The potential role of circRNA_004229 in hair/epidermal regulation after MED1 ablation in keratinocytes

Background/Aims: Mediator complex subunit 1 (MED1) is an important transcriptional co-activator involved in multiple signaling pathways. Previous studies indicated an essential role of MED1 in hair cycling and wound repair through regulating the transcription of mRNAs. Circular RNAs (circRNAs), as a novel class of non-coding RNAs, are involved in various skin biological functions. Our study aimed to investigate the circRNAs expression profile in MED1 epidermal conditional knockout mice (KO), and provide potential candidates as well as the mechanism underlying the circRNAs regulation in both hair follicles and epidermis. Method: Microarray based circRNA expression was determined in MED1 KO mice and wild type mice (WT). The expression level was further confirmed by qRT-PCR. We predicted a possible interaction network of circRNA/microRNA/mRNA by bioinformatics and constructed them with Cytoscape software. Expression of several candidate target mRNAs was verified using qRT-PCR. A TUNEL assay was performed to assess the apoptosis level of MED1 KO and WT skin. Results: Here we identified 109 (34-up, 75-down) distinct circRNAs through microarrays that are differently expressed in MED1 KO mice compared with WT mice (FC > 2 and p-value < 0.05), suggesting a potential role of circRNAs in epidermal regulation. Among these circRNAs, circRNA_004229 was found to decrease significantly after MED1 deletion. The most likely potential targets miRNA for circRNA_004229 include miR-149-5p and miR-207, which possibly further impede the expression of their target mRNA, Tnfrsf19 and Perp, respectively. Apoptosis was suppressed in MED1 KO mice, which implies a potential role of circRNAs in regulating epidermal biological processes including apoptosis. Conclusion: Our study determined the expression profile of circRNAs in MED1 KO skin, and provided hints that circRNA_004229 might be involved in the regulation of keratinocytes in both hair follicles and interfollicular epidermis through a ceRNA mechanism.