Abstract
Sertoli cells are the crucial coordinators to guarantee normal spermatogenesis and male fertility. Although circular RNAs (circRNAs) exhibit developmental-stage-specific expression in porcine testicular tissues and have been thought of as potential regulatory molecules in spermatogenesis, their functions and mechanisms of action remain largely unknown, especially in domestic animals. A novel circBTBD7 was identified from immature porcine Sertoli cells using reverse transcription PCR, Sanger sequencing, and fluorescence in situ hybridization assays. Functional assays illustrated that circBTBD7 overexpression promoted cell cycle progression and cell proliferation, as well as inhibited cell apoptosis in immature porcine Sertoli cells. Mechanistically, circBTBD7 acted as a sponge for the miR-24-3p and further facilitated its target mitogen-activated protein kinase 7 (MAPK7) gene. Overexpression of miR-24-3p impeded cell proliferation and induced cell apoptosis, which further attenuated the effects of circBTBD7 overexpression. siRNA-induced MAPK7 deficiency resulted in a similar effect to miR-24-3p overexpression, and further offset the effects of miR-24-3p inhibition. Both miR-24-3p overexpression and MAPK7 knockdown upregulated the p38 phosphorylation activity. The SB202190 induced the inhibition of p38 MAPK pathway and caused an opposite effect to that of miR-24-3p overexpression and MAPK7 knockdown. Collectively, circBTBD7 promotes immature porcine Sertoli cell growth through modulating the miR-24-3p/MAPK7 axis to inactivate the p38 MAPK signaling pathway. This study expanded our knowledge of noncoding RNAs in porcine normal spermatogenesis through deciding the fate of Sertoli cells.
Highlights
Spermatogenesis is an extraordinarily complex and orchestrated process, which is mainly subdivided into three phases, including the mitosis, differentiation, and proliferation of spermatogonial stem cells, the meiotic of spermatocytes, and the differentiation of haploid spermatids [1]
We found that circBTBD7, a novel circular RNA (circRNA) originated from the BTB (POZ) domain containing 7 (BTBD7) gene, promotes cell cycle progression and cell proliferation, whereas it impedes cell apoptosis in immature porcine Sertoli cells. circBTBD7 elevates the mitogen-activated protein kinase 7 (MAPK7) gene expression through acting as an endogenous sponge of the miR-24-3p
To analyze the primary mode of action of the circBTBD7, its subcellular location was checked in immature porcine Sertoli cells using RNA-fluorescence in situ hybridization (FISH) assay
Summary
Spermatogenesis is an extraordinarily complex and orchestrated process, which is mainly subdivided into three phases, including the mitosis, differentiation, and proliferation of spermatogonial stem cells, the meiotic of spermatocytes, and the differentiation of haploid spermatids [1]. In multiple spermatogenic cell types, Sertoli cells, the sole somatic cells within the seminiferous tubules, play key regulatory roles in guaranteeing the testis development, normal spermatogenesis process, and even male fertility [2,3]. In the neonatal and prepubertal periods, the immature and proliferation state, Sertoli cells arrest the meiosis progression of pro-spermatogonia, promote the Leydig cell differentiation, and further give priority to testis development and formation [2]. Sertoli cells enter a mature and nonproliferation state, and their functional roles switch to guarantee the spermatozoa development through providing a stable microenvironment and morphogenetic support, as well as secreting several functional factors [3,4]. The regulatory mechanisms of Sertoli cell proliferation are poorly understood, especially in domestic animals
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