Phosphorylation of the neurogenic transcription factor SOX11 on serine 133 modulates neuronal morphogenesis

Elli-Anna Balta,Elisabeth Kremmer,Dieter Chichung Lie,Marius Ueffing,Felix Von Zweydorf,Christian Johannes Gloeckner,Julia Von Wittgenstein,Benjamin Martin Häberle,Iris Schäffner,Birgit Heim,Kathrin Steib,Marie-Theres Wittmann,Elisabeth Sock

doi:10.1038/s41598-018-34480-x

Abstract

The intellectual disability gene, Sox11, encodes for a critical neurodevelopmental transcription factor with functions in precursor survival, neuronal fate determination, migration and morphogenesis. The mechanisms regulating SOX11’s activity remain largely unknown. Mass spectrometric analysis uncovered that SOX11 can be post-translationally modified by phosphorylation. Here, we report that phosphorylatable serines surrounding the high-mobility group box modulate SOX11’s transcriptional activity. Through Mass Spectrometry (MS), co-immunoprecipitation assays and in vitro phosphorylation assays followed by MS we verified that protein kinase A (PKA) interacts with SOX11 and phosphorylates it on S133. In vivo replacement of SoxC factors in developing adult-generated hippocampal neurons with SOX11 S133 phospho-mutants indicated that phosphorylation on S133 modulates dendrite development of adult-born dentate granule neurons, while reporter assays suggested that S133 phosphorylation fine-tunes the activation of select target genes. These data provide novel insight into the control of the critical neurodevelopmental regulator SOX11 and imply SOX11 as a mediator of PKA-regulated neuronal development.

Highlights

The intellectual disability gene, Sox[11], encodes for a critical neurodevelopmental transcription factor with functions in precursor survival, neuronal fate determination, migration and morphogenesis
We show that the three phosphorylatable serine residues surrounding the DNA binding High-mobility group (HMG)-box, i.e., serine 30 (S30), S133, and S137, modulate SOX11’s
While the combined mutation of all three N-terminal serines into phospho-mimetic or non-phosphorylatable amino acids abolished transcriptional activity, single mutants of S30 and S133 can activate transcription. This could be potentially explained by S137, which may further contribute to the ability of SOX11 to transactivate

Summary

Introduction

The intellectual disability gene, Sox[11], encodes for a critical neurodevelopmental transcription factor with functions in precursor survival, neuronal fate determination, migration and morphogenesis. We report that phosphorylatable serines surrounding the high-mobility group box modulate SOX11’s transcriptional activity. In vivo replacement of SoxC factors in developing adult-generated hippocampal neurons with SOX11 S133 phospho-mutants indicated that phosphorylation on S133 modulates dendrite development of adult-born dentate granule neurons, while reporter assays suggested that S133 phosphorylation fine-tunes the activation of select target genes. These data provide novel insight into the control of the critical neurodevelopmental regulator SOX11 and imply SOX11 as a mediator of PKAregulated neuronal development. We provide evidence that phosphorylation of SOX11 on S133 modulates dendritic morphogenesis in vivo

Methods

Results

Conclusion