An Interstitial 17q11.2 de novo Deletion Involving the CDK5R1 Gene in a High-Functioning Autistic Patient.

We describe a 32-year-old male patient diagnosed with high-functioning autism spectrum disorder carrying a de novo 196-kb interstitial deletion at chromosome 17q11.2. The deletion was detected by array CGH (180K Agilent) and confirmed by quantitative PCR on genomic DNA. The deleted region spans the entire PSMD11 and CDK5R1 genes and partially the MYO1D gene. The CDK5R1 gene encodes for a regulatory subunit of the cyclin-dependent kinase 5 responsible for its brain-specific activation. This gene has been previously associated with intellectual disability in humans. A reduction in CDK5R1 transcript was detected, consistent with the genomic deletion. Based on the functional role of CDK5R1, this gene appears as the best candidate to explain the clinical phenotype of our patient, whose neuropsychological profile has more resemblance with some of the higher brain function anomalies recently described in the CreER-p35 conditional knockout mouse model than previously described patients with intellectual disability.

Evidence that ITGB3 promoter variants increase serotonin blood levels by regulating platelet serotonin transporter trafficking.

Elevated serotonin (5-HT) blood levels, the first biomarker identified in autism research, has been consistently found in 20-30% of patients with Autism Spectrum Disorder (ASD). Hyperserotonemia is mainly due to greater 5-HT uptake into platelets, mediated by the 5-HT transporter (SERT) located at the platelet plasma membrane. The protein complex involved in platelet SERT trafficking and externalization includes integrin ß3, the beta subunit of the platelet membrane adhesive GP IIb/IIIa. Integrin ß3 is encoded by the ITGB3 gene, previously identified as a quantitative trait locus (QTL) for 5-HT blood levels in ASD at single nucleotide polymorphism (SNP) rs2317385. The present study aims to identify the functional ITGB3 gene variants contributing to hyperserotonemia. ITGB3 gene sequencing in 20 individuals selected on the basis of rs2317385 genotypes defined four haplotypes encompassing six SNPs located in the ITGB3 gene promoter region, all in linkage disequilibrium with rs2317385. Luciferase assays in two hematopoietic cell lines, K-562 and HEL 92.1.7, demonstrate that ITGB3 gene promoter activity is enhanced by the presence of the C allele at rs55827077 specifically during differentiation into megakaryocytes (P < 0.01), with modulatory effects by flanking SNPs. This same allele is strongly associated with (a) higher 5-HT blood levels in 176 autistic individuals (P < 0.001), (b) greater platelet integrin ß3 protein expression (P < 0.05) and (c) enhanced SERT trafficking from the cytosol toward the platelet plasma membrane (P = 4.05 × 10-11). Our results support rs55827077 as the functional ITGB3 gene promoter variant contributing to elevated 5-HT blood levels in ASD and define a mechanistic chain of events linking ITGB3 to hyperserotonemia.