Distinct Genetic Risk Based on Association of MET in Families With Co-occurring Autism and Gastrointestinal Conditions

Vanderbilt University, 8114 MRB3, 465 21st Ave South, Nashville, TN 37232, USA.
PEDIATRICS (Impact Factor: 5.47). 04/2009; 123(3):1018-24. DOI: 10.1542/peds.2008-0819
Source: PubMed


In addition to the core behavioral symptoms of autism spectrum disorder, many patients present with complex medical conditions including gastrointestinal dysfunction. A functional variant in the promoter of the gene encoding the MET receptor tyrosine kinase is associated with autism spectrum disorder, and MET protein expression is decreased in the temporal cortex of subjects with autism spectrum disorder. MET is a pleiotropic receptor that functions in both brain development and gastrointestinal repair. On the basis of these functions, we hypothesized that association of the autism spectrum disorder-associated MET promoter variant may be enriched in a subset of individuals with co-occurring autism spectrum disorder and gastrointestinal conditions.
Subjects were 918 individuals from 214 Autism Genetics Resource Exchange families with a complete medical history including gastrointestinal condition report. Genotypes at the autism spectrum disorder-associated MET promoter variant rs1858830 were determined. Family-based association test and chi(2) analyses were used to determine the association of MET rs1858830 alleles with autism spectrum disorder and the presence of gastrointestinal conditions.
In the entire 214-family sample, the MET rs1858830 C allele was associated with both autism spectrum disorder and gastrointestinal conditions. Stratification by the presence of gastrointestinal conditions revealed that the MET C allele was associated with both autism spectrum disorder and gastrointestinal conditions in 118 families containing at least 1 child with co-occurring autism spectrum disorder and gastrointestinal conditions. In contrast, there was no association of the MET polymorphism with autism spectrum disorder in the 96 families lacking a child with co-occurring autism spectrum disorder and gastrointestinal conditions. chi(2) analyses of MET rs1858830 genotypes indicated over-representation of the C allele in individuals with co-occurring autism spectrum disorder and gastrointestinal conditions compared with non-autism spectrum disorder siblings, parents, and unrelated controls.
These results suggest that disrupted MET signaling may contribute to increased risk for autism spectrum disorder that includes familial gastrointestinal dysfunction.

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    • "who constituted 41 % of the sample (Campbell et al. 2009; Wang et al. 2011). Published case series also report high prevalence of GI symptoms in ASD (Molloy and Manning- Courtney 2003; Valicenti-McDermott et al. 2006) but without population-based controls. "
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    • "The reduced HGF expression in the serum was observed in ASD patients who have severe GI tract problems (23). Furthermore, a significant polymorphism in the receptor tyrosine kinase MET promoter region was observed in ASD patient group having GI problem in a genetic analysis study (24). MET signaling activate N-mehtyl-D-aspartate (NMDA) mediated receptor function and increase glutamatergic synapse formation and post synaptic protein clustering in mature neuron (25-27). "
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    • "The variants found so far are mostly associated with differences in the metabolism, rather than in brain structure. The MET promoter variant rs1858830 allele “C”, found at increased rates in autism, is associated with neuronal growth and development, but also is involved in immune function and gastrointestinal repair [19,20]. The fact that this genetic variant is present in 47% of the general population gives credence to the assertion that there is an environmental component to the development of autism. "
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