Characterization and pharmaceutical treatment of the Shank3Δ11 knockout mouse model

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Date

2024-12-18

Authors

Bauer, Helen Friedericke

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Dissertation

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Abstract

Phelan-McDermid syndrome (PMS) is a rare genetic disorder defined by global developmental delay, intellectual disability, muscular hypotonia, autism spectrum disorders, and various physical, behavioral, and neurological symptoms. It is caused by a deletion of chromosome 22 or mutations in the SHANK3 gene. This gene encodes a protein localized at glutamatergic synapses, functioning as a master scaffolding protein that connects receptors with the actin cytoskeleton at postsynaptic sites. In recent years, several genetic animal models have been developed to study the pathophysiology of SHANK3 haploinsufficiency. This study investigated the development of behavioral phenotypes in the Shank3Δ11 transgenic mouse model, focusing on differences in sex and genotype. Motor functions, social and repetitive behaviors, the two core symptoms of autism, cognitive and memory functions, as well as anxiety and avoidance behavior were examined at two developmental stages corresponding to human adolescence and early adulthood. Both heterozygous and homozygous Shank3 knockout (KO) mice were compared to wildtype (WT) controls. Shank3-KO mice exhibited impaired motor coordination and endurance, while muscle strength remained unaffected. Only minor changes were observed in social behavior, yet the animals showed pronounced stereotypic and repetitive behaviors. They also demonstrated increased avoidance behavior and slightly elevated anxiety. Cognitive flexibility was somewhat impaired, while spatial memory and orientation remained unchanged. The phenotype was generally stable over time, and female mice exhibited similar characteristics to males, though they were less affected in motor function and repetitive behavior. In all tests, heterozygous Shank3-KO mice either displayed normal behavior or a milder phenotype compared to homozygous counterparts. This study supports the face validity of Shank3-KO mice as a model for mimicking PMS pathology. Following phenotypic characterization, the effects of i.n. insulin, lithium, and zinc treatments were investigated in a small cohort of young homozygous Shank3-KO mice. Treatment began in postnatal week four, with behavioral tests conducted in treatment weeks 3 to 5. I.n. insulin did not enhance behavioral alterations in Shank3-KO mice. However, lithium and zinc supplementation positively influenced motor performance in the Rotarod test. This study also involved the validation of various commercial and homemade SHANK3 antibodies, revealing that some antibodies lacked specificity or showed cross-reactivity family members SHANK1 and SHANK2, which share a close homology. One validated antibody was then further used to study SHANK3 isoform-specific expression in the hippocampus, striatum, cerebellum, and cortex of both heterozygous and homozygous Shank3-KO mice, compared to WT levels. A distinct brain region-specific isoform pattern was observed. Despite certain SHANK3 isoforms still being expressed due to the knockout strategy used, we found a brain region- and sex-specific downregulation of some isoforms. Interestingly, heterozygous Shank3-KO mice displayed either intermediate or WT levels of SHANK3, possibly explaining their milder phenotype in most behavior tests. The comprehensive characterization of this mouse model allows to further investigate the pathophysiology and potential pharmaceutical intervention in PMS preclinical, as effective treatment approaches are currently lacking in the clinical settings.

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Faculties

Medizinische Fakultät

Institutions

Institut für Anatomie und Zellbiologie
UKU. Klinik für Neurologie
Internationale Graduiertenschule für Molekulare Medizin

Citation

DFG Project uulm

EU Project THU

Other projects THU

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CC BY 4.0 International

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DOI external

DOI external

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Periodical

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DFG Project THU

item.page.thu.projectEU

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Keywords

SHANK3, Phelan-McDermid syndrome, Mouse model, Autismus, Autismus, Tierversuch, Nerve tissue proteins; Genetics, Autism spectrum disorder; Genetics, Mice, Knockout; Genetics, Models, Animal, Zinc, Lithium, Insulin, DDC 610 / Medicine & health