Zebrafish frk Gene Knockout Shows Social Impairments Relevant to Autism and Delays Brain Development by Increasing Cell Proliferation.

Fyn-related kinase (FRK), which belongs to the Src family of non-receptor protein tyrosine kinases, functions during the cell cycle. Here, we report an autistic patient with an intragenic mutation of FRK and two other autism-related genes. Circumventing the barrier of murine model studies, we generated the CRISPR/Cas9-engineered frk -/- zebrafish. We found that frk-knockout led to early developmental abnormalities. Frk -/- fish exhibited autism-like behavior, including impaired social communication, repetitive stereotypic behavior, altered anxiety level, and cognitive dysfunction in both larvae and adults, which could be rescued by the transgenic neuron-specific re-expression of frk. GO and KEGG analysis of RNA-sequencing data found that the frk-knockout-induced DEGs were mainly concentrated in processes and functions related to cell metabolism. PPI network analysis of the detected DEGs suggested that the cyp24a1/tp53 pathway may play a key role in frk-knockout-induced autism. Furthermore, we found that the numbers of BrdU+ cells were significantly increased in the frk -/- larval brains. Inhibition of Cyp24a1 or activation of tp53 reduced cell proliferation and partially ameliorated social impairments in frk -/- zebrafish. Overall, our work established an autism model of frk-knockout with an assessable behavior phenotype in zebrafish and provided key insights into cell proliferation and the influence of the cyp24a1/tp53 pathway-regulated cell proliferation on frk-knockout-induced autism-like behaviors.