechanism.
Heritability in autism is about 90%, making it one of the most heritable complex disorders. About 10% of cases can be explained by genetic syndromes and chromosomal abnormalities, but genetic studies have not provided substantial insight into the 90% of cases where autism is idiopathic.
Using the North America as part of the Autism Genetic Resource Exchange (AGRE), researchers found that among the AGRE families, 5 children with autism in 4 independent families carried de novo deletions in a region on chromosome 16p11.2.
Deletion and duplication events [on a region of chromosome 16p11.2] were observed in nearly 1% of multiplex families with autism [in AGRE], in 1% of subjects with autism in Iceland, and in more than 1.5% of clinical samples from subjects with developmental delay," the group writes. This prevalence is similar to that of the most common known cause of autism (duplication of the Prader-Willi/Angelman region), which is estimated to occur in 1% of subjects with autism.
The study findings support the notion that large, spontaneous deletions and duplications contribute to the molecular causes of autism, but the discovery of significant associations for rarer loci may require screening tens of thousands of DNA samples from patients rather than a few thousand samples.
In the second study, they found that chromosome 7q35 appeared to be linked to autism. Further investigation showed that a common polymorphism in the CNTNAP2 gene is significantly associated with autism. The children with autism tended to have inherited the thymine rather than adenine variant of CNTNAP2. Children with autism were 20% more likely to have inherited the thymine variant from their mothers than from their fathers.
N Engl J Med. Published 08. and Am J Hum Genet. 2008;82:160-164.
The genetics of autism . . . are basically puzzles with many pieces, and this is 1 of those pieces, but there are many more that need to be found" to provide insight into the disease mechanism.
Heritability in autism is about 90%, making it one of the most heritable complex disorders. About 10% of cases can be explained by genetic syndromes and chromosomal abnormalities, but genetic studies have not provided substantial insight into the 90% of cases where autism is idiopathic.
Using the North America as part of the Autism Genetic Resource Exchange (AGRE), researchers found that among the AGRE families, 5 children with autism in 4 independent families carried de novo deletions in a region on chromosome 16p11.2.
Deletion and duplication events [on a region of chromosome 16p11.2] were observed in nearly 1% of multiplex families with autism [in AGRE], in 1% of subjects with autism in Iceland, and in more than 1.5% of clinical samples from subjects with developmental delay," the group writes. This prevalence is similar to that of the most common known cause of autism (duplication of the Prader-Willi/Angelman region), which is estimated to occur in 1% of subjects with autism.
The study findings support the notion that large, spontaneous deletions and duplications contribute to the molecular causes of autism, but the discovery of significant associations for rarer loci may require screening tens of thousands of DNA samples from patients rather than a few thousand samples.
In the second study, they found that chromosome 7q35 appeared to be linked to autism. Further investigation showed that a common polymorphism in the CNTNAP2 gene is significantly associated with autism. The children with autism tended to have inherited the thymine rather than adenine variant of CNTNAP2. Children with autism were 20% more likely to have inherited the thymine variant from their mothers than from their fathers.
N Engl J Med. Published 08. and Am J Hum Genet. 2008;82:160-164.