Background
DYRK1A maps to the Down syndrome critical region at 21q22. Mutations in this kinase-encoding gene have been reported to cause microcephaly associated with either intellectual disability or autism in humans. Intellectual disability accompanied by microcephaly was recapitulated in a murine model by overexpressing Dyrk1a which mimicked Down syndrome phenotypes. However, given embryonic lethality in homozygous knockout (KO) mice, no murine model studies could present sufficient evidence to link Dyrk1a dysfunction with autism. To understand the molecular mechanisms underlying microcephaly and autism spectrum disorders (ASD), we established an in vivo dyrk1aa KO model using zebrafish.MethodsWe identified a patient with a mutation in the DYRK1A gene using microarray analysis. Circumventing the barrier of murine model studies, we generated a dyrk1aa KO zebrafish using transcription activator-like effector nuclease (TALEN)-mediated genome editing. For social behavioral tests, we have established a social interaction test, shoaling assay, and group behavior assay. For molecular analysis, we examined the neuronal activity in specific brain regions of dyrk1aa KO zebrafish through in situ hybridization with various probes including c-fos and crh which are the molecular markers for stress response.ResultsMicroarray detected an intragenic microdeletion of DYRK1A in an individual with microcephaly and autism. From behavioral tests of social interaction and group behavior, dyrk1aa KO zebrafish exhibited social impairments that reproduce human phenotypes of autism in a vertebrate animal model. Social impairment in dyrk1aa KO zebrafish was further confirmed by molecular analysis of c-fos and crh expression. Transcriptional expression of c-fos and crh was lower than that of wild type fish in specific hypothalamic regions, suggesting that KO fish brains are less activated by social context.ConclusionsIn this study, we established a zebrafish model to validate a candidate gene for autism in a vertebrate animal. These results illustrate the functional deficiency of DYRK1A as an underlying disease mechanism for autism. We also propose simple social behavioral assays as a tool for the broader study of autism candidate genes.Electronic supplementary materialThe online version of this article (10.1186/s13229-017-0168-2) contains supplementary material, which is available to authorized users.
SignificanceEmotion-related responses, such as fear and anxiety, are important behavioral phenomena in most animal species, as well as in humans. However, the underlying mechanisms of fear and anxiety in animals and in humans are still largely unknown, and anxiety disorders continue to represent a large unmet medical need in the human clinic. Animal models may speed up discovery of these mechanisms and may also lead to betterment of human health. Herein, we report the identification of a chemokine-like gene family, samdori (sam), and present functional characterization of sam2. We observed increased anxiety-related responses in both zebrafish and mouse knockout models. Taken together, these results support a crucial and evolutionarily conserved role of sam2 in regulating anxiety-like behavior.
The zebrafish has become an appropriate animal model in the analysis of numerous human brain disorders. A variety of neuropsychiatric conditions and neurodevelopmental disorders are comorbid with abnormal social behavior. Given the translational relevance of zebrafish, multidisciplinary studies employing behavioral, neurobiological, and molecular methods with this species may provide insights into human central nervous system (CNS) disorders. Many of these studies impinge upon our ability to properly induce and quantify the behavior of zebrafish, a relatively understudied aspect of this species. In this study, we investigate how the body size of conspecifics relative to that of the test subject influences social (shoaling) responses in zebrafish. We found a robust preference by wild-type (WT) test zebrafish toward big conspecifics, but not toward smaller conspecifics. Additionally, we tested an autism-relevant zebrafish knockout (KO) model. The dyrk1aa KO zebrafish showed impaired social preference compared with WT in the social behavior test. Our results confirm the effect of relative body size on social preference and that the social preference task developed for zebrafish may uncover the function of genes and biological mechanisms potentially associated with human CNS disorders.
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