J Psychiatry Neurosci 2017;42(1):37-47
Tzyy-Nan Huang, PhD; Yi-Ping Hsueh, PhD
Background: Human genetic studies have indicated that mutations in calcium/calmodulin-dependent serine protein kinase (CASK) result in X-linked mental retardation and autism-spectrum disorders. We aimed to establish a mouse model to study how Cask regulates mental ability.
Methods: Because Cask encodes a multidomain scaffold protein, a possible strategy to dissect how CASK regulates mental ability and cognition is to disrupt specific protein–protein interactions of CASK in vivo and then investigate the impact of individual specific protein interactions. Previous in vitro analyses indicated that a rat CASK T724A mutation reduces the interaction between CASK and T-brain-1 (TBR1) in transfected COS cells. Because TBR1 is critical for glutamate receptor, ionotropic, N-methyl-d-aspartate receptor subunit 2B (Grin2b) expression and is a causative gene for autism and intellectual disability, we then generated CASK T740A (corresponding to rat CASK T724A) mutant mice using a gene-targeting approach. Immunoblotting, coimmunoprecipitation, histological methods and behavioural assays (including home cage, open field, auditory and contextual fear conditioning and conditioned taste aversion) were applied to investigate expression of CASK and its related proteins, the protein–protein interactions of CASK, and anatomic and behavioural features of CASK T740A mice.
Results: The CASK T740A mutation attenuated the interaction between CASK and TBR1 in the brain. However, CASK T740A mice were generally healthy, without obvious defects in brain morphology. The most dramatic defect among the mutant mice was in extinction of associative memory, though acquisition was normal.
Limitations: The functions of other CASK protein interactions cannot be addressed using CASK T740A mice.
Conclusion: Disruption of the CASK and TBR1 interaction impairs extinction, suggesting the involvement of CASK in cognitive flexibility.
Submitted Nov. 18, 2015; Revised Feb. 16, 2016; Revised Mar. 18, 2016; Accepted Mar. 22, 2016; Early-released June 28, 2016
Acknowledgements:T.-N. Huang is supported by a postdoctoral fellowship of Academia Sinica. Y.-P. Sueh is supported by grants from Academia Sinica (AS-103-TP-B05) and the Ministry of Science and Technology (MOST 103-2321-B-001-002 and 104-2321-B-001-050).
Affiliations: From the Graduate Institute of Life Sciences, National Defense Medical Center and the Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.
Competing interests: Both authors have a patent pending for “A pharmaceutical composition for treating autism-spectrum disorders which comprises clioquinol” in Korea and the United States. Y.-P. Hsueh has a patent pending for “Increase of protein synthesis ameliorates synaptopathy-related neurological disorders” in Taiwan and the United States.
Contributors: Both authors designed the study. T.-N. Huang acquired the data, which both authors analyzed. Both authors wrote and reviewed the article and approved the final version for publication.
Correspondence to: Y.P. Hsueh, Institute of Molecular Biology, Academia Sinica, 128, Academia Rd., Sec. 2, Taipei, 11529, Taiwan; email@example.com