High-resolution SNP genotyping platform identified recurrent and novel CNVs in autism multiplex families

Abstract

Single nucleotide polymorphisms (SNPs)-based genotyping using microarray platform is now frequently used to detect copy number variants (CNVs) in the human genome. Here, we report CNVs identified using Illumina Human Omni 2.5 M oligonucleotide microarrays in 11 multiplex families with autism spectrum disorder (ASD) referred to Autism Research and Treatment Center (ART) and Madinah Maternity and Children Hospital (MMCH). Of the 11 families, 22 patients with ASD (all males) and their parents, were recruited for the present study. In total, 43 individuals were genotyped with high-resolution array. Abnormal microarray results were seen in all 22 patients with ASD. A total of 17 shared CNVs were selected for further analysis. Out of these 17 CNVs, we discovered one novel CNV, previously not described, and 16 recurrent CNVs that overlap with the genomic imbalances defined in the autism database, autism chromosome rearrangement database and database of genomic variants. Recurrent CNVs include 11 common and 5 rare CNVs. All rare CNVs are duplications except a 16-kb deletion on chr2q36.3. Rare gain of copy numbers includes a 2-kb duplication on chr9q21.13, overlapping duplications of 107 kb and 181 kb on chrXp22.33 in 2 different families and a 10-kb duplication on chr18q21.13. A novel loss of copy number on chr3q23 was found in four ASD cases. This CNV results in deletion of intron 2 of calsyntenin 2 (CLSTN2) encoding synaptic protein calsyntenin 2. CLSTN2 is expressed exclusively in the brain, with high levels occurring in cortical gamma-aminobutyric acid (GABA)ergic interneurons and in medial temporal lobe regions. These results verify the diagnostic relevance of genome-wide small common and rare CNVs and provide further evidence of the high diagnostic yield of microarray for genetic testing in children with ASD.