Identification and Molecular Analysis of m6A-circRNAs from Cashmere Goat Reveal Their Integrated Regulatory Network and Putative Functions in Secondary Hair Follicle during Anagen Stage

Abstract

N6-methyladenosine (m6A) is the most abundant modification in linear RNA molecules. Over the last few years, interestingly, many circRNA molecules are also found to have extensive m6A modification sites with temporal and spatial specific expression patterns. To date, however, little information is available concerning the expression profiling and functional regulatory characteristics of m6A modified circRNAs (m6A-circRNAs) in secondary hair follicles (SHFs) of cashmere goats. In this study, a total of fifteen m6A-circRNAs were identified and characterized in the skin tissue of cashmere goats. Of these, six m6A-circRNAs were revealed to have significantly higher expression in skin at anagen compared with those at telogen. The constructed ceRNA network indicated a complicated regulatory relationship of the six anagen up-regulated m6A-circRNAs through miRNA mediated pathways. Several signaling pathways implicated in the physiological processes of hair follicles were enriched based on the potential regulatory genes of the six anagen up-regulated m6A-circRNAs, such as TGF-beta, axon guidance, ribosome, and stem cell pluripotency regulatory pathways, suggesting the analyzed m6A-circRNAs might be essentially involved in SHF development and cashmere growth in cashmere goats. Further, we showed that four m6A-circRNAs had highly similar expression trends to their host genes in SHFs of cashmere goats including m6A-circRNA-ZNF638, -TULP4, -DNAJB6, and -CAT. However, the expression patterns of two m6A-circRNAs (m6A-circRNA-STAM2 and -CAAP1) were inconsistent with the linear RNAs from their host genes in the SHFs of cashmere goats. These results provide novel information for eluci-dating the biological function and regulatory characteristics of the m6A-circRNAs in SHF development and cashmere growth in goats.