Characteristics of Circular RNA Expression Profiles of Porcine Granulosa Cells in Healthy and Atretic Antral Follicles.

Li Meng,Hengxi Wei,Chi Chiu Wang,Shouquan Zhang,Jian Tao,Zhihong Zhao,Yaodi Liang,Li Li,Marcel Jaklofsky,Katja Teerds

doi:10.3390/ijms21155217

Abstract

Circular RNAs (circRNAs) are thought to play essential roles in multiple biological processes, including apoptosis, an important process in antral follicle atresia. We aimed to investigate the potential involvement of circRNAs in granulosa cell apoptosis and thus antral follicle atresia. CircRNA expression profiles were generated from porcine granulosa cells isolated from healthy antral (HA) and atretic antral (AA) follicles. Over 9632 circRNAs were identified, of which 62 circRNAs were differentially expressed (DE-circRNAs). Back-splicing, RNase R resistance, and stability of DE-circRNAs were validated, and miRNA binding sites and related target genes were predicted. Two exonic circRNAs with low false discovery rate (FDR) high fold change, miRNA binding sites, and relevant biological functions—circ_CBFA2T2 and circ_KIF16B—were selected for further characterization. qRT-PCR and linear regression analysis confirmed expression and correlation of the targeted genes—the antioxidant gene GCLC (potential target of circ_CBFA2T2) and the apoptotic gene TP53 (potential target of circ_KIF16B). Increased mRNA content of TP53 in granulosa cells of AA follicles was further confirmed by strong immunostaining of both p53 and its downstream target pleckstrin homology like domain family a member 3 (PHLDA3) in AA follicles compared to negligible staining in granulosa cells of HA follicles. Therefore, we concluded that aberrantly expressed circRNAs presumably play a potential role in antral follicular atresia.

Highlights

Each estrous cycle, a cohort of small antral follicles in, is recruited to enter the pool of growing antral follicles
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We showed that the p53/PHLDA3 pathway might participate in granulosa cell apoptosis

Summary

Introduction

A cohort of small antral follicles in, is recruited to enter the pool of growing antral follicles. From this pool, dominant follicles are selected by a process highly dependent on follicle-stimulating hormone (FSH) [1,2]. Granulosa cell death by apoptosis is the main cause of antral follicular atresia [5]. Initiation of granulosa apoptosis can be triggered by extrinsic factors, such as inflammation, and intrinsic factors, such as oxidative stress [6]. The underlying regulatory mechanism, which determines whether granulosa cells of selected antral follicles will undergo apoptosis, is still not fully characterized

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Conclusion