Expression Profiling Of Circular RNAs In The Fetal Hippocampus With Down Syndrome

Down syndrome(DS)is one of the most leading causes of intellectual disability and cognitive impairment due to a naturally-occurring extra copy of chromosome 21,i.e.,trisomy 21.Epigenetic changes mediated by non-coding RNA in the hippocampus of DS patients have been confirmed by studies;recently,a new class of non-coding RNA molecules,circRNA(circRNA),has received extensive attention,circRNA has a variety of molecular functions,tissue-specific expression,and the central nervous system enrichment.During neuronal development,the expression of circRNA is regulated by synaptic plasticity,suggesting it’s specific neuronal functions.At present,the expression profiles and potential function of circRNA in the fetal hippocampus from DS patients remain widely exclusive and largely undefined.OBJECTIVEThis study intends to screen differentially expressed circRNA in the hippocampus of Down syndrome and normal diploid fetal brain by gene array technology.The network analysis and functional analysis are executed by circRNA array data combined with reported miRNA,mRNA data.This study lays the foundation for further reserach of circRNA’s mechanism in the DS development.METHODSEight fetuses with G-banding karyotype are selected as the experimental group,and 6 fetuses with diploid pregnancy of the same gestational age are used as the control group.The hippocampus of fetal brain tissue is isolated.After quality control,samples are tested by circRNA Array,then use Agilent Feature Extraction(v10.7)Software extraction data to analysis of differential expression of circRNA.QRT-PCR is used to verify array results.Then we predict and analyze the binding sites of differentially expressed circRNA between miRNA and mRNA.Enrichment analysis is used to predict the function of differentially expressed(DE)circRNA.RESULTS(1)CircRNA has different expression in hippocampal samples of fetal with Down syndrome(FC≥2,Adjusted P<0.05).(2)Differentially expressed circRNA may act as miRNA sponge to regulate the level of neurological disorder related miRNA in DS.(3)Analysis of the DE circRNA parent gene shows that DE circRNA is associated with many neurobiological pathways such as synaptic vesicle cycling,axon guidance,long-term potentiation(LTP)and long-term depression(LTD),which may lead to DS patients’ abnormal phenotypes,such as learning and memory deficits,intellectual disabilities and early-onset Alzheimer’s disease.(4)Three circ-GRIK1 s are transcribed from GRIK1 s.Their target genes are identified to be associated with several nervous pathogenesis,including axon guidance,MAPK signaling,phosphatidylinositol signaling,glioma,and brain-derived neurotrophic factor(BDNF)signaling.CONCLUSIONSCircRNA has differential expression changes in DS fetal hippocampal samples.DE circRNA may regulate the levels of miRNAs associated with DS neurological disorders.The parental genes of DE circRNA and the final target genes of three Circ-GRIK1 s derived from GRIK1 have been shown to be associated with many neurobiological pathways,which may lead to abnormal phenotypes such as intelligent disorders in DS patients.Our results provide an important basis for further elucidation of the potential molecular biological functions of DE circRNA in chronic neurodegenerative diseases or intellectual disabilities in patients with DS.