24974
Role of ANK2 in Autism Spectrum Disorder
ANK2 encodes a member of the ankyrin family of proteins (Ankyrin B) that link integral membrane proteins (e.g. L1CAM) to the underlying spectrin-actin cytoskeleton. Ankyrins play key roles in activities such as cell motility, activation, proliferation, cell-cell contact and the maintenance of specialized plasma membrane domains. Loss-of-function variants in ANK2cause a dominantly-inherited cardiac arrhythmia with increased risk for sudden cardiac death, initially termed type 4 long QT Syndrome, and more recently renamed the “Ankyrin-B” Syndrome. Recent next generation DNA sequencing projects in autism spectrum disorder (ASD) cohorts (the Simons Simplex Collection) have revealed several heterozygous de novo ANK2 missense and nonsense mutations marking ANK2 as a ‘high-confidence’ autism candidate gene. Additionally, our lab has identified individuals with ANK2 sequence changes who not only have cognitive and behavioral deficits, but also have abnormalities of the corpus callosum. These genetic findings highlight the importance of ANK2 in neurodevelopment, but how mutations in ANK2 lead to these brain disorders is still unknown.
Objectives:
To determine the interaction between ANK2 and L1CAM and its role in ASD development and abnormalities of the corpus callosum.
Methods:
whole genome sequencing and breaking point analysis were performed in a patient with a balanced chromosomal translocation t (4; 8) (q25; q23), quantitative PCR and Western blot were used to compare ANK2 and L1CAM expression among ASD patients from the SSC cohort. Immunohistochemistry (IHC) was used to show overlapping expression pattern of ANK2 and L1CAM during corpus callosum development in mouse.
Results:
We reported an expected and significant decrease in expression of ANK2 mRNA and protein in patient compared to control PBMC’s. We also investigated the abundance of the neuronal adhesion protein, L1CAM. We found that L1CAM protein abundance is decreased in patients with ANK2 mutations (one with a balanced chromosomal translocation through ANK2 t (4; 8) (q25; q23), and in two other ASD patients with nonsense mutations in ANK2) and that L1CAM expression is rescued after transient transfection of ANK2 into a cell line from one patient carrying a nonsense mutation in ANK2.
Conclusions:
Our results suggest that disruption of the normal interaction and balance between ANK2 and L1CAM may play an important role in ASD and other neurodevelopmental disorders such as agenesis of the corpus callosum (ACC). Moreover, this linkage between ACC and ASD has implications for the mechanistic overlap for these two groups of disorders.