M 6 A transcriptome-wide map of circRNAs identified in the testis of normal and AZ-treated Xenopus laevis

Background Evidence showed that N 6 -methyladenosine (m 6 A) is strongly associated with male germline development. However, the role of m 6 A methylation on circRNAs in amphibians remains unknown. In this study, we conducted m 6 A sequencing analysis to explore the m 6 A transcriptome-wide profile of circRNAs in testis tissues of Xenopus laevis ( X. laevis ) with and without treatment with 100 µg/L atrazine (AZ). Results The analysis showed that m 6 A modification of circRNAs enriched in sense overlapping in testes of X. laevis . We identified the differential m 6 A modification sites within circRNAs in testes of AZ-exposed X. laevis and compared that with animals from control group. The results showed that a total of 1507 methylated m 6 A sites was induced by AZ (760 up-methylated and 747 down-methylated). The cross-analysis exhibited a negative correlation of differentially methylated m 6 A peaks and circRNAs expression level. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that 20 key pathways may be involved in the mechanism of testis damage of AZ-exposed X. laevis . Conclusions These findings indicated that differentially m 6 A-methylated circRNAs may play important roles in abnormal testis development of AZ-exposed X. laevis . This study is the first report about a map of m 6 A modification of circRNAs in male X. laevis and provides a basis for further studying on the function and mechanism of m 6 A methylation of circRNAs in the testis development of amphibian.