SHANK2 Mutations Result in Dysregulation of the ERK1/2 Pathway in Human Induced Pluripotent Stem Cells-Derived Neurons and Shank2(-/-) Mice.

Anne-Kathrin Lutz,Andrea Pérez Arévalo,Richard Delorme,Tobias M Boeckers,Valentin Ioannidis,Thomas Bourgeron,Maria Demestre,Nadine Stirmlinger

doi:10.3389/fnmol.2021.773571

Abstract

SHANK2 (ProSAP1) is a postsynaptic scaffolding protein of excitatory synapses in the central nervous system and implicated in the development of autism spectrum disorders (ASD). Patients with mutations in SHANK2 show autism-like behaviors, developmental delay, and intellectual disability. We generated human induced pluripotent stem cells (hiPSC) from a patient carrying a heterozygous deletion of SHANK2 and from the unaffected parents. In patient hiPSCs and derived neurons SHANK2 mRNA and protein expression was reduced. During neuronal maturation, a reduction in growth cone size and a transient increase in neuronal soma size were observed. Neuronal proliferation was increased, and apoptosis was decreased in young and mature neurons. Additionally, mature patient hiPSC-derived neurons showed dysregulated excitatory signaling and a decrease of a broad range of signaling molecules of the ERK-MAP kinase pathway. These findings could be confirmed in brain samples from Shank2(−/−) mice, which also showed decreased mGluR5 and phospho-ERK1/2 expression. Our study broadens the current knowledge of SHANK2-related ASD. We highlight the importance of excitatory-inhibitory balance and mGluR5 dysregulation with disturbed downstream ERK1/2 signaling in ASD, which provides possible future therapeutic strategies for SHANK2-related ASD.

Highlights

Keratinocytes grown from hair roots of the patient, the father, and the mother were reprogrammed to human induced pluripotent stem cells (hiPSC), following previously published protocols (Supplementary Figure 1A and Linta et al, 2012)
Molecular implications of SHANK2 deletion have been studied in mouse models (Schmeisser et al, 2012; Won et al, 2012) and hiPSCs and derived neurons (Zaslavsky et al, 2019). hiPSCs offer the unique possibility to study human-derived cells that harbor a patient-specific “real-life mutation.”
We showed that a heterozygous SHANK2 deletion leads to a variety of alterations during early development and to profound alterations in the mitogen-activated protein kinases (MAPK) extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway

Summary

Introduction

SHANK proteins (SHANK1, SHANK2/ProSAP1, and SHANK3/ProSAP2) (Boeckers et al, 1999, 2002; Sheng and Kim, 2000; Grabrucker et al, 2011) function as postsynaptic anchoring platforms for receptor complexes and signaling molecules (Tu et al, 1999; Boeckers et al, 2001; Roussignol et al, 2005) and are involved in synapse formation and modulation (Sala et al, 2001; Boeckers et al, 2005). Other hypotheses concentrate on the critical role of dysregulated mRNA translation (Monteiro and Feng, 2017; Joo and Benavides, 2021) or signaling pathways (Zoghbi and Bear, 2012; Kleijer et al, 2014). In this respect, the extracellular signal-regulated kinase (ERK) pathway seems to play a central role in the pathogenesis of ASD (Faridar et al, 2014; Vithayathil et al, 2018). Syndromic forms of ASD, including Rett syndrome and Fragile X syndrome, show dysregulation of the ERK-signaling cascade (Vithayathil et al, 2018)

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Results

Conclusion