The Role Of The Autism Risk Gene Chd8 In Early Cerebellar Development

Autism Spectrum Disorder(ASD)is a neurodevelopmental disorder characterized by impaired social interaction,limited interests,and repetitive stereotyped behaviors.The etiology and pathogenic mechanism of autism are still unclear.Lesions in multiple brain regions are associated with autism,and there is growing evidence that the cerebellum is also involved.A large number of autistic patients have cerebellar defects,including reduced cerebellar volume and reduced number and morphology of Purkinje cells.Animal model studies have also shown that abnormalities in the cerebellum.Especially,Purkinje cells lead to autism-like symptoms.CHD8 is one of the high-risk genes for autism that discovered in recent years.Studies have reported that knocking out Chd8 in granulosa cell of mice leads to developmental defects and abnormal functions,but knocking out Chd8 in postnatal Purkinje cells has not been significantly affected.In this study,we used zebrafish as a model to study the role of chd8 in the development of the cerebellum.We found that mutations of chd8 lead to abnormal gene expression of cerebellar granule cell precursors,and a decrease in the number of differentiated mature granule cells,and a variable reduction in cell clusters that will develop into cerebellar subregions in the future.These results suggest that the role of chd8 in granulosa cell development in zebrafish is similar to that in mice.Surprisingly,we found that the chd8 mutation resulted in a reduction of cerebellar Purkinje cell precursors and a substantial reduction in the overall number of differentiated and mature Purkinje cells,with an altered distribution pattern,indicating the differentiation,maturation and migration of Purkinje cells.These results appear to contradict findings in mice,which may be related to the timing of Chd8 knockout in mice postnatally,so we speculate that Chd8 may regulate Purkinje cell development during the embryonic period,as we observed the mutations of chd8 in zebrafish lead to developmental defects in Purkinje cell precursors.At the same time,we found the expression level of retinoic acid-related orphan receptor(roraa),which is closely related to Purkinje cell development,was reduced in chd8 mutants,which is similar to the phenomenon of reduced expression of RORA in the cerebellum of autistic patients.Cerebellar Purkinje cell developmental defects caused by chd8 mutations are partially ameliorated by treatment with RORA’s transcriptional agonist SR1078 early in embryonic development,which shows that chd8 regulates Purkinje cell development in early embryonic development.In conclusion,this research found that the autism gene chd8 not only regulates the development of cerebellar granule cells,but also regulates the early development of Purkinje cells.It lays an experimental foundation for further research on the pathogenic mechanism of chd8 involved in autism by regulating cerebellar development,and also provides a potential research target for improving autism symptoms.