Constitutional mislocalization of Pten drives precocious maturation in oligodendrocytes and aberrant myelination in model of autism spectrum disorder

Hyunpil Lee,Charis Eng,Stetson Thacker,Nicholas Sarn,Ranjan Dutta

doi:10.1038/s41398-018-0364-7

Abstract

There is a strong genetic association between germline PTEN mutation and autism spectrum disorder (ASD), making Pten-mutant models exemplary for the study of ASD pathophysiology. We developed the Ptenm3m4 mouse, where Pten is largely restricted from the nucleus, which recapitulates patient-like, autism-related phenotypes: behavioral changes, macrocephaly, and white matter abnormalities. This study aimed to investigate the contribution of oligodendrocyte (OL) lineage differentiation and functional changes in myelination to the white matter phenotype. OL lineage differentiation and myelination in Ptenm3m4 mice was studied using immunohistochemical and electron microscopic analyses. We also used primary oligodendrocyte progenitor cells (OPCs) to determine the effect of the Ptenm3m4 mutation on OPC proliferation, migration and maturation. Finally, we assessed the myelinating competency of mutant OLs via co-culture with wildtype dorsal root ganglia (DRG) neurons. The in vivo analyses of Ptenm3m4/m3m4 murine brains showed deficits in proteolipid protein (Plp) trafficking in myelinating OLs. Despite the increased expression of myelin proteins in the brain, myelin deposition was observed to be abnormal, often occurring adjacent to, rather than around axons. Mutant primary OPCs showed enhanced proliferation and migration. Furthermore, mutant OPCs matured precociously, exhibiting aberrant myelination in vitro. Mutant OPCs, when co-cultured with wildtype DRG neurons, showed an inability to properly ensheath axons. Our findings provide evidence that the Ptenm3m4 mutation disrupts the differentiation and myelination programs of developing OLs. OL dysfunction in the Ptenm3m4 model explains the leukodystrophy phenotype, a feature commonly associated with autism, and highlights the growing importance of glial dysfunction in autism pathogenesis.

Highlights

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired reciprocal social interaction accompanied by restricted interests and repetitive behaviors[1]
We investigated the levels of myelinating OL markers: myelin basic protein (Mbp), proteolipid protein (Plp), myelin oligodendrocyte protein (Mog) and myelin associated glycoprotein (Mag) in the cortex of the Ptenm3m4/m3m4 mice
We found evidence for an increase in OL lineage cells in the Ptenm3m4/m3m4 mouse, an increase in proliferation of oligodendrocyte progenitor cells (OPCs) without an increase in OLs (Fig. 1). This finding was partially explained by the increased apoptosis that was observed in OLs in the Ptenm3m4/m3m4 brain (Supplementary Fig. S3)

Summary

Introduction

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impaired reciprocal social interaction accompanied by restricted interests and repetitive behaviors[1]. As with all complex diseases, there are variable genetic and environmental contributions, it is well-established that there is a significant genetic component to ASD. The genetic architecture of ASD is complex, there are cases of strong, monogenic associations, such as with PTEN. Of children diagnosed with ASD and macrocephaly, 7–17% harbor germline PTEN mutations[2,3,4,5]. Syndromic models of ASD may help illuminate shared features of the disorder. The constitutional Ptenm3m4 model, which recapitulates many of the behavioral, morphological, and molecular features of ASD, has been leveraged to study common mechanisms of ASD pathogenesis[6,7].

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