The RNA M~6A Modification Landscape Of The Major Human Tissues From Fetuses In The Second Trimester Of Pregnancy

The m6A methylation is the most prevalent modification of eukaryotic mRNA and lincRNA,and is conserved in many species from yeast to human.m6A is regulated by the methyl-transferase METTL3/METTL14 complex and the demethylase FTO/ALKBH5,and can be recognized by YTH family proteins etc.m6A is involved in multiple physiological processes such as signal transduction,mRNA translation,degradation,alternative splicing and miRNA processing.Disorders of m6A can cause changes in stem cell pluripotency,abnormal embryonic development,and even cancer.The research of m6A modification will provide theoretical basis and important clues for related fields.At present,the researches on m6A are mostly carried out in cultured cells in vitro,there are few studies on m6A in different tissues of m6A in vivo,especially human.Therefore,we have studied the distribution and function of RNA m6A in the major human tissues.First,we collected 21 tissue samples of human fetuses from the eight major tissue types:brain,liver,lung,kidney,heart,stomach,placenta,and skeletal muscle.The results of m6A transcriptome analysis in each tissue were obtained by our improved total RNA immunoprecipitation method combined with second generation sequencing technology.A total of 90,644 m6A peaks were detected in each tissue,and more than half of the m6A peaks were first discovered.These m6A genes are closely related to tissue development.Comparing to published brain mRNA m6A sequencing results,our whole RNA m6A sequencing results show that many m6As in each tissue are located in intron and intergenic regions.Next,in order to study the dynamic characteristics of m6A methylation,we further analyzed the differences in m6As in human tissues.By examining the genomic distribution of the tissue difference m6As,it was found that about half of the tissue-differential m6As existed in the intron,suggesting that the co-transcriptional process such as splicing may be related to the tissue-differential m6As.Subsequently,we examined the relationship between tissue-differental m6As and their host gene expression levels,and found that the host gene with tissue differential m6As had lower expression levels in all tested tissues than with constitutive m6As.The gene-related m6As gene is associated with tissue-related developmental processes,suggesting that m6A may play a role in cell differentiation and organ development.Finally,the main research in published work is m6A on mRNA,and less work is focused on m6A on lincRNA.Therefore,we studied m6A on lincRNA in various tissues.We found that the kidney,placenta and brain contain the most abundant lincRNA m6As.A lincRNA with m6A is more likely to havealternative splicing.e-lincRNA is a class of lincRNAs transcribed from enhancers.Through analysis,we found that in most tissues,more than half of e-lincRNAs were modified by m6A.These results suggest that m6As may be involved in eRNA function.Through m6A studies of specific human samples,we obtained data on genome-wide mtA analysis,tissue difference m6As genomic distribution,and m6A enrichment on e-lincRNA in human tissues.These research results fill the gaps in m6A research in human tissue in these years,enrich the information of m6A in human tissues,and have inspiring and driving functions for the future m6A research.