Zinc deficiency and low enterocyte zinc transporter expression in human patients with autism related mutations in SHANK3

Simone Hagmeyer,Juergen Bockmann,Thomas Bourgeron,Andreas M Grabrucker,Leonhard Linta,Stefan Liebau,Ann Katrin Sauer,Tobias M Boeckers,Katharina Mangus,Guillaume Huguet,Stefanie Pfaender

doi:10.1038/srep45190

Abstract

Phelan McDermid Syndrome (PMDS) is a genetic disorder characterized by features of Autism spectrum disorders. Similar to reports of Zn deficiency in autistic children, we have previously reported high incidence of Zn deficiency in PMDS. However, the underlying mechanisms are currently not well understood. Here, using inductively coupled plasma mass-spectrometry to measure the concentration of Zinc (Zn) and Copper (Cu) in hair samples from individuals with PMDS with 22q13.3 deletion including SHANK3 (SH3 and multiple ankyrin repeat domains 3), we report a high rate of abnormally low Zn/Cu ratios. To investigate possible underlying mechanisms, we generated enterocytes from PMDS patient-derived induced pluripotent stem cells and used Caco-2 cells with knockdown of SHANK3. We detected decreased expression of Zn uptake transporters ZIP2 and ZIP4 on mRNA and protein level correlating with SHANK3 expression levels, and found reduced levels of ZIP4 protein co-localizing with SHANK3 at the plasma membrane. We demonstrated that especially ZIP4 exists in a complex with SHANK3. Furthermore, we performed immunohistochemistry on gut sections from Shank3αβ knockout mice and confirmed a link between enterocytic SHANK3, ZIP2 and ZIP4. We conclude that apart from its well-known role in the CNS, SHANK3 might play a specific role in the GI tract.

Highlights

The Phelan McDermid Syndrome (PMDS/22q13.3 deletion syndrome) is a rare genetic disorder characterized by symptoms of the autism spectrum that go along with mental retardation, muscular hypotonia, and severely delayed language development
Similar to many reports of Zn deficiency or decreased Zn/Cu ratio in autistic children[17,18,19,20,21,22,23,24], we have previously reported a high incidence rate of Zn deficiency in blood samples of PMDS patients that was associated with the occurrence of seizures, ADHD or other attention and hyperactivity issues, and signs of immunodeficiency[25]
Using the above mentioned protocol, we found that the expression levels of SHANK3 that are significantly reduced in PMDS patient derived cells follow a similar expression pattern as seen for ZIP2 and ZIP4 (Fig. 5a)

Summary

Introduction

The Phelan McDermid Syndrome (PMDS/22q13.3 deletion syndrome) is a rare genetic disorder characterized by symptoms of the autism spectrum that go along with mental retardation, muscular hypotonia, and severely delayed language development. PMDS is caused by a heterozygous deletion of the 22q13.3 region including SHANK3 (SH3 and multiple ankyrin repeat domains 3, known as proline-rich synapse-associated protein 2 (ProSAP2)). SHANK3 is a scaffolding protein of the postsynaptic density (PSD) of excitatory synapses[4,5,6] known to be closely associated with autism spectrum disorders (ASD)[7,8,9,10,11]. Heterozygous loss of SHANK3 is considered to be the main cause for the neurological phenotype in PMDS since patients with small deletions or point mutations in the SHANK3 gene often develop a phenotype close to that of PMDS including intellectual and speech impairment, hypotonia and ASD1,12–14. The genotype-phenotype correlation in PMDS and SHANK3 mutations is quite complicated. Children with ASD frequently suffer from GI problems such as diarrhea, constipation, bloating, abdominal pain, and gastroesophageal reflux[26]

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Conclusion