| Autism is a neurodevelopment disorder characterized by three core symptom domains: ritualistic-repetitive behaviors, impaired social interaction, and impaired communication and language development. One common genetic variant under investigation is the promoter polymorphism of the MAOA gene that influences MAOA expression levels so that "low activity" alleles are associated with increased serotonin levels in the brain. In this study we genotyped the MAOA promoter polymorphism in a group of 29 males (age 2-3 yrs) with autism and a group of 39 healthy pediatric controls for whom brain MRI data was available. We found a consistent association between the "low activity" allele and larger brain volumes for regions of the cortex in children with autism but not in controls. Our study of MAOA suggests that is a genetic modifier for the autism phenotype. We were also interested in investigating rare copy number variants associated with autism. Recent studies have highlighted etiologically relevant recurrent copy number changes in autism, such as 16p11.2 deletions and duplications, as well as a significant role for unique, novel variants. We used Affymetrix 250K GeneChip Microarray technology (either NspI or StyI) to detect microdeletions and duplications in a subset of children with autism. In order to enrich our sample for potentially pathogenic CNVs we selected children with autism who had additional features suggestive of chromosomal loss associated with developmental disturbance (positive criteria filter) but who had normal cytogenetic testing (negative criteria filter). We identified families with the following features: at least one child with autism who also had facial dysmorphology, limb or digit abnormalities, or ocular abnormalities. To detect changes in copy number we used a publicly available program, Copy Number Analyser for GeneChipRTM (CNAG) Ver. 2.0. We identified novel deletions and duplications on chromosomes 1q24.2, 3p26.2, 4q34.2, 6q24.3 and 1 1p13-14. Several of these deletions and duplications include new and interesting candidate genes for autism such as syntaxin binding protein 5 (STXBP5 also known as tomosyn), leucine rich repeat neuronal 1 (LRRN1 also known as NLRR1), and PAX6. |
