Identification and Molecular Analysis of m(6)A-circRNAs from Cashmere Goat Reveal Their Integrated Regulatory Network and Putative Functions in Secondary Hair Follicle during Anagen Stage

SIMPLE SUMMARY: Cashmere is a natural, high-end textile material. It is derived from the secondary hair follicle (SHFs) tissue in the skin of cashmere goats. Previous studies have indicated that m(6)A modifications in circRNA molecules play important roles in a variety of cells through multiple mechanisms. However, little information is available on the expression profile and functional regulatory characteristics of m(6)A-modified circRNA (m(6)A-circRNA) in SHFs of cashmere goats. In this study, a total of 15 m(6)A-circRNAs were identified. Six of these m(6)A-circRNAs were revealed to have significantly higher expression in skin at anagen than at telogen. To gain insight into the potential regulatory mechanisms of the anagen up-regulated m(6)A-circRNAs, we constructed the regulatory networks along with related pathways in SHFs of cashmere goats. In addition, we found that the expression trends of four m(6)A-circRNAs in the SHFs during SHF cycles were highly similar to their host genes. However, the expression patterns of two m(6)A-circRNAs were inconsistent with the linear RNAs from their host genes in the SHFs of cashmere goats. These results will provide new insights to elucidate the biological functions and regulatory features of m(6)A-circRNA in SHF development and cashmere growth in goats. ABSTRACT: N(6)-methyladenosine (m(6)A) is the most abundant modification in linear RNA molecules. Over the last few years, interestingly, many circRNA molecules are also found to have extensive m(6)A 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 m(6)A modified circRNAs (m(6)A-circRNAs) in secondary hair follicles (SHFs) of cashmere goats. In this study, a total of fifteen m(6)A-circRNAs were identified and characterized in the skin tissue of cashmere goats. Of these, six m(6)A-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 m(6)A-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 m(6)A-circRNAs, such as TGF-beta, axon guidance, ribosome, and stem cell pluripotency regulatory pathways, suggesting the analyzed m(6)A-circRNAs might be essentially involved in SHF development and cashmere growth in cashmere goats. Further, we showed that four m(6)A-circRNAs had highly similar expression trends to their host genes in SHFs of cashmere goats including m(6)A-circRNA-ZNF638, -TULP4, -DNAJB6, and -CAT. However, the expression patterns of two m(6)A-circRNAs (m(6)A-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 m(6)A-circRNAs in SHF development and cashmere growth in goats.