Figure 1.

circSTK40 is upregulated in the midluteal-phase endometrial tissues of patients with RIF

(A and B) Microarray cluster and volcano plot of differentially expressed circular RNAs (circRNAs) in midluteal-phase endometrial tissues between controls (n = 8) and RIF patients (n = 8). (C) The expression levels of circSTK40 validated in the midluteal-phase endometrial tissues of controls (n = 16) and RIF patients (n = 16). Ct values were normalized to β-ACTIN. (D) Schema illustrating the production of circSTK40. circSTK40 was formed by back-splicing of exons 4 and 5 of the STK40 gene. (E) The back-splicing junction site of circSTK40 was validated by Sanger sequencing (arrow). (F) The relative levels of circSTK40 and mSTK40 after RNase R treatment (n = 3). (G) The expression levels of circSTK40 in primary human endometrial epithelial cells (ECs) and stromal cells (SCs) (n = 3). (H) Separation of cytoplasmic and nuclear RNA from THESCs and measurement of circSTK40 expression levels by quantitative real-time PCR (n = 4). (I) Subcellular localization of circSTK40 was detected by RNA fluorescence in situ hybridization assay in THESCs. U6 and 18S RNA served as the nuclear and cytoplasmic localization controls, respectively. Scale bars represent 5 μm. Data are presented as the mean ± SEM. Student’s t test. ∗p < 0.05, ∗∗p < 0.01, and ∗∗∗p < 0.001; n.s., non-significant.