Alterations in the Autism-Related Gene CEP290 Affects Neurite Formation and Differentiation
While autism is classified as a neurodevelopmental condition, the defined spatiotemporal molecular mechanisms contributing to the establishment of the altered neurophysiology observed in individuals with autism are largely unknown. Large-scale genetic screening implicated several genes, mutations of which may contribute to phenotype found in ASC. CEP290, a protein that is tightly linked to the formation of primary cilium, has been identified among these ASC candidate genes. The primary cilium is a microtubule rich structure protruding out from the cell which has been shown to be crucial for normal cell migration, polarity and division. Moreover, the primary cilium retains a highly specialized nanoenvironment within the cell which serves as the specific compartment for certain types of cell signaling and for cell-environment communication. In particular, Sonic Hedgehog signaling, a cell communication pathway necessary for proper tissue development and maintenance, is preferentially localized to the primary cilium. However, to-date not much is known about the role of the primary cilium in neurodevelopment and in the establishment of mature neural circuits. Mutations in the CEP290 gene are involved in ciliopathies, i.e. severe multi-organ disorders that are related to dysfunctional primary cilia. Additionally, CEP290 has also been implicated in cancer as well as in intellectual disability syndromes and in individuals with autism. However, how CEP290 plays a role in regulating brain function is still unclear.
In this study we set out to analyze the impacts of dysfunctions in the CEP290 gene at a cellular and molecular level in order to dissect the pathways of disrupted neurodevelopment in an autism-related model system.
Methods: Using live cell imaging, immunocytochemistry and molecular techniques we assess the changes in morphological, proliferative and cell signaling mechanisms caused by alterations of CEP290. We employ shRNA techniques to target CEP290 expression and evaluate knockdown efficiencies by Western Blot. Monitoring of cells over 7 days using IncuCyte (Essen Biosciences) allows us to perform detailed analysis on changes in neurite formation and establishment, to make accurate calculations on proliferation rates, and in assessing cell viability and culture quality.
CEP290 is localized to the primary cilium in Neuro-2a cells. Overexpression as well as knockdown of CEP290 leads to reduced retinoic acid-induced neurite outgrowth and diminished neurite arborization indicating that disruption in CEP290 expression might be involved in the regulation of proper neuronal differentiation and maturation. Moreover, cells overexpressing CEP290 displayed a higher rate of proliferation resulting in a disrupted balance between proliferation and differentiation within the cell population.
Conclusions: In summary, our present investigation into the cellular functions of CEP290 have the potential to provide novel insight into the role of primary cilium in neurodevelopmental conditions such as autism.