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Background: Increasing evidence suggested N6-methyladenosine (m6A) modification is crucial for male germline development. However, m6A modification of lncRNAs gains a little attention in amphibians in recent years. Xenopus laevis (X. laevis) was chosen to be an ideal model organism for testing environmental endocrine disrupting chemicals (EDCs) exposure and resultant effects. Atrazine (AZ) as an endocrine disrupt can effect development of testis in amphibians. Our previous study revealed that m6A is a highly conserved modification across the species. Results: The results of m6A sequences showed that m6A-methylated lncRNAs enriched in intergenic region in testes of X. laevis. We further examined the differential expression of lncRNAs m6A sites in testes of AZ-exposed and compared with that in animals from control group. The results indicated that up to 198 differentially methylated m6A sites were detected within 188 lncRNAs, in which 89 significantly up-methylated sites and 109 significantly down-methylated sites. Data from KEGG pathway analysis indicated that AZ-affected lncRNAs m6A sites were mainly involved in 10 pathways in which 3 mutual pathways were found in the result of differentially m6A-methylated mRNAs. Conclusions: These findings suggested that differentially m6A-methylated lncRNAs and these 3 pathways may act on regulatory roles in abnormal testis development of AZ-exposed X. laevis. This study for the first time provides insights into the profile of lncRNAs m6A modifications in amphibian species. [ABSTRACT FROM AUTHOR]

Recent discovery of reversible N 6 -methyladenosine (m 6 A) methylation on messenger RNA (mRNA) and mapping of m 6 A methylomes in mammals, plant and yeast revealed potential regulatory functions of this RNA modification. However, the role of the m 6 A methylomes in amphibious is still poorly understood. Here, we examined the m 6 A transcriptome-wide profile in testis tissues of Xenopus laevis (X. laevis) with and without treatment with 100 μg/L atrazine (AZ) through m 6 A sequencing analysis using the latest Illumina HiSeq sequencer. The results revealed that m 6 A is a highly conserved modification of mRNA in X. laevis. Distinct from that in mammals, m 6 A in X. laevisis enriched around the stop codon and start codon, as is reported in plant. We then investigated the differential expression m 6 A in testes of AZ-exposed X. laevis and compared that with the X. laevis in the control group by m 6 A sequencing. The results indicated that AZ leads to altered expression profile in 1380 m 6 A modification sites (696 upregulated and 684 downregulated). KEGG pathway analysis indicates that the "NOD-like receptors", "tight junction", "Peroxisome proliferator-activated receptors", "adherens junctions", "Glycerophospholipid metabolism" and "Fatty acid biosynthesis" signaling pathways may be associated with abnormal testis development of X. laevis due to exposure to AZ. Analysis results showed a positive correlation between m 6 A modification and mRNA abundance, suggesting a regulatory role of m 6 A in amphibious gene expression. Our first report of m 6 A transcriptome-wide map of an amphibian species X. laevis presented here provides a starting roadmap for uncovering m 6 A functions that may affect/control amphibian testis development., Competing Interests: Declaration of competing interest The authors declare they have no actual or potential competing financial interests., (Copyright © 2019 Elsevier Ltd. All rights reserved.)