“…Based on the hypothesis that linear transcripts and their circular counterparts could have potential biological and molecular relationships [55][56][57], we chose genes having an important function in SPZ biology, whose linear transcripts are abundant in SPZ or testis, as hosts for candidate circRNAs. More specifically, we focused on components of the endocannabinoid system (CNR1, CNR2, FAAH, NAPEPLD) [58][59][60][61][62], modulators of protein folding (DNAJB1, DNAJB3 [2,63], HSP90AA1 [64]; HSPA1B, HSPD1 [65]), intragonadic regulators (AR, ESR1, ESR2, GNRH1, GNRHR, GPER1, KISS1, KISS1R) [2,3,66,67]; (LEP, LEPR) [68]; MTHFR [69], PIWIL1 [70]; RARA [71]; RXFP1 [72]; SIRT1 [73]] and epididymal markers (ADAM7 [74], GLIPR1L1 [75], NPC2 [76], SPAM1 [77]). Querying circBase database (http://www.circbase.org/), we found that only six of the previously selected linear RNAs had HS and MM homologous circular isoform counterparts.…”