PTEN controls alternative splicing of autism spectrum disorder-associated transcripts in primary neurons

Phosphatase and tensin homologue (PTEN) is the main antagonist of the phosphatidylinositol-3-kinase (PI3K)/AKT/mTOR signalling pathway and mutated in 10%-20% of individuals with autism spectrum disorder (ASD) exhibiting macrocephaly. Hyperactive mTOR signalling is responsible for some aspects during PTEN-ASD progression, e.g. neuronal hypertrophy and -excitability, but PI3K/mTOR-independent processes have additionally been described. There is emerging evidence that PTEN regulates gene transcription, spliceosome formation and pre-mRNA splicing independently of PI3K/mTOR. Altered splicing is a hallmark of brains from individuals with idiopathic and PTEN-ASD, however, molecular mechanisms are yet to be identified. We performed RNA-sequencing (RNA-Seq), followed by analysis of altered transcript splicing in Pten-deficient primary cortical mouse neurons, which we compared with published data from PTEN-deficient human neuronal stem cells. This analysis identified that transcripts were globally mis-spliced in a developmentally regulated fashion and cluster in synaptic and gene expression regulatory processes. Strikingly, splicing defects following Pten-deficiency represent a significant number of other known ASD-susceptibility genes. Furthermore, we show that exons with strong 3' splice sites are more frequently mis-spliced under Pten-deficient conditions. Our study indicates that PTEN-ASD is a multifactorial condition involving the dysregulation of other known ASD-susceptibility genes.