Cytoplasm-predominant Pten associates with increased region-specific brain tyrosine hydroxylase and dopamine D2 receptors in mouse model with autistic traits.

Xin He,Thomas W Frazier,Qi Yu,Charis Eng,Stetson Thacker,Todd Romigh

doi:10.1186/s13229-015-0056-6

Abstract

BackgroundAutism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by impairment in social communication/interaction and inflexible/repetitive behavior. Several lines of evidence support genetic factors as a predominant cause of ASD. Among those autism susceptibility genes that have been identified, the PTEN tumor suppressor gene, initially identified as predisposing to Cowden heritable cancer syndrome, was found to be mutated in a subset of ASD patients with extreme macrocephaly. However, the ASD-relevant molecular mechanism mediating the effect of PTEN mutations remains elusive.MethodsWe developed a Pten knock-in murine model to study the effects of Pten germline mutations, specifically altering subcellular localization, in ASD. Proteins were isolated from the hemispheres of the male littermates, and Western blots were performed to determine protein expression levels of tyrosine hydroxylase (TH). Immunohistochemical stains were carried out to validate the localization of TH and dopamine D2 receptors (D2R). PC12 cells ectopically expressing either wild-type or missense mutant PTEN were then compared for the differences in TH expression.ResultsMice carrying Pten mutations have high TH and D2R in the striatum and prefrontal cortex. They also have increased phosphorylation of cAMP response element-binding protein (CREB) and TH. Mechanistically, PTEN downregulates TH production in PC12 cells via inhibiting the phosphoinositide 3-kinase (PI3K)/CREB signaling pathway, while PTEN reduces TH phosphorylation via suppressing MAPK pathway. Unlike wild-type PTEN but similar to the mouse knock-in mutant Pten, three naturally occurring missense mutations of PTEN that we previously identified in ASD patients, H93R, F241S, and D252G, were not able to suppress TH when overexpressed in PC12 cells. In addition, two other PTEN missense mutations, C124S (pan phosphatase dead) and G129E (lipid phosphatase dead), failed to suppress TH when ectopically expressed in PC12 cells.ConclusionsOur data reveal a non-canonical PTEN-TH pathway in the brain that may work as a core regulator of dopamine signaling, which when dysfunctional is pathogenic in ASD.Electronic supplementary materialThe online version of this article (doi:10.1186/s13229-015-0056-6) contains supplementary material, which is available to authorized users.

Highlights

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by impairment in social communication/interaction and inflexible/repetitive behavior
Ptenm3m4 mutant mice have increased tyrosine hydroxylase (TH) in the prefrontal cortex and striatum To address whether the TH and dopamine pathway in the brain plays an important role in ASD, we first examined the TH protein levels by Western blot in the cerebrum of male littermates aged 8 weeks (Fig. 1b)
Consistent with the TH data, we found significantly increased D2 receptors (D2R) in the striatum and prefrontal cortex of the mutant mice (Fig. 1d)

Summary

Introduction

Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by impairment in social communication/interaction and inflexible/repetitive behavior. Several lines of evidence support genetic factors as a predominant cause of ASD Among those autism susceptibility genes that have been identified, the PTEN tumor suppressor gene, initially identified as predisposing to Cowden heritable cancer syndrome, was found to be mutated in a subset of ASD patients with extreme macrocephaly. Autism spectrum disorder (ASD) is a group of neurodevelopmental disorders characterized by impairments in social interaction and communication, along with the presence of inflexible/repetitive behaviors [1]. We first identified germline PTEN mutations in a subset of patients with ASD and extreme macrocephaly [11], an observation that was subsequently confirmed by multiple independent groups [12,13,14]. They have an overgrowth of white matter and deficits in working memory and processing [15]

Methods

Results

Discussion

Conclusion